The processing deformation of aluminum alloy shells, especially thin-walled shells, is a common technical problem. Therefore, it is necessary for machining plants to analyze the causes of deformation and take appropriate measures to prevent it.
1. The material grade and structural complexity of the aluminum shell will affect the deformation of the shell
The amount of deformation of CNC machined aluminum shell is related to the complexity of the shape, aspect ratio and wall thickness, which is directly related to the rigidity and stability of the material. Therefore, when designing aluminum shell products, the influence of these factors on the deformation of the workpiece should be minimized.
Especially in the processing and customization of the shell of the larger parts, the structure should be reasonable. The hardness and porosity of the aluminum alloy material blank should be strictly controlled before processing to ensure the quality of the blank and reduce the deformation of the workpiece caused by it.
2. The deformation of the aluminum shell caused by the machining center processing and clamping
When machining aluminum shells and clamping material blanks, the correct clamping surface should be selected first, and the appropriate clamping force should be selected according to the position of the clamping surface. Therefore, the clamping surface and the stressed surface should be as consistent as possible, so that the clamping force acts on the workpiece.
When clamping forces in multiple directions act on the workpiece, the order of the clamping forces should be taken into account. The clamping force should be applied first to make the workpiece contact with the bracket and avoid excessive excess. The clamping force, which is mainly used to balance the cutting force, should be used in the subsequent operation.
3. Deformation caused by machining parameters of aluminum shell
In the cutting process of the machining center machine tool, the shell is affected by the cutting force, resulting in elastic deformation corresponding to the direction of the force, which is what we often call deformation in machining. In terms of machining parameters and tool selection, corresponding measures should be taken to deal with this deformation.
On the one hand, it can reduce the resistance formed by the friction between the tool and the workpiece, and on the other hand, it can improve the heat dissipation effect when the tool cuts the workpiece, so as to reduce the residual internal stress on the workpiece.
When milling large surfaces of thin-walled casing parts, the single-edge milling method is often used. The tool parameters adopt a large entering angle and a large rake angle to reduce the cutting resistance. Because this tool is light and fast, it reduces the deformation of thin-walled parts, so it is widely used in production.
In the process of customizing thin-walled aluminum shells, a reasonable tool angle is crucial to the magnitude of the cutting force during the machining process, the thermal deformation generated during the machining process, and the microscopic quality of the workpiece surface. The size of the rake angle of the tool determines the cutting deformation of the tool and the sharpness of the rake angle.
The large rake angle reduces the cutting deformation and friction, but if the rake angle is too large, the tool wedge angle is reduced, the tool strength is weakened, the tool heat dissipation is poor, and the wear is accelerated. Therefore, when machining aluminum alloy thin-walled cavities, high-speed tools and cemented carbide tools are generally used. The right choice of tool is the key to dealing with the deformation of aluminium shell workpieces.
In machining, the heat generated by the friction between the CNC machine tool and the workpiece will also deform the workpiece, so high-speed cutting is often used. In high-speed machining, due to the short chip removal time, most of the cutting heat is taken away by the chip, which reduces the thermal deformation of the workpiece; Secondly, when working in a high-speed machining center, the deformation of aluminum shell processing can also be reduced due to the reduction of the softened part of the cutting layer material, which is conducive to ensuring the accurate size, shape and size of the shell.
In addition, the cutting fluid of the CNC machine tool machining center is mainly used to reduce friction and reduce the cutting temperature during the cutting process. The proper selection of cutting fluid plays an indispensable role in improving the durability, surface quality and machining accuracy of the tool. Therefore, in order to prevent the parts from deforming during machining, it is necessary to use a special cutting fluid with an appropriate concentration.
The use of a reasonable amount of stock removal process in CNC machining is an important part of ensuring the accuracy of parts. When machining thin-walled aluminum shells with high processing accuracy, symmetrical processing is generally used to balance the stress generated on the opposite side and achieve a relatively stable state, and the processed workpiece will be as smooth as possible.
However, when a large number of cuts are used in a certain process, the workpiece will be deformed due to the imbalance between tensile and compressive stresses. The deformation of thin-walled aluminum shell during cutting in the machining center is multifaceted, and some factors such as the clamping force when clamping the workpiece, the cutting force when cutting the workpiece, etc., will have an impact on the deformation.
4. Deformation of the aluminum shell in the natural state after the machine tool of the machining center is dismounted
After the aluminum shell is processed, there is internal stress in the machined part itself, and deformation may also occur. In order to solve this situation, some workpieces need to be divided into roughing and finishing, that is, after roughing, aging treatment or heat treatment is carried out to remove internal stress, and then finishing.