Written By Mark Batson Baril
What is a "Progressive Cutting Tool" and should everyone be using this type of tooling in their diecutting operation?
There are many different types of tooling for many different specialty applications that involve diecutting. Progressive cutting tools typically fall into the category of male/female or matched metal tooling. They can also include steel rule die or milled punch shapes as well. For the sake of this answer we are talking about a single tool where all of the component cuts are made within this one tool. What this type of tool does so well is cut very complicated shapes from difficult to process materials (AKA - the stuff nobody wants to work with). The shape will often include interior knock-out, slits, embosses, and unusually shaped perimeter cuts. Because the tool would be very difficult to build as a one stage, one strike does it all type of tool, the final shape is accomplished through a series of steps that the material progresses through. As to whether or not everyone should be using this type of tooling - the answer lies in the complexity of the shapes you tend to cut and whether or not you have the type of machinery, designers, and tool makers to run a tool like this.
The typical machine that runs a progressive tool is a punch press or a flatbed platen type press with some type of accurate incremental feed system. The key to having all your options open during the tool design phase is to have a machine that has an open bottom or clearing bolster plate, an open back or side(s) for clearing waste and feeding, and a feed system that is tied directly to the motion of the machine. For moderately to large tolerances (± .062" 1.57mm) the feed system must hold the material accurately the entire time it is in motion and while it is stopped. In this type of tool there is no registration while in the tool except for side guides. For more accurate alignment throughout the process (±.005" .127mm) the feed unit must hold and place the material accurately and then just as the impression is made the feed unit must allow the material to move freely and settle on the pre-punched locating holes (pilots). Having a finely tuned feed unit with a material release is critical to the entire process.
The typical tool layout will have a series of stages where various cuts take place. The natural stages occur in this progression -
- 1. The material enters the tool and the first impression cuts a series of two or four pilot holes that will allow for exact registration during the balance of the cuts. The more piloting holes you have the more accurate the product will be. The pilot holes make the location by sliding onto or being centered by a tapered male pin in each stage of the tool. Other part related holes, shapes or slits can also be cut at this point.
2. During the second, third, or fourth stage(s), other cuts, embosses, etc…, can be made all in perfect registration using the pilot holes. The real beauty of the cuts made during the several progressive stages of cutting is that extremely unusual or complex shapes can be made via multiple cuts at one image.
3. During the last stage, the final perimeter cut is made and the final finished part is typically blanked through the tool into the part collector below. Because of the way the stages have been planned, the final part will have no chance of nicks or uncut areas in any of the normal joint areas related to a steel rule die.
During all the cutting, the material web is never asked to carry a part that has been pushed back into the web after a cut as is often the case with a steel rule or combo male-female/steel rule die. Each cut stage strips the waste away and only during the final cut does the web become weakened by the missing part. Because of this, the press can be run at maximum speed and accurate parts can be delivered waste free very quickly given just about any material type or part shape.
All in all this type of tool should win the "REALLY COOL TOOL AWARD".
This is one of those great areas to explore with just the right project and I hope that one day you have the need to buy, help plan, or run one in your shop too.