# The Ultimate Guide to Setting Out Sheet Metal

##
1. What is lofting?

Table of Contents

The so-called setting out is to accurately draw all or part of the projection map of the structure in a certain proportion (usually 1:1) based on the construction drawings and according to the structural characteristics of the product, construction needs and other conditions, process the structure, and sometimes carry out preliminary expansion and necessary calculations, and finally obtain the data, samples, rods and sketches required for construction.

Generally speaking, it refers to displaying the specifications, shapes and actual dimensions of parts specified in the drawings on the ground (or platform), that is, “putting out the actual samples”. In this process, the first step is to find the reference coordinate line correctly.

##
2. Purpose or function of setting out

- Check whether the dimensions and relevant connection positions in the drawing are correct.
- Verify dimensional changes and material substitutions in drawings.
- For some parts on the drawing that are difficult to calculate accurately, the correct size and the accuracy of each connection position can be obtained through lofting.
- For some dimensions that are difficult to inspect, make a sample for fast and effective inspection.

##
3. Setting out and marking off technology

###
3.1 Setting out Technology

Setting out and marking off is the first process of manufacturing cold work products, and it is a work from drawings to the determination of part size and shape. The work quality of this process directly affects the final product quality. Setting out and marking off is a very important and meticulous work. It is a work in which mental work is more than physical work. It is also a work in which hundreds of dimensions are measured every day without allowing one size error. Because full scale lofting can directly calculate the size and shape of parts, it is widely used. The calculation method of lofting has no error in the size of lines drawn during lofting, which is convenient and fast, and is increasingly widely used. Computer lofting has also entered the professional welding structure factory, and the process preparation department directly inputs the drawing size to generate the blanking template or gas cutting blanking program. Therefore, the workload of setting out is greatly reduced and the quality of products is improved.

####
3.1.1 Setting out platform

Lofting refers to the working process of drawing the construction drawing according to a certain proportion to obtain the blanking size and shape of the parts, the bending clamp template, the expanded drawing template for blanking, and the sample bar and sample box for blanking.

The setting out platform, also known as the setting out floor, is mainly used for setting out, sample making and size taking. The area of the platform is mainly determined according to the size of the product structure and the operating conditions of the plant. It is better to choose an environment with good lighting, no interference, low noise and no dust, so that the blanking personnel can concentrate on setting out and making templates, and improve the work efficiency of setting out and the accuracy of template making. The setting out platform is generally made of U-steel and I-steel as the skeleton, which is fixedly made of 8-10mm thick steel plates, or paved with wood plates. The platform plate surface shall be smooth and flat, and there shall be no gap at the splicing. Always keep the platform clean and dust-free.

For the convenience of setting out, cross vertical datum line and common angle line can be marked on the center of the platform, and sample and print marks. Unit length: 1m, 2m, 3m and other dimensions can be marked on the center line, and sample and print marks. Brackets or circles are used for each mark, and data are marked, as shown in Figure 1. You can also use various colors of lead oil and pink lines to draw horizontal and vertical lines similar to coordinate paper on the surface of the lofting platform, so as to avoid the trouble of repeatedly making right angle lines during lofting, reduce the size and angle errors, and facilitate the drawing of lines and the inspection of the template.

Fig. 1 Foundation line on setting out platform

####
3.1.2 Setting out datum

When setting out according to the drawings, first find out the design basis, understand the designer’s intention, determine the starting point of size, and ensure the use of components after production. On the design drawing, the points, lines and surfaces used to determine the positions of other elements are called design datum. When setting out, the design datum of the drawing is generally selected as the setting out datum. Therefore, it is required to carefully analyze the drawings and find out the design basis of the drawings before setting out.

There are three types of design basis in common steel structure drawings:

1). Use mutually perpendicular contour lines (or planes) as the datum

For the support shown in Fig. 2 (a), the service surface of the component is obviously the left angle steel surface and the lower angle steel surface. The mutually perpendicular left contour line and the lower contour line are the design basis of the construction drawing, and also the basis for setting out.

2). Take two mutually perpendicular center lines as datum

As shown in Figure 2 (b), the use surface of the inner angle steel ring is the inner ring surface or outer ring surface of the angle steel ring. Two mutually perpendicular center lines are the design basis of the construction drawing and also the setting out basis.

3). Take a contour line and its vertical centerline as the datum

In the construction drawing shown in Figure 2 (c), the dimensions in the height direction are based on the bottom contour line, so the bottom contour line is the datum in the height direction; The width direction is symmetrical to the centerline, so the centerline is the benchmark in the width direction. They are the design basis of the drawing and also the setting out basis.

Fig. 2 Selection of Setting out Datum

####
3.1.3 Use of line drawing tools

1). Tape measure

- (1) The inside of the tape measure is a spring, which is pulled back by its elasticity. If the tape retracts into the tape box or loses its elasticity during use, open the tape box and rewind it.
- (2) When measuring the size, sometimes the hook is bent outward, which affects the size accuracy, so it should be checked in time. When measuring, try not to give a section to avoid wrong measurement.
- (3) When measuring and drawing parallel lines, pay attention to the direction of the measuring ruler. The tape itself has errors, and when the dimensional accuracy is required to be high, the tape scale should be checked with the demanding product party to avoid trouble.
- (4) When measuring the suspension size, the downward deflection of the tape due to its own weight shall be considered.
- (5) After the tape is bent, the dimensional accuracy will be affected, and the tape shall be kept in the retracted state. If the draw back force of the ruler bar is insufficient, open the ruler box and tighten it, then fasten the box cover and tighten the screws.

2). Compass

Due to the different specifications of compasses, several compasses should be used when drawing the expansion drawing. When drawing lines, a compass should be used to fix the constant size. The tip of the compass should be welded with an alloy steel tip to make it wear resistant. When drawing galvanized sheet, do not draw with force if the line is not cut. When the compass is too tight or too loose, you can knock the vibration rivet or smash the rivet. When the tip of the compass is not sharp enough, the repeated measurement of the distance will result in large dimensional errors.

3). Pink thread

The chalk line shall be lifted vertically to avoid forming an arc due to skew. The ink line or oil line can also be made with pink line, and the diameter of the pink line shall not be greater than 1mm. Pink string can be used after being boiled with water.

4). Sample punch

The sample punch can be ground with a waste drill bit. The tip is ground into a 45 ° – 60 ° cone and used after quenching.

During the proofing punch, first tilt the punch, align the tip, and then tap it vertically with a small hammer.

5). Flat ruler and square ruler

Flat ruler and square ruler are usually made of 1-3mm thick stainless steel, which can be used to draw straight lines or smooth curves after bending. The angle and straightness of the square should be checked frequently. Tap the edge of the ruler to adjust the angle and straightness. When using, be careful not to smash the ruler.

####
3.1.4. Fabrication of sample plate, sample rod and sample box

1). Classification of samples

Template can be divided into hole template, material template, clamp template and positioning template. See Figure 3 for the shape of sample plate, sample bar and sample box.

Figure (a) is the part to be drilled, and Figure (b) is the sample plate of the number hole when drilling.

Figure (c) is a lacing plate part, and Figure (d) is a blanking and line drawing template with the same shape as the lacing plate.

Figure (e) is a clamping template for checking the bending degree of parts.

Figure (f) shows the assembly between the vertical plate and the bottom plate. Figure (g) is a template for drawing lines at the assembly position of the vertical plate or directly positioning the parts with the template for assembly.

Figure (h) is the schematic diagram of the parts of the perforated angle steel. After the center line of the hole is drawn with the line drawing plan, the position of the hole is drawn with the sample bar marked with the hole pitch as shown in Figure (i), and the sample punch is printed.

Figure (j) is the schematic diagram of the plug channel steel. When drawing lines, use the sample box made of the sample iron shown in Figure (k) to draw lines on the channel steel.

Fig. 3 Template, sample rod and sample box

2). Materials used for making samples

The materials often used for making templates are cardboard, linoleum paper and thin iron sheet.

- (1) Cardboard. The common specification is 800mm × 1100mm. The advantage of using cardboard to make templates is that it is relatively economical, and it is suitable for making unfolding templates of small workpieces. You can use a pencil or ball point pen to directly put samples on the cardboard, or directly draw some small workpiece templates, with high accuracy. However, it is easy to deform due to moisture and is not suitable for long-term retention. When drawing lines, it should be noted that the lines cannot be drawn on the wet steel plate, and they should be stored in a dry place.
- (2) Linoleum paper. The general specification is 1m × (15-20) m, which is used to make a larger sample. Generally, the actual sample is set out on the platform. The line is drawn by covering the sample method. If the width is not enough, the sample can be spliced. The sample iron is cut into diamond shaped pieces, which are spliced like a book. The disadvantage is that undercooling becomes brittle and overheating becomes soft, which affects the marking accuracy and is not convenient for long-term storage.
- (3) Thin iron plate. Hot rolled low carbon steel sheet or galvanized sheet. Common thickness 0.35-0.5mm, width 1000mm × The template is made of 2000mm thin iron plate, and the longer template can be made of 1m wide thin coiled plate or spliced. It can be spliced by seaming or connected by small rivets. Since the iron plate template is not easy to deform, it can be stored for a long time. After it is made, it should be painted with anti rust paint to facilitate writing marks and prevent corrosion. When saving, place them in the order of product number, and hang them on the crossbar like clothes.

