Case Study: Automotive Transmission Gear Fine Blanking Line

Press: HS-FINEB HF-650 (650-ton triple-action hydraulic CNC fine blanking press). The HF-650 was selected based on force calculations: blanking force 2,800 kN for the gear profile (material shear strength 420 MPa, shear-line length 157 mm including 25 teeth, thickness 4 mm), V-ring force 900 kN (32% of blanking force for 16MnCr5), counter-pressure 500 kN (18% of blanking force). The 650-ton capacity provides 15% force reserve above the calculated total.

Die: 5-station progressive die in tungsten carbide (K20 grade) with TiCN PVD coating on cutting edges. Station 1: pierce pilot holes and center bore; Station 2: pierce gear tooth root relief holes; Station 3: blank external gear profile with V-ring; Station 4: coin tooth flank surfaces; Station 5: shear-off and eject finished gear. Die area: 450 × 380 mm. Shut height: 320 mm. Pitch: 52 mm. Material utilization: 62%.

Material Handling: Servo-driven coil feeding system (Lenze drive) with 52 mm pitch, pilot registration at Stations 1 and 3, hydraulic scrap shear synchronized at 1:1 stroke ratio. Coil: 16MnCr5 strip, 4.0 mm thickness, spheroidized annealed to HV 160 (carbide spheroidization rate verified at 92% by metallographic examination), strip width 55 mm.

Timeline: The project was executed over 16 weeks from order to full production. Weeks 1-6: press manufacturing and factory acceptance test at HS-FINEB facility in Huangshi, including trial blanking of sample gears. Weeks 7-8: shipment to Southeast Asia, installation and utility connection (electrical power, hydraulic oil fill, compressed air). Weeks 9-10: die trial — first 500 parts produced at reduced speed (20 SPM) for dimensional verification and edge quality inspection. Weeks 11-12: parameter optimization — V-ring force tuned from initial 950 kN to final 900 kN after die-roll measurements showed 0.42 mm (10.5% of thickness), which was reduced to 0.35 mm at the optimized setting. Weeks 13-14: production ramp to 45 SPM with SPC baseline established over 5,000 parts. Weeks 15-16: operator training certification and full-volume production handover.

Die trial findings: Initial die trial revealed that the Station 4 coining force was insufficient to produce the required tooth flank surface finish (Ra 0.6 µm versus target 0.4 µm). The coining station insert was reworked to increase the coining stroke by 0.05 mm, and the dwell time was extended from 60 ms to 80 ms. After rework, tooth flank Ra improved to 0.3 µm — exceeding the specification. The die cutting edges were then TiCN-coated, increasing expected die life from 60,000 to 120,000 strokes between sharpenings.

Operator training: Two operators and one maintenance technician received 10 days of on-site training covering CNC HMI operation, recipe management, die changeover procedures, daily maintenance routines (hydraulic oil level checks, filter condition monitoring, lubrication point servicing), and troubleshooting for common fault conditions including mis-feed detection, die protection sensor trips, and hydraulic pressure deviation alarms.

The implementation of the HF-650 fine blanking line delivered measurable improvements across cost, quality and productivity metrics:

Hobbing elimination: The gear hobbing operation was eliminated entirely, saving $0.15 per part in machining cost and eliminating the associated tooling, coolant and maintenance costs. At 120,000 parts per month, this represents $18,000 monthly savings ($216,000 annually).

Scrap reduction: Scrap rate decreased from 8% (conventional stamping plus hobbing) to 2% (fine blanking), primarily due to the elimination of stamping edge defects that caused hobbing rejection. At 120,000 parts per month with a material cost of $0.45 per part, the scrap reduction saves approximately $3,240 monthly in material alone, plus the avoided cost of processing defective parts through carburizing before rejection.

Production rate: The line achieves 45 SPM, producing 120,000 gears per month on a single shift (7.5 hours effective production time). The previous process required two shifts to meet the same volume. The freed shift capacity enables the customer to take on additional production without capital investment in a second press.

Quality consistency: The CNC-controlled force profile and closed-loop motion control of the HF-650 produce consistent edge quality across production runs. Statistical process control (SPC) data over the first six months showed Cp = 1.67 and Cpk = 1.55 on the critical tooth profile dimension — well above the customer's Cpk ≥ 1.33 requirement.

Die life and maintenance: The tungsten carbide progressive die achieved 120,000 strokes between sharpenings with TiCN-coated cutting edges, compared to the 60,000-stroke baseline for uncoated carbide. Scheduled sharpening takes 4 hours and is performed during shift changes to avoid production downtime. Total die life is projected at 3 million strokes before insert replacement, corresponding to approximately 25 months of production at the current volume. The HS-FINEB field service team provides annual preventive maintenance including hydraulic oil analysis, filter replacement, slide guideway parallelism verification and proportional valve response testing.