Gear material selection impacts everything from torque capacity to noise levels, and POM (polyoxymethylene) offers unique advantages that metal gears can’t match. Understanding when to choose POM over traditional metal materials can solve noise, weight, and corrosion challenges that would be costly or impossible to address with steel or aluminum alone.
Use POM gears for quiet, low-maintenance applications under 100 Nm torque and 100°C. Best for precision instruments, medical devices, and consumer electronics where noise reduction and corrosion resistance outweigh maximum strength requirements.
Compare POM and steel for gear torque, temperature, and chemical resistance—plus when the trade-offs justify switching from metal to plastic gearing.
Table of Contents
When should I choose POM over metal for gears?
Choose POM when quiet operation, corrosion resistance, and maintenance-free performance outweigh maximum torque capacity. POM gears handle significantly lower torque than steel but eliminate lubrication requirements, reduce noise by 15-20 dB, and weigh 85% less. Best for precision instruments, medical devices, and consumer electronics where noise and maintenance matter more than raw strength.
Quick Decision Checklist:
- Noise requirements critical → POM reduces gear noise by 15-20 dB
- Limited maintenance access → POM eliminates lubrication schedules
- Chemical exposure present → POM resists acids, solvents, and corrosion
- Weight savings needed → POM weighs 85% less than steel equivalents
From our machining experience, engineers often over-specify steel when POM meets functional requirements at lower total cost. POM’s inherently low coefficient of friction (typically 0.1-0.3 against steel) provides natural lubrication, eliminating maintenance that makes steel expensive over time. We’ve specified POM for medical devices where chemical compatibility prevented corrosion, and audio equipment where noise reduction was critical.
Glass-fiber reinforced POM increases load capacity by 50% when bridging toward steel performance. However, avoid POM for high-shock applications, temperatures above 100°C, or safety-critical mechanisms.
Cost reality: POM costs 40% more upfront but saves 60% over 5 years through eliminated maintenance and reduced assembly complexity.
Design Takeaway: Specify POM when noise, weight, or maintenance drive requirements. Reserve steel only for applications genuinely requiring maximum torque where POM’s benefits don’t justify the strength trade-off.
What torque can POM gears handle vs steel?
POM gears handle 20-30% of steel gear torque capacity for equivalent sizes, but torque limits vary significantly by module and tooth count. Module 1, 16T POM gears: 0.2 Nm capacity. Steel equivalent: 0.8-1.5 Nm depending on grade. Use this 4:1 ratio as initial sizing guidance.
Quick Sizing: Required torque under 5 Nm → POM suitable | 5-20 Nm → Glass-filled POM | Above 20 Nm → Steel required
We’ve machined 500+ gear sets where engineers initially spec’d steel at 15 Nm but POM at 25 Nm proved more cost-effective. Glass-fiber reinforced POM increases load capacity by 50%, bridging mid-range applications. Recent medical device project: switched from M2 steel gear (8 Nm) to M3 POM gear (6 Nm capacity) – 40% cost reduction including eliminated lubrication system.
POM endured the highest cycle numbers compared to other thermoplastic gears in durability testing, with gradual wear patterns versus steel’s sudden fracture failure mode. Standard POM gear life reaches 10⁶ cycles at 50% rated torque, making reliability predictable for maintenance scheduling.
Design Takeaway: Use 25-30% steel torque as POM sizing guideline. Verify with supplier calculations for your specific module and application duty cycle.
What temperature limits should I consider for POM gears?
Continuous POM gear operation: 100°C maximum. Brief spikes: 120°C limit. Below -40°C: brittleness risk. Long-term operating temperature range of POM is -50°C to 100°C. Above 100°C, expect 50% life reduction per 10°C increase.
Temperature Rule: Under 80°C → Full performance | 80-100°C → Reduce load 25% | Above 100°C → Steel required
From automotive projects, we’ve seen POM gears fail at 110°C in transmission applications – teeth wore 300% faster than predicted. Medical device success at 37°C body temperature shows zero maintenance over 5-year device life. Above 100°C, POM exhibits increased creep and reduced dimensional stability, while self-lubrication properties degrade rapidly beyond this threshold.
Critical consideration: thermal cycling within ±40°C range causes 0.1mm dimensional shift on 50mm gears, affecting backlash control. We recommend temperature sensors in applications approaching 90°C operating temperature to prevent unexpected failures.
Design Takeaway: Budget thermal management if ambient exceeds 60°C. Install temperature monitoring in critical applications approaching design limits.
What tolerances can POM gears achieve?
POM CNC machining holds ±0.01 mm on critical features, ±0.05 mm standard production tolerances. High-precision operations achieve ±0.005 mm under controlled conditions. Achievable tolerances match steel for most gear applications under 100mm diameter.
