In the process of machining, workpiece deformation is easily caused by various machining errors or manual wrong operation. Deformation is a complex problem, we must analyze the causes of deformation before we can take corresponding measures. So, what are the main factors that can easily cause deformation of workpiece in the machining process?

Material and Structure of Workpiece

The size of the deformation is directly proportional to the complexity of the shape, aspect ratio and wall thickness size, and directly proportional to the rigidity and stability of the material. Therefore, the influence of these factors on the deformation of the workpiece should be minimized as much as possible when designing the part.

Causes and Solutions of Deformation

1. Thermal Expansion: Materials will expand when subjected to heat, which may lead to changes in the dimensions of the workpiece. Solution: Use appropriate cooling methods to control the temperature, or choose materials with smaller coefficients of thermal expansion. 2. Unreasonable Structure: The wall thickness of each part of the workpiece varies greatly, the aspect ratio of the workpiece is too large and the shape of the workpiece is too complicated, which will lead to deformation caused by uneven distribution of stress. Solution: Try to simplify the shape of the parts in the design stage, reduce the aspect ratio, and keep the wall thickness uniform. 3. Material Hardness: Workpieces with high material hardness are easily affected by internal stress during the cutting process, which causes deformation. Solution: Adjust the cutting parameters, use suitable cutting tools or adopt appropriate heat treatment process to minimize the impact of material hardness on deformation. 4. Organizational Structure: The crystal structure and organization of the material may also lead to deformation of the machined workpiece. Solution: Consider the crystal structure and organization of the material when selecting the material, and choose the appropriate heat treatment process to improve the mechanical properties and stability of the material. 5. Residual Stress: If there is a large internal stress in the material, it may cause deformation of the workpiece during subsequent processing, assembly or use. Solution: Adopt appropriate heat treatment process, such as aging treatment and tempering, to minimize the effect of residual stress. 6. Material Selection: Different materials have different deformation characteristics in machining. Solution: Select appropriate materials according to the specific application requirements, taking into account the coefficient of thermal expansion, hardness, processing performance and other factors of the material.

Fixtures and Clamping Methods

Incorrect clamping or fixing methods may lead to vibration, displacement or deformation of the workpiece during machining, and these can cause deformation of the workpiece.

Causes and Solutions of Deformation

1. Improper Fixture Selection: Fixtures should provide adequate support and stability, using inappropriate fixtures may cause deformation of the workpiece. Solution: Select the appropriate type and size of fixture to ensure that the fixture is able to clamp the workpiece evenly and provide sufficient support area. 2. Inappropriate Clamping Method: Selection of an inappropriate clamping method may result in displacement or deformation of the workpiece, especially at high cutting forces. Solution: Select the appropriate clamping method according to the shape and material of the workpiece and ensure that the clamping method provides sufficient stability. 3. Excessive Clamping Force: Excessive pressure may be exerted on the workpiece, causing it to deform plastically. Solution: Control the clamping force to ensure the stability of the workpiece during machining while avoiding deformation caused by excessive clamping force. 4. Uneven Clamping Force: It may cause deformation of the workpiece in the clamping area. Solution: Adjust the clamping force to ensure that the clamping force is evenly distributed over the entire surface of the workpiece to avoid centralized clamping. 5. Insufficient Rigidity of Fixture: It leads to deformation of the fixture itself, which is transmitted to the workpiece to cause deformation of the workpiece. Solution: Choose the fixture with sufficient rigidity to ensure that the fixture will not deform significantly under the cutting force. 6. Improperly Adjusted Fixture: Critical to ensure clamping force and stability. Solution: Carefully adjust the fixture before machining to ensure that the workpiece is correctly clamped and the fixture is adjusted to meet the machining requirements. 7. Poor Support: The workpiece needs adequate support during machining, otherwise warping and other deformations may occur. Solution: Consider the shape and size of the workpiece and provide sufficient number and location of suitable support points. The most effective way to solve the clamping deformation is to improve the stiffness of the part. An increase in the contact area between the workpiece and the fixture helps to reduce the deformation of the workpiece during the clamping process.

During Machining These deformations may originate from factors such as cutting forces, thermal influences, material properties, and processing methods.

