Manufacturability review of a 4-part m0.6 planetary gear set in 16MnCr5, Grade 7: planet span 6.495–6.503 mm, ring pin 42.741–42.751 mm, 60±3 HRC, case depth 0.3 mm, 10/100/1000 sets.
In August 2026, a Swiss manufacturer of actuators (Actuator 6016, 3D-printed housing) sent drawings for a planetary gear set to Geyon Transmission: 4 parts, module 0.6, accuracy Grade 7, material 16MnCr5 case-hardened, tooth flank 60±3 HRC, case depth 0.3 mm, with quantities quoted at three tiers — 10 sets, 100 sets, and 1000 sets — and the customer’s concern was whether the tolerances could be held at volumes of 500 to 5000 pieces. Geyon Transmission completed an item-by-item review of the 4 drawings, checked tooth thickness, pin span, material and heat treatment process, and provided manufacturing feasibility recommendations and an inspection item list. For this small-module planetary gear set, the bottleneck is not machining — it is the tolerance bandwidth and batch-to-batch consistency.
The customer is a Swiss actuator manufacturer, and this generation of the product uses a 3D-printed gearbox housing containing a precision gear drive. The gear set has four parts: two sun gears (one with profile shift x=0.25), one planet gear, and one internal ring gear (z=72, profile shift x=0.75). All are made of 16MnCr5 (1.7131) case-hardened, with a tooth flank hardness requirement of 60±3 HRC, the ring gear at 59±3 HRC, and a case depth of 0.3 mm. The contact person comes from a mechanical engineering background with solid technical grounding, and the drawings clearly specify a 20° pressure angle, ISO 53 involute tooth profile, and ISO 2768-mK general tolerances.
The inquiry does not follow a “just give us a price” approach. The customer listed 13 items for us to respond to, which in addition to unit price, tooling cost, material specifications, lead time, and payment terms, also include design recommendations on manufacturability, as well as where the unit price inflection point falls as volume increases. It is clear they are selecting a long-term engineering partner for an ongoing production project.
The teeth are very small. Module 0.6, planet gear pitch diameter 14.4 mm, ring gear 43.2 mm. With small teeth and narrow tooth spaces, the space available for a hob or grinding wheel to reach in is limited, and both machining allowance and cutting parameters must be calculated separately.
The tolerance bandwidth is very narrow. The planet gear’s span over 4 teeth W4 is required to be 6.495 to 6.503 mm — a 0.008 mm band; the ring gear pin span is 42.741 to 42.751 mm — 0.010 mm. These dimensions are directly affected by heat treatment distortion; after case hardening the tooth thickness will grow, and by how much must be controlled through process data and compensation values.
The internal ring gear is difficult to grind. For the z=72 internal ring gear, grinding still uses an internal gear grinding head, where the wheel diameter is small and rigidity is poor, making grinding parameters more demanding than for external teeth.
Three volume tiers, one process. 10 sets, 100 sets, 1000 sets — what the customer wants to see is that the same process can consistently hold accuracy in both small batches and mass production, not just that a nice-looking sample can be made.
Inspection items must be clearly stated in advance. Batch consistency is proven with data, and the customer wants to know at the quotation stage which items — tooth thickness, pin span, tooth profile, helix, hardness, case depth — are measured piece by piece and which are sampled.
The review proceeded in three steps.
Step one, drawing verification. The 4 drawings (including 3 STEP models) were analyzed item by item: number of teeth, module, profile shift coefficient, pressure angle, tooth profile standard, nominal values and upper/lower limits for tooth thickness and pin span — all entered into the review table. For pitch diameter, span over teeth, and pin span, the reference basis was confirmed with the customer to avoid each side using its own calculation method.
Step two, material and heat treatment confirmation. 16MnCr5 is a conventional choice among carburizing steels, and the difficulty lies in the case depth being as shallow as 0.3 mm. With the case depth set so shallow, the furnace time and carbon potential window become narrow, and batch-to-batch variation is easily amplified. Geyon follows process parameters for shallow-layer carburizing, uses measured values from trial parts for distortion, and then works backward to determine the grinding allowance for tooth thickness.
Step three, process route and inspection plan. Gear blanks are turned to preserve datums, hobbing leaves grinding allowance, and grinding follows heat treatment; the planet gear’s external teeth use form grinding, and the ring gear uses internal gear grinding. Inspection focuses on span over teeth and pin span, supplemented by a gear measuring center for tooth profile and helix; hardness and case depth are recorded by batch. There are three inspection stages — incoming, in-process, and outgoing — and full production is released only after first-article full-dimension confirmation.
The review also responded to the customer’s requested manufacturability recommendations: the matching relationship between the sun gear’s profile shift coefficient and the planet gear’s tooth thickness, the entry chamfer for internal tooth grinding of the ring gear, and the position tolerance datum for the planet carrier during assembly. Explaining these clearly at the quotation stage saves trouble compared with adjusting after the parts are made.
| Item | Content |
|---|---|
| Parts | Planetary gear set of 4 pieces: sun gear ×2, planet gear, internal ring gear |
| Module / number of teeth | m0.6; sun gear and planet gear 24 teeth each, ring gear 72 teeth |
| Profile shift coefficient | Sun gear s1 x=0.25, ring gear x=0.75 |
| Pitch diameter | Planet gear 14.4 mm, ring gear 43.2 mm |
| Accuracy requirements | Grade 7, ISO 2768-mK general tolerances, pressure angle 20°, ISO 53 tooth profile |
| Key dimensions | Planet gear span over teeth 6.495~6.503 mm; ring gear pin span 42.741~42.751 mm |
| Material / heat treatment | 16MnCr5 (1.7131) case-hardened, planet gear and sun gear 60±3 HRC, ring gear 59±3 HRC, case depth 0.3 mm |
| Quantity tiers | 10 sets / 100 sets / 1000 sets |
| Review output | Item-by-item verification of 4 drawings completed; process route, inspection item list, and manufacturability recommendations submitted |
The above parameters come from the RFQ drawings and technical documents provided by the customer in August 2026, and the review conclusions are engineering confirmation items and do not yet involve mass delivery data.
First, the parts with narrow tolerances were calculated clearly up front. A 0.008 mm tooth thickness band does not rely on the machinist’s feel — it relies on heat treatment distortion data plus grinding allowance compensation, and the basis for this must be provided at the review stage.
Second, the window for shallow-layer carburizing was explained in advance. A 0.3 mm case depth is sensitive to furnace parameters, and the customer knowing how we control it is more useful than submitting a report after the fact.
Third, inspection items were put on the table at the quotation stage. What is measured piece by piece, what is sampled, and what reports are issued — this saves the customer a round of back-and-forth when they take it for internal evaluation.
Do you also have a gear set with small module, narrow tolerances, and multiple volume tiers that needs evaluation? Send over the drawings and inspection requirements, and the Geyon Transmission engineering team will first conduct a drawing review and reply with the process route, inspection items, and quotation. Grinding accuracy can reach DIN 3, and reports on pitch, tooth profile, helix, hardness, and case depth can be issued according to DIN/ISO/AGMA standards.
More information: Precision Gear Manufacturing Capabilities | Industries Served | Custom Gear Engineering Review | Drawing Review and Quotation
Upload a 2D/3D drawing (STEP, DXF, PDF) — we reply with a quote and lead time.