Professional CNC Milling of White POM Parts: Precision Solutions for Engineering Plastics

In industrial applications that demand high strength, low friction, and high dimensional stability, POM (Polyoxymethylene) plastic stands out as an ideal metal replacement due to its exceptional comprehensive properties. Especially for precision parts requiring self-lubrication, fatigue resistance, and excellent insulation, white POM not only offers a clean and aesthetically pleasing appearance but also meets rigorous engineering requirements. However, POM material is prone to generating internal stress during machining. Inappropriate processes can lead to part warping, dimensional instability, or surface quality defects.

We specialize in providing customized CNC milling solutions for white POM parts to global industrial clients. Through the deep integration of material science, precision machining technology, and post-processing techniques, we ensure every part meets stringent mechanical performance and dimensional stability standards while maintaining an attractive appearance. Our parts are widely used in medical devices, food processing equipment, precision transmission systems, and the electronics industry.

Core Technological Breakthrough Overcoming POM Machining Challenges to Balance Performance and Precision

The core of producing high-quality POM parts lies in understanding and controlling its unique material characteristics:

• Internal Stress Management: While POM is prone to internal stress in injection molding, CNC milling from solid blanks fundamentally avoids this issue. Nonetheless, we further minimize machining stress through optimized tool paths and cutting parameters to ensure long-term dimensional stability of the parts.
• Moisture Absorption Control: POM has low moisture absorption but is still slightly hygroscopic. We strictly control raw material storage and the machining environment. For critical applications, we perform appropriate conditioning treatments to prevent dimensional changes in the use environment.
• Thermal Deformation Control: POM has poor thermal conductivity, causing heat to easily accumulate during machining. We employ specialized cooling strategies (such as compressed air cooling) and sharp tools to prevent dimensional deviations and surface melting caused by material overheating and softening.
• White Aesthetic Preservation: White POM easily shows stains and machining marks. We implement full-process cleanliness control from material selection to machining, cleaning, and packaging, ensuring delivered parts retain a pristine white appearance.

Key Insight: Our production data analysis indicates that over 70% of POM part dimensional instability issues stem from overheating due to tool wear or failure to account for POM's different thermal expansion coefficient compared to metal. We address these issues through strict tool management systems and material-based temperature compensation programming.

Integrated Manufacturing Process Flow Optimized for POM

We employ a proven process chain specifically optimized for the characteristics of white POM.

2.1 Precision CNC Milling: Low-Temperature, High-Efficiency Forming

• Specialized Tooling Strategy: We use sharp, polished high-speed steel or carbide end mills with large helix angles to ensure smooth chip evacuation and avoid surface scorching from chip re-cutting. We strictly enforce tool life monitoring, replacing tools before sharpness degrades.
• Machining Parameter Optimization (for White POM):

  1. High spindle speed, medium-to-low feed rate: Employing a small feed per tooth (e.g., 0.03-0.08mm) and a higher spindle speed achieves shear cutting, reducing heat generation.

  2. Moderate depth of cut: Axial depth is typically no more than 1-2 times the tool diameter, with a small radial depth of cut (stepover) to control cutting forces.

  3. Compressed air cooling: Continuous, dry compressed air blowing effectively removes heat and clears chips, avoiding potential contamination or material property changes from water-based coolants.

• Key Point: Programming utilizes climb milling, and tool paths are optimized to reduce non-cutting moves and abrupt direction changes, thereby achieving better surface finish and dimensional consistency.

2.2 Professional Deburring and Edge Treatment

Leveraging POM's good toughness, we employ fine manual scraping, low-temperature tumbling, or specialized plastic deburring equipment. For parts with extremely high requirements, cryogenic deflashing technology can be used to achieve perfect, uniform edge rounding (e.g., R0.1-R0.3) without any residual burrs.

2.3 Stress Relief and Dimensional Stabilization Treatment (Available on Request)

For parts operating over a wide temperature range or requiring extremely high dimensional stability, we offer professional heat treatment (annealing) services. Through precisely controlled heating, soaking, and slow cooling processes, machining-induced internal stress is effectively eliminated, minimizing subsequent dimensional changes in the part.

2.4 Cleaning and Packaging

Final cleaning is performed in a separate cleanroom, using specialized cleaners and ultrapure water or isopropyl alcohol to ensure removal of all oils and particulates. Anti-static, dust-free vacuum-sealed or cleanroom packaging is used to prevent contamination during transport and storage.

