POM injection molding is a favored choice for manufacturing high-quality POM parts. In this article, we explore the key properties of POM material and essential aspects of the injection molding process.
What Is POM Plastic?
POM is a crystalline engineering thermoplastic that boasts a combination of strength, stiffness, and dimensional stability. Key properties of POM include low friction, excellent wear resistance, and chemical resistance to fuels, solvents, and mild acids. It offers thermal stability up to 100–120°C. However, due to its high crystallinity, POM exhibits a shrinkage rate of 1.8–3.5%. In addition, POM is sensitive to strong acids, alkalis, and UV radiation. It typically falls into two major categories: homopolymer and copolymer. Homopolymer POM offers superior tensile strength (up to 72 MPa) and stiffness. Copolymer POM excels in thermal stability and chemical resistance, particularly against alkalis and hot water.
Advantages of POM Injection Molding
POM’s unique properties deliver a suite of advantages, making POM plastic injection molding ideal for demanding applications.
- Fatigue Resistance: POM exhibits exceptional fatigue resistance, enduring multiple load/unload cycles without failure. Homopolymer POM offers higher fatigue strength compared to copolymers.
- Creep Resistance: POM injection molding produces parts with excellent resistance to creep, the slow deformation under persistent mechanical stress. This allows POM to withstand long-term loading with minimal permanent deformation.
- High Strength: POM boasts outstanding mechanical properties, including high rigidity, tensile strength (up to 72 MPa), and flexural strength. Homopolymer POM is better than copolymers in these properties.
- Low Friction: With a low coefficient of friction, POM’s lubricity is excellent, reducing wear in sliding applications.
- Food Safety: Certain POM grades comply with FDA standards, making POM plastic injection molding suitable for food processing equipment.
- Dimensional Stability: Despite a high shrinkage rate (1.8–3.5%) during molding, POM maintains excellent dimensional stability post-cooling.
- Corrosion Resistance: POM resists most fuels and solvents, making it a top choice for molding fuel tanks and chemical storage components.
- Heat Resistance: POM injection parts withstand continuous service temperatures up to 105°C. Homopolymers offer higher instantaneous heat resistance, while copolymers provide better long-term thermal stability.
POM Injection Molding Service
POM Injection Molding Process
The POM injection molded process involves several meticulous steps, each critical to part quality and consistent production.
- Material Preparation: While POM typically shows low moisture absorption, drying at 80-100°C for 2-4 hours before processing to eliminate moisture helps prevent hydrolytic degradation and surface defects during molding.
- Machine and Mold Setup: The injection molding machine must be set with precision, typically maintaining barrel temperatures between 190-230°C for homopolymers and 190-210°C for copolymers. Mold temperatures usually range from 80 to 100°C, optimized for part geometry and wall thickness.
- Melting: The dried POM is fed into the injection molding machine’s barrel, heated to 190–230°C for homopolymers or 190–210°C for copolymers.
- Injection: Molten POM is injected into the mold. Back pressure should be minimal to maintain melt integrity.
- Cooling and Solidification: After filling, the mold cools the part to solidify the resin while controlling shrinkage.
- Ejection and Finishing: Once solidified, parts are ejected using pins. POM’s smooth surface finish often requires minimal post-processing.
Important Precautions for POM Injection Molding
While POM injection offers numerous benefits, it comes with challenges that require careful attention to ensure quality and safety. Below are critical precautions for POM plastic injection molding:
- Temperature Control: Exceeding 230°C risks thermal degradation, releasing toxic formaldehyde gas. Maintain barrel temperatures at 190–230°C and monitor closely to avoid hazards.
- Shrinkage Management: POM’s high shrinkage rate (1.8–3.5%) demands precise mold design. Incorporate uniform cooling channels (8–12 mm wide) and draft angles (1–5°) to prevent warpage and ensure easy ejection.
- Mold Material: Use wear-resistant materials like P20 or H13 steel to withstand POM’s abrasiveness.
- Injection Parameters: Medium-fast injection speeds and pressures (40–130 MPa) prevent defects like ripples or voids. Back pressure should be minimal to reduce melt degradation. Adjust based on part thickness for optimal results.
- Material Handling: Clean the barrel with polyethylene (PE) or polypropylene (PP) before and after processing to avoid contamination.
Applications of POM Injection Molding
POM’s mechanical properties and reliability make it popular in various industrial applications:
Automotive: Components such as fuel system parts, interior trims, gears, and safety restraints.
Medical: Surgical instruments, insulin pens, and drug delivery systems.
Industrial: Conveyor belts, valves, pump housings, and fittings
Consumer Goods: From zippers to appliance components like washing machine agitators.
Electronics: Gears, bearings, and connectors.
Choose Zhongde for POM Injection Molding
Although the POM injection molding process has many challenges, working with an experienced manufacturer can help avoid these problems. Zhongde’s advanced facilities and expert engineers deliver tailored solutions for even the most complex injection molding plastics projects. Whether it is intricate gears or robust fuel system parts, Zhongde’s customized solutions ensure success. Contact Zhongde today to get tailored POM injection molding solutions for your project.
