Tips on Injection Molding Technolog of POM Plastic parts
What is POM?
POM,,also calles as acetal, Polyoxymethylen is a kind of thermoplastic plastic particles with high hardness and rub resistance. The resin is applied to the production of precisions parts requiring highstiffness, low friction, and excellent dimensionalstability. The POM injectin molding is a crystalline plastic process with an obvious melting point. Once the melting point is reached, the melt viscosity decreases rapidly. When the temperature exceeds a certain limit or the melt is heated for too long, it will cause decomposition. Copper is a catalyst for POM degradation, therefore avoid using copper or copper materials on the areas contacting with POM melt.
English name: Polyoxymethylene (Polyformaldehyde)
Properties of POM Plastics
Density: 1.41-1.43 g / cubic cm
Molding shrinkage: 1.2–3.0%
Molding temperature: 170-200 ℃
Drying conditions: 80-90 ℃ for 2 hours
Eingeering plastic POM
The main reinforcing materials are glass fiber, glass ball or carbon fiber, etc., and glass fiber is the most commonly used.The mechanical properties of 2% can be improved by 2%.The thermal deformation temperature is increased by more than 50 ℃.
High-speed lubricating POM
In POM, graphite, F4, graphite, lubricating oil and low molecular weight PE are added to improve the lubricating property.For example, adding 5 phr F4 to POM can reduce friction coefficient by 60% and increase wear resistance by 1%. Twice as much.
For example, the wear resistance and limit PV value can be greatly improved by adding liquid lubricating oil to POM.In order to improve the dispersion effect of oil, carbon black, barium hydroxide sulfate, ethylene propylene rubber and other oil absorbent carriers need to be added.
The friction of 5% oil POM is increased by 72%, and the limit PV value can reach 3.9MPa.
In short,POM plastic is a thermoplastic engineering plastic with high density and high crystallization. It has good physical, mechanical and chemicalperformance, especially excellent friction resistance. Thus, the material can be compared with iron and steel, and the weight is lighter than steel, so it is called a resin better than steel.
Pom Molding Guide
- POM can not be dried before processing, it is best to preheat the reasin to about 80Celsius degree during the process of injection. The rule is good to keep stability of part dimension.
- The moldingtemperature of POM is should be controlled tightly within the range (0~215 ℃). If residence time in the barrel is a little longer or temperature exceeds 220 ℃, POM will decompose and produce highly irritating formaldehyde gas.
- During the molding process,holding pressure of POM materialneeds to be as high as that of injection processure in order to reduce the pressure.Screw speed should not be too high, the residual amount should be small as well.
4.The shrinkage of the POM Molded Product is large and it is easy to shrink or deform.
POM is hot and the mold temperature is high up to 80℃- 100℃. The injection molded part is is very hot when demoulding. Take care not to scald finger while taking products without using robot hands.
- POM Injection Parts should be molded under processing conditions of medium pressure, medium speed, low material temperature, higher mold temperature. For precision injection molding, temerpature control box shall be used.
6.POM is with high mechanical strength and rigidity
7.Highest fatigue strength
Drying condition: if the material is stored in a dry environment, there is usually no need for drying.
Melting temperature: Homopolymer material 190~230 ℃;
Copolymer material 190-210 ℃.
Mold temperature: 80-105 ℃. In order to reduce the shrinkage after molding, increase mold temperature.
Injection speed: medium or high injection speed.
Runner and gate: you can use any type of gate. If tunnel gate is used,it is best to use a short type. For homopolymer materials, it is recommended to use hot injector runner. The hot runner of the department can also use the external hot runner.
POM plastic application
POM has low friction coefficient and good geometric stability, which is especially suitable for manufacturing gears and bearings due to its resistance.
Since POM has characteristics of high temperature, it could be aoso used in pipeline devices such as pipe valves, pump shells, lawn equipment and so on.They could be used as replacement for most of the color metal, automotive parts, machine tool, instrument interiors, bearings, fasteners, gears, spring plates, pipes, transportation vehicle.
In short POM has a very low friction coefficient and is very good resin.
With over 20 years of experience in POM injection molding, HS Mold is an better alternative for yur injeicion tooling project!