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Why do precision CNC machined parts deform? How to avoid deformation?

2023/11/8 9:20:31 click:

Precision hardware processing is the process of turning, milling, drilling, polishing, grinding and other processing of raw materials according to customer requirements, and turning them into various high-precision parts that meet the actual needs of users. However, in the actual processing process, there will always be deformation. So why do precision CNC machined parts deform?

Possible reasons for deformation of precision metal processing parts:

1-Internal functions lead to changes in part machining accuracy. During the processing of parts, they are usually clamped by three clamps to ensure the stability of the workpiece during processing. When the processing time is too long, the chuck of the machine tool will loosen and the stress on the part will reduce and deform. (P.S.: When deformation occurs due to changes in external factors such as force, humidity, temperature, etc., an internal force interacts between various parts of the object. The internal force per unit area is called stress.)

2- Improper heat treatment is prone to deformation. When processing some thin and small parts, heat treatment must be carried out. This requires the operator to have strong professional knowledge, otherwise the parts will easily bend and deform.

3-Part processing caused by external forces will cause deformation. When processing parts, unevenness between the lathe and the fixture will lead to uneven strength in fixing the parts, and deformation will easily occur.


So how to avoid deformation during metal processing?

1- Separate roughing and finishing. The purpose is to reduce cutting forces and cutting heat. In this way, the deformation of nested parts caused by rough machining can be corrected during finishing.

2-Reduce the impact of clamping force. The clamping force can be reduced by:

a) When using radial clamping, the clamping force should be distributed over a larger area to reduce the clamping force per unit area of the workpiece. When positioning by holes, it is advisable to use open mandrel clamping.

b) The position of the clamping force should be selected at a part with strong rigidity.

c) Change the direction of the clamping force and change the incoming clamping to axial clamping.

3-Reduce the influence of cutting force on deformation. This can be done by:

a) Increase the main deflection angle and main rake angle of the tool to make the cutting edge sharp during processing and reduce the radial cutting force.

b) The inner and outer circular surfaces are processed simultaneously to offset the cutting forces.

c) Reduce the impact of heat treatment deformation. Place heat treatment between rough machining and finishing machining. After heat treatment, sleeve parts will generally produce large deformations, which can be corrected during finishing.

4- Reasonably select the processing gap.

5-In the stamping die structure, the pressure plate should be connected with the pressure plate at the plane contact point and have a certain pressure

6-If the edge of the die is found, trim it appropriately;

If the deformation of the hardware workpiece has occurred, how to repair the deformation?

Several common ways to repair hardware deformation include heat treatment, mechanical repair, cold working, chemical repair, and welding repair.

1-Heat treatment method. For small hardware products, flame heating can be used to repair them. First heat the deformed part to the appropriate temperature, and then gently tap it with a hammer or other tool to restore it to its original shape. For larger pieces of hardware, a fire grill or other heating device can be used for repair. It should be noted that the heating temperature and time need to be controlled to avoid overheating, which will cause more serious deformation.

2-Mechanical repair method

Mechanical repair method refers to the method of using mechanical force to repair hardware products. Common mechanical repair tools include hammers, pliers, clamps, etc. For larger hardware products, you can use a clamp to clamp the deformed part, and then use a hammer to gently tap it back to its original shape. It should be noted that when using mechanical repair tools, be careful to avoid secondary damage to the hardware.

3-Cold working method

Cold working method refers to the method of repairing hardware products under normal temperature conditions. Common cold working methods include bending, stretching, pressing, etc. For hardware products with small deformation, you can bend, stretch and other operations by hand or tools to restore them to their original shape. For hardware products with large deformation, special cold processing equipment can be used to repair them. It should be noted that the strength and angle must be controlled during cold working to avoid new deformation or damage.

4-Chemical repair method

Chemical repair method refers to the method of using chemicals to repair hardware products. Common chemical repair drugs include corrosives, solvents, etc. For hardware products with corroded surfaces, corrosives can be used to remove the corrosion layer and then be repaired. For hardware products with serious deformation, solvent can be used to soften the deformed part, and then mechanical force can be used to repair it. It is important to pay attention to safety when using chemicals to avoid harm to the human body and the environment.

5.Welding repair method

Welding repair method refers to the method of repairing hardware products using welding technology. Common welding methods include arc welding, argon arc welding, etc. For broken or cracked hardware products, welding technology can be used to weld them together to repair the broken or cracked parts. It should be noted that when performing welding repairs, the welding temperature and time must be mastered to avoid excessive or insufficient welding, which will lead to unsatisfactory repair results.

The above are the reasons and solutions for the deformation of hardware.

Yixin Precision Metal & Plastic Ltd specializes in CNC machining, customized hardware machining, custom processing of samples and drawings, and other services. Welcome to call +8618938911183.