Protecting Your Investment in Punch Tooling
Have you ever looked at a home appliance and wondered how it was made? Chances are that many of the components were produced on a Computer Numerical Control (CNC) punch press. CNC uses computers to contorl large machine tools. CNC tools include lathes, mills, routers, grinders, lasers and, of course, punch presses. CNC punch press machines include turret style machines, rail style machines and punch/laser combinations among others. CNC punch presses were introduced in the 1950s and have evolved into very versatile fabrication machines for the sheet metal industry.
These machines have the flexibility for numerous different punching styles. They can punch a single round, shaped or special shaped hole; multiple holes at once, with the use of specially crafted tool sets; or use a single tool to nibble (multiple hits with the same tool in succession) special contours. Custom designed forming tools can also be used to create a variety of forms in the sheet metal while still in the machine, eliminating hte need for many secondary operations. There are endless opportunities to put these tools to use, making it even more important to protect these tools for the long run, reducing your overall costs and increasing your bottom line.
Increasing Lifespan of Tooling
Punch press tooling can be a costly investment when tooling isn’t properly cared for. However, with care and proper maintenance, these tools can last for years, or potentially the lifetime of a machine. Maintenance includes sharpening, tool storage and lubrication. Proper tool setup and usage is important to the longevity of a tool. The process in which tools are used can also play a vital role in the lifetime of the tooling, whether it is normal punching, nibbling, blanking, contouring or forming.
Tool maintenance involves sharpening the punch and die when the cutting edges become less than ideal. How does the user know when they’ve become less than ideal? Punched parts begin to have a burr around the edges that is more prevalent than with sharp tools. The sound that the punch makes when punching a hole starts to sound different; it is typically louder than the sharp tools. Sheets may also start to stick to the punch point when the punch is retracting, causing sheets to «slap» on the table. Cutting edges are visibly broken down. When any of these start to occur, it is probably a sign to sharpen the tools. For the maximum tool life (up to double the expected life or more), sharpen the tools more often, taking off small amounts of material (0.004″ – 0.008″ / 0.1mm – 0.2 mm) with each sharpening. This is achieved by sharpening the tools before a noticeable radius (approximately 0.010″ / 0.25mm) is worn onto the punch tips. The bigger the radius that forms on the punch tip, the more material that has to be removed to make the tools sharp again. Proper wheel choice, grinding techniques and good coolant use can help the user achieve high quality results while helping to maximize tool life.
Proper tool storage can play a role in the life span of punch press tooling. Tools that are left out in the open collect airborne oil and accumulate dust. If not cared for properly, the oil and dust gets into keyways, grease grooves, springs and other punch assembly components. It can then be transferred to the punch press where it could damage turret bores and tool holder assemblies. During the punching cycles these elements start to rub and wear down tooling and machine components. It is important to remember that proper care of tooling extends to more than just being in the machine.
Tool lubrication is another way to achieve a longer lifespan. Keeping internal components clean and free from dirt allows them to slide and interact freely, reducing friction and wear. Some machines come equipped with automatic tool and sheet lubrication systems and using these features can aid in punch press life. Sheet lubricators add a fine mist of oil to the sheet metal just before punching takes place. This helps the punch point cut through the material faster while also lubricating the punch point, allowing the tool to pull out of the metal with reduced drag and improving stripping. Lubrication to the punch tip also helps reduce heat buildup to the punch while reducing potential galling of the punch point.
CNC punch press tooling can be a big investment. Taking the time and effort to protect these tools is also an investment. However, taking the time and effort to properly maintain, store and use these tools can provide years (and in many cases, decades) of productive hole punching and forming while increasing the profit margin from the initial investment made.