Technopolymer vs. steel gears: complete guide to metal replacement
Metal replacement isn't about simply replacing metal with plastic. It's about understanding when a technopolymer can do better than the metal component you're using now.
Replacing steel, brass or bronze with an advanced technopolymer isn't a fallback choice: it can bring concrete advantages in weight, performance and environmental impact. But it requires accurate technical data, application tests and a dedicated design. A technopolymer gear isn't an identical copy of a steel one: it's a component redesigned around the material's characteristics.
Technical characteristics compared
Steel and technopolymers follow different design logics. Steel excels in mechanical strength: it withstands high loads and guarantees structural stiffness that maintains precision to a tenth of a millimeter. Technopolymers offer advantages instead in weight, noise, friction, lubrication and corrosion resistance.
Among the technopolymers most used for gears are glass-fiber PA6 (PA6+GF), POM-C (polyoxymethylene) and PK (polyketone). They answer to different application logics and cover a wide range of industrial needs.
| Property | PA6 + glass fiber | POM-C (polyoxymethylene) | PK (polyketone) | Gear steel |
|---|---|---|---|---|
| Specific weight | about 1.36 g/cm³ | about 1.41 g/cm³ | $about 1.24–1.3 g/cm^3$ | about 7.8 g/cm³ |
| Tensile strength | 110 (COND.)–175 (DAM) MPa | 65–75 MPa | 70–80 MPa | 800–1,200 MPa |
| Elastic modulus | 5.5 (COND.)–9 (DAM) GPa | 2.8–3.2 GPa | 1.5–1.8 GPa | 190–210 GPa |
| Friction coefficient | medium | low | low | low only with lubrication |
| Corrosion | resistant in industrial environments | excellent chemical resistance | excellent chemical resistance | requires protection or alloys |
| Continuous temperature | up to 110–120°C with load | about 80–90°C | up to 100°C | over 200°C, up to 400–500°C |
| Dimensional stability | sensitive to moisture | excellent, low moisture absorption | stable, low moisture absorption | very high |
Advantages of metal replacement with PA6+GF, POM-C and PK
Weight reduction and improved energy efficiency
The specific weight of PA6+GF, POM-C and PK ranges between 1.3 and 1.4 g/$cm^3$, against about 7.8 g/$cm^3$ for steel. The mass saving can reach 80–85%.
Less mass means less rotational inertia: a direct advantage in high-speed applications or in transmission systems where efficiency and response speed matter. It also means lower overall energy consumption, components easier to handle and mount, lower operating costs.
Corrosion resistance and chemical compatibility
In many environments, steel requires surface treatments, stainless alloys or protective coatings to resist oxidation and electrochemical corrosion. Technopolymers start out resistant.
PA6+GF, POM-C and PK answer to different needs, though. PA6+GF offers the highest mechanical strength among the three and an excellent cost/performance ratio: in humid environments, calculate the clearance taking into account moisture absorption, a parameter managed at the design stage. POM-C is preferable when dimensional stability is the priority and loads are moderate. PK is the choice for chemically aggressive environments or when you want to eliminate maintenance entirely.
These materials are particularly suited to the food, pharmaceutical and medical sectors, where the absence of corrosion and the possibility of frequent washing and sterilization are essential requirements.
Quiet operation and reduced wear
Technopolymer gears damp vibration and shocks better than steel. The result is quieter operation, relevant in household appliances, medical devices and industrial automation where acoustic comfort is a requirement.
Technopolymers often also have self-lubricating properties that allow dry running or running with minimal lubrication. Less maintenance, less risk of contamination from lubricants, lower costs: a concrete advantage in regulated sectors.
Design and functional integration
Injection molding allows complex geometries and the integration of multiple functions into a single piece. Separate seals or inserts, in many cases, are no longer needed. Fewer components to assemble, fewer failure points, lower production costs.
This flexibility also lets you optimize the tooth geometry to compensate for the lower stiffness relative to steel, maintaining high performance over time.
Limitations and design considerations
The mechanical strength and elastic modulus of technopolymers are lower than steel. This limits their use in applications with high loads, repeated shocks or extreme temperatures.
At the design stage, plan compensations: increase the module or tooth width, evaluate the life cycle and the real operating conditions.
The maximum service temperature is another factor to keep under control. PA6+GF reaches about 110–120°C with load, PK about 100°C, POM-C about 80–90°C. If you exceed these limits, metal remains the necessary choice.
Don't size the technopolymer gear as if it were steel. The tooth geometry must be redesigned: a direct transfer of the dimensions almost always leads to underestimating the real stresses.
Typical applications and selection criteria
PA6+GF gears are generally the right choice for demanding industrial applications that need good mechanical strength and stiffness: reducers, conveyors, automatic machines. It offers the best cost/performance ratio among the three materials and superior toughness.
POM-C is preferable for gears that require dimensional precision, quietness and high speeds with low torque: compact gearmotors and precision automation are the typical application field.
PK is the most suitable solution for critical environments with requirements for chemical resistance, thermal stability and low maintenance. Food, pharmaceutical and medical packaging are the sectors where it's chosen most often.
Before starting series production, consider these points:
- Assess load, speed, environment and operating temperature precisely, not by estimate.
- Account for the moisture absorption of PA6+GF and calculate the mating clearances accordingly.
- Verify material compatibility with the reference standards for your sector.
- Optimize the tooth geometry to compensate for the lower stiffness relative to steel.
- Prototype and test durability before moving to series.
If your system's operating conditions fall outside the standard parameters, write to the technical office We calculate the right configuration for you.