Due to the high cost of iron plate, disposable templates are usually made of cardboard or linoleum paper.

The sample rod is generally 25mm × 0.8mm or 20mm × 0.8mm steel strip. It can also be made of steel bars, wooden planks and other materials.

3). Sample passing method

Generally, draw lines directly on the sample materials. When it is not convenient to draw lines directly on the sample material or only draw the expanded drawing on the sample material when drawing the expanded drawing, the drawing on the platform should be passed over to the sample material. This method is called the sample passing method.

- (1) Direct setting out method. When the dimensions are complete on some drawings, but it is not necessary to expand or set out to obtain the dimensions, blanking can be done by preparing the part size table, instead of using it as a template. If it is not convenient to draw lines directly on the steel plate, or if the parts are irregular and have a large number, they can be directly drawn on the sample material with a ratio of 1:1 according to the drawing.
- (2) Sample passing method. The method of transferring the drawings on the platform to the template is simple, and different methods are adopted according to personal habits. Two sampling methods are described below.
- The sample passing example of linear shape is shown in Figure 4, and Figure (a) is the drawing on the lofting platform. When passing the sample, as shown in Figure (b), first extend each side, cover the sample on the pattern, as shown in Figure (c), connect the straight lines, as shown in Figure (d), and the pattern will pass over the sample.

The sample in this example can also be drawn by using the triangle method in turn, but the error is large.

Figure.4 Cover Sampling Method

See Figure 5 for an example of curve pattern sampling method. Figure (a) is the drawing on the platform. After extending each plain line, cover the sample material as shown in Figure (b), and connect each plain line as shown in Figure (c) as an auxiliary line mn. Measure the distance from the line mn to the curve on the template to get the figure to be covered.

Fig. 5 Method of curve passing sample

4). Fabrication of sample rod and sample box

When drawing lines on the section steel, accurately measuring the length is the key to the marking accuracy. Measuring the length with a tape is troublesome and error prone, so the sample rod is often used for marking off in batch production. The sample bar shall be marked with the part code, specification of profile steel, hole diameter, end shape, number of symmetrical left and right pieces, middle cut position, etc. Different symbols can be used to represent different meanings.

When the section of profile steel is large or long, the sample rod should be clamped with a clamp. When there is a plug at the end, the end shape can be drawn with a local template after the length line is drawn.

The sample box is the drawing template of the end of the section steel. During setting out, after drawing the end shape, fold the sample iron into a right angle or groove shape, and form an I-shaped box. When marking straight head, the template replaces the square ruler, which improves the speed and accuracy of line drawing.

When making the sample bar, you can paint the steel strip and draw a line, or you can mark the steel strip with flat spade print or sample punch print and lead oil.

Common angle steel, channel steel and I-beam sample box are shown in Figure 6.

Fig. 6 Schematic Diagram of Drawing Sample Box

####
3.1.5. Machining allowance and lofting error of parts

When the thickness of the steel plate is greater than 6mm, there should be a gap between the welded joints. If the steel plate is cut, it should be reduced by 1-2mm. When cutting materials by gas cutting, the greater the plate thickness, the wider the kerf, and the size after gas cutting shall be consistent with the required size.

For parts to be machined after gas cutting, machining allowance shall be reserved when marking off. The larger the size of the part, the thicker the plate, and the larger the machining allowance. However, excessive allowance will increase the cutting amount and waste materials and working hours. Generally, 2-5mm margin shall be reserved for machining periphery, and 2-4mm thickness shall be increased.

The setting out error is generally limited to 0.5-1mm. Cumulative setting out error, marking error, blanking error, assembly error, welding deformation, and the final error is generally 2-5mm. Therefore, be very careful in setting out and marking off.

####
3.1.6. Loft Instance

1). Setting out of chamber ear base

See Figure 7 for the ear seat of the bin body. As a whole, this is a support, which is welded by 8mm thick ordinary steel plate. According to the technical requirements on the drawings, the holes on the base plate of the bearing shall not be drilled first. The support is composed of upper and lower parts, and parts 2 and 4 are not connected together. From the point of view of setting out, if the number of production units is small, it is only necessary to make a blanking size table, not a sample. If the number of units produced is large, Part 1 can be used as a local blanking template.

Fig. 7 Product drawing of chamber body ear seat

Parts 2, 3, 4 and 6 are internal rib plates of components, and the tolerance of blanking height can only be negative. Considering that there is no gap between plates during assembly, the height of rib plate can be 0-1mm smaller.

The blanking size and local blanking sample of part 1 are shown in Figure 8. Figure 8 (a) is a part drawing of Part 1. When drawing a line, if you do not want to draw 30 °, you can calculate the right angle side length, as shown in Figure 8 (b). In triangle ABC, AB/AC=tan 30 °, so AB=AC × tan30°=134 × 0.577=77.4mm. When actually drawing lines, you can first draw the dimensions shown in the figure, and then draw angle lines with the local template shown in Figure (c).

The blanking size of other parts can be directly marked after checking the size shown in the parts list.

Fig. 8 Blanking drawing of chamber body padeye 1

2). Setting out of rectangular pipe and rectangular pipe torsional connector

Here is an example of using triangle method to unfold lofting.

During the installation of ventilation ducts, the upper and lower openings may be twisted due to the production and installation errors of components. As shown in Figure 9, the upper and lower openings are rectangular pipes of different sizes, and the upper openings are twisted. Since the upper and lower openings are twisted, it is impossible to connect them with four flat plates, but they can be connected with eight triangular planes. As shown in Figure 10, the members are connected into triangles 125, 158, 148, etc.

The upper and lower openings are parallel and both are in the horizontal plane. The projected side lengths of the upper and lower openings on the top view are real lengths. Other straight lines connecting the upper and lower openings need to be real long. The method to calculate the real length is to measure the projection length of each line on the top view as a right angle edge, and the distance h between the upper and lower openings of the front view as another right angle edge. The hypotenuse is the real length of the line.

After the real length of each line is calculated, triangles can be drawn in turn to obtain the expanded diagram. Given the three sides of a triangle, it is easy to draw a triangle. First, measure the side length 58 on the top view, then draw an arc with 5 and 8 as the center, and the real length of 51 and 81 lines as the radius, and intersection point 1. Then, take the straight line 18 as the bottom of the triangle, take 1 and 8 as the centers, and take the real length of 14 and 84 as the radius to draw an arc to intersect point 4. Draw each triangle in turn until the expanded drawing is completed.

Fig. 9 Real length diagram of rectangular connecting pipe with twisted upper and lower openings

Fig. 10 Unfolded view of rectangular tube with twisted upper and lower openings

###
3.2. Marking Technology

Marking off is the process of drawing the outline of a part on a metal material. Drawing part drawings on metal materials according to the part size table and blanking template is also an important process, which needs to be completed carefully.

####
3.2.1. Precautions during marking off

- (1) Prepare pencil, chalk line, tape, lead oil, sample punch, hammer, sample plate, material list and other line drawing tools.
- (2) Review the drawing to check the blanking size, so as to avoid waste products.
- (3) Before marking off, check whether the material, specification and surface quality of metal materials meet the requirements of drawings. For example, plate thickness deviation, angle steel thickness deviation, angle steel edge width and other dimensions, if the deviation is too large, the overall size of the product will be affected. If the model of section steel is changed, the associated part size shall be modified.
- (4) If the bending of sheet and section steel will affect the size of parts before marking off, the material shall be leveled or leveled before marking off.
- (5) When marking off materials, the part number of the parts must be clearly written and marked.
- (6) If the size of steel plate is insufficient and splicing is required, it shall comply with relevant regulations. Generally, it is not allowed to splice wide plates with narrow strips.
- (7) When drawing the unfolded material of the pressure vessel barrel, the unfolded length of the circumference shall be measured along the rolling direction of the steel plate. The bending line of the bending part shall be inclined to the rolling direction.
- (8) For the parts to be cut, the cutting sequence shall be considered when marking off, and the line drawing shall be reasonable.
- (9) Pay attention to saving materials. Draw large pieces first and then small pieces. When drawing more small pieces, you should first go to the leftover material warehouse to find small pieces. When using leftover materials, pay attention to whether the materials meet the requirements.

####
3.2.2. Draw lines on components

Some components also need to draw lines in the production process, and sometimes they need to make assembly card templates. Here are some examples.