Tolerance Guide: Non-critical → ±0.05 mm | Mating surfaces → ±0.01 mm | Ultra-precision → ±0.005 mm (3x cost)
We machine POM gears to ±0.008 mm for precision instruments – equivalent accuracy to ground steel at 60% lower total cost. POM’s very low coefficient of thermal expansion (10.5 x 10^-5/°C) enables tight tolerance parts that maintain precision across temperature variations where steel gears require compensation.
Machining reality: setup time doubles for ±0.01 mm features, but tool wear remains minimal due to POM’s excellent machinability. Each tolerance tightening from ±0.05 mm to ±0.01 mm adds 25% to machining cost, making selective tolerancing critical for cost control.
Design Takeaway: Specify ±0.01 mm only where backlash control demands it. Standard ±0.05 mm tolerances cost 40% less while maintaining functional performance.
Need precision POM gears fast?
Tight tolerance machining available • Material + cost feedback in 24h
Does POM gear machining cost more than metal?
POM gear machining costs 50-90% less than steel gear machining due to eliminated secondary operations. Plastic gears made of rubber in general do not require secondary processing, so the cost is 50% to 90% lower than stamped parts and machined metal gears. No heat treatment, grinding, or surface coatings required.
Cost Decision Matrix: Project budget tight → Choose POM | Volume above 1000 pieces → POM advantage increases | Custom tooling needed → Steel may be competitive
Authority-Based Cost Analysis:
- Heat treatment elimination: Steel requires 1400°F carburizing per ASTM A304
- Grinding elimination: Steel gears need Ra 0.8 μm finish per ISO 1328
- Surface treatment elimination: Corrosion resistance without zinc plating per ASTM B633
We’ve machined 200+ gear sets where POM eliminated heat treatment cycles entirely. Aerospace project: POM gears avoided expensive AS9100-compliant heat treatment documentation, saving 3 weeks lead time. Cost-Effectiveness: Relatively cheap compared to other engineering plastics, thus offering good value for money spent on performance.
Manufacturing reality: POM machines at 300 SFM vs steel at 150 SFM, doubling productivity. Single-pass finishing vs steel’s rough-finish-grind sequence cuts cycle time 60%.
Design Takeaway: Calculate total project cost including lead time and secondary operations. POM typically wins unless torque requirements force impractical gear sizing.
How much noise reduction do POM gears provide?
POM gears reduce noise and vibration by 10-15% versus steel in identical applications. A significant improvement of 10% to 15% lower noise and lower vibration is achieved using polymer planet gears instead of metallic planet gears . Steel against steel generates up to three times as much noise than does steel against plastic.
Noise Threshold Decision: Current noise above 60 dB → POM provides significant benefit | 45-60 dB → Moderate improvement | Below 45 dB → Minimal perceptible difference
Measured Acoustic Performance:
- The difference is as much as 9 dB between steel-steel vs steel-plastic combinations
- Frequency spectrum: POM eliminates high-frequency gear whine at 2-8 kHz range
- Vibration damping: softer material provides a higher damping factor, making plastic gears quieter than metal gears
Paper mill case study: Replaced steel pinion gears with PA6G – the noise disappeared, and one could stand next to the machine during operation. Home healthcare bed manufacturer switched to acetal gears and significantly reduced operating noise per DuPont case study.
Design Takeaway: Measure baseline noise with calibrated sound meter before specifying POM. Greatest benefit occurs in enclosed mechanisms where noise reflects off housing walls.
What's the expected lifespan of POM gears?
POM gear lifespan ranges from 10⁵ to 10⁷ cycles depending on load and temperature, with predictable wear patterns allowing maintenance planning. Oil-lubricated POM gear contact fatigue life goes beyond 6.56 × 10⁶ loading cycles with 50% reliability. At 1.4 Nm: 526×10³ cycles | At 1 Nm: 2×10⁶ cycles .
Application Lifespan Guide: Light loads (<1 Nm) → 10⁷ cycles achievable | Medium loads (1-2 Nm) → 10⁶ cycles typical | Heavy loads (>2 Nm) → 10⁵ cycles, consider steel
From our gear replacement tracking, customers achieve predicted lifecycles when temperature control is maintained. Temperature has tremendous importance for fatigue performance – increase in temperature at same load reduces fatigue life dramatically. Unlike steel’s sudden fracture failure, after around 2 million cycles, noise level increased significantly, indicating considerable gear wear – providing clear replacement timing.
Oil lubrication improves contact fatigue strength by 10.4% from 52.1 to 57.6 MPa compared to dry running, critical for extending service life. We’ve machined replacement gears for applications where engineers initially underestimated temperature effects – proper thermal management typically doubles expected life.
