Page 26 - MetalForming Magazine March 2022

FABRICATION
Audit Your
CNC Punching
Operations
...to uncover countless opportunities to reduce waste, optimize overall equipment effectiveness, improve quality and save big dollars.
BY BRAD F. KUVIN, EDITORIAL DIRECTOR
Sixty-eight percent of typical man- ufacturing costs are in materials and labor. That allows plenty of opportunity to recover lost earnings in the sheet metal-processing segment of your business by focusing on real- izing labor and material savings.
So go the findings of the typical audit of CNC punching departments within the walls of sheet metal fabri- cators, as performed by tooling man- ufacturer Mate Precision Technologies. As described to MetalForming by Mate regional sales manager Peter Visser, even the best shops with highly skilled labor and well-maintained equipment can improve productivity, gain capacity and fortify the bottom line by imple- menting best practices related to how they handle their tooling.
“Consider one recent example,” says Visser, “where we estimated excessive, wasted setup time of 2.5 hr./machine, per shift, every working day. With a loaded labor rate of $50/hr. in the punching department, that adds up to $260,820 worth of lost productivity annually.”
Focusing, then, on how a shop han- dles its punching tooling and subse- quent machine setups between jobs,
Visser sees tremendous cost-savings opportunities for fabricators that follow tool-handling best practices. Among them:
• Create centralized tool-storage locations with min/max levels and a clear reordering process, and incorpo- rate that data into an ERP system.
• Post standardized setup instruc- tions at each workstation.
• Create an organized storage system for punch press tooling.
• Establish a consistent tool-main- tenance protocol with well-defined specifications.
• Regularly inspect for damaged punches, dies, punch holders, rails and die holders to verify that they are within acceptable dimensional tolerances.
• Use available specialty tools when- ever possible to reduce or eliminate secondary operations.
“As fabricators look for ways to improve manufacturing efficiency, some opportunities are more obvious than others,” explains Visser. “One of the most inefficient, frequently overlooked techniques is nibbling large holes with a small punch. Generally, parts smaller than 3.5-in. diagonal or diameter should be punched out in a single hit.”
While nibbling works, this process causes problems that negatively affect the machine and the workpiece, including:
• Punching debris that damages tur- ret bores
• Increased production time due to numerous hits
• Excessive tool wear that requires more frequent maintenance and replacement
• Machine wear and tear
• Rough or scalloped edges on the workpiece that require secondary operations.
“This last problem—post-punch rework—unfortunately is a common practice in fabrication shops,” Visser says, “but it doesn’t have to be. Fabri- cators can avoid this rework with a simple change in the punching process and a minor investment in tooling.”
The 80-Percent Rule
When it comes to punching part con- tours, “avoid nibbling at all costs,” Visser advises, while preaching what he calls the 80-percent rule of punching. That is, rather than nibbling contours, use a punching tool that, with each punching stroke, allows at least 80 percent of the
24 MetalForming/March 2022
www.metalformingmagazine.com