Brief description of thin-walled parts CNC machining process improvement

With the development of industry, the application of thin-walled parts is becoming more and more widespread. But the CNC machining process of thin-walled parts still has many problems, which affect the efficiency of processing and the quality of the parts, so it is necessary to continuously improve the CNC machining process of thin-walled parts to improve the quality of processing.

0. Introduction

Thin-walled parts have a variety of advantages, such as being lightweight and having a wide range of applications. Still, the rigidity and strength of thin-walled parts are relatively poor, easy to deform, and other situations in the process, so the thin-walled parts CNC machining process should be optimized to improve the quality of the parts.

1. Thin-walled parts overview

Thin-walled parts refer to the wall thickness of less than 1mm metal parts and play an important role in industrial production. Thin-walled parts have lightweight, material saving and other characteristics, and the overall structure is more compact, so the use of thin-walled parts is more. However, thin-walled parts also have certain defects, such as poor rigidity, strength relatively weak, processing easy to deform, and other situations; the quality of parts processing caused a serious impact, so only continuous improvement of thin-walled parts CNC machining process to improve the quality of parts.

2. Thin-walled parts of the CNC machining stage

CNC machining of thin-walled parts can be divided into three stages, mainly including roughing stage, the semi-finishing stage, and the finishing stage.

• (1) Roughing stage: mainly for thin-walled parts for simple processing, according to the specific type and characteristics of the parts, need to choose the appropriate processing technology, such as rough turning and other processes for a thin-walled set of processing.
• (2) Semi-finishing stage: the semi-finishing stage is mainly for the second surface of the thin-walled parts to ensure that the precision of the second surface of the thin-walled parts can meet the requirements. After processing the secondary surface, the spare parts of thin-walled parts must be removed to improve the quality and accuracy of thin-walled parts.
• (3) finishing stage: finishing mainly uses precision turning parts outer circle this way to thin-walled parts for fine machining so that the precision of thin-walled parts can fully meet the requirements.

3. Thin-walled parts of the influence of CNC machining process factors

3.1 Part clamping

Part clamping plays an important role in thin-walled parts; if the quality of the part clamping is not qualified, it will cause unclamping and other situations, directly affecting the quality of thin-walled processing parts even causing safety accidents. Part processing has high requirements for clamping stiffness; if the stiffness does not meet the requirements or the stress of the part and the direction of deviation may lead to part deformation.

3.2 Cutting angle

When cutting, parts will be affected by various factors, such as cutting speed, feed speed, and cutting angle, of which the cutting angle is the more important influencing factor. Cutting speed, cutting angle, and other factors will affect the cutting amount of the tool and then affect the quality of the part. If the front and rear angles of the cutting tool change, the deformation of the tool cutting and the friction situation will also change. For example, suppose the front and rear angles become smaller. In that case, the friction and deformation of the cutting process will increase, and the degree of deformation of thin-walled parts will also increase, affecting the machining quality of the parts. In addition, the deviation angle also affects the precision of the part, so the deviation angle should be strictly controlled.

3.3 Tooling and path

Tool walking is an important part of the CNC machining of thin-walled parts; before the tool walking needs to be combined with the processing needs of thin-walled parts to reasonably set the tool walking and path, to ensure that the tool can follow the plan to walk the tool. If the tool does not follow, the plan will damage the precision of the part, so the importance of tool walking should be increased.

3.4 Process Routing

The machining process route greatly impacts the processing efficiency and product quality of thin-walled parts. Suppose the details of the deformation treatment and vibration phenomenon still need to be fully considered when designing the process route. In that case, it will affect the processing efficiency and product quality, so the details must be fully considered when designing the process route to improve the efficiency.

