Views: 0 Author: Site Editor Publish Time: 2025-08-02 Origin: Site
Table of Contents |
1. What is POM |
2. Key Properties of POM Plastic |
3. Advantages and disadvantages of POM Injection Molding |
4. Applications Of POM Injection Molding |
5. POM Injection Molding Design Guidelines |
6. Factors To Consider During POM Injection Molding Process |
7. Succeeding With POM Injection Molding |
In the world of precision plastic parts, POM (Polyoxymethylene)—also known as acetal or Delrin—is a highly versatile engineering thermoplastic. Renowned for its excellent dimensional stability, low friction, and high mechanical strength, POM is a top choice for producing durable and complex injection molded components. Whether you're manufacturing automotive gears, electronic connectors, or consumer product housings, understanding the characteristics and molding behavior of POM is essential to achieving optimal product performance and manufacturing efficiency.
At Alpine Mold, with over 23 years of experience in plastic injection mold manufacturing, we’ve worked extensively with POM across a wide range of industries. In this article, we’ll walk you through everything you need to know about POM injection molding—from material properties and design tips to processing considerations and real-world applications—so you can make informed decisions for your next plastic product.
POM (Polyoxymethylene), also called acetal or Delrin, is a high-performance engineering plastic known for its strength, stiffness, and wear resistance. It is widely used in POM injection molding to produce precise and durable plastic components.
There are two main types of POM: homopolymer (offering higher strength and stiffness) and copolymer (providing better thermal and chemical resistance). Due to its excellent mechanical properties, POM injection molding is commonly applied in automotive, electronics, and industrial products and more.
POM (Polyoxymethylene), also known as acetal or polyacetal, is widely recognized in plastic injection molding for its outstanding balance of mechanical performance and processing efficiency. As a semi-crystalline thermoplastic, POM resin exhibits several critical properties that make it a preferred POM molding material in high-precision applications.
POM offers a high modulus of elasticity and excellent tensile strength, giving POM plastic molded parts superior rigidity even under mechanical stress. This makes it ideal for load-bearing applications that require dimensional stability over time.
One of POM’s defining properties is its naturally low coefficient of friction. This makes it suitable for POM injection molded components used in dynamic environments such as gears, sliders, and bearings where smooth motion and wear resistance are essential.
Thanks to its low moisture absorption and controlled crystallinity, POM resin maintains consistent part geometry during and after the POM plastic molding process. This is crucial for producing components that require tight tolerances.
POM resists many fuels, solvents, and lubricants, making it a suitable POM molding material for use in automotive fuel systems, plumbing parts, and electrical housings.
With a melting point of approximately 175°C, POM maintains its mechanical integrity under moderate thermal loads, allowing it to perform reliably in under-the-hood automotive and industrial environments.
POM is naturally insulating, making it suitable for POM injection molding of electrical components and connectors requiring strong dielectric properties.
The POM injection molding process is widely favored for producing high-precision, high-performance plastic components, particularly in applications that demand excellent dimensional stability and low friction. However, like any engineering material, POM (Polyoxymethylene) comes with its own set of strengths and limitations during molding.
Excellent Moldability: POM offers good flow characteristics and low melt viscosity, making it suitable for complex geometries and tight-tolerance parts in high-volume POM molding production.
High Dimensional Accuracy: The material maintains excellent shape stability after molding, making POM molded parts ideal for precision components like gears, bearings, and housings.
Low Friction & Wear Resistance: Ideal for moving or sliding parts, POM injection molded components exhibit long-term performance in mechanical systems without the need for lubrication.
Fast Cycle Times: The thermal properties of POM allow for shorter cooling times, contributing to efficient, cost-effective POM injection molding in mass production.
Chemical & Fuel Resistance: POM resists a wide range of solvents, fuels, and oils, which enhances its durability in automotive, industrial, and consumer electronics applications.
Disadvantages
Thermal Sensitivity: POM is sensitive to high processing temperatures and can degrade if held too long in the barrel, requiring precise thermal control during the injection molding process.
Poor UV Resistance: Standard POM grades degrade under long-term UV exposure unless stabilized, limiting their use in outdoor applications without additives.
Limited Bonding & Paintability: POM’s low surface energy makes it difficult to bond, print, or paint without special surface treatment.
