To receive an accurate, production-ready quotation for a custom planetary gear set within 24 hours, your RFQ package should include: (1) 2D PDF drawings (defining datum tolerances, heat treatment, and gear data tables) paired with 3D STEP/IGES models; (2) Complete gear mesh parameters for Sun, Planet, and Ring (Module/DP, tooth counts Z_s/Z_p/Z_r, pressure angle, helix angle & hand, profile shift x, and span measurement Mk); (3) Planet carrier pin-circle diameter and true position tolerance; and (4) Target assembled backlash, duty cycle torque, and batch quantity.
Key Engineering & Manufacturing Takeaways
- ✓Never send a single planet gear drawing in isolation—always provide the mating sun gear, internal ring gear, and carrier center distance so the manufacturer can verify mesh backlash.
- ✓Specify tooth thickness using Span Measurement (Mk over k teeth) or Dimension Over Pins (MdK) rather than chordal tooth thickness alone.
- ✓Clearly distinguish between pre-grinding hobbing data and final post-heat-treatment ground tooth data.
- ✓If drawings are unavailable, shipping the complete worn assembly (sun + planets + ring + carrier) enables 100% accurate CMM reverse engineering.
1. The Complete Planetary Gear Drawing Data Table Checklist
Every individual gear print (Sun Gear, Planet Pinion, and Internal Ring Gear) must include a standardized gear spline/tooth data block in the corner of the 2D drawing. Before submitting your prints to a manufacturer, verify that these 10 parameters are explicitly stated:
Table: Mandatory Gear Data Table Parameters for Sun, Planet, and Internal Ring Drawings
| Parameter Symbol & Name | Sun Gear / Shaft (External) | Planet Pinion (External, N pcs) | Internal Ring Gear (Internal Annulus) |
|---|---|---|---|
| 1. Normal Module (m_n) or DP | Required (e.g., m_n = 3.0 mm) | Must exactly match Sun & Ring | Must exactly match Sun & Planet |
| 2. Number of Teeth (Z) | Z_s (e.g., 18 teeth) | Z_p (e.g., 27 teeth) | Z_r (e.g., -72 internal teeth) |
| 3. Normal Pressure Angle (α_n) | Typically 20° (or 25° high torque) | Matches Sun & Ring (20° / 25°) | Matches Sun & Planet (20° / 25°) |
| 4. Helix Angle (β) & Hand | 0° (Spur) or e.g., 12° RH | 0° or 12° LH (Opposite to Sun) | 0° or 12° LH (Same hand as Planet!) |
| 5. Profile Shift Coefficient (x) | e.g., x_s = +0.25 | e.g., x_p = -0.25 or calculated | e.g., x_r = 0.00 or balanced |
| 6. Accuracy Standard & Grade | DIN 3962 Grade 5 or 6 (Ground) | DIN 3962 Grade 5 or 6 (Ground) | DIN 3962 Grade 6 or 7 (Shaped/Nitrided) |
| 7. Span (Mk) or Over-Pins (MdK) | Specify ball/pin Ø and tolerance | Specify grouped tolerance (Δ ≤ 0.004 mm) | Specify between-pins measurement (MdK) |
| 8. Operating Center Distance (a_w) | a_sp (Sun-to-Planet center distance) | Matches carrier pin radius R_c | a_pr (Planet-to-Ring = a_sp) |
| 9. Micro-Geometry Modification | Profile relief Cα (e.g., 8 µm) | Lead crowning Cβ (e.g., 6–12 µm) | Standard involute or tip chamfer |
| 10. Metallurgy & Hardness | 18CrNiMo7-6, 58–62 HRC, ECD 0.8–1.2 mm | 18CrNiMo7-6, 58–62 HRC + Bore Honed | 42CrMo Plasma Nitrided 650+ HV |
2. Critical Geometric Dimensioning & Tolerancing (GD&T) on Non-Tooth Datums
A DIN 5 ground gear tooth profile is useless if the reference bore or bearing journal has excessive radial runout. Ensure your drawings lock down these datum tolerances:
- ▸Planet Gear Bore (Datum A): Hold size tolerance to ISO H6 or G6, cylindricity ≤ 0.004–0.005 mm, surface finish Ra ≤ 0.2–0.4 µm, and pitch circle radial runout (Fr) relative to Datum A within DIN 5/6 limits.
- ▸Sun Gear Shaft Journals (Datum A-B): Bearing journal total indicated runout (TIR) ≤ 0.005 mm, cylindrical grinding finish Ra ≤ 0.4 µm, and DIN 5480 spline pitch circle concentricity ≤ 0.010 mm.
- ▸Planet Carrier Pin Holes: True position of all N pin holes relative to the central bearing datum axis held within ≤ 0.010–0.015 mm, and pin-hole-to-datum-face perpendicularity ≤ 0.008 mm per 100 mm.
3. Ordering Without Drawings: How to Ship Physical Samples for Reverse Engineering
When sourcing replacement planetary gear sets for legacy excavators, wind turbines, or discontinued European industrial reducers where OEM prints are unavailable, do not measure the outside diameter with hand calipers and guess the module—profile-shifted gears will deceive standard formulas.
Instead, ship one complete stage (1 Sun Gear + at least 2 Planet Pinions + 1 Internal Ring Gear, or the Planet Carrier) to our Wenling metrology lab. Using our Zeiss 3D CMM, optical projector, Klingelnberg gear analyzer, and spectrometer, we generate full production CAD drawings for your engineering sign-off prior to manufacturing.
Sourcing Custom Planetary Gear Sets Built to Your Prints?
ZhongYi manufactures matched sun gears, CNC profile-ground planet pinions (with parabolic lead crowning and honed needle bearing bores), 5-axis machined planet carriers, and plasma-nitrided internal ring gears in our 2,800+ m² Zhejiang factory.
Engineering FAQ
Frequently Asked Technical Questions
Direct answers to common design, tolerance, and procurement questions on this topic.
What CAD file formats does ZhongYi accept for quotation?▼
We accept 2D engineering drawings in PDF, DWG, or DXF formats paired with 3D solid models in STEP (.stp/.step), IGES (.igs), Parasolid (.x_t), or SolidWorks (.sldprt) formats.
How fast can ZhongYi provide a DFM review and formal price quote?▼
Our engineering and export team at Jinzhuo Technology / ZhongYi Gear provides a comprehensive DFM feasibility review and itemized FOB/CIF/DDP quotation within 24 hours of receiving your complete drawing package.
Can you sign a Non-Disclosure Agreement (NDA) before we send proprietary planetary gearbox drawings?▼
Absolutely. We routinely execute bilateral NDAs with North American and European robotics, defense, automotive, and industrial OEMs before receiving confidential CAD files.