How to reduce tool vibration in NC machining?
In CNC milling, vibration may occur due to the limitations of cutting tools, toolholders, machine tools, workpieces or fixtures. To reduce vibration, some strategies need to be considered.
1) For face milling, the direction of cutting force must be considered.
- a) Use 90 ° When milling cutter, the cutting force is mainly concentrated in the radial direction. Under the condition of long overhanging, the milling cutter will swing; However, when Milling Thin-walled / vibration sensitive parts, low axial force is advantageous.
- b）45 ° Milling cutter can produce uniform distribution of axial force and radial force.
- c) The circular cutter guides most of the force upward along the spindle, especially when the cutting depth is small. In addition, 10 ° The milling cutter transfers the main cutting force to the spindle, so as to reduce the vibration caused by the long tool overhanging.
2) Choose the smallest possible diameter for the process.
3) DC should be 20-50% larger than AE.
4) Select sparse and / or unequal pitch cutters.
5) Light weight milling cutter is advantageous, such as the milling cutter with aluminum alloy body.
For unstable thin-walled workpiece, large main deflection angle = small axial cutting force is used; Under the condition of long tool overhanging, small main deflection angle = high axial cutting force is used.
Using coromantcapto ® Modular toolholder system can assemble the required length of tool, while maintaining high stability and minimum jumping.
- 1) Keep the tool assembly as rigid and short as possible.
- 2) Choose the v-core as large as possible: ug5209 lead CNC course extension rod diameter / size.
- 3) Use Coromant capto for oversized cutters ® Connecting rod, avoid using reduced diameter connecting rod.
- 4) For small size cutters, use tapered extension if possible.
- 5) In the process where the last tool is in the depth of the part, the lengthened tool is used at the predetermined position. Adjust the cutting parameters according to each tool length.
- 6) If the spindle speed exceeds 20000 rpm, use dynamically balanced cutting tools and toolholders.
Oversized milling cutter
Be sure to use the shortest possible tool length and lengthen it one after another
Vibration reducing milling cutter
If the overhang is more than 4 times the tool diameter, the milling vibration trend may become more obvious ™ Vibration reduction milling cutter can significantly improve productivity.
To reduce the cutting force:
- 1) choose the official account with sharp cutting edges: UG programming base camp light load trough -L and thin coating material.
- 2) Use a blade with a small tip radius and a small parallel edge band
- Sometimes, the vibration trend can be reduced by adding more damping to the system. The cutting edge with larger negative rake angle and slightly worn cutting edge are used.
- 05. Cutting parameters and tool path programming
- 1) Be sure to position the cutter off center relative to the milling surface.
- 2) For kapr90 ° Long edge milling cutter or end milling cutter, using small diameter cutting depth (maximum AE = 25% × DC) and large axial cutting depth (maximum AP = 100% × De)。
- 3) In face milling, small cutting depth AP and high feed FZ, round blade or high feed milling cutter with small main deflection angle are used.
- 4) The vibration in the corner can be avoided through the programming of large arc tool path. See inner corner milling.
- 5) If the chip thickness becomes too thin, the cutting edge will rub rather than cut, causing vibration. In this case, the feed per tooth should be increased.
The machine condition may have a great influence on the milling vibration trend. Excessive wear of spindle bearing or feed mechanism will lead to poor machining performance. Carefully choose the machining strategy and cutting force direction to make full use of the stability of the machine tool.
Each machine tool spindle has a v-core which is easy to vibrate: ug5209 is unstable area. The stable cutting area is described by the stability diagram and increases with the increase of rotation speed. Even if the speed increase is as low as 50 rpm, the cutting process can change from unstable state to stable state.
Workpiece and fixture
When Milling Thin-walled parts/ base parts and / or poor fixture rigidity, consider the following points:
- 1) The fixture should be close to the machine table.
- 2) In order to obtain the most stable cutting conditions, the tool path and feed direction are optimized towards the position with the highest machine / fixture strength.
- 3) Avoid machining along the direction where the workpiece is not fully supported.
- 4) When the rigidity of fixture and / or workpiece is poor in a certain direction, the vibration trend can be reduced by back milling.
When the rigidity of the fixture is poor, the feed direction toward the machine tool table is used
Note that the first cut should be performed at 1 / 2 of the second cut depth, the second cut at 1 / 2 of the third cut depth, and so on.
Source: China Flange 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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