Analysis on the processing process and characteris

Processing process and characteristic analysis of belt axle

figure 6-36 shows the working drawing of belt axle. There are two main technical conditions in the belt axle on March 1: one is the depth of carburized layer, which should be controlled within the range of 1.2-1.5 mm; Second, the outer circle ￠ 22 f 7 needs to be carburized and quenched, and its hardness is hrc58 ~ 63. It can be seen that only ￠ 22 f 7 parts need carburization, and the rest parts cannot be carburized. For parts that do not need carburization, you can increase the allowance to be carburized. The main features are: remove the carburized layer after driving or apply anti-seepage materials at the places that do not need carburization. The machining allowance should be slightly greater than the carburization depth on one side, so the diameter of the right end is ￠ 25 mm, the carburization allowance on one side is 2.5 mm, and the plastic material testing machine should also be placed at both ends of the total length to detect the standard carburization allowance of 3 mm each. Before grinding the excircle, due to the quenching process, the center holes at both ends are easy to produce oxide skin and deformation during quenching, so a process of grinding the center hole is added

table 6-14 shows the processing process of belt axle

4. According to the stress state of the sample and the application speed of the experimental force, it can be divided into static force and dynamic force testing machines; Machining process characteristics of slender shaft

(I) technological characteristics of turning slender shaft

1. The rigidity of slender shaft is very poor, and the clamping is improper during turning. It is easy to bend and deform due to the action of cutting force and gravity, resulting in vibration, which affects the machining accuracy and surface roughness

2. The slender shaft has poor thermal diffusion performance, and will produce considerable linear expansion under the action of cutting heat. If both ends of the shaft are fixed supports, the workpiece will be bent due to elongation

3. because the axis is long, the time of one-time cutting is long, and the tool wear is large, which affects the geometric accuracy of parts

4. when turning slender shafts, due to the use of tool heel, if the two support blocks supporting the workpiece do not have appropriate pressure on the parts, the machining accuracy will be affected. If the pressure is too small or does not contact, it will not work and cannot improve the stiffness of the parts; If the pressure is too high, the part is pressed against the turning tool, the cutting depth increases, and the turning diameter is small. When the tool holder continues to move, the support block is supported at the outer circle of the small diameter, and the support block is separated from the workpiece. The cutting force makes the workpiece move outward, the cutting depth decreases, and the turning diameter becomes larger. Then the tool holder follows the large diameter circle, and the workpiece is pressed against the turning tool, so that the turning diameter becomes smaller, which changes continuously and regularly, The slender workpiece will be turned into a "bamboo" shape, as shown in figure 6-37

(II) advanced turning method of slender shaft - reverse tool walking turning method

Figure 6 – – 38 is the schematic diagram of reverse tool walking turning method. The characteristics of this method are:

1. The left end of the slender shaft is wrapped with a circle of steel wire, which is clamped by a three jaw self centering chuck to reduce the contact area, so that the workpiece can freely adjust its position in the chuck and avoid bending moment during clamping, The deformation occurring in the cutting process will not produce internal stress due to the clamping of the chuck

2. The tailstock center is changed into an elastic center. When the workpiece is linearly expanded and extended due to cutting heat, the center can automatically retreat to avoid bending deformation caused by thermal expansion

3. three support blocks and tool rest are used to improve the rigidity of the workpiece and the stability of the axis, and avoid the "bamboo" shape

4. change the cutting direction, so that the bed saddle moves from the spindle box to the tailstock, so that the workpiece is pulled, and it is not easy to produce elastic bending deformation