1. Correctly determine the number of gear teeth
First, use a hob reasonably. We must choose the modulus, the same pressure angle, the similar helix angle, the difference in the coefficient of displacement within 0.1mm, so that the root difference will not be too large. If the difference is large, you can also fine-tune the installation angle of the hob to achieve the required root diameter on the drawing. If it is found that the gear tooth tip is made wider, the root diameter becomes smaller and the condition is not serious, the angle of the tool holder may be appropriately increased, so that the tooth tip of the rolled-out gear will be sharpened. The root diameter becomes smaller.
Next, confirm the workpiece blank size. The machining of gear blanks prior to machining occupies an important position in the entire gear machining process. Regardless of improving productivity or ensuring the processing quality of gears, we must pay attention to the processing of gear blanks. Therefore, in the technical requirements of gears, attention should be paid to the dimensional accuracy of the addendum circle, because the detection of the tooth thickness is based on the tooth tip circle, and the precision of the tooth tip circle is too low, which inevitably makes the measured tooth thickness value. Can not correctly reflect the size of the tooth gap.
Third, the direction of additional movement should be accurate. At present, in the metal cutting machine tool books and related materials, the determination of the additional moving direction of the workpiece when rolling the helical helical gear is: in the process of the hob moving the spiral lead of the workpiece vertically, when the hob is in the direction of the spiral of the gear At the same time, the workpiece should be rotated one more revolution, that is, the direction of additional workpiece movement is the same as that of workpiece development. Conversely, when the hob is in the opposite direction of the spiral of the gear, the workpiece should be rotated less than one revolution. It can be seen that the additional motion is the motion that forms the gear helix. The additional direction of motion is related to the direction of the motion, the milling method, and the spiral direction of the workpiece. Therefore, the additional movement must be accurate to ensure the quality of the gear processing.
2. The tooth shape should be symmetrical
Tooth processing is the key to gear machining. The choice of the solution depends on many factors, such as equipment conditions, gear accuracy grade, surface roughness, hardness and so on. First, ensure the installation accuracy of the hob. The hob is mounted on the mandrel of the gear hobbing machine and it is necessary to use a dial gauge to verify that the radial runout of the bosses at both ends of the hob is not more than 0.005 12" 11/1.
At the same time, it is necessary to be in place. When the hob is hobbing the gear, usually only a few middle teeth cut the workpiece, so these teeth are easy to wear. In order to make the teeth wear evenly and prolong the durability of the hob, one or several pitches can be moved along the axis of the hob by manual or maneuvering after cutting a certain number of gears to improve the life of the hob. Second, control the quality of the hob sharpening. The utility model actively adopts a knife edge grinding machine, which has the characteristics of high precision, low price, convenient operation and flexibility.
The use of high-precision linear guides and precision indexing discs ensures the accuracy of hob sharpening. The independent grinding wheel dressing device and the spiral feed and knife setting device of the hob greatly increase the operational flexibility and the working efficiency of the sharpening hob. Third, check the installation and operation of the exchange gear. The exchange gear is a replaceable gear set used to change the cutting speed or feed of the machine (see cutting amount) and to exchange gears for position use in applications. By using the exchange gear, the original lift (down) speed can be converted into a drop (boost) speed transmission, and the gear ratios are reciprocal to each other. Therefore, in order to ensure the normal operation of the lathe, the installation and operation of the exchange gear must be checked in time.
3. Avoid tooth error
First of all, a reasonable choice of workpiece clamping. There are two major requirements for fixtures in CNC machining: First, the fixture should have sufficient accuracy and rigidity; second, the fixture should have a reliable positioning reference. When selecting a fixture, it is necessary to generally consider the adjustable fixture, the combination fixture and other applicable fixtures, and avoid the use of special fixtures to shorten the production preparation time. When using batch production, special fixtures were considered and the structure was simple. It is quick and easy to load and unload workpieces to reduce machine downtime.
Secondly, full consideration is given to the use of new processes, new technologies, and new materials along with the development of specialized manufacturing of blanks. At present, there are more and more applications of new processes, new technologies, and new materials in the production of blanks, such as precision casting, precision forging, The use of cold rolling, cold extrusion, powder metallurgy and engineering plastics has become increasingly widespread. These methods can greatly reduce the amount of mechanical processing, save materials, and have very significant economic benefits.
Third, make a good choice for positioning. The selection of the gear positioning reference often varies due to the different shapes and shapes of the gears. The shaft gear is mainly used for top positioning, and the cone is blocked when the aperture is large. The top positioning accuracy is high, and the benchmark can be unified.