1). Edge removal and opening of head

Figure 11 shows the line drawing method after head pressing. Figure 11 (a) shows the center of the head measured in different directions with a self-made T-shaped ruler. Figure (b) shows the delineation of an elliptical head with a drawing needle. Figure (c) is a method to find the center of the head by using a right angle bending rule. First draw a circle with the diameter of the head on the bottom plate. After placing the head, measure the center of the head with a right angle ruler and a tape.

2). Drawing method of opening on cylinder

The method of drawing a line on the cylinder after the cylinder is rolled is shown in Figure 12. When the corner lap angle is used for welding between the manhole pipe and the cylinder, the drawing template of the opening can be regarded as an ellipse, the long semi axis is the arc length S in the figure, and the short semi axis is the outer radius r of the cylinder. If the circular tube penetrates the tube, the drawing method is the same.

Figure 11 Marking of head

Figure 12 Manhole Drawing

3). Drawing of manhole stiffening plate (Figure 13)

Manhole reinforcement plate must be rolled before blanking. After the steel plate is rolled round, draw a line on the bent steel plate with a sample plate. The method of drawing the sample plate is the same as that of drawing the manhole in the above example.

4). Solution of the plain line on the cylinder body

- (1) During blanking, draw the four center lines of the cylinder and the position line of the pipe orifice on the unfolded material, and print the sample for stamping, and then print the line according to the sample after rolling. The disadvantage of this method is that in the process of rolling, it is difficult to find the sample after rolling due to the peeling of oxide skin.

Figure 13 Drawing method of manhole stiffening plate

- (2) As shown in Figure 14, after the cylinder is erected, lift the plumb bob with angle steel head, reinforcement, etc., measure the distance between the plumb line and the cylinder, adjust the cylinder to make the distance consistent, and then draw the plain line of the cylinder according to the plumb line by visual inspection.
- (3) As shown in Figure 14, after the cylinder is rolled, use the upper roll of the plate bending machine to draw a plain line according to visual inspection or lighting, then take down the cylinder plate to measure the outer circumference of the cylinder, and draw other plain lines.
- (4) Use the theodolite to draw the isoline. First, use the theodolite to measure, cushion the cylinder to be horizontal, then let one person measure, and the other person draw marks to determine the isoline.

Figure 14 Solution of the Plain Line on the Cylinder

####
3.2.3. Reasonable utilization of materials

In order to save steel, it is necessary to compare various schemes for line drawing and layout, and adopt the most economical scheme for blanking.

1). Solve the cutting problem of section steel with linear programming method

Linear programming theory in mathematical classification can solve the problem of reasonable cutting stock. For example:

A component needs 100 pieces of 3m and 4m long angle steel respectively, and there is only 10m long angle steel in the warehouse. How do you make the most reasonable blanking?

Solution: There are only three blanking methods for 10m long angle steel: cut 3m, 3m and 3m long sections, leaving 1m residual material; Intercept 3m, 3m and 4m without residue; Cut two sections with a length of 4m and 4m, and the residual material is 2m.

Assume that each section method requires x1, x2 and x3 pieces of raw materials with a length of 10m, then 3×1+2×2 pieces of angle steel with a length of 3m, x2+2×3 pieces of angle steel with a length of 4m, and 100 pieces of angle steel with a length of 3m and 4m respectively, so the conditions should be met.

The most reasonable blanking method should be to minimize the raw materials used, that is, to minimize the function S=x1+x2+x3. The simplex method can be used to solve:

x1=0，x2=50，x3=25.

That is to say, the first blanking method is not adopted, but the second and third blanking methods are adopted.

Use the second method of 3m, 3m and 4m without waste to remove 50 pieces of angle steel and measure 100 pieces of 3m and 50 pieces of 4m materials.

The third blanking method is adopted for 25 pieces of materials: 50 pieces of 4m long materials are produced for 4m and more than 2m.

75pcs 10m long raw materials are shared, which is the most economical material consumption.

2). Reasonable marking method

The utilization rate of materials refers to the ratio of the total area of parts to the total area of steel plates. When blanking, the utilization rate of raw materials must be maximized. Here are some common ways to save materials.

- (1) Draw big materials first and then small materials. When marking off materials, it is the most common method to draw large and long materials first, and then use the remaining parts to draw small and short pieces.
- (2) Establish leftover material warehouse. Large non-standard welding structure manufacturers have leftover material warehouses, which are stacked according to the material, thickness, section steel specification and other indicators to facilitate marking off. When small pieces are numbered, they should be found in the leftover material warehouse first.
- (3) Splicing. For large number of hollow plates, the method of butt welding shall be preferred, such as diaphragms of crane main beams, flanges of large structural members, etc. As shown in Figure 15, Figure (a) is the diaphragm of the main beam of the crane. If the whole material is cut, only 6 parts can be drawn according to the scale shown in the figure. The splicing blanking can splice 8 parts, so the splicing method is often used in production.

Figure 15 (b) shows the blanking scheme for large flanges. Since the flange edge is relatively wide, 4 flanges are produced for splicing blanking. In addition, the cost of welding and correction is wasted, so it is not suitable for splicing. When the flange width is narrow and the diameter is large, as shown in Figures (c) and (d), nearly two flanges can be added, and splicing can be considered.

Fig. 15 Cutting with splicing method

3. Layout set No

Inserting parts of different shapes and drawing lines together can save raw materials. In case of mass production, it is particularly necessary to compare and analyze various layout schemes. If the local size can be modified to facilitate the set number, the design department can be contacted to negotiate to modify the local size.

####
3.2.4. Marking of section steel bending parts

The section steels often used are: angle steel, channel steel and I-beam. The blanking of section steel bending parts is relatively simple. The cut bending parts retain the shape of non bending edges, and the expansion length of the bending edges is calculated according to the central arc of the wall thickness. The unfolded length of the bending piece without opening shall be calculated according to the center or center of gravity of the section.

1). Blanking of angle steel frame

(1) Angle steel inner bent frame. When the angle steel is bent, the straight edge outside is called internal bending. As shown in Figure 16 (a. The bent vertical edge shall be cut according to the lining, as shown in Figure 16 (b). Heat and bend with a gas welding gun, and then carry out simple correction after bending. The interface is generally selected in the middle of the straight edge.

(2) Angle steel outer bending frame. When bending angle steel, as shown in Figure 16 (c), when the straight edge is inside, it is called external bending. When bending outwards, the spread length is still cut according to the lining, as shown in Figure (d). After cutting, bend and add four square plates with angle compensation. After welding, grind them with a grinding wheel.

(3) Splice angle steel frame. Without affecting the use, the splicing method shown in Figure 16 (e) is often used. Blanking and welding are simple, and the deformation is small. It is widely used in ventilation ducts.

Fig. 16 Blanking of angle steel frame

2). Arc cut of angle steel

When the angle steel is bent inward and the bending part is smoothly transited, as shown in Figure 17, the non bending side is directly drawn according to the required shape, and the notch is generally selected on the corner parting line. The developed length of the bending edge is calculated according to the arc length of the plate thickness center.

Figure 17 Arc notch of internal angle steel

3). Channel steel side fillet cut

As shown in Figure 18, when the upper and lower wing plates of the bending channel steel form an arc, the shape of the channel steel web remains unchanged, and the development length of the bending edge is still calculated according to the plate thickness center. The arc shown in the figure is just 1/3 of the whole circle. After calculating the circumference according to the plate thickness center, take 1/3 of it.

Figure 18 Arc Cut of Channel Steel Side Bend

4). Calculation of blanking length of angle steel ring and channel steel ring

The formula for calculating the blanking length of angle steel ring, channel steel ring and I-shaped steel ring is very simple. When the bending section is symmetrical, the expansion length is calculated according to the center. When the section is asymmetric, it shall be calculated according to the arc length at the center of gravity of the section.

Here are four examples, as shown in Figure 19. It can be seen from the figure that when the section of the section steel is symmetrical, the developed length is π (d+b) according to the center of the section steel, d is the internal diameter, and b is the width of the section steel.

When the section of profile steel is asymmetric, it shall be calculated according to the section center of gravity distance of profile steel. In case of internal bending, the external diameter minus the distance between two centers of gravity is used as the development diameter. For external bending, the internal diameter plus 2 times of the center of gravity distance of the section steel shall be used as the development diameter.

Figure 19 Calculation of blanking length of angle steel and channel steel ring

5). Fabrication of blanking sample box for oblique section I-beam

Blanking sample box shall be made for blanking sample plate of inclined section steel and plug sample plate between section steel. This paper introduces the manufacture of the sample box by taking the oblique section I-beam as an example. See Figure 20. The surface plain lines of I-beam shown in the figure are vertical lines, and the projection on the front view reflects the real length. Take the length of the isoline on the main view and the length of each section on the top view as the bottom edge of the expanded view to draw the expanded view. Bend the galvanized sheet to form the sample box shown in the figure.