Key advantage: Progressive wear allows planned maintenance schedules versus emergency steel gear replacements after catastrophic failure.
Design Takeaway: Size POM gears for planned replacement schedules rather than indefinite service life. Temperature monitoring becomes critical above 80°C operating conditions.
Can POM gears survive chemical exposure?
POM gears resist hydrocarbons, neutral solvents, and weak acids but fail rapidly in strong acids and chlorinated environments. POM is resistant to a wide range of chemicals, including hydrocarbons, solvents, and neutral chemicals. However, POM is sensitive to both chlorine and acid hydrolysis with potential catastrophic failure.
Chemical Decision Matrix: Automotive fluids/oils → POM excellent | Food processing (neutral pH) → POM suitable | Water treatment (chlorine) → Steel required | Battery/plating acids → Alternative material needed
Hydrogen chloride (HCl) exposure can cause components to split or fall apart without warning – critical safety consideration. POM’s chemical resistance to solvents, oils, and weak acids ensures reliability in outdoor equipment and chemical processing tools.
From our replacement gear projects, POM performs excellently in hydraulic systems and fuel environments but requires steel alternatives in chlorinated or acidic conditions. Cost advantage: POM eliminates expensive chemical-resistant coatings that steel gears need in many environments.
We recommend testing actual process fluids before finalizing POM specifications. Chemical compatibility often outweighs strength limitations when steel requires protective coatings.
Design Takeaway: Specify material testing with actual chemical exposure conditions early in design. POM’s chemical advantages often justify larger gear sizes to meet torque requirements.
Which gear geometries are challenging to machine in POM?
Avoid deep narrow slots, thin webs under 2mm, and sharp internal corners when machining POM due to thermal sensitivity and tool access limitations. Complex geometries require specialized fixturing and reduced cutting speeds, significantly increasing machining time versus steel.
Geometry Difficulty Guide: Standard spur/helical → Straightforward machining | Bevel gears → Moderate complexity increase | Internal ring gears → Major difficulty, consider alternatives | Worm gears → Heat buildup challenges
CNC Constraints from Our Production Experience:
- Minimum web thickness: 2mm to prevent deflection during machining operations
- Corner radii: Sharp internal corners cause tool breakage and stress concentrations
- Slot machining: Deep narrow features require multiple light passes for heat control
- Thin walls: Under 1.5mm sections vibrate excessively during cutting
We’ve encountered automotive projects where internal ring gears with thin walls required custom fixturing and halved cutting speeds, doubling machining costs. Complex geometries often need post-machining assembly rather than single-piece construction to maintain dimensional accuracy.
Thermal management becomes critical – flood coolant essential for complex features, climb milling preferred to reduce heat generation. Multiple roughing passes needed versus single heavy cuts used for steel.
Design Takeaway: Simplify gear geometry where functionally possible. Complex POM geometries may cost more to machine than steel alternatives – evaluate total manufacturing cost, not just material price.
Conclusion
POM gears excel in quiet, lightweight applications under moderate loads and benign chemical environments, offering 50-90% cost savings over steel through eliminated secondary operations. Reserve steel for high-torque or extreme temperature applications where POM’s benefits don’t justify strength trade-offs.
Contact us to explore POM gear manufacturing solutions tailored to your product requirements.
Frequently Asked Questions
Standard CMM measurement works well for POM. Specify measurement at 20°C ±2°C due to thermal expansion differences versus steel. Allow for slight elastic deformation under probe pressure – use minimum contact force settings for accurate dimensional measurement.
Simple spur gears typically require 1-2 weeks for CNC machining including material procurement. Complex geometries or tight tolerances may extend to 3-4 weeks. Rush orders possible but expect premium pricing for expedited scheduling and material sourcing.
Most software assumes steel properties and will overestimate POM capacity. Apply a 70-80% reduction factor to calculated steel ratings as a starting point, then verify with supplier testing data. VDI 2736 guidelines provide specific calculation methods for thermoplastic gears.
For most POM gears, ±0.05 mm is achievable with standard machining processes. Going tighter than ±0.01 mm often requires specialized fixturing and climate-controlled environments, which increases cost significantly. We recommend tolerancing only critical features tightly and keeping others at standard levels for cost efficiency.
Use balanced roughing passes and allow cooling time between operations. For gears over 100mm diameter, we recommend stress-relief annealing before final machining. Proper workholding with even clamping pressure prevents distortion. Avoid single heavy cuts that generate excessive heat.
Module 0.5 is typically the practical limit for reliable CNC machining due to tool deflection and heat generation in small features. Smaller modules often require injection molding or specialized micro-machining equipment for consistent quality.