High Shrinkage Rate: Compared to other engineering plastics, POM can exhibit noticeable shrinkage during cooling, which must be accounted for in mold design.
Potential Formaldehyde Emission: Degraded POM can release formaldehyde gas, requiring proper ventilation and thermal stability management during molding.
Thanks to its strength, dimensional stability, and low friction properties, POM plastic molding is widely used to produce durable, high-precision components across various industries. Below are the main application areas of POM injection molding:
Fuel system housings, door lock covers, window lift gear shells, windshield wiper motor housings, headlight adjustment gearboxes, air duct connectors, steering column shrouds, interior trim clip casings, exterior mirror gear enclosures, and more.
Printer gear covers, electrical connector housings, switch enclosures, laptop hinge shells, camera gear modules, cooling fan blade bases, headphone joint parts, optical drive gear housings, and more.
Bearing housings, bushing sleeves, roller frames, conveyor guide shells, sensor housing units, sprocket covers, timing gear enclosures, cable routing blocks, and more.
Inhaler bodies, surgical handle housings, blood analyzer gear shells, insulin pump covers, diagnostic device clips, infusion set connectors, dental tool handles, catheter control unit covers, and more.
Coffee machine gearboxes, dishwasher spray arm brackets, blender gear housings, mixer drive covers, curtain rail sliders, vacuum cleaner gear modules, electric fan bearings, washing machine latch enclosures, and more.
Sliding door track covers, window lock shells, cabinet hinge arms, drawer runner housings, adjustable foot gliders, curtain track brackets, door handle gearboxes, and more.
To ensure optimal part quality, durability, and processing efficiency, POM injection molding must follow strict design principles tailored to its unique material characteristics. Acetal resins like POM have excellent dimensional stability and machinability, but achieving consistent results still requires careful attention to wall thickness, flow behavior, draft angles, gate types, and venting.
Maintain a uniform wall thickness between 0.8–3.0 mm for optimal POM injection molding performance.
Below 0.8 mm: High risk of short shots, flow hesitation, and poor filling.
Above 3.0 mm: Likely to cause sink marks, internal voids, and residual stress.
Uneven thickness: Can lead to warpage and dimensional instability during cooling.
Best practice: Keep wall thickness variation within ±10% across the part to ensure consistent flow and reduce cooling defects.
For standard vertical walls, a draft angle of 0.5° to 1.5° per side is recommended to ensure smooth ejection and minimize surface stress.
For textured surfaces, increase the draft angle to 2.0°–3.0°, depending on the texture depth and the required ejection force, to avoid drag marks or surface defects.
In cases involving deep cavities or long core features, increasing the draft angle helps prevent scuffing and reduces the risk of sticking during ejection.
To enhance part strength and manufacturability in POM injection molding, consider the following design guidelines:
Thickness: Limit rib thickness to 40%–60% of the nominal wall thickness to avoid sink marks.
Height: Should not exceed 3× the wall thickness to maintain structural integrity without causing flow issues.
Support: Reinforce bosses with gussets to prevent deformation during molding or use.
Fillet Radius: Apply 0.25–0.5 mm fillets at the base of the boss to reduce stress concentration.
Spacing: Maintain a minimum distance of 2× wall thickness between the boss and adjacent walls to ensure proper material flow and filling.
Proper rib and boss design not only improves strength but also helps prevent common defects like warping, sink marks, and short shots in POM parts.
Sharp corners should be avoided in POM injection molding designs to minimize stress concentrations that can lead to cracking or premature part failure.
Internal radii: Recommended minimum of 0.6 mm to facilitate smooth melt flow and reduce flow hesitation.
External radii: Ideally matched to the wall thickness or at least 1.0 mm for a smooth transition, enhancing structural strength and appearance.
Incorporating well-designed radii and fillets not only improves mold filling but also enhances the mechanical performance and durability of the finished part.
Proper gate type, size, and placement are essential for achieving consistent part quality in POM injection molding. Gate design should ensure balanced flow, reduce weld lines, and support clean part separation.