Figure 20 Fabrication of inclined section I-beam blanking sample box

6). Setting out and Blanking Instructions for Multiple Elbows with Arbitrary Angles of Multiple Equal Diameter Circular Tubes

(1). This component is a multi section equal diameter circular pipe elbow. The angle and number of elbows can be adjusted within a certain range, and the straight pipe length can be extended at both ends of the elbow.

(2). In the diagram, d is the inner diameter of the circular pipe, a is the angle of the elbow, R is the radius of the corner of the center line of the elbow, L11 and L2 are the lengthened lengths of the two end segments, and b is the thickness of the plate. It is required that 180>＝ a>0, d, b>0, R>=d. If the pipe is narrow, d<R>0.6 * d is allowed, but the pipe resistance will increase. The above data shall be input after being determined by the operator.

(3). The elbow shall be cut into t sections. The value of t shall be input according to the actual number of sections. When calculating, it shall be calculated by half section at both ends and one section in the middle, that is, the turning angle of each section is a/(t-1). T must be an integer. It is required that 3<=t<=30. The greater the value of t, the smoother the elbow will be. However, the workload and cost will increase. Generally, 15<=a/(t-1)<=25 is taken.

(4). There are two ways to calculate the intersecting lines of the circular pipe of this component. One is to calculate the blanking length of each plain line at the bevel with the radius from the center of the circle to the center of the plate, that is, the “plate mid diameter” method; One way is to calculate the length of each plain line at the high end bevel with the inner radius, and the other way is to calculate the length of each plain line at the low end bevel with the outer radius. If the plate is thin or thick, but the groove is made based on the center line of the plate, it is recommended to use the plate pitch diameter for blanking; If the plate is thicker and the component is not beveled, it is recommended to use the modified radius method for blanking, otherwise the weld is wider and the angle will be 1 larger during splicing.

(5). This expansion diagram is an approximate expansion method. The circumference of a circular pipe must be n equally divided to calculate the real length of each line segment. The value of n is determined by the operator according to the diameter and accuracy requirements, but it must be an integral multiple of 4. The larger the value of n, the higher the accuracy of the expanded map, but the workload of drawing the expanded map increases accordingly. Generally, n=16~36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used for blanking or drawing the template in 1:1, and the n value can be larger.

(6). The developed drawing adopts the parallel line method for setting out and blanking, that is, the whole pipe is divided into several parallel lines for calculation and setting out. The output data varies according to different blanking methods. If sheet blanking is selected, the unfolded length and intersection length are calculated with the center of the sheet as the diameter. The operator can draw lines on the sheet directly according to the unfolded drawing and relevant data; If the finished pipe is selected for blanking, the outer diameter of the pipe plus the thickness of the sample material shall be taken as the diameter for calculation. The sample shall be loaded and unloaded according to the relevant data, and then the sample shall be wrapped outside the finished pipe for marking and blanking. For details, please refer to the unfolding diagram and follow the following method for setting out (take the unfolding materials at both ends as an example):

- Draw an arbitrary line segment with a length of 1 equal to S, divide the line segment into n equal parts, and the length of each segment is equal to m.
- Draw vertical lines of line segments through each bisection point, and measure ha (1) – ha (n/2+1) length on each vertical line in turn according to the figure.
- The points measured by connecting the smooth curve are the expanded drawing of the circular tube.
- The middle section has n-2 sections in total, and each section has the same size, which is the combined size of the two half sections. The expanded drawing can be drawn by reference.
- When blanking the whole elbow, you can refer to the elbow layout diagram for layout and lofting, which can save materials.

7). Description for setting out and blanking of arbitrary eccentric connecting pipe with upper circle and lower rectangular flat mouth

(1). In this example, the upper opening is circular, and the lower opening is rectangular. The diameter of the circle and the length and width of the rectangle can be any number, and can be used as the connection pipe component with eccentric image. When px and py are not 0, they are double eccentric circular connecting pipes. If one of px and py is 0, it is a single eccentric circular moment connecting pipe. If px and py are both 0, it is the right center circular connecting pipe.

(2). In the diagram, d is the inner diameter of the circular opening, L is the length of the inner side of the rectangle, w is the width of the inner side of the rectangle, h is the height of the nozzle, px and py are the eccentric distances between the center of the circular opening and the center of the rectangle in x and y directions, and b is the thickness of the plate. D, L, w, h, b>0, px, py can be any real number.

(3). The positive and negative values of px and py shall be determined according to the rectangular coordinate system formed by taking the rectangular center as point o and two vertical centerlines. When the center of the circle is on the right of point o, px is positive; when the center is on the left, px is negative; when the center 2 is above point o, py is positive; when the center is below point o, py is negative; when it coincides with point o, it is 0. Pay special attention to the positive and negative values of px and py. If you enter them incorrectly, you may not be able to draw the expansion diagram correctly.

(4). The circumference of the circular opening must be divided into n equal parts to calculate the real length of each prime line. The value of n must be an integral multiple of 4. The operator can determine the value according to the diameter and accuracy requirements and then input it. The larger the value of n, the higher the accuracy of the expanded drawing, but the workload of drawing the expanded drawing increases accordingly. Generally, n=16~36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used for blanking or drawing the template in 1:1, and the n value can be larger.

(5). The triangle method is used for setting out and blanking of the expanded drawing, that is, the entire expanded drawing is divided into several triangles for calculation and setting out. The output data has been processed for plate thickness, and can be loaded and unloaded directly according to the data. For details, please refer to the expansion diagram and loft as follows:

- Draw an arbitrary straight line segment with the length equal to L, and the points at both ends are A and D.
- According to the figure, take two points A and D as the center, La (n/4+1) and Ld (1) as the radius, and draw an arc to intersect a point. Then draw arcs on both sides of the intersection point with the intersection point as the center, m as the radius, and intersect with the arcs drawn with two points A and D as the center, La (n/4) and Ld (2) as the radius, respectively. Draw the intersection points of lines La (n/4)~La (1), Ld (2)~Ld (n/4+1) and m arcs in this order.
- According to the figure, draw an arc with two points A and D as the center, w as the radius, intersect with the arc drawn with the intersection of La (1) and Ld (n/4+1) as the center, Lb (1) and Lc (n/4+1) as the radius, and obtain two new intersection points B and C.
- With the intersection of Lb (1) and La (1), the intersection of Lc (n/4+1) and Ld (n/4+1) as the center of the circle, and m as the radius, draw arcs on both sides of the intersection, respectively intersect with the arcs drawn with B and C as the center of the circle, and Lb (2) and Lc (n/4) as the radius. Draw the intersection points of each line segment of Lb (2)~Lb (n/4+1), Lc (n/4+1)~Lc (1) and m arc in this order.
- Draw an arc with two points B and C as the center, Lp as the radius, intersect with the arc drawn with the intersection of Lb (n/4+1) and Lc (1) as the center, hp as the radius, and obtain the intersection points E and F.
- Connect the points E, B, A, D, C and F with straight lines according to the drawing, and connect the intersection points with smooth curves to obtain the expanded drawing of connecting pipes.

(6). The output expansion diagram is calculated according to the inward crimping processing lofting, which is drawn based on the whole figure. In order to save materials, the blanking can also be cut into two pieces along the hs line, or cut into several pieces from any place.

8). Description for setting out and blanking of equal diameter circular pipe at any angle tee

(1). This example is the expanded drawing calculation of all components of tee components with equal diameter circular pipes intersecting at any diameter, plate thickness and angle.

(2). In the diagram, d is the inner diameter of the circular pipe, L is the length of the main pipe, L1 is the distance from the pipe edge to the intersection of the two centerlines, h is the length of the branch pipe, a is the angle between the centerlines of the two pipes, and b is the thickness of the plate. It is required that 0<a<=90, h, L1>(d+2 * b)/(2 * Tan (a/2)), and L>L1+d/2+b. The above data shall be input after being determined by the operator.

(3). The circumference of the branch pipe must be divided into n equal parts to calculate the real length of each prime line. The value of n is determined by the operator according to the diameter and accuracy requirements, but it must be an integral multiple of 4. The larger the value of n, the higher the accuracy of the expanded drawing, but the workload of drawing the expanded drawing increases accordingly. Generally, n=16-36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used to draw the sample plate in 1:1. The value of n can be larger.

(4). The developed drawing adopts the parallel line method for setting out and blanking, that is, the whole pipe is divided into several parallel lines for calculation and setting out. The output data varies according to different blanking methods. If sheet blanking is selected, the unfolded length and intersection length are calculated with the center of the sheet as the diameter. The operator can draw lines on the sheet directly according to the unfolded drawing and relevant data; If the finished pipe is selected for blanking, the outer diameter of the pipe plus the thickness of the sample material shall be taken as the diameter for calculation. The sample shall be loaded and unloaded according to the relevant data, and then the sample shall be wrapped outside the finished pipe for marking and blanking. For details, please refer to the expanded schematic diagram and follow the following method for setting out:

Branch pipe blanking method:

- Draw an arbitrary line segment whose length is equal to S, divide the line segment into n equal parts, and the length of each segment is equal to m;
- Draw vertical lines of line segments through each bisection point, and measure the length of ha (1) – ha (n/2+1) on each vertical line in turn;
- The points measured by smooth curve connection according to the figure are the expansion diagram of the branch pipe.

