Why plastic gears need their own standard
You can't just run a polymer gear through ISO 6336. Thermoplastics behave differently, and VDI 2736 captures the differences that decide the design.
Temperature drives strength
A polymer's permissible stress falls sharply with temperature. VDI 2736 estimates the tooth-root and flank temperatures and reads strength from temperature-dependent S-N curves.
Wear is a failure mode
Unlike steel, dry-running plastic pairs can fail by wear before they fatigue. The guideline gives a wear check based on a material wear coefficient.
Deformation matters
Low modulus means teeth deflect under load, affecting contact and meshing — checked against a permissible deformation.
What the gear design tool computes
Thermoplastic gear rating aligned with VDI 2736, with exact coefficient evaluation in line with ISO 6336 / DIN 3990.
Root bending capacity
Tooth-root fatigue stress against the temperature-dependent permissible bending stress, giving the root safety factor — the governing check for thermoplastic gears.
Temperature-dependent strength
You set the operating tooth temperature and lubrication condition; permissible stress is read from temperature-indexed material data for the selected polymer.
Steel–plastic and plastic–plastic pairs
Rate the pairing you're actually building — a steel pinion driving a plastic wheel, or an all-plastic mesh — in a single calculation.
Wear & deformation checks (coming soon)
Linear wear over service life and tooth deformation, each against its permissible limit per VDI 2736 Part 2.
Method C and modified Method B
VDI 2736 offers calculation routes that trade rigour for the data you actually have on a polymer:
- Method C. The VDI default — a simplified estimate for early feasibility, useful before you have full S-N and wear data for the polymer.
- Modified Method B. The detailed analytical route, with adjusted assumptions where full temperature-dependent material data isn't available.
How to run a VDI 2736 rating
Pick the polymer & geometry
Choose the thermoplastic from a material database, then define teeth, module, helix angle and profile shift.
Set load & duty conditions
Enter torque or power, speed, required life, the operating tooth temperature and the lubrication condition.
Calculate & check the limits
Read the root safety factors for both gears — the governing check for thermoplastics — alongside the full geometry results.
Material data: ratings draw on a plastic-gear material database covering common gear polymers — PA66, POM, PEEK and PEEK-CF — with temperature-dependent strength data, and additional material grades on the roadmap.
Frequently asked questions
What does VDI 2736 cover?+
The load capacity of thermoplastic gears. Part 1 covers materials, Part 2 the cylindrical-gear load-capacity calculation, Part 3 crossed-helical and worm gears, and Part 4 strength-parameter testing. Zenomiq implements the Part 2 cylindrical-gear calculation.
Which calculation methods are supported?+
Method C (the VDI default) and modified Method B — so you can rate a polymer gear whether or not you have full temperature-dependent material data.
Why does tooth temperature matter so much?+
A thermoplastic's permissible stress drops sharply with temperature. In Zenomiq you set the operating tooth temperature, and the rating reads the permissible stress from temperature-dependent material data — so a realistic temperature estimate is one of the most important inputs.
Does it check wear and deformation, not just stress?+
The VDI 2736 guideline defines wear and deformation checks in addition to root bending. Zenomiq rates root bending — the governing failure check for thermoplastic gears — today; the wear and deformation checks are coming soon.
Do I need to install or license anything?+
No install or license — it runs in your browser. You sign in (it takes seconds) and can use the free tier calculation modules right away; upgrade only when you need more.