4. Thin-walled parts CNC machining process improvement strategy

4.1 Optimization of CNC simulation machining process

According to the actual situation can be seen, thin-walled parts processing load array and deformation are related and show a negative correlation, so we can analyze the CNC simulation of thin-walled parts machining process according to the formula F = KU (where F refers to the thin-walled parts processing load array, K refers to the thin-walled parts of the lightness matrix, U refers to the thin-walled parts during processing (the deformation of the thin-walled part). This means that the chance of deformation of thin-walled parts can be reduced by adjusting F and K. This will improve the CNC machining process of thin-walled parts and improve the quality of the parts. Generally, when increasing the K value or decreasing the F value, the part’s strength can be enhanced by a reasonable choice of raw materials. If you do not change, the raw materials can be used to fill the metal material to enhance the strength of raw materials. In practice, you can simulate the CNC machining of thin-walled parts according to the formula F = KU and adjust K and F according to the actual situation to improve the quality of the CNC machining process.

4.2 Improve the part clamping process

Part clamping has an important impact on the quality of the CNC machining process of thin-walled parts, so the part clamping process needs to be studied in depth to ensure that the part clamping can meet the requirements. 

• First, ensure the part clamping compact structure and hanging depth is short. In the CNC machining of thin-walled parts, the parts clamping will rotate with the spindle, so the center of gravity of the parts clamping should be reasonably controlled so that the center of gravity of the clamping can be close to the top of the spindle, to effectively control the size of the inertia force and rotation force, and improve the quality of parts processing.
• Secondly, the rigidity and strength of the part clamping should be reasonably set to enhance the rigidity and strength of the clamping. At the same time, it is also necessary to select the overhang length according to the actual situation of thin-walled parts to ensure that the length meets the requirements. Second, the need to improve the importance of balance and counterweight issues. Balance and counterweight problems will directly affect the vibration of the parts clamping, so it should be reasonable to choose the weight loss holes or counterweight blocks to maintain the balance of the parts clamping and reduce the centrifugal effect of the parts clamping in the rotation.
• Third, the need to enhance the durability and safety of the clamping mechanism. Enhance the durability of the clamping mechanism can effectively reduce the chance of damage to the clamping, reduce processing costs, increase the clamping force of the parts clamping, enhance the safety of the parts clamping can avoid the emergence of unclamping situation, reduce the safety risks. Fourth, the installation of parts and clamping must ensure that the parts clamping and CNC machine tool are a complete fit, thereby reducing machining errors.

4.3 Reasonable optimization of the tool path

Reasonable control of the tool path and cutting volume is conducive to optimizing the thin-walled parts CNC machining process, so the tool path and cutting volume should be studied in depth. The thin-walled sleeve to go to the processing need to be based on the thin-walled sleeve surface roughness, spindle rotation speed, feed speed, and back eat tool amount to calculate the path and cutting volume. First of all, it is necessary to calculate the roughness of the surface of the thin-walled sleeve according to this formula  and then specify the cutting volume according to Table 1.

Table.1 Cutting volume selection table for thin-walled sleeve

Project	Feed rate/mm	Back draft/mm	Rotation speed r/min
Cylindrical rough turning tool	0.4	3	600
Cylindrical precision turning tool	0.15	0.1	1200
Cylindrical semi precision turning tool	0.15	0.9	1200

After specifying the cutting volume, it is necessary to plan the cutting path. The roughing process can be used in a one-time roughing and step roughing method for processing so that the previous twelve tool path can be optimized, so that the tool along the X, Y direction for translation movement is conducive to the removal of thin-walled parts of the excess material, improve the accuracy of the parts. At the same time, it is necessary to reasonably increase the front and rear angle of the tool to reduce the friction and deformation strength and reduce the chance of deformation of thin-walled class parts.

4.4 Optimize the construction process

Technicians need to comprehensively analyze the processes and stages of CNC machining of thin-walled parts to identify and solve the problems in the machining process and improve the quality of machining. When designing the process route, the vibration phenomenon, deformation situation, and other details must be fully considered, and each processing step that may cause problems should be optimized. At the same time, it is also necessary to analyze the force situation and clarify the machining orientation to avoid the vibration of the part.

5. Conclusion

In CNC machining, thin-walled class parts are easily affected by various factors such as cutting angle, part clamping, etc. Therefore, it is necessary to actively improve the CNC machining process to eliminate the influencing factors and ensure the quality of thin-walled class parts.
Author: Wang Lijuan