Recommended Gate Thickness (based on part geometry):
Thin-wall parts (≤ 1.2 mm wall): 0.6–1.0 mm
Medium-wall parts (1.2–2.5 mm): 1.0–1.5 mm
Thick-wall parts (≥ 2.5 mm): 1.5–2.0 mm
Common Gate Types:
Submarine (tunnel) gates – Ideal for automatic degating and aesthetic surfaces
Edge gates – Suitable for large or thick-walled components
Pin-point gates – Best for small, high-precision parts with minimal gate vestige
POM can release formaldehyde gas when exposed to excessive heat or degradation, making effective venting essential during injection molding. Proper venting helps prevent defects such as gas entrapment, burn marks, and short shots, while also protecting mold components from corrosion.
Recommended vent depth: 0.015–0.025 mm
Vent width: 3.0–6.0 mm, sufficient to allow trapped gases to escape without flash formation
Critical venting zones: near weld lines, flow ends, deep ribs, and complex cavity areas
Ensuring adequate venting in these areas facilitates smoother melt flow, reduces internal stresses, and improves overall surface finish.
POM exhibits relatively low and consistent shrinkage rates, which vary based on part geometry, wall thickness, and processing parameters. Typical shrinkage ranges are:
Unfilled POM: approximately 1.8% to 2.2%
Glass-filled POM grades: reduced shrinkage of about 0.8% to 1.2%, with anisotropic behavior influenced by flow direction
Mold design must factor in material grade, flow orientation, and processing temperature.
Thanks to POM's excellent dimensional stability and low shrinkage variation, it is well-suited for manufacturing precision parts with tight tolerances.
For standard molded components, dimensional tolerances of ±0.05 mm can typically be achieved with proper mold design and process control.
For critical applications such as gears or sealing components, post-molding machining can be applied to reach tolerances of ±0.01–0.02 mm.
To ensure dimensional consistency, it is essential to use uniform wall thickness, optimized gate design, and controlled molding conditions (e.g., mold temperature and cooling rate).
As an ISO-certified POM Injection Mold factory, we leverage 23 years of process mastery to navigate these critical parameters.
Process Parameter |
Technical Specification |
Industry Insights from POM Mold Experts |
Material Pre-Treatment |
• Drying: 80-90°C for 2-3 hrs (≤0.2% moisture) |
POM absorbs moisture slowly but requires drying to prevent silver streaks – a key checkpoint in professional POM Injection Molding |
Melt Temperature |
190-215°C |
Thermal degradation occurs rapidly above 220°C. Our PIM factory uses multi-zone PID controls to avoid localized overheating |
Mold Temperature |
80-120°C |
Higher mold temps (≥100°C) enhance crystallinity for better mechanical properties – critical for precision POM molded components |
Injection Speed |
Medium-High |
Fast injection minimizes flow marks but requires balanced gate design to avoid jetting |
Holding Pressure |
40-70% of injection pressure |
Over-packing causes internal stress; under-packing increases shrinkage. Our POM Injection Mold factory optimizes via cavity pressure sensors |
Cooling Time |
15-60 sec/mm thickness |
Extended cooling reduces warpage but impacts cycle efficiency – requires scientific mold cooling layout |
Screw Design |
• L/D: 18-22:1 |
Shallow-flight screws prevent shear-induced degradation during plasticizing |
Venting Strategy |
• Depth: 0.015-0.03 mm |
Inadequate venting causes diesel effect (burn marks) – our PIM factory uses simulation to optimize vent placement |
Post-Molding Handling |
• Annealing: 120-160°C (for stress relief) |
Stress cracking can occur 24-48 hrs after molding without proper conditioning |
To achieve consistent, high-quality results with POM injection molding, manufacturers must understand the material’s unique behavior, follow strict design guidelines, and control every aspect of the molding process. From selecting the right POM grade to managing wall thickness, shrinkage, and gate design—each detail affects the final part’s performance and reliability.
With 23 years of professional experience, Alpine Mold delivers comprehensive solutions for POM plastic injection molding—from custom mold design to precise, high-quality production. As a trusted POM injection mold company, we specialize in manufacturing tight-tolerance parts, managing complex geometries, and maintaining consistent quality. If you seek a reliable POM injection molding manufacturer, Alpine Mold is your dedicated partner, committed to turning your high-performance part concepts into reality. Contact us to get a quote today!
