Fine Blanking for Automotive Seat Mechanisms

Seat Recliner Gears: Involute Teeth at AGMA Q8 Without Hobbing

Seat recliner mechanisms use partial gear segments — typically a 120° to 180° arc of a full gear — with involute tooth profiles cut at module 1.5 to 2.5 depending on the seat class and load rating. The gear segment blanked from S420MC or 22MnB5 boron steel at 4-6 mm thickness must achieve AGMA Q8 quality: tooth-to-tooth composite tolerance of 0.025 mm, total composite tolerance of 0.050 mm, and tooth surface finish below 1.6 µm Ra.

Conventional production of recliner gear teeth requires blanking the segment profile, then hobbing the involute teeth on a separate gear cutting machine — a two-step process with 15-30 seconds of additional cycle time per part and tooling costs for the hob. Fine blanking eliminates the hobbing step because the die cavity contains the complete involute tooth profile, ground into the carbide die plate by wire-EDM. The V-ring compresses material into each tooth cavity, producing a 100% shear zone on both the tooth flank and the tooth root — surfaces that hobbing would leave with tool marks and a fracture zone at the tooth tip.

The HF-320 press with 3200 kN total pressure, 1600 kN V-ring force and 800 kN counter-pressure is the production standard for seat recliner gear segments in module 1.5-2.0 at 4-5 mm material thickness. For heavier seat applications (commercial vehicle seats, SUV third-row seats) in 22MnB5 at 6 mm, the HF-400 provides the additional 800 kN of blanking force required to maintain full shear zone depth on the larger tooth profiles.

Slide Rail Components: 800-1200 mm Length with 0.05 mm/m Flatness

Seat slide rails are the longest fine-blanked components in the automotive interior. The upper rail, lower rail and ball retainer form a telescoping track that permits fore-aft seat adjustment over a 200-280 mm travel range. The total rail length runs 800-1200 mm depending on vehicle platform, and flatness across the full length must hold to 0.05 mm per meter to ensure smooth sliding action without binding or rattle.

Fine blanking achieves this flatness through the counter-pressure pad, which applies uniform holding force across the entire rail blank during the cutting stroke. The 100% shear edge on the rail cross-section — particularly the internal channel that guides the ball bearings — eliminates the burr and fracture zone that would create friction points in the sliding interface. Conventional stamping of slide rails requires post-blanking straightening and channel deburring, adding 20-40% to the per-part cost; fine blanking eliminates both operations.

For multi-station progressive die production of slide rail components, the HF-650 press with 6500 kN total pressure, 600×600 mm working table, and 50 SPM cycle rate provides the force and die space for multi-cavity layouts. The progressive die configuration feeds coil stock through stations that pierce ball retainer holes, form the rail channel, blank the component profile and crop to length — all in a single press cycle per feed pitch.

Deburring and Cleaning for Seat Safety Components

While fine blanking produces 100% shear edges with no fracture zone, a micro-burr can still form at the die-roll transition on some component geometries — particularly at tooth root radii and hole edges. For seat safety components that undergo 30,000+ engagement cycles, even a 0.05 mm burr can accelerate wear on the mating surface. Post-blanking vibratory deburring and ultrasonic cleaning remove this micro-burr without rounding the functional edge.

HS-FINEB provides deburring and polishing equipment matched to the seat component production line, with media and process parameters selected per material grade and component geometry. The combined fine blanking + deburring + cleaning cell delivers parts ready for assembly — no secondary machining, no manual deburring, no edge inspection sorting.