Cutting method of supervisor:

- Draw a rectangle whose length is equal to L and width is equal to S. This is the expanded drawing of the circular tube;
- Draw a line segment parallel to the length sideline as the centerline according to the midpoint of the expanded drawing, and then measure the length of La (1) – La (n/2+1) on the centerline with the width sideline as the benchmark, and draw vertical lines on both sides of the centerline through each point;
- The length of ms (1) – ms (n/2+1) is measured symmetrically on each vertical line based on the centerline.

Connect all points with a closed smooth curve, which is the cut for connecting branch pipes.

9). Setting out and blanking instructions for intersecting multi section elbows of reducing straight pipes

(1). This example is a tee formed by the vertical intersection of multiple elbows of reducing round straight pipes. The elbow intersected by straight pipes is a component of 3 to 12 sections. The straight pipe can deviate from the centerline of the lower opening of the elbow within a certain range. There are two options for intersection: plug-in and horseback riding.

(2) In the figure, d1 is the inner diameter of the round pipe elbow, d2 is the inner diameter of the straight pipe, a is the deflection angle of the elbow, R is the radius of the elbow corner, t is the number of elbow joints, h is the height from the upper opening of the straight pipe to the lower opening of the elbow, p is the distance from the centerline of the straight pipe to the centerline of the lower end of the elbow, b1 is the thickness of the elbow plate, and b2 is the thickness of the straight pipe plate. The above data can be entered after the operator determines it according to the drawings or known conditions. It is required that d2, b1, b2>0; d1>d2； R>=d1*0.54+b1； p<r-(r+d1/2)*Cos(a)-d2/2； 0<a<=180； 3<＝t<=12； The value of h shall be subject to the expansion diagram. If the value is too small, please re-enter the data as prompted.

(3) The circumference of a circular pipe needs n equal parts to calculate the real length of each prime line. The value of n must be an integral multiple of 4, which is determined by the operator according to the diameter and accuracy requirements. The larger the value of n, the higher the accuracy of the expanded drawing, but the workload of drawing the expanded drawing increases accordingly. Generally, n=16-36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used to draw the sample plate in 1:1. The value of n can be larger.

(4) There are two types of intersection of two pipes: plug-in type and horseback riding type. The plug-in type is calculated by inserting the branch pipe into the inner wall of the main pipe. The horseback riding type is calculated by contacting the outer wall of the main pipe with the branch pipe. When blanking, the opening of the plug-in main pipe is larger and the length of the branch pipe is longer.

(5) The developed drawing adopts the parallel line method for setting out and blanking, that is, the whole pipe is divided into several parallel lines for calculation and setting out. This component is only calculated as the expanded drawing of straight pipe, and the cut of elbow is cut on site after the elbow is processed. The output data varies according to different blanking methods. If sheet blanking is selected, the unfolded length and intersection length are calculated with the center of the sheet as the diameter. The operator can draw lines on the sheet directly according to the unfolded drawing and relevant data; If the finished pipe is selected for blanking, the outer diameter of the pipe plus the thickness of the sample material shall be taken as the diameter for calculation. The sample shall be loaded and unloaded according to the relevant data, and then the sample shall be wrapped outside the finished pipe for marking and blanking. For details, please refer to the expanded schematic diagram and follow the following method for setting out:

- Draw an arbitrary line segment with the length equal to S2, divide the line segment into n equal parts, each of which is equal to m2, and measure the length of Lu (1) – Lu (j) symmetrically from the midpoint to both sides.
- Draw the vertical line of the line segment through each bisection point, take the middle vertical line as the benchmark, measure the height of La (1) – La (n/2+1) on each vertical line in turn, and measure the height of ya (1) – ya (j) on each special point.
- Take ya (1) – ya (j) point as the inflexion point, and connect each bisection point with a smooth curve, which is the expanded diagram of the circular tube.

10). Setting out and Blanking Instructions for Arbitrary Angle Multi section Elbow of Long Pipe

(1). This example is a multi section equal diameter long circle elbow component whose section is an equal diameter long circle, which is bent along a narrow side, and the angle and number of elbow segments can be adjusted at will.

(2). In the diagram, L is the internal length of the long pipe, w is the internal width of the long pipe, a is the angle of the elbow, R is the radius of the corner at the centerline of the elbow, and b is the thickness of the plate. It is required that 180>a>0, w, b>0, L>w, R>=w, if the pipe is narrow, d<R>0.6 * d is allowed, but the pipe resistance will increase. The above data shall be input after being determined by the operator.

(3). The elbow shall be divided into t sections for blanking. The two ends of the elbow shall be calculated as half section, and the middle section shall be calculated as one section. T must be an integer. It is required that t>=3. The greater the value of t, the smoother the elbow will be. However, the workload and cost will increase. Generally, 15<=a/(t-1)<=25 is taken.

(4). There are two ways to calculate the intersection line of each section of circular pipe in this component. One is to calculate the cutting length of each plain line at the bevel with the radius from the center of the circle to the center of the plate, that is, the “plate mid diameter” method; One way is to calculate the length of each plain line at the high end bevel with the inner radius, and the other way is to calculate the length of each plain line at the low end bevel with the outer radius. If the plate is thin or thick, but the groove is made based on the center line of the plate, it is recommended to use the plate pitch diameter for blanking; If the plate is thick and the component is not beveled, it is recommended to use the modified radius method for blanking, otherwise the weld will be wider and the angle will be larger during splicing.

(5). This expansion diagram is an approximate expansion method. The circumference of the circular arc of the long pipe must be n equally divided to calculate the real length of each line segment. The value of n is determined by the operator according to the diameter and accuracy requirements, but it must be an integral multiple of 4. The larger the value of n, the higher the accuracy of the expanded map, but the workload of drawing the expanded map increases accordingly. Generally, n=16~36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used for blanking or drawing the template in 1:1, and the n value can be larger.

(6). The developed drawing adopts the parallel line method for setting out and blanking, that is, the arc part of the entire long pipe is divided into several parallel lines for calculation and lofting. The operator can directly load and unload materials on the plate according to the data. For details, refer to the developed diagram and loft as follows (taking the expanded materials at both ends of the half section as an example):

- Draw an arbitrary line segment with the length equal to S+Lp × 2. Divide the line segment into four parts according to the figure, with the length of Lp, S/2, Lp and S/2 respectively. Divide the S/2 segment into n equal parts, with the length of each part equal to m.
- Draw the vertical line of the line segment through each bisection point, and measure the ha (1) – ha (n/2+1) length on each vertical line in turn according to the figure.
- The straight line is used to connect the points at both ends of Lp, and the smooth curve is used to connect the points measured in the S/2 line segment, which is the expanded drawing of the elbow end joint of long pipe.
- The middle section has n-1 sections in total, and each section has the same size, which is the combined size of the two half sections. You can draw an expanded drawing by reference.

11). Setting out and blanking instructions for long pipe long multi section elbow

(1). This example is a multi section equal diameter long circle elbow component whose section is an equal diameter long circle, which is bent along the longer side, and the angle and number of elbow segments can be adjusted at will.

(2). In the diagram, L is the internal length of the long pipe, w is the internal width of the long pipe, a is the angle of the elbow, R is the radius of the corner at the centerline of the elbow, and b is the thickness of the plate. It is required that 180>a>0, w, b>0, L>w, R>=w, if the pipe is narrow, d<R>0.6 * d is allowed, but the pipe resistance will increase. The above data shall be input after being determined by the operator.

(3). The elbow shall be divided into t sections for blanking. The two ends of the elbow shall be calculated as half section, and the middle section shall be calculated as one section. T must be an integer. It is required that 12>=t>=3. The greater the value of t, the smoother the elbow will be. However, the workload and cost will increase. Generally, 15<=a/(t-1)<=25 is taken.

(4). This expansion diagram is an approximate expansion method. The circumference of the circular arc of the long pipe must be n equally divided to calculate the real length of each line segment. The value of n is determined by the operator according to the diameter and accuracy requirements, but it must be an integral multiple of 4. The larger the value of n, the higher the accuracy of the expanded map, but the workload of drawing the expanded map increases accordingly. Generally, n=16~36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used for blanking or drawing the template in 1:1, and the n value can be larger.

