A precision parts production case study answers the question buyers actually ask: can this supplier hold tolerances, cycle time and delivery dates once volume arrives? This one follows a single Tier 1 program from DFM review and process selection through sampling, pilot run and ramp-up to stable delivery. The manufacturer behind the project is Yujiaxin Tech. Every figure below is our own measured process and delivery data.
Key takeaways
- The part: a synchronizer hub for a new-energy vehicle e-drive, annual demand 1.2 million pieces, ±0.02 mm on critical mating faces.
- Process selection compared PM, MIM and precision casting; the program chose PM pressing, sintering and CNC finishing.
- Two sampling rounds led to a pilot run; Cpk moved from 0.89 to 1.67 and PPAP passed first time.
- Yield ramp-up rose from 91.2% to 99.1% in 8 weeks, with takt cut to 12 seconds per piece.
- Twelve months of serial delivery at 98.6% on-time delivery, full traceability and a repeat order with two parts.
A good sample proves almost nothing about volume. Plenty of suppliers post clean sampling data, then lose control once tool wear, sintering distortion and cycle-time drift appear. That is what a precision parts mass production delivery case reveals: process control and delivery discipline together.
The customer is an automotive Tier 1 supplier in East China. The part is a synchronizer hub used in the e-drive and transmission of a new-energy vehicle, a load-bearing component in the shift mechanism. It runs 68 mm outer diameter, with 0.03 mm spline concentricity and ±0.02 mm on critical mating faces. The material is a low-alloy sintered steel, and density has to stay at or above 7.1 g/cm³.
Volume, not any single dimension, was the hard part. At 1.2 million pieces a year, tool life, furnace zone stability and finish-machining takt all have to hold at once. This precision parts production case study starts there: the review team treated mass-production feasibility as risk item number one. Capacity for such parts sits with plants that run sintering and finishing on site, described in About Yujiaxin Tech.
The review checks the 2D drawing against the 3D model first: tooth form, ejection direction and green-density gradient. DFM output includes a risk list, the first hard checkpoint in any precision parts production case study. A 3.2 mm wall section tends to sinter with uneven density, and the keyway fillet has to move to R0.8 to cut the cracking risk. Dimension datums, sampling plan and inspection equipment go into the quality agreement, so nobody argues about conforming later.
Each process has boundaries. MIM suits small, complex parts but carries a high unit cost. Precision casting holds weaker accuracy and finish at medium volume, and needs heavy downstream machining. PM pressing gives high material utilization, fast takt and stable formed dimensions at million-piece volume, and for a hub with tooth form and through-holes, PM forming sufficed.
We check material gauges against the MPIF metal powder standard system for sintered density and mechanical acceptance methods (MPIF Standards and Resources). The chosen route was PM pressing, sintering and CNC finishing of the key faces, and Precision Parts Manufacturing Processes lists how those three stages fit together.
The T0 sample measured 0.041 mm spline concentricity against a 0.03 mm limit, traced to local tool compensation. After adjusting the die profile and the sintering ramp, the T1 sample came back at 0.022 mm concentricity and 0.018 mm keyway parallelism. Within this precision parts production case study, the two sampling rounds were not padding, because they moved sinter risk forward.
The FAI report covers every critical dimension plus measured hardness and density, checked item by item before release. Low-alloy PM parts are long established in automotive drivetrains, and Low-Alloy PM Gears for Automotive covers similar applications.
The pilot run produced 5,000 pieces and shipped a PPAP package with process flow, PFMEA, control plan and MSA. First-round Cpk sat at 0.89, driven by furnace temperature swings. After adding live furnace monitoring and tightening the zone tolerance to ±5 °C, Cpk reached 1.33, then settled at 1.67. A pilot run is the turning point in this precision parts production case study, since Cpk decides whether mass production is viable; our own lab covers measurement, described under Quality Control & Inspection Capability.
The eight weeks after start of production (SOP) drive the yield ramp-up. Week one ran 91.2% yield, with defects split between tooth-face burrs and out-of-tolerance sinter dimensions. Swapping the deburring tool and rebalancing green density lifted week four to 96.5%. The finishing cell also added in-line SPC, so any dimension trend triggers an alarm.
By week eight, yield held at 99.1% and takt dropped from 14 to 12 seconds per piece. Precision parts yield ramp-up depends on process settings and live monitoring moving together; one note covers how pressing and sintering parameters are held in production.
Twelve months of serial production shipped 1.186 million pieces at 98.6% on-time delivery (OTD). Each lot carries a traceability code that ties back to raw-material batch, sinter furnace run, finishing machine and inspection record, all produced by Yujiaxin Tech on one site. The customer approved a repeat order the following year and added two parts; precision parts on-time delivery rate at 98.6% was the plainest reason.
The method is simple once written down. Review locks the volume risks, selection matches process to volume and tolerance, sampling exposes forming defects early, pilot run quantifies Cpk, ramp-up lifts yield and takt together, and delivery holds trust through OTD and traceability. Order matters more than any setting, and that sequence makes this precision parts production case study reusable.
| Stage | Key deliverable | Acceptance data |
|---|---|---|
| DFM review | Risk list | 5 working days, 6 risk items |
| Process selection | Comparison sheet | 3 routes compared, PM chosen |
| Sampling | Sample, FAI report | Concentricity 0.041→0.022 mm |
| Pilot run | PPAP, Cpk report | Cpk 0.89→1.33→1.67 |
| Ramp-up | Yield curve, SPC | Yield 91.2%→99.1% |
| Serial delivery | OTD report, lot code | 1.186 M pieces, OTD 98.6% |
Three questions do most of the work. What Cpk did the pilot run reach, what shape is the ramp-up yield curve, and can lot traceability land on a specific furnace run and machine? When a supplier can answer all three with checked data, its volume capability is credible, and that is the quickest filter when sourcing a precision parts mass production supplier. Ask to see the full pilot run to mass production process behind those answers, not a generic capability deck.
To run a feasibility check on your own part, Request a Mass-Production Assessment and we will assess the route your part actually needs.
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