Purchased component
Gearbox Gears (sintered steel / plastic)
Mixing & compacting → Sintering → Sizing → Heat treatment → Final inspection
✓ Expert reviewed All content on this page has been reviewed by a senior motor engineer.
Process flow
5 main process steps, with the equipment and instruments used at each step, their main suppliers, and the technical control points.
- 1
Mixing & compacting
Iron-based powder (e.g. Fe-Cu-C) is mixed with lubricant and compacted into gear shapes.
⚙ Powder Compacting Press (PM)Automated- International
- To be added
- Mainland China
- To be added
Technical control points:
- ▪Green density and weight — Per process sheet (e.g. 6.8–7.0 g/cm³)Check: Weighing; frequent sampling
- ▪Cracks and tooth fill — No cracks; teeth fully formedCheck: Visual check; sampling
- 2
Sintering
Compacts are sintered in a protective atmosphere, bonding the particles.
⚙ Mesh-belt Sintering FurnaceAutomated- International
- To be added
- Mainland China
- To be added
Technical control points:
- ▪Temperature and atmosphere — About 1,120 °C; dew point and carbon potential per processCheck: Furnace log and dew-point meter; continuous
- ▪Dimensional change and hardness — Per process sheetCheck: Sampling each batch
- 3
Sizing
Sintered gears are re-pressed in a sizing die to improve accuracy and surface finish.
⚙ Powder Compacting Press (PM)Automated- International
- To be added
- Mainland China
- To be added
Technical control points:
- ▪Gear runout and tooth thickness — Per drawingCheck: Gear roll tester / over-pin measurement; sampling
- 4
Heat treatment
Highly loaded output-stage gears are case-hardened or steam-treated for wear resistance.
Technical control points:
- ▪Hardness and case depth — Per drawingCheck: Hardness tester and metallography; each batch
- ▪Distortion — Gear accuracy still within class after heat treatmentCheck: Gear roll tester; sampling
- 5
Final inspection
Gears are checked for composite deviation, bore size and appearance.
⚙ Double-flank Gear Roll TesterTest instrumentSemi-automaticManual- International
- To be added
- Mainland China
- To be added
⚙ CMM, Roundness & Runout GaugesTest instrumentSemi-automaticManualTechnical control points:
- ▪Total composite deviation — Per the gear class on the drawingCheck: Double-flank roll test; sampling per lot
Incoming inspection & approval tests
- Gear accuracy (double-flank composite deviation)ISO 1328-2 or AGMA class per drawing
- Density and hardness (PM gears)Density per MPIF 35 / ISO 5755 material code; apparent hardness
- Tooth strengthStatic tooth-break or locked-output torque test per specification
- Plastic gear material and dimensional stabilityMaterial certificate (e.g. POM, PA66); dimensions after moisture conditioning
Buyer FAQ
- Powder-metal, plastic or machined gears?
- Powder-metal gears are cheap and strong for high-volume small gearboxes. Plastic (POM, PA) gears are quiet and need no lubrication-sensitive coatings but have lower load and temperature limits. Hobbed or ground steel gears carry the highest loads and accuracy.
- How is gear accuracy specified?
- By an ISO 1328 / AGMA grade, and for small gears in production usually by double-flank roll testing (total and tooth-to-tooth composite deviation). Specify the master gear and test centre distance.
- What causes gearbox noise?
- Run-out and profile errors in the gears, misaligned or loose shafts in the housing, wrong backlash and poor lubrication. Roll-test the gears and measure the assembled gearbox noise.