POM Injection Molding

What is POM Injection Molding Material?

POM (Polyoxymethylene), commonly known as acetal or Delrin®, is a high-performance engineering thermoplastic renowned for its exceptional mechanical properties. This semi-crystalline polymer comes in two main variants:

Homopolymer (POM-H) – Higher mechanical strength
Copolymer (POM-C) – Better chemical/thermal stability

Key Characteristics of POM:

Outstanding stiffness and dimensional stability
Low friction coefficient (self-lubricating)
Excellent fatigue and creep resistance
Good chemical resistance to solvents and fuels
High crystallinity (70-80%) leading to sharp melting point

Why is POM So Commonly Used?

POM dominates precision engineering applications due to its unique combination of properties:

Metal Replacement – Frequently substitutes for zinc/aluminum in gears and bearings
Wear Resistance – Performs better than nylon in continuous friction applications
Dimensional Precision – Minimal post-molding shrinkage (1.8-2.5%)
Cost Efficiency – More affordable than PEEK while offering similar mechanical performance

Typical Applications Include:

Automotive: Fuel system components, door locks
Industrial: Gear wheels, conveyor belt parts
Consumer: Zippers, pen clips
Medical: Metered-dose inhaler components

Is POM Toxic or Harmless?

POM presents some important safety considerations:

Processing Concerns:

Releases formaldehyde gas when overheated (>230°C)
Requires adequate ventilation during molding

Final Product Safety:

Biocompatible grades available for medical use
FDA-compliant versions for food contact applications
Non-toxic in solid state at room temperature

Important Note: Avoid using POM in applications involving strong acids or chlorine exposure.

POM Injection Molding Process Conditions

Parameter	Recommended Value	Critical Notes
Drying	2-3 hrs at 80-100°C	Must reach <0.2% moisture
Melt Temperature	190-210°C (POM-C)	Homopolymers need 200-230°C
Mold Temperature	80-120°C	Higher temps reduce shrinkage
Injection Speed	Fast	Prevents premature solidification
Hold Pressure	60-80% injection pressure	Critical for dimensional control
Cooling Time	20-40 sec/mm wall thickness	Insufficient cooling causes warpage

Processing Tips for POM Injection Molding:

Use Hot Runner Systems – Prevents material stagnation
Maintain Sharp Transitions – Avoid flow-restricting designs
Post-Mold Annealing – Heat to 160°C for 30 min to relieve stresses
Avoid Overpacking – Can lead to excessive internal stresses

POM injection molding delivers unparalleled precision for high-wear, high-precision components. While requiring careful temperature control to prevent degradation, its exceptional mechanical properties and dimensional stability make it indispensable for moving parts across industries. For applications demanding higher thermal resistance, consider POM composites with PTFE or glass fiber reinforcement.

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