Planetary Gearbox
Machined Components

The ±0.003mm planet carrier pin bore position accuracy is structural — it is a consequence of the machining process architecture rather than skilled operator intervention. CNCPioneer's planet carrier pin bore programs use single-setup C-axis indexed drilling on MAZAK mill-turn centers: the carrier datum face and registration bore are finish-machined first, establishing the coordinate origin for all subsequent operations. The carrier remains in the same chucking throughout — no rechucking, no setup transfer. All pin bores are drilled and reamed sequentially from this one spindle datum, with the MAZAK C-axis positioning the carrier between bore operations at rotary accuracy of ±0.001°. The critical accuracy factor is that all three or four pin bores share the same machining coordinate origin — their positions relative to each other are governed by the CNC machine's positioning accuracy rather than by part re-registration error. CMM verification then measures all pin bore center positions simultaneously: radial position from carrier center (confirming equal load-path geometry), angular spacing between adjacent bores (confirming angular load sharing uniformity), and axial parallelism of all pin bores to each other (confirming planet gear tilt angle uniformity). This three-axis simultaneous verification, not sequential individual bore checks, is what confirms the ±0.003mm mutual position accuracy. In volume production, the same programs run on the same MAZAK spindles with zero-point fixturing ensuring setup repeatability — the ten-thousandth planet carrier has the same pin bore position accuracy as the first prototype.

Wire EDM (electrical discharge machining with a wire electrode) cuts internal tooth forms in hardened GCr15 HRC 62–65 by thermal erosion — the wire electrode traverses the tooth profile path, eroding material without mechanical cutting force. This non-contact process is the only practical manufacturing method for machining precision internal involute tooth forms in fully hardened material. The alternative — gear hobbing or broaching before hardening, then hardening the ring gear — introduces heat treatment distortion of 0.010–0.050mm in the tooth form, which then requires a grinding operation to correct. Internal tooth grinding for ring gears is a specialized and expensive process: the grinding wheel must enter the bore, limiting wheel size and requiring long-reach setups that compromise grinding accuracy for large internal pitch circle diameters. Wire EDM on the hardened ring gear blank eliminates this distortion-and-regrind sequence entirely: the blank is hardened first (before any tooth form exists), then wire EDM cuts the final tooth profile in the fully hardened state in two passes — a rough-cut first pass that removes most material, followed by two skim passes that progressively improve profile accuracy. The two-pass skim sequence achieves ±0.003mm profile accuracy and Ra 0.4μm flank surface simultaneously — the hardened surface being wire EDM'd has no subsequent process that could re-introduce heat treatment distortion. The resulting ring gear internal tooth form in GCr15 HRC 62–65 provides the contact fatigue life (10⁸+ cycles at rated Hertz contact stress) required for robot actuator planetary gearboxes at ten-million-step walking cycle targets.

Yes — complete matched planetary gearbox component sets are a standard CNCPioneer program. A single-stage planetary set contains 8–20 precision-machined components: planet carrier body with measured and installed planet pins, ring gear (tooth form verified against sun and planet gear module and pressure angle), sun gear shaft (blank runout verified), planet gear bodies (external tooth form verified), output flange, needle roller bearing race elements, and stage housing body. Inter-component dimensional verification proceeds as follows: (1) planet carrier pin bore positions are CMM-measured and recorded; (2) ring gear internal pitch circle diameter and tooth form are verified on gear measurement center against the nominal module and pressure angle used for sun and planet gear manufacturing; (3) sun gear shaft blank runout is CMM-verified and compared against the ring gear's pitch circle diameter to confirm sun gear will orbit within the ring gear without interference; (4) planet gear body external tooth form and pin bore concentricity are verified against the planet pin dimensions in the carrier. These four inter-component checks confirm the assembled planetary set will achieve the designed load-sharing geometry and that all gear meshes are geometrically consistent before the components leave CNCPioneer's facility. Each matched set ships with a matched set verification record identifying all four inter-component checks, individual component CMM and gear measurement records, and a matched set Certificate of Conformance enabling the robot actuator assembly facility to confirm assembly compatibility without incoming inspection re-measurement.

Prototype: standard planet carrier bodies (20CrMnTi, 42CrMo4, or 7075-T6) — 7–10 business days; ring gear wire EDM programs in GCr15 requiring through-hardening before EDM — 10–14 business days; sun gear shafts and output flanges (17-4PH H900) — 7–10 days; planet gear bodies requiring case hardening and gear grinding — 12–16 days; complete matched planetary gearbox component sets — 14–18 business days to allow inter-component dimensional verification. Development quantities (10–100 units): 2–4 weeks with SPC data accumulation on pin bore position and ring gear tooth form. PPAP Level 3 qualification: 6–8 weeks from prototype approval including gear measurement center capability studies. Volume production: 2–3 week monthly releases on blanket orders with dedicated MAZAK and wire EDM capacity at Cpk ≥1.67 on IATF special characteristics. Volume economics: relative to single-piece prototype pricing, expect –25–35% per unit at 10–25 pieces, –40–55% at 100–500 pieces, –55–65% at 2,000–10,000+ pieces. China planetary gearbox components manufacturers economics: 40–60% below equivalent US, European, and Japanese suppliers at all volume levels, with IATF 16949/AS9100D documentation included. For high-volume programs at 200,000+ planet carrier or ring gear sets annually, CNCPioneer provides dedicated capacity reservation agreements with guaranteed monthly quantities and committed per-unit pricing locked for 12-month contract periods.