Cutting force, blankholderforce & work
12.1
Eqn. 1
Eqn. 2
Eqn. 3
Eqn. 4
Eqn. 5
Eqn. 6
| Cutting power | FS | = | kN | ||
| Cutting force slanted edge | FS g | = | kN | ||
| Cutting force blunt edge | FS abr | = | kN | ||
| Blankholderforce | FN | = | kN | ||
| Stripper force | Fab | = | kN | ||
| Cutting work | W | = | J |
| Cutting edge length | lS | = | mm | |||
| Sheet thickness | s0 | = | mm | |||
| Tensile strength | Rm | = | MPa | |||
| Mean factor cutting | mS | = | ||||
| Constant | C | = |
Calc 1
Cutting power & cutting work
Example 1 A stamped part made of the material St14 has a cutting edge length of 200 mm and a sheet thickness of 0.8 mm. Under these conditions the following values for the cutting forces result:
- With a normal cutting edge the cutting force is 39 kN.
- With an inclined cutting edge, the cutting force is reduced to 31.5 kN.
- When using a worn punch, the cutting force increases up to 63 kN.
In addition, the punching process requires a cutting work of 13.9 Nm, a blankholderforce of 11.8 kN and a stripper force of 11.8 kN.
s0 | Ausschneiden | Lochen |
|---|---|---|
< 2,0 | 0,10 ... 0,15 | 0,12 ... 0,18 |
2,0 ... 3,5 | 0,12 ... 0,20 | 0,20 ... 0,25 |
>3,5 | 0,15 ... 0,20 | 0,25 ... 0,30 |
Tbl. 1 Correction value C for the stripper force F | ||
During the cutting process, the material in the cutting zone is plastically deformed. The smallest material particles are pressed in a ring onto the free surfaces of the stamp. Due to the resilience of the material to be cut, this radial pressure - similar to shrinkage stress - is maintained even during the retraction of the punch until the material is finally stripped off.*
*
Semmlinger, E.; Hellwig, W. / Spanlose Fertigung: Schneiden-Biegen-Ziehen / Vieweg Fachbücher / … / 1990 / 4. Auflage