Punch Radius
4.3
Fig. 1
Tool geometry for ① recoil draw ② flangeless draw
rb bottom radius rST punch radius rM die radius pN blankholder pressure uZ clearance
The rounding radius on the deep-drawing punch r St should be ≥ 4 to 5 times the sheet thickness:**
Eqn. 1
| Punch radius | rSt | = | mm |
| Sheet thickness | s0 | = | mm |
Calc 1
Punch radius rSt General
With small die radii r M, the punch radius r St must not be smaller than the drawing die radius r St > r M
Punch radius in second draw
The most favorable drawing conditions are achieved in the second draw with a die inlet angle of 45° and a punch radius of:*
Eqn. 2
| Punch radius | rSt | = | mm |
| Punch diameter | dSt | = | mm |
Calc 2
Punch radius rSt in the second draw*
Eqn. 3
| Punch radius | rSt | = | mm |
| Punch diameter | dSt | = | mm | |||
| Constant | C | = |
Calc 3
Punch radius rSt in second draw*
For redrawings, the relationship r St 2 ≈ r St 1 applieshowever > r M
*
Tschätsch, H. / Praxis der Umformtechnik / Vieweg / Wiesbaden / 2003 / 7. Auflage
*
Semmlinger, E.; Hellwig, W. / Spanlose Fertigung: Schneiden-Biegen-Ziehen / Vieweg Fachbücher / … / 1990 / 4. Auflage
*
Herold, G.; Kluge, M. / EFB-Forschungsbericht Nr. 61: Simulation des Formstempeltiefziehens im Weiterschlag / Europäische Forschungsgesellschaft für Blechverarbeitung e. V. / Hannover / 1994 / …
*
Grüning, K. / Umformtechnik / Vieweg Fachbücher / Braunschweig / 1986 / 4. Auflage