Fab shops are realizing the flexibility of the modern punch press in greater numbers. They are turning to punching technology to improve workflow and lower their cost per part by handling more operations on one machine. This is particularly true for forming processes.
The modern punch press makes it possible to bypass secondary operations and eliminate manual processes thanks to its optimized forming capabilities and special forming tooling.
Built into today’s punch press are features that facilitate its flexibility to complete multiple processes and complex 3D parts.
Adjustable ram speeds allow precise control over ram speed—both up and down—in hydraulic and servo-driven electric punching machines. This control enables the adjustment of ram position in minute increments (as small as 0.002 in.), improving punching accuracy that makes it possible to use wheel, knockout, countersinking, and embossing tooling. Greater ram speed control also permits machine operators to strip material from aggressive forming tools. Using a single-head punching machine, which has a lower spring force for stripping power than a turret punch press, operators can slow the ram’s retrack speed in some applications. That allows them to strip material off the tooling better.
Depth offset, a feature enabled by the adjustable ram stroke, allows the operator to electronically “dial in” results, making adjustments to meet engineering or end-user specifications for the part without removing tooling from the machine. This process is much faster than removing tooling from the machine, physically shimming, or changing dies. By making adjustments electronically, the same tool can be used across a range of material thicknesses, making tooling inventory much more adaptable.
Dwell time can be set for bottoming and coining operations. Doing so allows time for the material to stretch and relax before retracting the tooling. Dwell time is important to set the material flow and to develop dimensions in sizing and embossing. It also may be used to reduce stress in the sheet to prevent oil canning, a type of material buckling that causes an irregular surface.
Post- and prepunch delays can be used on hydraulic punch presses to allow time for hydraulic recovery between strokes, or on both hydraulic or servo-driven electric punch presses to provide extra stripping time. A prepunch delay allows time for hydraulic pressure to build up in between punches. A post-punch delay does the same but also allows time for the tool to recover if the springs decompress, or if the material needs to be stripped off a tool before moving the workpiece.
Programmable hover height allows the operator to program an exact hover height value based on the height of the form being produced. Traditionally, the operator would set a hover height that would be used until a form was punched; then they would reset to full-stroke mode. This could slow the machine hit rate and reduce productivity.