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There are many surfaces that require CNC machining of the shell and box, such as medical boxes, gearboxes, etc. Among these machined surfaces, plane machining accuracy is easier to ensure than hole machining accuracy. Therefore, the machining accuracy of the spindle hole (main hole) and the machining accuracy of the hole system in the box have become the key issues in this process. For example, we have made an audio aluminum alloy case. Its advantages are good heat dissipation, high CNC processing fit, four-star texture, and ease to take care of, if it can be used as a surface anode, the texture can reach five-star. Disadvantages: high processing conditions, high cost, and it is difficult to make individual shapes. The heat dissipation of wooden chassis is poor, and the price of high-end wood is higher. The following is a case of helical gearbox processing:

Therefore, VMT will pay attention to the following points in the arrangement of the process route:

(1) CNC machining sequence from face to hole

CNC machining the plane first, not only can remove the rough surface and sand inclusions on the surface but also can easily scribe and align the holes distributed on the plane. In addition, when the boring tool starts to bore, there will be no shock vibration or tool damage due to the uneven end face. Therefore, it is usually best to CNC machine the plane first.

(2) The roughing and finishing stages should be separated

The structure of the box is complex, and the precision of the main surface is high. The cutting force, clamping force and cutting heat generated in the rough CNC machining process have a great influence on the machining accuracy. If roughing is carried out immediately, the internal stress of the CNC machined parts caused by various reasons after roughing is not completely released, and cannot be eliminated during finishing, which will cause the box to deform after unloading and affect the final accuracy of the box. I think it is better to loosen the fixture several times during the roughing process, to release the internal stress as soon as possible, and ensure the CNC machining quality of the box to a greater extent.

(3) Decisions about centralization or decentralization of processes

The separation of the rough CNC machining and fine CNC machining stages of the box conforms to the principle of process dispersion. However, in order to reduce the number of machine tools and fixtures used in the production of small and medium-sized batch CNC machining, and reduce the handling and installation time of the box, the roughing and finishing stages can be relatively concentrated and placed on the same machine tool as much as possible.

(4) Arrange appropriate heat treatment process

The structure of the casting box is complex, the wall thickness is uneven, the cooling rate is inconsistent during casting, it is easy to generate internal stress, and the surface is hard. Therefore, sandblasting and tempering personnel should be reasonably arranged after casting.