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How to solve the problem of deformation of thin-walled sleeve parts in machining

Thin-walled sleeve parts are always prone to deformation in machining, with oval or “waist-shaped” phenomenon of small in the middle and large at both ends, which is not easy to ensure the machining quality of the parts. Its clamping design is often one of the most discussed points, the following we look at two thin-walled parts on turning, milling fixture design examples, how they are to solve the problem of deformation.

Machining scheme for thin-walled sleeve parts on milling machine

The thin-walled sleeve workpiece is shown in the figure, the keyway width is 6mm guaranteed by the keyway milling tool; the symmetry of the symmetry plane on both sides of the slot to φ45h6 axis is 0.05mm, the parallelism is 0.10mm; the slot depth size is 8mm.
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Positioning scheme and positioning elements

Determine the positioning scheme and select the positioning elements.
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Clamping scheme and design of clamping device

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▲Clamping mechanism
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▲Guidance and automatic release device in the clamping mechanism

Design of the clamping structure

1Positioning device
The long V-shaped block is the main positioning element in the fixture, eliminating 4 indeterminate degrees of the workpiece. It can be found in the relevant national standards or industry standards.
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Support sleeve.
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2. Clamping device
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▲Eccentric wheel
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Eccentric wheel holder
3Auxiliary device
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▲ Tool setting block
4Clamping device
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5General diagram of the fixture
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1.Clamping body 2.Cylindrical pin 3.Eccentric wheel holder 4.Eccentric wheel
5.movable V-block 6.tool setting block 7.fixed V-block

Thin-walled parts bore machining process scheme

The workpiece is processed by seamless steel pipe, the surface roughness of the inner hole and outer wall is Ra1.6μm, which can be achieved by turning, but the cylindricity of the inner hole is 0.03mm, which is a high requirement for thin-walled parts. In mass production, the process route is roughly as follows: material – heat treatment – turning end face – turning external circle – turning internal hole – quality inspection.
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The “bore machining” process is the key to quality control. We put aside the outer circle, thin-walled casing on the inside of the hole cutting is difficult to ensure 0.03mm cylinder.

Key technology of turning holes

The key technology of turning holes is to solve the problem of rigidity and chip removal of the internal hole turning tool. Increase the rigidity of the internal hole turning tool, take the following measures.
1. Try to increase the shank cross-sectional area, usually the tip of the internal hole turning tool is located on the top of the shank, so that the shank cross-sectional area is less than 1/4 of the hole cross-sectional area, as shown in the figure on the left below. If the tip of the internal hole turning tool is located on the center line of the shank, then the cross-sectional area of the shank in the hole can be greatly increased, as shown in the figure on the right below.
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2. The shank extension length can be 5-8mm longer than the workpiece length to increase the rigidity of the shank and reduce the vibration in the cutting process.

Solve the problem of chip discharge

Mainly control the direction of cutting outflow, coarse turning tool requires chip flow to the surface to be machined (front chip discharge), for this reason, use the positive edge inclination of the bore turning tool, as shown in the figure below.
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When fine turning, the chip flow is required to centerward tilting front chip discharge (hole center chip discharge), so when grinding the tool, pay attention to the grinding direction of the cutting edge, to the front tilting arc chip discharge method, as shown in the figure below Fine turning tool alloy with YA6, the current M type, its bending strength, wear resistance, impact toughness and anti-adhesion with steel and temperature are better.
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When sharpening the front angle grinding to round to arc-like angle 10-15 °, the rear angle according to the processing arc from the wall 0.5-0.8 mm (tool bottom line along the arc), c cutting edge angle k to § 0.5-1 for along the chip edge B point trimmed edge for R1-1.5. Vice rear angle grinding into 7-8 ° for the appropriate, E inside the edge of the A-A point grinding into a round outward chip discharge.

Processing method

1. It is necessary to make a shaft guard before processing. The main purpose of the shaft guard is to cover the thin-walled sleeve bore with the original size and fix it with the front and rear tops so that it can process the outer circle without deformation and maintain the quality and accuracy of the outer circle processing. Therefore, the processing of the guard shaft is a key link to the process of processing thin-walled casing.
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The processing of guard shaft embryo with 45 ﹟ carbon steel; turning end face, open two B-type top hole, rough turning outer circle, leaving a margin of 1 mm. by heat treatment tempering shape, and then fine turning leaving a margin of 0.2 mm grinding. Re-heat treatment crushed fire surface, hardness HRC50, and then by cylindrical grinding machine into the following figure, the accuracy of the requirements, after completion to be used.
2In order to make the workpiece finished at once, the embryo leave the clamping position and cut off allowance.
3Firstly heat treatment and tempering of the embryo, the hardness is HRC28-30 (the hardness of the machinable range).
4The turning tool is C620, firstly, put the front top into the spindle taper position and fix it, in order to prevent the deformation of the workpiece when clamping the thin-walled sleeve, add a thick sleeve with an open ring, as shown in the figure below.
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In order to maintain mass production, one end of the outer circle of the thin-walled sleeve is machined to a uniform size d, the ruler of t is axial clamping position, a thin-walled sleeve pressed to improve the quality of the inner hole when turning, to maintain the size. Considering that there is cutting heat generated, the workpiece expansion size is difficult to grasp. Need to pour sufficient cutting fluid to reduce the thermal deformation of the workpiece.
5Clamp the workpiece firmly with automatic centering three-jaw chuck, turn the end face and rough turn the inner circle. Leave a margin of 0.1-0.2mm fine turning, replace the fine turning tool to cut the balance of the processing to guard the shaft full over fit and roughness requirements. Remove the bore turning tool, insert the guard shaft to the front top, clamp with the tailstock top according to the length requirement, change the external turning tool to rough turn the external circle, and then finish turning to the drawing requirements. After passing the inspection, use the cutting tool to cut off the workpiece according to the required length. In order to make the workpiece disconnected when the cut is flat, the knife edge to be beveled grinding, so that the workpiece end face flat; guard shaft grinding small section is to cut off to leave a gap and grinding small, guard shaft to reduce the deformation of the workpiece, to prevent vibration, as well as cut off when falling touch the original cause.

The above method of processing thin-walled casing, solve the problem of deformation or cause size error and shape error and can not meet the requirements, practice has proved that the processing efficiency is high, easy to operate, and suitable for processing longer thin-walled parts, the size is easy to grasp, secondary completion, mass production is also more practical.

Source: China Thin-walled Parts 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.)

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