Page 31 - MetalForming March 2023 - PMA Chairman Jeff Aznavorian

Special Section
FABRICATION
28 MetalForming/March 2023 www.metalformingmagazine.com
CNC Punching:
POSITIVE STOP A POSITIVE ADVANTAGE
...for coining, embossing, lancing and more, but just make sure to mind the tool sharpening.
BY LOUIS A KREN, SENIOR EDITOR
ACNC punching machine delivers punching machine, force builds as the electrical knockouts (EKOs) and other
ram descends with the control opening the hydraulic valve to supply needed force,” says Erler, explaining typical machine operation.
In some cases, little machine control is available to stop the ram exactly when needed, and when using stag- gered tooling inserts, the valve con- trolling ram force must open and close repeatedly.
“That’s hard on the machine,” Erler says. “Where you need a consistent form—are there any scenarios where you don’t need a consistent form?— you’re much better off having stop fea- tures built into the tool. No machines provide the precision that precision forms require.”
Of course, non-full-material-break- through applications such as forming
tons of force to shape sheet
metal as desired. The force transfers to tooling, which smoothly and efficiently adapts that force to pro- duce cuts, bends and numerous fea- tures and fine details. For controlled- depth operations such as coining and embossing, positive-stop features on tools provide the fine-tuning needed for quality, repeatable performance while saving stress on the machine.
To learn more about the impor- tance, performance and maintenance of positive-stop tool features, Metal- Forming tapped the expertise of Susan Erler, product manager of the punching division at Wilson Tool International.
Reigning in Punch Force
“In practice, say in a hydraulic CNC
coining and embossing applications, for example, absolutely demand stop- ping capability built into the tooling, where material might require a raise of barely one material thickness. A small gap between the body of the tool and the tool cap, equal to the required material offset of the feature, provides for positive stop.
Positive-stop features are built into a variety of tools.
“We put positive stops in stamped- logo tools, for example, where users require a specific depth,” Erler offers. “We put it in lancing forms, again to achieve a consistent height. Once the tool bottoms out, with a properly set height adjustment, forms are consis- tent regardless of the pressure supplied by the machine. Most punching