Micro Worm Gears MIM Parts

Product Introduction

Qinhuangdao Zhongwei Precision Machine Parts Co., Ltd. mainly produces powder metallurgy products with cemented carbide, titanium, aluminum, copper, iron and stainless steel as raw materials; metal injection molding special-shaped parts (MIM); gears; metal plastic worm gears (1-7 head); spiral, straight bevel gear; all kinds of precision small modulus plastic hardware gear hobbing; and provide design and processing of various reducers, gearboxes; metal structure stamping parts; and other precision injection molding parts, etc. Products are widely used in household appliances (massage chairs, electric tools, etc.); medical equipment; office equipment (printers, fax machines); toys (model airplanes, robots, simulation car models), auto parts, fishing gear and many other industries. The company has self-export rights, and its products are exported to the United States, Germany, France, Spain, Canada, Japan and other parts of the world. The company firmly believes that "weigh the selection criteria of products with quality and price", and strives to satisfy customers with price, quality and integrity as the high purpose.

Metal injection molding micro-scroll manufacturing method
At present, in terms of driving motors, micro motors with a rotor diameter of 0.5mm and an outer diameter of several millimeters have been manufactured. However, due to the high speed and small torque of this kind of micro motor, in order to give full play to its performance, it is necessary to add a micro reducer with a transmission ratio of several hundred between the motor and the load (executive element). Among various transmission mechanisms, gear transmission is the most commonly used. Therefore, in order to miniaturize the reducer, it is necessary to realize the miniaturization of gears. 
The following is an introduction to the manufacturing method of micro gears, and the machining technology related to small gears of Ogasawara Co., Ltd. and their machining tools. 

• Manufacturing method of micro gears
1. Hob hobbing processing
Gears are usually cut on gear hobbing machines with hobs. When hobbing micro-gears (below m0.1), the tooth profile of the hob must be micro-machined. Because the tooth shape is small, in addition to the hob tooth shape error, the hob's aperture runout, end face runout, pitch and other errors will have a great impact on the accuracy of the micro gear. The precision and rigidity of hobbing machines, workpiece spindles, tool spindles, workpiece indexing mechanisms, and workpiece fixtures for processing, as well as the installation accuracy of hobs and workpieces, etc., will affect the manufacturing accuracy of micro gears. Therefore, it is necessary to improve The overall comprehensive accuracy of the manufacturing system. On this basis, by selecting materials that are easy to cut, it is relatively easy to realize mass production of micro-gears with the same modulus and different varieties. 

2. Injection molded plastic gears
Since plastic gears processed by injection molding can be mass-produced in a short period of time, they are often used for gears used in light loads such as office machines and home appliances. In recent years, with the continuous improvement of injection molding technology and the continuous improvement of the performance of injection molding materials, the precision of injection molding gears has also been greatly improved. The precision of injection molding gear molds and injection molding technology are important factors affecting the injection molding method. When making molds, wire cutting and EDM are mainly used. However, due to the influence of factors such as the wire diameter used and the discharge gap of the forming electrode, the improvement of the precision of the micro-gear mold is limited. Molds can also be fabricated by electroforming. The reference gear used in electroforming can be improved by cutting or grinding. The base gear can be thickened by electroplating. A female (concave) mold is obtained from a male (convex) reference piece by chemical dissolution. Due to the high precision of the reference gear and the lack of deformation caused by electroplating, it is possible to produce a micro gear mold with high precision. Due to the use of reference parts and the chemical dissolution method, molds with complex shapes can be processed. In addition to spur gears and helical gears, various types of molds such as bevel gears, face gears, worms, and worm gears can be manufactured. Mass production of plastic micro-gears is possible by using high-precision molds. However, due to its small tooth shape and easy deformation under force, it is more advantageous to use metal gears with high strength in the occasions of large load transmission and high transmission accuracy requirements. 

3. Metal sintering production method
Sintered metal gears (powder metallurgy gears) are sintered metal gears (powder metallurgy gears) formed by high-pressure molding of metal powder in a mold and then sintered and solidified at a high temperature. They have higher mechanical strength than plastic gears and are used under moderate load conditions. The mold forming method is suitable for mass production. However, after the mold is formed, it undergoes high-temperature sintering and the deformation is large. Therefore, in order to achieve the necessary precision, the gear needs to be finished after sintering. Due to the small tooth shape, the finishing of micro gears is difficult, and the metal particles of metal powder are relatively large, which limits the improvement of its shape accuracy and surface finish. If the forming mold adopts the reference gear electrode electrolytic machining method mentioned above in the injection molding plastic gear, the precision of the processed gear may be improved.

