Analysis of processing technology of typical sleeve parts (4)

(3) All processing points are performed in several installations, first processing the outer circle, and then processing the inner hole on the outer circular surface as a positioning reference. This kind of process scheme, such as clamping the workpiece with a general three-jaw self-centering chuck, will reduce the coaxiality of the workpiece due to the large eccentricity error of the chuck. Therefore, it is necessary to use a fixture with a high centering accuracy to ensure a high degree of coaxiality of the workpiece. Longer sleeves generally use this type of processing.

2. Method of preventing deformation

Thin wall sleeves are often deformed due to the influence of clamping force, cutting force and cutting heat during processing, resulting in reduced machining accuracy. Thin-walled sleeves that require heat treatment can cause uncorrectable deformation if the heat treatment process is improperly arranged. To prevent deformation of the thin-walled sleeve, the following measures can be taken:

(1) Reduce the influence of clamping force on deformation

1 The clamping force should not be concentrated on a certain part of the workpiece. It should be distributed over a large area so that the pressure per unit area of ​​the workpiece is small, thus reducing its deformation. For example, when the outer circumference of the workpiece is clamped by the chuck, soft jaws can be used to increase the width and length of the jaws, as shown in Figure 7-72. At the same time, the soft jaws should adopt self-tanning process measures to reduce installation errors and improve machining accuracy. Figure 7-73 shows the thin-walled workpiece clamped by the slotted sleeve. Because the contact surface between the slotted sleeve and the workpiece is large, the clamping force is evenly distributed on the outer circumference of the workpiece, which is not easy to deform. When the thin-walled sleeve is positioned with the hole as a reference, an open mandrel should be used.

2 A clamp that axially clamps the workpiece. As shown in Fig. 7-74, since the workpiece is axially clamped by the nut end face, the radial deformation caused by the clamping force is extremely small.

3 The auxiliary ribs with enhanced rigidity are made on the workpiece, and the claws of the special structure are clamped during machining, as shown in Figure 7-75. When the machining is finished, the flange is cut.

(2) Reduce the influence of cutting force on deformation

The commonly used methods are as follows:

1 reducing the radial force, usually by increasing the tool's lead angle.

2 The inner and outer surfaces are machined at the same time, so that the radial cutting forces cancel each other, as shown in Figure 7-75.

3 Roughing and finishing are carried out separately, so that the deformation generated during roughing can be corrected in finishing.

(3) Reduce the error caused by thermal deformation

The workpiece is expanded and deformed after being subjected to cutting heat during the machining process, thereby affecting the machining accuracy of the workpiece. In order to reduce the influence of thermal deformation on the machining accuracy, sufficient cooling time should be left between roughing and finishing, and sufficient cutting fluid should be injected during machining.

The heat treatment has a great influence on the deformation of the sleeve. In addition to the improved heat treatment method, when the heat treatment process is arranged, it should be arranged before the finishing, so that the deformation caused by the heat treatment is corrected in the subsequent process.

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