Causes and Solutions of Deformation

1. High Cutting Temperature: The high temperature generated during cutting may lead to localized expansion of the workpiece, causing deformation. Solution: Adopt appropriate cutting speed, feed rate and depth of cut or use coolant for cutting to reduce the cutting temperature. 2. Unstable Cutting Process: Vibration or unstable cutting force during cutting may cause deformation of the workpiece. Solution: Use high quality and stable tools that can reduce the cutting force. The use of vibration-damping tools can ensure the stability of the cutting process. 3. Residual Stress: The machining process may introduce residual stress, leading to deformation of the workpiece. Solution: Adopt appropriate heat treatment process, such as tempering and aging treatment, to reduce the residual stress. 4. Uneven Cooling: If the cooling rate of each part of the workpiece is not uniform, it may cause uneven distribution of thermal stresses, which may lead to deformation. Solution: Use appropriate cooling methods to ensure that all parts of the workpiece are cooled uniformly to reduce thermal stress. For example, use proper coolant or cooling gas to dissipate heat quickly and reduce the possibility of thermal deformation. 5. Tool Wear: This may lead to changes in cutting force, which may affect the shape of the workpiece. Solution: Replace tools regularly and ensure that they remain sharp to maintain a consistent cutting force. 6. Choice of Cutting Direction: It may lead to deformation of the workpiece in different directions. Solution: Select appropriate cutting direction according to the shape and material of the workpiece to minimize the effect of deformation. During the cutting process, the workpiece is subjected to the cutting force resulting in the phenomenon of cutter relieving. In order to solve this deformation problem, the tool can be improved, which can reduce the friction between the tool and the workpiece, improve the cooling capacity of the workpiece during the cutting process, and reduce the internal stress of the workpiece.

Post Machining

It may be caused by a variety of factors such as internal stresses generated during machining, stress release after material removal, temperature changes and so on.

Causes and Solutions of Deformation

1. Stress Release: During machining, a certain amount of residual stress will accumulate inside the workpiece. When these stresses are released after machining is completed, they may cause deformation of the workpiece. Solution: Prevent the generation of residual stresses by adopting appropriate heat treatment techniques or processes, such as aging treatment and tempering, to reduce or eliminate residual stresses. 2. Temperature Gradient: After machining is completed, the workpiece may be subjected to uneven temperature distribution, causing thermal expansion or contraction, which leads to distortion. Solution: Control the cooling rate after machining to avoid too fast or too slow cooling to minimize the temperature gradient. 3. Environmental Conditions: Changes in environmental conditions after machining is complete, such as temperature and humidity, may also cause deformation of the workpiece. Solution: Control temperature and humidity in the environment where the workpieces are stored and used, and avoid storage under extreme conditions.

Tips to Avoid Workpiece Deformation

To avoid deformation of workpieces in machining requires a combination of material, process, and tool selection throughout the machining process. The following are some suggestions to help minimize or avoid deformation of machined workpieces: 1. Suitable Material Selection: It is very important to select the right material before machining. Different materials have different coefficients of thermal expansion, hardness, thermal conductivity and other characteristics, and these factors will affect the deformation during machining. 2. Preheating the Material: For some large or thick workpieces, moderate preheating of the material before machining can be considered. This helps to reduce the temperature gradient inside the workpiece and reduces the risk of deformation. 3. Optimize Cutting Parameters: Carefully select and optimize cutting parameters, including cutting speed, feed rate and depth of cut, to control the temperature and cutting force during machining to reduce the impact on the workpiece. 4. Tool Selection and Maintenance: Use high-quality, sharp tools, and regularly check and replace tools to ensure the stability and consistency of the cutting process. 5. Proper Cutting Lubrication Cooling: Utilize sufficient cutting fluid to cool and lubricate the cutting tools to reduce the cutting temperature and minimize the possibility of workpiece deformation. 6. Reasonable Clamping and Fixture Design: Choose appropriate fixtures and clamping methods to ensure that the workpiece is firmly and evenly clamped. Consider the shape of the workpiece and use support points and pads to minimize distortion. 7. Accurate Process Planning: Develop accurate process planning, including process sequences and cutting paths. Reasonable machining sequence can minimize the accumulation of residual stresses and reduce the risk of distortion. 8. Heat Treatment Control: Where necessary, use appropriate heat treatment processes, such as tempering or aging, to minimize residual stresses and improve material stability. 9. Attention to Environmental Conditions: Control the temperature and humidity of the machining environment to avoid the effects of extreme temperature and humidity changes on the workpiece. 10. Quality Control: Introduce strict quality control procedures, including measurement and inspection, to ensure that the workpiece meets the specified size and shape requirements both during and after machining.

Summary

To summarize, for the deformation of workpieces, appropriate policies should be adopted for both workpiece materials and machining processes, and specific analyses should be carried out according to different situations. By comprehensively considering the above factors and taking appropriate preventive and corrective measures throughout the machining process, the possibility of deformation of machined workpieces can be effectively minimized, and the machining quality and accuracy of workpieces can be improved. We, CYCO, with over 20 years of CNC machining experience, specialize in providing precision machining and manufacturing services for all types of parts. As a high quality supplier of CNC machining services, our advanced equipment and professional team can ensure that we can provide you with precise and high quality CNC parts. To save your valuable time, choose to work with us directly! Start a new project by contacting us now!