4. Other manufacturing methods
Micro Worm Gears MIM Parts can be manufactured by semiconductor manufacturing method, photolithography method or laser processing method. Micro-gears with a size of tens of microns can be trial-manufactured by photoetching, and internal gears can be drawn by broaching. In the future, there will be more and more demand for micro gears, and new manufacturing methods and mass production technologies will continue to emerge.

• Trial production of micro gears
With the existing hob cutting technology, the trial production of the smallest possible modulus micro-gear was carried out.
The main parameters of the hob used: modulus m: 0.01, pressure angle α: 20°, number of tooth grooves: 12, outer diameter OD: φ25mm, inner hole diameter: φ10mm, hob width: 8mm, material: hard alloy.
Hob precision: Manufactured according to the company's 3A level hob precision. The company's universal tool microscope (UMM200) measures gears; the end face runout is measured by the company's radio micrometer ESM-01.
The main parameters of the trial-produced micro gear: modulus m: 0.01, pressure angle α: 20°, tooth type: involute, number of teeth Z: 100, outer diameter OD: φ1.02mm, material: B.S.
Since the contact gear measuring instrument cannot measure gears below m0.3, it is detected with a magnified image on a 200 times projector. The tooth shape accuracy of this measurement method can reach 2-3 μm. Using a high-precision hob and a modified high-precision gear hobbing machine, the installation accuracy of the hob and workpiece can be controlled within 1 μm. The manufactured micro-gears are detected, and the results show that the hobbing process 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-gear pairs was measured. Test results show that, with proper lubrication, the results are on par with normal sized gears.

• Trial-manufacture end gear reducer with miniature end gear
The measurement of the meshing efficiency of the miniature gears confirmed that it has the possibility of practical application, and then the variable planetary gear reducer was trial-produced by using the miniature face gears and pinions. Since the processing accuracy of mechanical parts becomes relatively poor after miniaturization, it is necessary to make the mechanism of the developed micro reducer insensitive to accuracy. For this reason, the axial position of each part of the reducer will be determined according to the adjustment of the gear meshing parts. The trial-produced reducer realizes backlash-free transmission by adjusting the axial position.
The parameters of the gear used in the trial production reducer are as follows: m: 0.05, α: 20°, Z1: 100, Z2: 21, Z3: 102, Z4: 100 (Z1, Z3, Z4 are end gears, Z2 is a pinion), Outer diameter: φ6.6mm, overall length: 7.4mm, reduction ratio is about 1:101, the relationship between transmission torque, reduction ratio and total power is as follows:
Input torque: τi=1
Output torque: τo=(η1η2Z4/Z1+η2η3Z4/Z3)/(1-η2η3Z4/Z3),
Speed ratio: μ=(Z4/Z1+Z4/Z3)/(1-Z4/Z3)=101
Total efficiency:
[(1-Z4/Z3)/(Z4/Z1+Z4/Z3)]×(η1η2Z4/Z1+η2η3Z4/Z3)/(1-η2η3Z4/Z3)=0.425 (where η1, η2, η3 =0.987)

• Trial production of broaches for machining internal gears
Internal gears are usually machined by gear shaping, but small diameter gear shapers are not suitable for machining miniature internal gears due to their large cutting resistance and insufficient tool strength; Due to the constraints, it is difficult to manufacture micro-gears, and it is not suitable for mass production. A more feasible method is to manufacture a broach with the same parameters as the internal gear of the product, and use it to draw the internal gear. The accuracy of the broach will be reflected in the drawn internal gear, so it is feasible to produce an internal gear with better accuracy.
The parameters of the trial-manufactured internal gear broach are: m: 0.14, α: 20°, Z: 74, number of cutting edges: 70, overall length: 170mm. Its accuracy is detected by a 200-fold projector, and the tooth profile error is only a few microns, which has practical accuracy.

• Trial production of worms and worm gears
Worm gear reducers are very effective for high-speed ratios and where the input and output shafts are not parallel. The company used the cutting method to trial-manufacture a small modulus worm and its paired helical gear used as a worm gear. 
The parameters of the trial worm: m: 0.03, α: 20°, number of heads: 1, outer diameter: φ0.5mm. The accuracy of the trial-produced worms and helical gears was tested by the Zeiss universal display (UMM200), and the errors were all within a few microns, which verified that it is feasible to manufacture miniature worms and worm gears by cutting. If the cutting tools, processing machines, and fixtures used in processing meet the requirements of high-precision processing conditions, it is feasible to process various types of micro-gears by cutting or grinding, which has been verified. 
The possibility of cutting or grinding gears with a modulus of less than 0.01 is still in the exploration stage. On the basis of manufacturing micro gears, it will be an important issue in the future to realize the manufacture and practical application of ultra-micro gears. Due to the relatively poor machining accuracy of miniaturized parts, it is necessary to consider adjustments to components that are not sensitive to accuracy during mechanism design.