A Rake face selection
Generally, tool regrinding is carried out on the rake face. The scraping cutter head is a complex tool. Starting from the simplified process, the rake face of the spiral bevel gear milling cutter head should be flat.
B. Flank selection
The selection of the back face of the scraping cutter head is much more complex than that of the front face. The selection of flank is not only directly related to the manufacturing and regrinding process of cutter head, but also closely related to the tooth profile error after regrinding, which should be considered in the design of carbide scraping milling cutter head. According to the current manufacturing process, the following three flanks can be selected.
(1) The post grinding cutter is most commonly used in the carbide scraping and milling cutter disc. The cylindrical helical surface can be obtained by axial post grinding, and the tooth profile error is small after regrinding. After grinding, the tool surface can be carried out as long as there is a needle tooth machine tool, and there are no difficult problems in the process.
(2) After circular grinding, the rotary flank with different axes from the axis of the milling cutter head can be obtained, among which the offset circular grinding method is the most widely used, and the axis of the rotary flank obtained is parallel to the axis of the cutter head. The tooth profile error caused by regrinding the flank is also relatively small. After circular grinding, the cutter face is mostly obtained by eccentric installation of the cutter head on the process cutter head and processing with an cylindrical grinder or tool grinder. It is necessary to have a process cutter head for command, which is difficult for non professional production factories.
(3) The blade surface is called sharp tooth after flat grinding.
Generally speaking, sharp teeth have the following advantages over shovel teeth:
① For the straight edge, the manufacturing process of sharp teeth is relatively simple;
② Sharp teeth can get a more reasonable back angle;
③ The surface quality of sharp tooth flank is better than that of shovel tooth;
④ The durability of sharp tooth milling cutter is higher than that of shovel tooth.
Carbide scraping milling cutter head adopts sharp tooth structure, which has some obvious advantages.
⑤ The manufacturing process of sharp tooth cutter head is simple. It does not need a special shovel machine tool like shovel teeth, nor a set of special process cutter head like circular grinding. The cost of diamond grinding wheel consumed in grinding is also much lower than that of shovel grinding and circular grinding.
⑥ Regrinding can be carried out on an ordinary tool grinder by means of separate regrinding and translational feeding. Because there is no need for special tool grinding machine, the one-time cost of scraping the hard tooth surface of spiral bevel gear is very low, which is especially suitable for medium and small batch production.
⑦ In the scraping process, the tool not only has normal wear, but also moves due to the performance of the blade material. Due to the influence of microstructure, welding and grinding thermal stress, as well as the impact and vibration in the cutting process, the blade will also have abnormal phenomena such as edge collapse, clamshell peeling and fatigue damage. This kind of damage may mainly occur on the rake face. At this time, the blade will be worn away, and the service life of the tool will be significantly shortened. The sharp tooth cutter head can regrind the front and rear cutter surfaces respectively in the separation regrinding, which can not only make full and effective use of cemented carbide, but also regrind the corresponding surface according to the tool wear, so that the regrinding work is greatly reduced.
To sum up, it can be seen that the choice of flank is not only related to the manufacturing process and regrinding quality, but also directly related to the production scale. When the production batch is large, the contradiction of improving productivity is more prominent. Adding one or two special grinding machine tools is not a big problem. The carbide scraping cutter head should adopt the method of shovel grinding the rear cutter surface and circumferential feed or translational feed. When the production batch is small or very small, the importance of productivity is reduced. Shovel grinding or flat grinding can be considered, and the back cutter surface can be separated and reground by translational feeding.
At present, the tooth profile design, error analysis and regrinding process of the scraping cutter head of shovel teeth and grinding teeth have been well solved, and the tooth surface contact area after scraping has been guaranteed. From the previous discussion, it is known that if the milling cutter head adopts sharp tooth cutter head, it has many advantages over the shovel tooth: for example, the front and rear cutter surfaces are flat, the manufacturing process is simple, and it can be processed on the surface grinder without shovel cutting equipment, so it is beneficial for medium and small factories to design and manufacture cemented carbide cutter head according to their needs; Regrinding can be carried out on ordinary tool grinder by separation method, so the equipment investment can be reduced; In addition, the sharp tooth cutter head can use a relatively large flank angle and obtain better flank quality, the service life of the cutter teeth can be improved, and the quality of the scraped tooth surface can be further improved. However, the analysis and calculation show that if the scraping cutter head with sharp tooth cutter head does not take compensation measures when regrinding the front cutter face, the tooth profile error after regrinding will be much higher than that after regrinding, which will reduce the gear accuracy, which has become a major obstacle to the wide application of this process in production.