(5). The developed drawing adopts the parallel line method for setting out and blanking, that is, the arc part of the entire long pipe is divided into several parallel lines for calculation and lofting. The operator can directly load and unload materials on the plate according to the data. For details, refer to the developed diagram and loft as follows (taking the expanded materials at both ends of the half section as an example):

- Draw an arbitrary line segment with the length equal to S1. Divide the line segment into four parts according to the figure. The length is S/2, Lp, S/2, Lp respectively. Divide the S/2 segment into n equal parts. The length of each part is equal to m.
- Draw the vertical line of the line segment through each bisection point, and measure the length of ha (1) – ha (n/4+1) and hb (1) – hb (n/4+1) on each vertical line in the two S/2 line segments according to the figure.
- The straight line is used to connect the points at both ends of Lp, and the smooth curve is used to connect the points measured in the S/2 line segment, which is the expanded drawing of the elbow end joint of long pipe.
- The middle section has n-1 sections in total, and each section has the same size, which is the combined size of the two half sections. You can draw an expanded drawing by reference.

12). Setting out and Blanking Instructions for Multi section Elbow at Any Angle of Tapered Pipe

(1). This example is a multi section reducing round pipe elbow component that can adjust the angle and number of elbow joints at will, that is, the calculation of the spread diagram of the ox angle elbow as the saying goes.

(2). In the figure, d1 and d2 are the inner diameters of the big and small ends of the elbow, a is the corner of the elbow, R is the corner radius of the centerline of the elbow, and b is the thickness of the plate. It is required that d1>d2>0, 0 °<a<=360 °, b>0, R>=d1. If the pipe is narrow, d1<R>0.6 * d1 is allowed, but the pipe resistance will increase. The above data shall be input after being determined by the operator.

(3). The number of elbow sections is t, and t must be an integer. Both ends are half sections. It is required that t>=2. The value of t is determined by the operator and then input. The larger t is, the smoother the elbow will be. However, the workload and cost will increase. Generally, 15<=a/t<=25 is taken.

(4). The expanded figure is an approximate expansion. The circumference of the cone tube must be divided into n equal parts to calculate the real length of each prime line. The value of n is determined by the operator according to the diameter and accuracy requirements and then input. n must be an integral multiple of 4. The larger the value of n, the higher the accuracy of the expanded figure, but the workload of drawing the expanded figure increases accordingly. Generally, n=16-36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used to draw the sample plate in 1:1. The value of n can be larger.

(5). The output data of the expanded drawing has been processed for plate thickness, and can be loaded and unloaded directly according to the relevant data. For details, please refer to the expanded diagram and loft as follows:

- Arbitrarily determine the origin o, draw arcs respectively with the origin as the center, Rs1 and Rs2 as the radius, take any point on the arc of Rs1, measure the arc length S1 along the arc from this point, or measure the chord length Lx, or use the expansion angle as to determine the included angle of the arc, after determining the arc length, connect the two points on the arc line to the origin o, and the area enclosed by the arcs of Rs1 and RS2 and the two straight lines is the developed area of the elbow;
- Divide the arc length S1 into n equal parts, each equal part of the arc length is m1, and each point is connected to the origin o;
- Take the origin as the base point, measure the length of Rd (1,1) – Rd (t, n/2+1) on the connecting line between each point and the origin, and connect the intercepted points with a smooth curve to obtain the expanded diagram of each section of the elbow.

13). Setting out and blanking instructions for three trouser tees of round pipe and regular cone pipe

(1). The main pipe of this component is a large-diameter circular pipe, and its two ends are small-diameter circular pipes. The middle part is a trouser shaped three section tee connected by a regular cone pipe. The height, left and right distance and small end diameter of the tee can take different values arbitrarily within the specified range, and the expanded drawing shall be calculated according to the butt joint form of the same plate thickness.

(2). In the diagram, d1 and d2 are the internal diameters of large and small circular tubes, h is the height of the centerline of the large circular tube, hp is the height of the centerline of the tapered tube, Lp is the left and right distance of the centerline of the tapered tube, L is the length of the centerline of the small circular tube, a is the deflection angle of the centerline of the large and small circular tubes, and b is the thickness of the plate. It is required that d1>d2>0, h>0.3 * d1 * Lp/hp, Lp>d1/2, L, hp>0.3 * d2 * hp/Lp, tan (a)>=Lp/hp, a<=90 °, b>0. The above data shall be input by the operator after confirmation according to the drawings or relevant data. If the input data does not meet the requirements, please re-enter according to the prompts.

(3). There are two ways to calculate the intersection line of each section of the component. One is to calculate the blanking length of each plain line at the bevel with the radius from the center of the circle to the center of the plate, that is, the “plate pitch diameter” method; One way is to calculate the length of each plain line at the high end bevel with the inner radius, and the other way is to calculate the length of each plain line at the low end bevel with the outer radius. If the plate is thin or thick, but the groove is made based on the center line of the plate, it is recommended to use the plate pitch diameter for blanking; If the plate is thick and the component is not beveled, it is recommended to use the modified radius method for blanking, otherwise the weld will be wider and the angle will be larger during splicing.

(4). The perimeter of each component must be divided into n equal parts to calculate the real length of each prime line. The value of n must be an integral multiple of 4, which is determined by the operator according to the pipe diameter and accuracy requirements before input. The greater the value of n, the higher the precision of the expanded drawing. However, the workload of drawing the expanded drawing increases correspondingly. Generally, it is more accurate to cut the material by manually drawing lines with n=16-36. The numerical control cutting machine is used to cut the material or the engraving machine is used to draw the template in 1:1. The value of n can be larger.

(5). The data output from the expanded drawing has been processed for plate thickness. The data output from the circular tube varies according to different blanking methods. If the plate blanking is selected, the expanded length and intersection length are calculated with the center of the plate as the diameter. The operator can directly draw lines and blanking on the plate according to the expanded drawing and relevant data; If the finished pipe is selected for blanking, the outer diameter of the pipe plus the thickness of the sample material shall be taken as the diameter for calculation. The sample shall be loaded and unloaded according to the relevant data, and then the sample shall be wrapped outside the finished pipe for marking and blanking. For details, please refer to the expanded schematic diagram and follow the following method for setting out:

Blanking method of large and small tubes:

- Draw an arbitrary line segment whose length is equal to S1 (S2). Divide the line segment into n equal parts, each of which is equal to m1 (m2) in length.
- Draw a vertical line of the line segment through each point on the line segment, and measure ha (1) – ha (n/2+1) or La (1) – La (n/2+1) on the vertical line of each bisection point in turn.
- The points measured with smooth curve according to the figure are the expanded figure of the circular tube.

Blanking method of taper pipe:

- Set an origin o arbitrarily, draw an arc with the origin as the center and Rs as the radius, and take any point on the arc. Measure the arc length S3 along the arc from this point, or measure the chord length Lx. You can also use the expansion angle as1 to determine the included angle of the arc;
- Divide the arc length S3 into n equal parts, each equal part of the arc length is m3, and each point is connected to the origin o;
- Taking the origin as the base point, measure the length of Ra (1) – Ra (n/2+1) on each bisector in turn according to the figure, and measure the length of Lt arc along the Rs arc from the bisector of two Ra (n/4+1) lines. These two points are the inflexion points of the outer curve, and then measure the length of Lb (1) – Lb (n/2+1) from the bisector to the origin. Connect the intercepted points with a smooth curve according to the figure to obtain the expansion diagram of the cone tube.

14). Setting out and blanking of multi section elbow at any angle for various equal diameter circular pipes

(1). This component is a multi section equal diameter circular pipe elbow. The angle and number of elbows can be adjusted within a certain range, and the straight pipe length can be extended at both ends of the elbow.

(2). In the diagram, d is the inner diameter of the circular pipe, a is the angle of the elbow, R is the radius of the corner of the center line of the elbow, L1 and L2 are the lengthened lengths of the two end segments, and b is the thickness of the plate. It is required that 180>＝ a>0, d, b>0, R>=d. If the pipe is narrow, d<R>0.6 * d is allowed, but the pipe resistance will increase. The above data shall be input after being determined by the operator.

(3). The elbow shall be cut into t sections. The value of t shall be input according to the actual number of sections. When calculating, it shall be calculated by half section at both ends and one section in the middle, that is, the turning angle of each section is a/(t-1). T must be an integer

3<=t<=30, the greater the value of t, the smoother the elbow will be, but the workload and cost will increase, generally taking 15<=a/(t-1)<=25.

(4). There are two ways to calculate the intersecting lines of the circular pipe of this component. One is to calculate the blanking length of each plain line at the bevel with the radius from the center of the circle to the center of the plate, that is, the “plate mid diameter” method; One way is to calculate the length of each plain line at the high end bevel with the inner radius, and the other way is to calculate the length of each plain line at the low end bevel with the outer radius. If the plate is thin or thick, but the groove is made based on the center line of the plate, it is recommended to use the plate pitch diameter for blanking; If the plate is thick and the component is not beveled, it is recommended to use the modified radius method for blanking, otherwise the weld will be wider and the angle will be larger during splicing.

(5). This expansion diagram is an approximate expansion method. The circumference of a circular pipe must be n equally divided to calculate the real length of each line segment. The value of n is determined by the operator according to the diameter and accuracy requirements, but it must be an integral multiple of 4. The larger the value of n, the higher the accuracy of the expanded map, but the workload of drawing the expanded map increases accordingly. Generally, n=16~36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used for blanking or drawing the template in 1:1, and the n value can be larger.

