Machining accuracy and precautions of CNC milling thin-walled parts
1.Basic introduction to CNC milling thin-wall processing technology
Thin-wall machining is a CNC machining technology that allows precise cutting and shaping of thin and delicate materials. However, the material thickness is often less than 2 mm, and it is difficult to process due to its delicate nature and easy deformation and warping. Therefore, research on CNC machining technology for thin-walled parts is crucial. This blog introduces the machining accuracy and precautions of thin-walled parts.
2.Current status and problems of thin-walled parts
Thin-walled parts have complex internal structures, which can easily cause various problems during CNC milling. Thin-walled parts have complex structures and low rigidity, and are easily deformed during processing, resulting in uneven thin-wall thickness and inappropriate size.
In order to ensure processing accuracy, fine processing and multiple light cutting without feed are often used. Although the quality of parts is improved, it increases consumption, wastes time, and reduces productivity.
3.Factors affecting the deformation of thin-walled parts during machining
1.Cutting force and cutting heat
Thin-walled parts have poor rigidity, and the deformation caused by milling force is difficult to predict. Chip deformation causes thermal stress on the surface of the part, which aggravates the deformation of the part under the action of cutting force and cutting heat.
2.Workpiece material characteristics
Thin-walled workpiece materials are mostly aluminum alloys, titanium alloys, etc., with small elastic modulus, high specific strength, and easy to rebound deformation. Increased part size and asymmetric structure will also increase deformation.
3.Clamping conditions
The clamping force of the fixture causes elastic deformation of thin-walled parts, affecting the surface shape and dimensional accuracy. The cutting force and clamping force interact to cause deformation.
4.Residual stress
Includes initial residual stress and processing residual stress. Cutting force and cutting heat break the balance of initial residual stress, and workpiece deformation causes internal stress to balance again.
5.Tool path
Different tool paths cause different residual stress release orders, resulting in different processing deformations. Multiple factors work together to affect workpiece deformation.
4.Methods to improve the machining accuracy of thin-walled parts
1.Processing using the overall rigidity of the part
During the cutting process, use the unprocessed part of the part as support as much as possible to keep the cutting in a good rigidity state and reduce cutting deformation and vibration.
2.Use auxiliary brackets
Tires can be added to the cavity or filling methods can be used to strengthen the support, increase the rigidity of the part, and suppress deformation.
3.Design strengthening ribs to improve rigidity
For thin-walled parts, adding process ribs is one of the common methods to improve rigidity.
4.Symmetrical layered milling
The initial residual stress of the blank is released symmetrically, and the upper and lower edges are processed in sequence according to the principle of equal removal to reduce processing deformation.
5.Optimize tool cutting methods
The tool cutting method has a direct impact on the processing deformation of the part, and a suitable cutting method needs to be selected.
6.Use CNC high-speed machining
Control deformation, use the “small cutting depth, fast cutting” method to reduce cutting force, quickly remove cutting heat, and eliminate deformation caused by processing.
7.Heat treatment to remove stress
Stress relief treatment is performed after rough machining, and multiple stress relief is performed for high-precision parts with severe deformation.
8.Reasonable selection of workpiece positioning and clamping methods
Reduce the influence of clamping force on deformation
5.At last
Thin-walled parts are widely used in aerospace and other fields, and require high precision. Research on optimizing the cutting process of thin-walled parts has theoretical and practical value. It can reduce the possibility of deformation and improve dimensional accuracy and processing effect through scientific management of deformation, adjustment of routes, integration of procedures, increase of rigidity, selection of parameters and other measures.