Dongying (Suzhou Dongying Electronic Technology Co., Ltd.) is a mold maker and injection molder in Suzhou, China. We build precision molds and run injection molding for overseas procurement, R&D and quality teams, including plastic gear components and gearbox components. Projects use mold handover, or Dongying holds the mold and supplies parts. For drawing and fit inputs, start with plastic gears, gear sets and gearboxes: drawings and fits.
POM and PA at a glance for worm stages
Short answer: POM favors low moisture swell and stable backlash against steel; PA favors toughness and higher load when moisture-related size change is designed in.
| General trend (grade-dependent) | POM (acetal) | PA6 / PA66 |
|---|---|---|
| Moisture uptake | Low; humidity size change usually small | High; size and stiffness shift with water |
| Friction / slip vs steel | Strong inherent slip in many gear grades | Tough; often needs grease or lubricant packages |
| Impact / toughness | Stiff and fatigue-capable | Strong impact absorption under torque spikes |
| Heat in continuous service | Fits many actuator worm stages; check HDT | Often preferred when heat pushes POM’s comfort zone |
| Small, dimension-critical gears | Favored when backlash must stay tight | Needs a conditioning plan |
| Typical mating | Plastic worm wheel vs steel worm | PA wheel vs steel worm |
Trends only—compare datasheets for the exact grades you shortlist, including lubricated and filled variants.
Why POM is often first for a plastic worm wheel
Short answer: POM worm gears are chosen when low moisture absorption, dimensional stability and inherent slip against a metal worm matter more than nylon-level toughness.
Celanese positions Hostaform / Celcon POM for strength, stiffness, wear and slip, fatigue and creep resistance, plus low moisture absorption that supports tight tolerances in moist environments (Celanese Hostaform / Celcon POM). The same supplier lists Hostaform among leading gear materials and notes Zytel PA when toughness and temperature resistance are the priority (Celanese, Gears applications). Ensinger’s POM overview likewise highlights low moisture uptake, sliding behavior and dimensional stability (Ensinger POM).
For a worm stage that usually means less humidity-driven swell at the tooth, more predictable backlash after molding, and a mesh that can run with grease or internally lubricated grades. Celanese processing guidance notes that Celcon acetal does not readily absorb moisture the way polyamides do, though drying still helps consistent molding (Celanese Celcon processing guide). Shock loads or higher continuous temperature may still push the shortlist toward PA.
When PA6 or PA66 makes more sense
Short answer: choose a PA plastic worm gear when toughness, higher load or elevated temperature outweigh dry-stable dimensions, and you control how moisture affects size and modulus.
BASF Ultramid polyamides are widely used where strength, rigidity and thermal stability matter (BASF Ultramid). DuPont design information on Zytel and Minlon explains that polyamides absorb moisture after molding, enlarging parts, lowering stiffness and raising toughness; the change is slow and reversible (DuPont design module via Distrupol). Ensinger’s PA66 overview stresses toughness with the same moisture caveat (Ensinger PA66).
If the worm wheel sits in a humid cabin, underhood or outdoor actuator, agree whether critical tooth and center-distance dimensions are inspected dry-as-molded, after conditioning to a stated humidity, or both. Prefer a named PA6 or PA66 grade and decide early whether glass fill is allowed—glass raises stiffness and heat capability but can be harder on a mating steel worm if finish and lubrication are not planned.
Mating metal, lubrication and the mold
Short answer: a smooth hardened steel worm against a plastic wheel is the usual durable pair; grease or internal lubricants change wear and mesh heat, and the resin family must be frozen before cavity design.
Hardened steel remains the preferred counterpart for load and heat removal. Rough metal accelerates wear on the plastic wheel. Plastic-on-plastic can work at light duty, but the driving member usually wears faster. Factory grease improves run-in and life for both POM and PA; PTFE- or solid-lubricant-modified grades are often shortlisted for dry or sparsely greased actuators. Confirm grease chemistry with the resin supplier. Water is a poor lubricant for polyamide gears because of moisture uptake.
| Mold / process item | Why POM vs PA matters |
|---|---|
| Shrinkage allowance | Different families; a late switch can force steel rework on teeth and bores. |
| Gate position and type | Sets weld lines on the rim and packing at thin tooth roots. |
| Cooling | Affects crystallinity, rim warpage and runout. |
| Drying | PA must be dried thoroughly; POM needs less aggressive moisture control but still benefits from dry feed. |
| Ejection and polish | Tooth flanks and root fillets need release suited to the grade. |
Run mold-flow with the actual grade when the rim is thin or total runout is tight. See mold making, manufacturing and tooling and supply scope.
