Analysis of machining technology of box/case metal parts

Box/case metal parts are typical parts of mechanical parts, such as lathe headstock, gear transmission case, gearbox body, etc. It is one of the basic parts of the machine, it will be the shaft, bearing, sleeve and gear in the machine and parts. The parts are each held in the correct mutual position and are coordinated to each other in accordance with a pre-designed transmission relationship to form a single unit. The assembled box parts and the design reference plane of the box are mounted on the machine. Therefore, the machining quality of the box not only affects the assembly accuracy and motion accuracy, but also has a decisive influence on the working accuracy, service performance and life of the machine.

The box/case requires a lot of surface machining, such as lathe bed head box, gear transmission box body, etc. In these machining surfaces, the plane machining accuracy is easier to guarantee than the hole machining precision, so the machining precision of the spindle hole in the box body, hole system processing Accuracy becomes a key issue in the process. Therefore, we need to pay attention to the following points in the process arrangement:

Machining sequence of the front plane and back holes.

First machining the plane not only removes the unevenness of the surface of the blank and the surface sand, but more importantly, when processing the holes distributed on the plane, it is convenient to scribe. And when the boring tool starts to boring, it is not necessary to cause impact vibration and damage to the tool due to unevenness of the end face. Therefore, it is generally preferred to machine the plane first.

The rough and finish machining stages should be separated.

The structure of the box is complex, the precision of the main surface is high, and the cutting force, clamping force and cutting heat generated during rough machining have a great influence on the machining accuracy. If rough machining is performed immediately, the rough machining is performed for various reasons. The internal stress caused by the deformation of the workpiece is not fully released, and it cannot be eliminated in the finishing process, which leads to the deformation of the box during the unloading process, which affects the final precision of the box. I think that in the roughing process, it is best to loosen the clamping device several times, so that the internal stress is released as soon as possible, and the machining quality of the box is ensured to a greater extent.

Decisions on concentration or dispersion of processes.

The rough and finish machining stages are separated according to the principle of process dispersion, but in medium and small batch production, in order to reduce the number of machine tools and fixtures, and reduce the number of handling and installation of the cabinet, the roughing and finishing stages can be relatively concentrate and place as much as possible on the same machine.

Arrange an appropriate heat treatment process.

The casting box has complex structure and uneven wall thickness. The cooling rate during casting is inconsistent, and internal stress is easy to occur, and the surface is hard. Therefore, after casting, the sandblasting, quenching and tempering treatments should be arranged reasonably to eliminate internal stress and improve subsequent processability.

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