Pom Injection Molding

POM injection molding is a highly efficient process for creating durable and precise plastic parts.This process plays a crucial role across a wide range of industries, from automotive and medical devices to consumer goods and industrial machinery.With its ability to deliver reliable results in demanding environments, POM injection molding has become an essential method for producing parts that require rigidity, accuracy, and long-term durability.

Polyoxymethylene (POM), also known as acetal, polyacetal, and polyformaldehyde, is a naturally white semi-crystalline engineering thermoplastic that includes both homopolymer and copolymer versions of acetal.Homopolymer acetal has a highly ordered crystalline structure for increased strength, but can be difficult to process because of its precise melt temperature. Copolymer acetal has a wider range of processing temperatures, but is mechanically weaker because it only has regions of crystallinity.

1.Polyoxymethylene has a very low coefficient of friction.
2.It also has excellent geometrical and dimensional stability.
3.It is impact resistant and also has a very high-temperature resistance.
4.POM is a tough and elastic material.
5.It has a good creep resistance even at low temperatures.
6.If the crystallization degree is higher, it can lead to higher shrinkage.

POM injection molding is the process of producing plastic products by injecting liquid POM into a mold via an injection molding machine. The injection molding process for POM is similar to that of other plastics, with specific technical and temperature requirements to suit this material. This process creates complex plastic parts with high precision, commonly used in mass production.

1.Material preparation: The POM plastic is dried before being fed into the machine to avoid moisture-related issues during melting. POM is dried at 80 °C for about 2-4 hours. Then, it is melted in the machine's chamber.
2.Injection into the mold: The molten POM at a temperature of 175 °C is injected into the mold under high pressure, typically ranging from 800 to 1200 bar, filling the entire cavity.
3.Cooling: After the POM is injected into the mold, the cooling process occurs to solidify the plastic and maintain its shape. Cooling is crucial as the shrinkage rate of POM is around 2%. Therefore, precision in size design must be considered.
4.Product removal: The finished product is removed from the mold manually or automatically, and if necessary, additional processing such as cutting or surface finishing may be applied.
5.Finishing treatment: In some cases, if the injection mold has not been processed or minor errors occur during molding, the product may still have some defects that need trimming for aesthetic appeal. However, the surface quality and dimensional accuracy of POM typically reduce the need for this finishing step.

Fatigue Resistance
POM has excellent fatigue resistance and can be used in applications that have multiple load/unload cycles, such as gears. Homopolymer POM has greater fatigue strength than copolymer POM.

Creep Resistance
Injection molded POM has good resistance to creep, the tendency of a solid material to undergo slow deformation when subjected to persistent mechanical stresses. POM can also be subjected to long-term loading with minimal permanent deformation.

High Strength
POM plastics have excellent mechanical properties for rigidity, tensile strength, and flexural strength - but homopolymer acetals have better mechanical properties. Applications for high-strength POM include conveyor belts and safety restraints.

Low Friction
POM has excellent lubricity because of its low coefficient of friction, so this engineering thermoplastic is ideal for applications where there's exposure to sliding friction. Injection molded POM also has good resistance to wear, aka the ability of a material to resist the progressive loss of surface volume due to mechanical actions (such as repeated rubbing).

Food Safe
Injection molded POM products can be made of grades that are rated as food safe in accordance with FDA, USDA, NSF, Canada AG, or 3-A Dairy material standards. Applications include injection molded plastic parts for food processing equipment.

Dimensional Stability
Although POM has a relatively high shrinkage rate during injection molding, this plastic provides excellent dimensional stability once parts have cooled. This enables injection molded POM to retain its form and maintain its tolerances in demanding applications.

Corrosion Resistance
Because POM plastic resists most fuels and solvents, it's often used to mold fuel tanks and chemical storage tanks. POM can be damaged by phenols, however, and it doesn't resist strong acids and bases.

Heat Resistance
Injection molded POM can withstand continuous service temperatures up to 105°C. Homopolymer POM has higher instantaneous heat resistance and copolymer POM has a better long-term thermal resistance. POM plastic is flammable, however, and it won't self-extinguish once it's ignited.

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