What to put in the RFQ for worm-gear material
Short answer: give duty cycle, environment, preferred grades, mating worm definition, lubrication plan and how tooth geometry will be accepted—not a request for a supplier performance promise.
Include the 3D model and drawing (module, pressure angle, tooth count, lead, center distance, runout or backlash notes); torque, speed and duty; humidity and fluids; preferred and alternate grades; mating worm material, hardness and finish; grease or dry-running intent; annual volume; mold handover vs part supply; and a sample plan stating dry vs conditioned checks. Dongying can comment on moldability from those inputs. Material, lubrication and endurance results remain customer design and validation items.
FAQ
Is POM or PA better for a plastic worm gear?
There is no single better grade. POM usually wins when low moisture swell, stable backlash and slip against a steel worm matter most. PA6 or PA66 usually wins when toughness, higher load or higher continuous temperature dominate and moisture size change is designed in. Freeze the family—and preferably the named grade—before cavity steel is cut, then confirm with your own duty-cycle tests.
Why does moisture matter more for PA worm gears than for POM?
Polyamides absorb ambient moisture after molding, which enlarges the part, lowers stiffness and raises toughness until equilibrium with service humidity. POM absorbs far less water, so tooth size and backlash shift less. For PA worm wheels, agree whether critical dimensions are checked dry-as-molded, after conditioning, or both, and use conditioned properties in strength checks when the part will run humid.
Can I run a POM or PA worm wheel dry against steel?
Both families appear in greased and sparsely lubricated actuators; many programs still apply assembly grease even with internally lubricated grades. PTFE- or solid-lubricant-modified POM and PA are often shortlisted for dry or low-grease duty, but mesh heat, speed and steel finish still decide life. Validate the exact grade against your worm finish and duty cycle rather than a generic “self-lubricating” claim.
Should the worm wheel use glass-filled PA?
Glass-filled PA raises stiffness and heat capability under load, but fibers at the tooth surface can increase wear on a mating steel worm if lubrication and finish are not controlled. Many worm wheels stay unfilled or use lubricant packages rather than high glass content. If glass fill is required for hub strength or heat, keep fiber level and surface strategy explicit in the RFQ and sample plan.
What drawings do you need to quote a molded worm gear?
Send the 3D model and drawing with tooth geometry, center distance, material shortlist, mating worm definition, lubrication intent, critical runout or backlash features, annual volume and mold-handover vs part-supply preference. Our guide on plastic gears, gear sets and gearboxes: drawings and fits lists the inputs buyers usually freeze before tooling.
Can Dongying mold both POM and PA worm gears?
Yes. We mold POM and PA gear and gearbox parts under mold handover or Dongying-held-mold part supply, including automotive actuator and window-regulator related samples on our plastic gear components and gearbox components pages. Share the duty, grade shortlist and drawings so we can comment on moldability; endurance and noise targets remain your validation scope.
Related pages
Sources
- Celanese, Hostaform / Celcon POM product overview: https://www.celanese.com/products/hostaform-celcon-pom-acetal-copolymer
- Celanese, Gears applications: https://www.celanese.com/applications/industrial-automation-and-gears
- Celanese, Celcon POM Processing and Troubleshooting Guide (PDF): https://www.celanese.com/-/media/Engineered-Materials/Files/Product-Technical-Guides/POM-044_Celcon_ProcessingGuideTG_AM_0913.pdf
- Ensinger, POM overview: https://www.ensingerplastics.com/en-us/shapes/engineering-plastics/pom
- Ensinger, PA66 overview: https://www.ensingerplastics.com/en-us/shapes/engineering-plastics/pa66
- BASF, Ultramid (PA) product overview: https://plastics-rubber.basf.com/global/en/performance_polymers/products/ultramid
- DuPont, Minlon and Zytel Design Information, Module II (PDF hosted by Distrupol): https://www.distrupol.com/Minlon_Zytel_Design__Info_Module_2.pdf
- DuPont, Zytel product family: https://www.dupont.com/products/zytel.html