(6). The developed drawing adopts the parallel line method for setting out and blanking, that is, the whole pipe is divided into several parallel lines for calculation and setting out. The output data varies according to different blanking methods. If sheet blanking is selected, the unfolded length and intersection length are calculated with the center of the sheet as the diameter. The operator can draw lines on the sheet directly according to the unfolded drawing and relevant data; If the finished pipe is selected for blanking, the outer diameter of the pipe plus the thickness of the sample material shall be taken as the diameter for calculation. The sample shall be loaded and unloaded according to the relevant data, and then the sample shall be wrapped outside the finished pipe for marking and blanking. For details, please refer to the unfolding diagram and follow the following method for setting out (take the unfolding materials at both ends as an example):

- Draw an arbitrary line segment whose length is equal to S, divide the line segment into n equal parts, and the length of each piece is equal to m.
- Draw the vertical line of the line segment through each bisection point, and measure the ha (1) – ha (n/2+1) length on each vertical line in turn according to the figure.
- The points measured by connecting the smooth curve are the expanded drawing of the circular tube.
- The middle section has n-2 sections in total, and each section has the same size, which is the combined size of the two half sections. You can draw an expanded drawing by reference.
- When blanking the whole elbow, you can refer to the elbow layout diagram for layout and lofting, which can save materials.

15). Setting out and blanking of reducing multi section elbow and straight pipe tee

(1). This example is a tee formed by the intersection of a reducing round straight pipe and a multi section elbow. The elbow has two or more sections that intersect with the straight pipe.

(2). In the figure, d1 is the inner diameter of straight round pipe, d2 is the inner diameter of round pipe elbow, h1 is the height of straight pipe, h2 is the height from the elbow center to the bottom of round pipe, L is the distance from the elbow port to the centerline of straight pipe, R is the radius of elbow corner, a is the deflection angle of elbow, t is the number of elbow joints, b1 is the thickness of straight pipe plate, and b2 is the thickness of elbow plate. The above data can be entered after being determined by the operator according to the drawings or known conditions. It is required that d2, b1, b2>0; d1>d2； R>=d2*0.54+b2； L>=R+d1/2-d2/2-R*Cos(a)； 0<a<=90； 2<＝t<=6； h2>=0； The value of h1 shall be subject to the expanded drawing. If the value is too small, please re-enter the data as prompted.

(3). The circumference of a circular pipe needs n equal parts to calculate the real length of each prime line. The value of n must be an integral multiple of 4, which is determined by the operator according to the diameter and accuracy requirements. The larger the value of n, the higher the accuracy of the expanded drawing, but the workload of drawing the expanded drawing increases accordingly. Generally, n=16-36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used to draw the sample plate in 1:1. The value of n can be larger.

(4). The developed drawing adopts the parallel line method for setting out and blanking, that is, the whole pipe is divided into several parallel lines for calculation and setting out. The output data varies according to different blanking methods. If sheet blanking is selected, the unfolded length and intersection length are calculated with the center of the sheet as the diameter. The operator can draw lines on the sheet directly according to the unfolded drawing and relevant data; If the finished pipe is selected for blanking, the outer diameter of the pipe plus the thickness of the sample material shall be taken as the diameter for calculation. The sample shall be loaded and unloaded according to the relevant data, and then the sample shall be wrapped outside the finished pipe for marking and blanking. For details, please refer to the expanded schematic diagram and follow the following method for setting out:

Section 1-k-1 blanking method of elbow:

- Draw an arbitrary line segment with the length equal to Lb (i), then draw an equal length parallel line at the height of ku (i) from the line segment, divide the two line segments from the midpoint to both ends, and the length of each segment is equal to m2; The Lb (i-1) length is measured at the midpoint of the line segment after the second section.
- Draw a vertical line through each bisection point, endpoint and Lb (i-1) point to connect the two line segments, with the lower line segment as the benchmark, measure the length of ela (i, 1) – ela (i, j) from the midpoint to both sides of each bisection vertical line according to the figure, and measure the length of Lz on Lb (i-1) line; With the upper part line segment as the reference, measure the length of ehb (i, 1) – ehb (i, j) from the midpoint to both sides of each bisector vertical line according to the figure, and measure the length of Lz at both ends;
- Take the two end points and Lb (i-1) point as the end points according to the figure, and connect the measured points with a smooth curve respectively, which is the expansion diagram of each pipe section.

Pipe blanking method of Section K and Section t:

- Section k partially intersects the straight pipe, and the expanded perimeter is equal to S2. Section t does not intersect the straight pipe. The blanking is the same as the end section of an ordinary multi section elbow, which can be drawn by reference in sequence;
- Draw a straight line segment, the length is equal to S2, divide the line segment into n equal parts, and the length of each piece is equal to m2; In addition, measure the length of La (k) on the line segment;
- Draw a vertical line of the line segment through each bisection point and Lb (k-1) point. With the straight line segment as the benchmark, measure the length of Ld (1) – Ld (n/2+1) on each bisection vertical line with the points at both ends as 1, then measure the length of hc (1) – hc (n/2+1) from the midpoint as 1, and then measure the length of pa (k-1) on the Lb (k-1) vertical line.
- Connect the points measured with smooth curve according to the figure, which is the expansion diagram of section k and section t.

Straight pipe blanking method:

- Draw a rectangle whose length is equal to S1 and width is equal to h1. This is the expanded diagram of straight pipe;
- Draw a line segment parallel to the width sideline as the center line according to the midpoint of the expanded graph, and then take the center line as the benchmark, measure the length of ms (1) – ms (n/4+1) symmetrically on both sides of the center line, then measure the length of Lu (1) – Lu (k-1) respectively, and draw parallel lines on both sides of the center line through each point;
- Measure the length of ha (1) – ha (n/2+1) on each bisector and the length of hu (1) – hu (k-1) on the Lu (1) – Lu (k-1) line according to the following sideline as the benchmark;
- Take the points of Lu (1) – Lu (k-1) as the inflection points, and connect the points of ha (1) – ha (n/2+1) with smooth curves between the points of Lu (1) – Lu (k-1), that is, the cut connecting the elbow.

Blanking method of complete intermediate section:

- If t-k>1, complete intermediate section t-k-1 shall be added;
- Draw a straight line segment, the length is equal to S2, divide the line segment into n equal parts, and the length of each piece is equal to m2.
- Draw a vertical line of the line segment on both sides of the line segment through each bisection point. With the line segment as the benchmark, measure the length of Lc (1) – Lc (n/2+1) on each bisection vertical line at both ends of the line segment according to the figure.
- The points measured with smooth curve according to the figure are the expanded figure of the complete middle section.

16). Setting out and blanking of Y-shaped tee with equal diameter and same plane at any angle

(1). This example is suitable for the calculation of unfolded drawings of various components of Y-shaped tee members with equal diameter circular tubes at any eccentric angle and length.

(2). In the diagram, d is the inner diameter of the circular pipe, h is the height of the main pipe, L1 is the length of branch pipe 1, L2 is the length of branch pipe 2, a1 is the deflection angle of branch pipe 1, a2 is the deflection angle of branch pipe 2, and b is the thickness of the circular pipe plate. It is required that h>(d+2 * b)/2, L1, L2>(d+2 * b)/(2 * Tan ((a1+a2)/2)), 0o<a1, a2<90o, and the above data shall be input after being determined by the operator.

(3). The circumference of each pipe shall be divided into n equal parts to calculate the real length of each plain line. The value of n shall be determined by the operator according to the diameter and accuracy requirements, but it must be an integral multiple of 4. The greater the value of n, the higher the precision of the expanded map, but the workload of drawing the expanded map increases accordingly. Generally, n=16-36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used to draw the sample plate in 1:1. The value of n can be larger.

(4). The developed drawing adopts the parallel line method for setting out and blanking, that is, the whole pipe is divided into several parallel lines for calculation and setting out. The output data varies according to different blanking methods. If sheet blanking is selected, the unfolded length and intersection length are calculated with the center of the sheet as the diameter. The operator can draw lines on the sheet directly according to the unfolded drawing and relevant data; If the finished pipe is selected for blanking, the outer diameter of the pipe plus the thickness of the sample material shall be taken as the diameter for calculation. The sample shall be loaded and unloaded according to the relevant data, and then the sample shall be wrapped outside the finished pipe for marking and blanking. For details, please refer to the expanded schematic diagram and follow the following method for setting out:

Blanking method of supervisor:

- Draw an arbitrary line segment whose length is equal to S, divide the line segment into n equal parts, and the length of each segment is equal to m;
- Draw vertical lines of line segments through the equal points, and measure ha (1) – ha (n/2+1) length on each vertical line according to the figure;
- Connect the points measured with smooth curve according to the figure, which is the expansion diagram of the main pipe.

