By Brad F. Kuvin, Editor
Technology enhancements to CNC punch presses give stamping operations and tool-and-die shops good reason to consider expanding their horizons.
CNC punch presses were once relegated to fabrication shops as workhorse punchers of holes of various shapes and sizes, and for edge-nibbling of fairly simple shapes. Forming tools then allowed fabricators to add louvers and lances to minimal form heights, 8 mm (0.3 in.) or so, but at a relatively slow speed without extreme precision.
Today, though, punch-press manufacturers deliver machines with comparatively fast forming capabilities and accuracies once relegated to hard-tooled stamping presses. Thanks to technology enhancements to CNC punch-press hydraulic systems, the use of electric punch drives, linear-motor technology and other improvements, traditional stamping houses and tool-and-die shops now see reason to invest in CNC punching machines.
"Many stampers find that CNC punching machines really help fill a void in the area of prototypes. Punching machines allow a stamper that has developed a prototype part, to be produced with a hard tool, supply limited production runs of the part while the stamping die is being machined," says Mike Morissette, punch product manager for Trumpf Inc., Farmington, CT. "Customers used to have to wait for hard tools before production could start. During this period, the stamper risked losing the production job to a competitor. Now, with new high-speed precision punching machines, the stamper can be the sole supplier, from prototype development to short-run production to volume stamping. We see stampers now using CNC punching machines to make part runs of 10,000 to 15,000 while the hard tools are being made-to fill a gap for their customers."
Punching machines also benefit the quoting process, allowing a stamper or tool-and-die shop to provide sample parts with RFQs in one day. This is particularly true with hybrid machines that combine laser cutting and punching. "The last five years have brought a transition to lower volumes and quicker turnaround on RFQs," says Lloyd Keller, national sales manager-forming for Murata Machinery, Inc., Charlotte, NC. "Hybrid machines fit perfectly where shops might run 500 to 2000 pieces. Presses also fit great for aftermarket support, to produce very small runs of parts produced on stamping presses in production. For example, hinges or brackets that might be ordered aftermarket in lot sizes of 50 or 100-a laser-punch combo makes sense here, rather than have to seek out, clean and install the hard tool in a stamping press."
Tighter Tolerances
Improved hydraulics and, in some presses, the use of electrically driven punch heads, have allowed stampers to consider using CNC punching machines on tight-tolerance parts such as card guides used in telecommunications equipment. "Where precision is critical in forms," says Patrick Canning, vice president, Finn-Power, Schaumburg, IL, "shops might look to electric machines, where we can deliver form repeatability of ±0.0004 in." |
Improved forming on punching machines also comes thanks to better hydraulics in newer machines, according to Bob Coscarelli, CNC product manager for Amada America, Buena Park, CA. "We see greatly improved control of the stroke-both its distance and dwell -so that the forming of louvers, lances, extrusions and the like occur quickly and very precisely," he says. "These hydraulic enhancements, along with improved controls introduced in the late 1990s, deliver, on average, a 30-percent improvement in productivity and quality for our customers."
Trumpf's Morissette concurs, adding: "Advances in hydraulics allow machines to stroke faster when upforming stiffening ribs. During high-speed beading of ribs, we can stroke at 2800 strokes/min. This higher speed, along with improved hydraulic control over tool-retract height, allows us to do more than form-we're really flowing the material now. This gives improved appearance."
