We have talked about the rough machining of the shaft. Rough machining is the basis of shaft finishing. For the parts that need finishing, there should be enough but not too much machining allowance to ensure the normal progress of finishing.

The requirements for fine turning are higher and should be carried out by skilled workers on more precise lathes. If the center hole of the rear axle of the rough turning is worn, the center hole must be re-corrected to obtain an accurate machining positioning reference, and then the fine turning can be carried out.

When fine turning, you must pay attention to ensure the size between the two bearing gears, which is what we call the shoulder, because its accuracy requirements are stricter, and other shaft gears are mostly based on it.

After the shaft finish turning is completed, the bearing position, shaft extension position and other parts should be ground. Similarly, during the finishing turning process, a suitable machining allowance should be left in the parts that need to be ground, and the grinding process should ensure the size. At the same time, it is necessary to ensure that the machined surface meets the sufficient roughness requirements.

For particularly large motor shafts, limited to the size and capability control requirements of the equipment, the parts that should be ground in theory are completed by fine turning, but this must be guaranteed by high equipment accuracy and personnel operating skills.

Fine turning of motor shafts

The requirements for fine turning are higher and should be carried out by skilled workers on more precise lathes. If the center hole of the rear axle of the rough turning is worn, the center hole must be re-corrected to obtain an accurate machining positioning reference, and then the fine turning can be carried out.

The dead center installation workpiece is relatively stable, but the wear is large. The rigidity of the movable center is poor, but it can avoid the wear between the workpiece and the center. Therefore, the movable center is widely used in high-speed cutting.

The clamping method of fine turning is roughly the same as that of rough turning. When finishing turning, the diameter and length of the other shaft files are all turned to the dimensions specified in the drawing , except for the steps that need to be ground to leave a grinding allowance (0.3 ~ 0.5 mm ) . The end face chamfer and the grinding wheel overrun groove are also turned out at the same time.

For small motors, in order to prevent the bending deformation of the shaft during press-fitting, the iron core is press-fitted after rough turning and knurling, and then the bearing position, shaft extension position and the outer circle of the iron core are fine-turned. Or first fine-tune the armature gear, commutator gear, shaft intermediate gear, fan gear, etc., enlarge the bearing gear by 0.3~0.5 mm according to the size of the drawing , press - fit the rotor, and then fine-tune the bearing gear, electric motor The outer circle of the pivot, the outer circle of the commutator and other parts to ensure the coaxiality of each part of the rotor.

When fine turning, you must pay attention to ensure the size between the two bearing gears, which is what we call the shaft shoulder, because its accuracy requirements are stricter, and other shaft gears are mostly based on it.

The direction of improving the productivity of turning machining is to improve the manufacturing accuracy of the blank to reduce the machining allowance; to increase the turning amount and reduce the number of passes to shorten the pass time and auxiliary time. The advanced technologies used include high-speed cutting, powerful cutting, multi-tool multi-blade machining, profiling turning, etc.

In order to improve the machining accuracy of turning, the factors affecting the machining accuracy should be analyzed according to the specific machining conditions, and corresponding measures should be taken. The clamping of the workpiece and the tool should be accurate and reliable: the rigidity of the process system should be good; the cutting edge of the tool should be carefully ground; the cutting depth and cutting amount are small, the cutting force is also small, so the elastic deformation of the process system is also small, and the quality of the machined surface can be improved. improve.

When the shaft is finished turning, a smaller depth of cut and pass amount are often used, so that higher machining accuracy and surface roughness can be obtained.

Shaft grinding

The parts where the bearings are installed at both ends of the motor shaft and the shaft extension require higher surface roughness. Although the use of fine turning can meet the requirements, but the productivity is low and the cost is high. It is more economical to use the semi-finishing and post-grinding process method.

When grinding, place the workpiece between the two dead centers and rotate it with a heart chuck and a dial. The purpose of using a dead center is to reduce the gap between the center and the shaft, eliminate vibration, and achieve the required machining accuracy.

When grinding the outer circle, longitudinal feed (longitudinal grinding method) is usually used, the grinding wheel performs the main cutting motion, the workpiece rotates and performs linear reciprocating motion (longitudinal feed) together with the worktable. The grinding allowance is ground with multiple longitudinal feeds. At the end of each reciprocating stroke, the grinding wheel cuts in laterally (radially). The vertical grinding method is characterized by high precision. For small motor shafts, transverse feed (horizontal grinding method) is sometimes used because the processing part is not long. The grinding wheel is only used for lateral feed. The width of the grinding wheel is slightly larger than the length of the part to be ground (generally more than 5~10 mm). During rough grinding, the lateral feed is 0.025 ~ 0.02 mm/workpiece per revolution) During fine grinding, the lateral feed is 0.001~ 0.012 mm / workpiece per revolution . The horizontal grinding method is characterized by high work efficiency, but the cylindricity deviation of the outer circle is relatively large, and the shape of the grinding wheel must be often trimmed with a diamond knife.