Blanking method of branch pipe 1:

- Draw an arbitrary line segment whose length is equal to S, divide the line segment into n equal parts, and the length of each segment is equal to m;
- Draw vertical lines of line segments through each bisection point, and measure the length of La (1) – La (n/2+1) on each vertical line according to the figure;
- The points measured with smooth curve according to the figure are the development diagram of branch pipe 1.

Blanking method of branch pipe 2:

- Draw a vertical line of line segment through each bisection point, and measure Lb (1) – Lb (n/2+1) length on each vertical line according to the figure;
- The points measured with smooth curve according to the figure are the expanded figure of branch pipe 2.

17). Setting out and blanking of orthogonal tee with reducing belt feeding

(1). This component is a tee formed by the vertical intersection of reducing circular pipes, plus two semicircles and two or three corner plates for feeding. The ventilation resistance of this component is smaller than that of the component without feeding.

(2). In the figure, d1 is the internal diameter of the main pipe, d2 is the internal diameter of the branch pipe, L1 is the length of the main pipe, L2 is the length from the side of the main pipe to the intersection of the centerline of the two pipes, h is the height from the centerline of the main pipe to the branch pipe orifice, Lp is the horizontal distance of the feeding, hp is the vertical height of the feeding, b1 is the thickness of the main pipe plate, b2 is the thickness of the branch pipe plate, and the above data will be entered by the operator after being determined according to the drawings or known conditions. It is required that d2, b1, b2>0; Lp、hp>0； L2>d2/2+b2+Lp； L1-L2>d2/2+b2+Lp； h>=d1/2+b1+Lp； d1>d2. If the value does not meet the requirements, please re-enter the data as prompted.

(3). The circumference of a circular pipe needs n equal parts to calculate the real length of each prime line. The value of n must be an integral multiple of 4, which is determined by the operator according to the diameter and accuracy requirements. The larger the value of n, the higher the accuracy of the expanded drawing, but the workload of drawing the expanded drawing increases accordingly. Generally, n=16-36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used to draw the sample plate in 1:1. The value of n can be larger.

(4). There are two ways to intersect the two pipes: plug-in type and horseback riding type. The plug-in type is calculated by inserting the branch pipe into the inner wall of the main pipe. The horseback riding type is calculated by contacting the outer wall of the main pipe with the branch pipe. When blanking, the opening of the inserted main pipe is larger, and the length of the branch pipe is longer.

(5). The developed drawing adopts the parallel line method for setting out and blanking, that is, the whole pipe is divided into several parallel lines for calculation and setting out. The output data varies according to different blanking methods. If sheet blanking is selected, the unfolded length and intersection length are calculated with the center of the sheet as the diameter. The operator can draw lines on the sheet directly according to the unfolded drawing and relevant data; If the finished pipe is selected for blanking, the outer diameter of the pipe plus the thickness of the sample material shall be taken as the diameter for calculation. The sample shall be loaded and unloaded according to the relevant data, and then the sample shall be wrapped outside the finished pipe for marking and blanking. For details, please refer to the expanded schematic diagram and follow the following method for setting out:

Branch pipe blanking method:

- Draw a straight line segment, the length is equal to S2, divide the line segment into n equal parts, and the length of each piece is equal to m2;
- Draw the vertical line of the line segment downward through each bisector, and measure the height of ha (1) – ha (n/4+1) on each bisector vertical line in turn according to the figure, taking the two ends and the midpoint of the line segment as the starting point.
- According to the figure, the n/4+1 line is taken as the turning point, and each point is connected with a smooth curve, which is the expansion diagram of the branch pipe.

Feeding method of replenishment:

- Draw a straight line segment, the length is equal to S2/2, divide the line segment into n/2 equal parts, and the length of each piece is equal to m2;
- Draw vertical lines on both sides of the line segment from the midpoint of the line segment to the lower and upper sides of the line segment according to the figure. Measure the height of ka (1) – ka (n/4+1), kb (1) – kb (n/4+1) on each bisector vertical line according to the figure;
- The points measured by smooth curve connection according to the figure are the expanded drawing of the feeding circular arc plate.
- The triangle plate is a flat plate, which can be cut according to the drawing.

Blanking method of supervisor:

- Draw a rectangle with the length equal to L1 and the width equal to S1, which is the expanded drawing of the main pipe profile;
- Draw a line segment parallel to the width sideline as the center line according to the midpoint of the expanded drawing, and then take the center line as the benchmark, measure the length of ms (1) – ms (n/4+1) symmetrically on both sides of the center line, and draw parallel lines on both sides of the center line through each point;
- Measure the length of La (1) – La (n/4+1) and Lb (1) – Lb (n/4+1) from the starting point of the centerline on each bisector with the plate edge as the benchmark according to the figure;
- According to the figure, four corners are taken as turning points, and smooth curves are used to connect the measured points, and straight lines are used to connect the corners, which is the expansion diagram of the main pipe.

18). Setting out and blanking of inclined cut round pipe

(1). Oblique cut tube The round tube is the simplest of sheet metal components. When the round tube intersects an inclined plane, it is cut according to this component. In the figure, d is the inner diameter of the pipe, a is the angle of the bevel, h is the center height of the pipe, and b is the thickness of the pipe plate. The above data are determined by the operator and then entered. It is required that d, b>0, 0o<a<=90o, h>0.6 * (d+b) * Tan (a).

(2). There are two ways to calculate the bevel of the circular pipe of this component. One is to calculate the blanking length of each element line of the bevel with the radius from the center of the circle to the center of the plate, that is, the “plate pitch diameter” method; One way is to calculate the length of each plain line at the high end bevel with the inner radius, and the other way is to calculate the length of each plain line at the low end bevel with the outer radius. If the plate is thin or thick, but the groove is made based on the center line of the plate, it is recommended to use the plate pitch diameter for blanking; If the plate is thick and the component is not beveled, it is recommended to use the modified radius method for blanking, otherwise the weld will be wider and the angle will be larger during splicing.

(3). The circumference length of a circular pipe must be divided into n equal parts to calculate the length of each pixel line. n must be an integral multiple of 4. The operator can input it after determining the diameter and accuracy requirements. The larger the value of n, the higher the accuracy of the expanded drawing, but the workload of drawing the expanded drawing increases accordingly. Generally, n=16-36 can be used for accurate blanking by manual line drawing, and the numerical control cutting machine or engraving machine can be used to draw the sample plate in 1:1. The value of n can be larger.

(4). Each data of the expanded drawing has been processed for plate thickness, and the output data will vary according to different blanking methods. If the plate blanking is selected, the expanded length and intersection length will be calculated with the center of the plate as the diameter. The operator can directly draw lines on the plate and blanking according to the expanded drawing and relevant data; If the finished pipe is selected for blanking, the outer diameter of the pipe plus the thickness of the sample material shall be taken as the diameter for calculation. The sample shall be loaded and unloaded according to the relevant data, and then the sample shall be wrapped outside the finished pipe for marking and blanking. For details, please refer to the expanded schematic diagram and follow the following method for setting out:

- Draw an arbitrary line segment whose length is equal to S, divide the line segment into n equal parts, and the length of each piece is equal to m.
- Draw vertical lines of line segments through each bisection point, and measure La (1) – La (n/2+1) on each vertical line in turn.
- The points measured with smooth curve connection are the expanded diagram of the circular tube.

###
Conclusion

Setting out and marking off is the first process for manufacturing cold work products. The level of senior setting out personnel in the factory often represents the level of the structure manufacturer. It is better for the workers in the prototype room to work for a period of time in the blanking shearing, gas cutting, cold bending, fire bending and other processes, and then to assemble the plate and profile steel products in the assembly process. They should be familiar with the production methods of various products, and after obtaining certain experience, they can work in the prototype room easily.

This chapter also introduces the lofting method of actual steel structure by taking the structural member “ear seat” as an example. When setting out, riveters often need to carry out unfolding setting out, which will be described in detail in the next chapter.

Marking off is the process of drawing part drawings on metal materials according to the blanking dimension table and template prepared during lofting. Marking technology includes the method of drawing lines on steel plates, the method of drawing lines on metal structures, and the method of drawing lines on section steels.

It is relatively simple to draw lines on the steel plate by using the parts list and template. To draw lines on the section steel, an accurate square and a small line drawing error are required to ensure the accuracy of the section. After the sample box is made, the line can be drawn on the section steel accurately and quickly. This section introduces the method of making the sample box by taking the oblique section I-beam as an example.

As required by the production process, some parts or components should be marked with lines. This paper introduces some practical problems such as how to draw lines on the surface of metal components, how to find the datum of drawing lines, and how to find the center of curved surface.

When the number of products is large, how to save cutting is very important. It is necessary to consider several cutting plans and compare them to find the most economical plan.

Source: China Pipe Fittings Manufacturer – Yaang Pipe Industry (www.epowermetals.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at [email protected]