In the Field of Precision Cnc Machining, Various Errors Can Occur During the Machining Process

CNC machining is a method of controlling machine tool motion and the machining process through computer digitization and information digitization. So, what errors may occur in the CNC machining process?

Firstly, principle errors in CNC machining are caused by adopting approximate machining motion modes or approximate tool profiles. As long as the principle errors are within an acceptable range, this processing method remains feasible. Manufacturing errors, installation errors, and wear during machine tool use directly impact the machining accuracy of CNC machined parts. This includes errors in the rotary motion of the machine tool spindle, linear motion of the machine tool guide, and errors in the machine tool transmission chain.

Secondly, errors in CNC machining tools, including manufacturing errors, installation errors, and wear, can affect the machining accuracy of the workpiece. During the cutting process, the cutting edge and cutting surface of the tool experience intense friction with the workpiece and chips, leading to tool wear. Fixture errors in CNC machining involve positioning errors, clamping errors, fixture installation errors, and tool setting errors. These errors are mainly related to the manufacturing and assembly precision of the fixture.

Lastly, CNC machining positioning errors primarily include errors in the misalignment of reference points and errors in the manufacturing of positioning components. When machining workpieces on the machine tool, multiple geometric features on the workpiece must be selected as positioning references during the machining process. Inaccurate manufacturing errors in positioning components only occur when using the adjustment method in CNC machining, not when using the trial-cutting method.

Factors Causing Workpiece Deformation in Mechanical Machining

During the mechanical machining process, various machining errors or other operator errors can easily lead to workpiece deformation. This problem is challenging to solve. First, it is necessary to identify the specific reasons for deformation and then take measures to address them. Therefore, what are the main factors causing workpiece deformation in mechanical machining?

Workpiece Clamping-Induced Deformation:

Workpiece clamping can easily cause deformation. To avoid such deformation, suitable clamping points should be chosen, and appropriate clamping force should be applied based on the position of the clamping points. It is essential to keep the clamping points and support points close to the machining surface to minimize deformation. The most effective method to address clamping deformation is to enhance the stiffness of the workpiece.

Material and Structural Factors:

The magnitude of deformation is proportional to the complexity of the shape, aspect ratio, and wall thickness of the workpiece. It is also proportional to the stiffness and stability of the material. Therefore, in the design of parts, efforts should be made to minimize these factors' impact on workpiece deformation. Particularly, the structure of large parts should be rationalized. Before machining, defects such as hardness and looseness should be strictly controlled to ensure the quality of the blank and reduce workpiece deformation.

Deformation During Machining:

In the cutting process, the workpiece undergoes elastic deformation due to the action of cutting forces. This is the elastic deformation in the direction of force. To address this deformation, tool improvements can be made to reduce friction between the tool and the workpiece, enhance the cooling capacity during the cutting process, and reduce internal stress in the workpiece.

Post-Machining Stress-Induced Deformation:

After mechanical machining, the workpiece itself has a relatively balanced internal stress state. Although the shape of the workpiece is relatively stable at this time, the removal of some materials and subsequent heat treatment can change the internal stress. Therefore, a balancing force needs to be applied. This can be achieved through heat treatment. Folding the workpiece to a certain height, pressing the fixture into a flat state, and then placing the fixture and workpiece together in a heating furnace. Depending on the material of the workpiece, different heating temperatures and times can be selected. After heat straightening, the internal structure of the workpiece can be kept stable.

For workpieces prone to deformation in mechanical machining, corresponding improvements should be made in the blanks and machining processes. The above points outline the main factors that can cause workpiece deformation in mechanical machining. Training for operators in large machining plants should pay attention to ensuring that operators understand these main factors leading to workpiece deformation.