At present, micromotors with rotor diameter of 0.5mm and outer diameter of several millimeters have been manufactured in driving motor. However, due to the high speed and small torque of this kind of micro motor, it is necessary to add a micro reducer with transmission ratio of several hundred between the motor and the load (actuator) to give full play to its performance. In various transmission mechanisms, gear transmission is the most commonly used. Therefore, in order to make the reducer miniaturized, it is necessary to realize the miniaturization of gear. *

The following is a brief introduction to the manufacturing method of micro gears, the small gears of Ogasawara Co., Ltd. and their machining tools. *

Manufacturing method of micro gear

1. Hob hobbing

Generally, hobs are used to cut gears on hobbing machines. When hobbing micro gear (below m0.1), the tooth profile of hob must be micro machined. Because of the small tooth profile, in addition to the hob tooth profile error, the error of the hob such as aperture runout, end face runout and pitch will have a great impact on the accuracy of the micro gear. The precision and stiffness of hobbing machine, workpiece spindle, cutter spindle, workpiece indexing mechanism and workpiece fixture, as well as the installation accuracy of hob and workpiece, will affect the manufacturing accuracy of micro gear. Therefore, it is necessary to improve the overall comprehensive accuracy of the manufacturing system. On this basis, it is easy to produce micro gears with the same modulus and different varieties by selecting the easy cutting materials. A kind of

2. Injection molded plastic gear

Plastic gears processed by injection molding can be produced in large quantities in a short period of time, so they are mostly used in office machines, household appliances and other light loads. In recent years, with the continuous improvement of injection molding technology and the performance of injection molding materials, the precision of injection molding gear is also greatly improved. The precision of injection mold for gear injection and injection molding technology are important factors affecting the injection molding method. In the production of mold, the main use of wire cutting and EDM. However, due to the influence of wire diameter and discharge gap of forming electrode, the improvement of precision of micro gear mould is limited. The mould can also be made by electroforming. The precision of reference gear used in electroforming can be improved by cutting or grinding. The reference gear can be thickened by electroplating. Through chemical dissolution, the male (convex) reference part is obtained to obtain the female (concave) mold. Because of the high precision of the reference gear, the electroplating treatment will not produce deformation, so it is possible to make a high precision micro gear mold. With the help of chemical dissolution method, molds with complex shapes can be manufactured by using reference parts and chemical dissolution method. Besides spur gears and helical gears, various types of dies such as bevel gears, end face gears, worm gears and worm gears can be manufactured. The use of high-precision mould makes it possible to produce plastic micro gears on a large scale. However, due to its small tooth profile and easy deformation under stress, it is more advantageous to use metal gear with high strength in the case of high load transmission and high transmission accuracy. A kind of

3. Metal sintering process

The mechanical strength of sintered metal gear (P / M gear) is higher than that of plastic gear, so it can be used under medium load condition. Mold forming method is suitable for mass production. However, after the die is formed, it will deform greatly after high temperature sintering. Therefore, in order to achieve the necessary precision, the gear must be finished after sintering. Because of the small tooth shape, it is difficult to finish the micro gear, and the metal particles of the metal powder are large, which limits the improvement of the shape accuracy and surface finish of the micro gear. The precision of the gear can be improved if the electrode electrochemical machining method of the reference gear mentioned in the injection molding plastic gear is used. A kind of

4. Other manufacturing methods

Micro gears can be manufactured by semiconductor manufacturing method, light etching method or laser processing method. Micro gears with tens of micrometers can be produced by light etching method, and internal gears can be drawn by broach. In the future, there will be more and more demands for micro gears, and new manufacturing methods and mass production technologies will also appear. *

Trial production of micro gear

Using the existing hob cutting technology of the company, Ogasawara Co., Ltd. has carried out the trial production of the possible minimum modulus micro gear. *

The main parameters of the hob are: modulus M: 0.01, pressure angle α: 20 °, tooth groove number: 12, outer diameter od: φ 25mm, inner hole diameter: φ 10mm, hob width: 8mm, material: cemented carbide. *

Hob accuracy: according to the company's Grade 3A hob accuracy manufacturing. Zeiss's universal tool microscope (umm200) is used to measure gears, and esm-01 is used to measure the end face runout.

The main parameters of trial produced micro gear are: modulus M: 0.01, pressure angle α: 20 °, tooth profile: involute, number of teeth Z: 100, OD: φ 1.02mm, material: B.S.

Because the contact gear measuring instrument can't measure the gear below m0.3, the tooth profile accuracy of this method can reach 2 ~ 3 μ m by using the enlarged drawing on the 200 times projector. The installation accuracy of hob and workpiece can be controlled within 1 μ m by using high-precision hob and improved high-precision hobbing machine. The results show that hobbing can be used to manufacture high precision micro gears. *

In order to further study the practical value of micro gears, the meshing loss of micro gears was measured. The test results show that under proper lubrication