The concept of precision plastic gear mould and the key points of manufacturing process have done some brief analysis, hope these share to the mold personnel to be helpful. Although simply introduced, but as long as the master points, the follow-up to the gear mold will be analogy, easy.
The concept and application of precision gear mould
1 Precision gear refers to the parameter size and performance requirements are very high, the parameters include the tooth top round diameter, the tooth root round diameter, modulus, the dimension of roundness (also known as normal), the degree of round tooth thickness, pressure angle, oblique angle of teeth, tooth circle run-out tolerance and so on; performance includes
material selection and other assembly size accuracy requirements.
2 in the application, a representative product such as printers and copiers internal transmission, the common CD-ROM drive bracket, if the gear is not up to the precise requirements, will appear stent movement instability, accompanied by vibration or swing-type, a large voice, Through this we can have a perceptual understanding of the precise concept and its necessity.
3 Precision gear In the precision is graded, GB is the higher the level of precision, the Japanese standard is the level of the smaller the more sophisticated. To JIS standards, most precision mold factory can only do 4-level, 5-level gear, can do
3-grade plastic gear has been a very high level.
Second, precision plastic gear type:1 from the teeth of the axial tilt angle: straight gears, helical gears, combined straight gear, combined helical gear and the combination of straight bevel gear. The concept of the combination is that spur gears or helical gears are distributed in the upward ladder of the shaft, one injection forming.
2 There are two main types of transmission: meshing transmission gears and belt drive gears.
Third, the selection of mold embryo:
The precision of mould embryo will directly affect the manufacture and injection precision of moulds, and will also affect the life of die. The experience shows that the general precision of mould embryo is difficult to meet the requirement of precision gear mould.
IV. Selection of Plastic materials:
There are two main types: Pom and PA (pa+gf%). Do not exclude other raw materials, such as: Polysulfone and so on. The most fundamental reason for the choice of POM and pa materials is that the surface of the POM and PA products has good self-lubricating property.
Other common causes: good abrasion resistance, good impact resistance and fatigue resistance; Secondly, the POM products are rigid, excellent in resisting creep, PA products are good in toughness and can be filled with gf% when necessary to enhance their rigidity. In general, the Pom gears can be meshed with each other and the PA gears are used in meshing transmission with the POM gears.
Five, die structure design related points:
1) Gate: generally uses 3 or 6 point balanced pouring, the micro-gear is usually only used single point of pouring.
2) Die cavity arrangement: common have $number cavity. Small gears can reach 6 or 8 cavities, and the gears of different shapes can form 3 cavities. The most representative is 4 cavities.
3 Mold Mode: The center of the common cylinder and ejector ejection. For helical gears, the bearing auxiliary top out, the position of the bearing is sheathed on the needle and sleeve on the core of the die two, the two modes of principle are the same. Because the product is small, mold embryo is also small, the Thimble board generally does not need to add the Secretary and EGP.