Precision Tool & Die Stamping
Fineblanking Die Clearance & V-Ring Tooling Vector Prepress Guide
Master the micro-clearance CAD/CAM vector prepress, V-ring impinger positioning, and punch corner radiusing for 100% clean-cut fineblanked components.
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1. Fineblanking Physics & Clean-Shear Mechanics
Fineblanking is a specialized metal stamping process capable of producing fully sheared, 100% burnished edges with optical surface smoothness and zero fracture break. Widely utilized in automotive transmission gears, clutch plates, seat recliner mechanisms, and medical surgical tools, fineblanking replaces multi-step stamping, milling, and grinding operations with a single press stroke.
The process relies on three synchronized hydraulic forces operating in a triple-action press:
- V-Ring Clamping Force (F_v): Stripper plate equipped with an annular knife-edge V-ring tooth impinges into the strip scrap web, generating hydrostatic compressive stresses that prevent lateral metal migration.
- Main Punch Shearing Force (F_s): Advances with an ultra-tight radial clearance of
0.5% to 1.0%of sheet thicknesst(compared to 8-15% in conventional stamping). - Counterforce (F_c): A hydraulic ejector opposes the punch from below throughout the entire cutting stroke, clamping the part firmly and preventing bending, dish distortion, or rollover.
2. Engineering Specifications & Tolerances
| Material Grade | Sheet Thickness (t) | Optimal Clearance (c / %t) | V-Ring Height (hv) | Cutting Edge Radius (r_p) |
|---|---|---|---|---|
| C45 / 1045 Carbon Steel (Annealed) | 2.0 – 6.0 mm | 0.6% – 0.8% t (12–48 µm) | 0.18 – 0.22 t | 0.05 – 0.10 t |
| 16MnCr5 Case Hardening Steel | 3.0 – 8.0 mm | 0.5% – 0.7% t (15–56 µm) | 0.20 – 0.25 t | 0.08 – 0.12 t |
| S355MC High-Strength Steel | 2.5 – 10.0 mm | 0.7% – 1.0% t (17–100 µm) | 0.15 – 0.20 t | 0.05 – 0.08 t |
| Austenitic 304 Stainless Steel | 1.5 – 5.0 mm | 0.5% – 0.6% t (8–30 µm) | 0.22 – 0.28 t | 0.10 – 0.15 t |
| Al 6082-T6 / 5754-H111 | 2.0 – 8.0 mm | 0.8% – 1.2% t (16–96 µm) | 0.18 – 0.22 t | 0.04 – 0.08 t |
3. CAD/CAM DXF Vector Die Contouring & Wire EDM Rules
- Cutting Edge Micro-Radiusing: In fineblanking punch DXFs, sharp 90° corners must be replaced with tangential micro-fillets (minimum radius
R = 0.05 - 0.15 * t) to eliminate localized shear stress concentration and micro-cracking. - V-Ring Offset Distance (a): Position the V-ring profile vector exactly
0.6 * t to 1.2 * taway from the cutting die perimeter. Placing it too close damages the die land; placing it too far destroys the hydrostatic clamping effect. - Wire EDM Skim Offsets: When exporting fineblanking punch/die DXF contours for wire EDM, calibrate 4-pass skim schedules to achieve radial clearances within ±0.002 mm (2 µm) and surface finish Ra < 0.2 µm.
- Die Land Relief Taper: Ensure the die cutting land extends
2.0 - 4.0 mmbefore a 0.5° to 1.0° angular relief draft to allow smooth slug and part ejection without galling. - Closed Loop Polyline Integrity: All fineblanking DXF profiles must be verified as continuous closed polylines with zero self-intersections or duplicate vertex nodes.
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