Typical Application Areas

• Medical Devices and Diagnostic Equipment: Gears, pump bodies, sliders, housings for drug delivery devices (following ISO 13485 guidelines, biocompatible-grade POM materials available).
• Food and Beverage Processing Equipment: FDA-compliant bearings, bushings, valve components, conveyor chain links, offering both fatigue resistance and chemical resistance.
• Precision Transmission and Automation: Lightweight gears, cams, links, timing belt pulleys, providing low-noise, self-lubricating operation.
• Electronics and Electrical Insulation: Bobbins, insulating spacers, connector housings, test fixtures, utilizing its excellent dielectric strength and low moisture absorption.
• Fluid Handling Systems: Chemically resistant valve seats, sealing gaskets, flow meter components.

Value and Quality Control Considerations

Value Proposition:

• Metal Replacement: Significant weight reduction, lower operational inertia, no need for additional lubrication (self-lubricating), reducing system complexity and maintenance costs.
• Performance-to-Cost Ratio: In applications requiring fatigue resistance, creep resistance, and low friction, POM offers higher overall value compared to many engineering plastics and some metals.
• Design Freedom: CNC milling enables rapid realization of complex geometries, suitable for prototypes and production runs with low volumes and high complexity.

Core Quality Checkpoints:

• Raw Material Verification: Material certification (compliance with FDA, USP Class VI, etc.), color batch consistency.
• Post-Machining Inspection: Full dimensional inspection via Coordinate Measuring Machine (CMM), focusing on flatness of thin-walled areas and key mating dimensions.
• Surface and Appearance: Visual inspection of surface finish, scorching, scratches; quantitative measurement using a surface roughness tester.
• Functional Testing (Optional): Friction coefficient testing, dimensional stability thermal cycling tests.

Frequently Asked Questions (FAQ)

Q1: Is there a performance difference between white POM and other colors (like black) POM?
A1: The fundamental mechanical properties (strength, stiffness) are primarily determined by the resin itself, with minimal influence from color additives. However, black POM typically uses carbon black for coloring, which offers some conductivity and lubricity, potentially resulting in slight differences in anti-static properties and wear resistance. White POM usually employs inorganic pigments, offering more stable and pure color, but may have slightly lower UV stability compared to black grades containing carbon black. The key is selection based on the application's aesthetic and secondary performance needs.

Q2: What are the advantages and disadvantages of CNC-milled POM parts compared to injection-molded POM parts?
A2:

• CNC Milling Advantages: No mold costs, extremely short lead times, suitable for prototypes and small-batch production; material is solid blank, offering isotropic mechanical properties and no weld line weaknesses; capable of machining highly complex geometries with flexible design changes.
• Injection Molding Advantages: Extremely low per-part cost for high-volume production; efficient for molding parts with complex textures or hollow structures.
• Conclusion: For production quantities below several hundred to a thousand pieces, or applications with extremely high requirements for part consistency, absence of internal stress, and high strength, CNC milling is the superior choice.

Q3: What tolerances and surface finish can your POM parts achieve?
A3: Thanks to POM's excellent machining stability and our process control:

• Standard Tolerances: For medium-sized parts (<100mm), linear tolerances can be consistently achieved at ±0.05 mm, with key features reaching ±0.025 mm.
• Surface Finish: Through finish machining, surface roughness Ra values can reach 0.8 μm or better, presenting a fine matte or slight gloss effect.
• Note: Since POM's coefficient of thermal expansion is higher than that of metals, the difference between operating and ambient temperatures should be considered when designing tolerances.

Our Machining and Processing Capabilities

• Precision Forming: 3-axis and 5-axis CNC milling, high-speed machining centers, suitable for complex contours and thin-walled structures.
• Secondary Processing:

  1. Professional Deburring: Manual, tumbling, cryogenic deflashing.

  2. Heat Treatment: Dimensional stabilization annealing.

  3. Surface Treatment: Precision polishing, sandblasting (to achieve a uniform matte surface).

• Cleaning and Packaging: Cleanroom cleaning, anti-static vacuum packaging.

Common Material Specifications

• POM-C (Copolymer): Better dimensional stability and alkali resistance.
• POM-H (Homopolymer): Higher mechanical strength and stiffness, better fatigue resistance.
• Compliant Grades: Provide medical/food-grade white POM materials compliant with standards such as FDA 21 CFR 177.2470, USP Class VI, EU 10/2011.

Typical Machining Capability Reference

• Standard Machining Tolerance: ±0.05 mm
• Finish Machining Tolerance: Up to ±0.025 mm (depending on feature)
• Surface Roughness: Ra 0.8 μm (standard), Ra 0.4 μm (finish machined)

Quality System
ISO 9001:2015 Quality Management System. Can follow medical device production-related quality control guidelines per customer requirements.

Disclaimer: The process parameters and performance described herein are based on production experience with standard white POM-C/H materials under controlled conditions. Optimal methods and parameters may vary depending on specific part geometry, material grade, machining equipment, and final application environment. Comprehensive prototype testing and material validation are strongly recommended prior to volume production to ensure product suitability for the specific application. All performance data should be confirmed through actual testing.