Joe Sampair, Mathias Die Company, South Saint Paul, MN, USA
There are few things worse than a die that grows dull before its time. For too long the physical condition of the cutting die has been ignored as the key element to improving the many aspects and results of using steel rule dies (SRD) to cut your substrates. Yes, articles have been written on the different qualities of steel, wood and rubber being used in your dies. Yes, there have been articles written to help implement standard processes and procedures for steel rule die construction and storage. However, rarely have I seen an article written discussing how tooling should be used and set up to gain the best possible finished part for your customer.
The condition of the die (mainly the cut edge of the rule in the die) affects every aspect of the job. To list a few: the finished aesthetic quality of the part, controlling the tolerance of finished cut part throughout the run, type and amount of ejection required in the die, time spent making-ready on the die or bringing it up to cut, how long the cut, or kiss cut, lasts before it requires additional makeready work, how long the die will last before re-knife is necessary.
With this in mind, being specialty diecutters ourselves, we set out several years ago to develop an advanced diecutting method—one that will work to improve on all aspects and results of diecutting. Most important for the pencil sharpeners will be the minimizing, and in many cases elimination, of the cost of re-knifing dull dies. When you see it from the diecutter's or diemaker's perspective, the benefits stretch well beyond the bottom line.
After testing and failing with countless types of pads and press stops (bearer) combinations, we finally found the winning combination.
Here's the winning combination. Use a .014-inch (.36 mm) polyester (Mylar A) pad to cut against; combine with non-hardened steel magnetic press stops that measure .014-inch higher than your rule height. The results allow you to simulate hard tool results utilizing what have long been considered "disposable soft tooling." The press stops we provide are magnetic, thus portable, and are mounted outside your sheet size to bear off against the steel cutting plate of the press. Let the stops bear the brunt of the press's damaging tonnage and let the rule do what it is designed to do—which is cut the substrate at hand.
It's not exactly as easy as this, but for those of you who have already implemented the process and have given the system a chance to perform, you and your operators will concur that the long- and short-term results are remarkable.
Let's explore for a moment, the benefits of using the "Stop and Pad System of Diecutting". Then we will outline what we consider the most effective and efficient way to apply the procedure.
Reducing or Eliminating the Costs of Re-Ruling
This one is obvious! Keep the die sharp and the die will perform many times over and will allow you to invest in a higher quality die at the onset of a project.
Cut MakeReady Frustrations and Time
At the onset of our implementation of the "Stop and Pad System," even our own diecutters were convinced that the time spent making-ready would increase. The fact is we cut our makeready times by an estimated 50%. The system is so forgiving, it allows you to move from one setup to the next very expeditiously. For the very short runs it has allowed us to forgo the makeready altogether. It has given our apprentice diecutters the confidence they need to quickly gain experience without the fear of destroying an expensive die.
When diecutting rigid materials, as your die wears or begins to dull, your makeready must be adjusted along with increased pressure on the press as you move through your run. I am sure you have all had those jobs where it sounds like a shotgun firing each time you cycle your press. Some substrates require a tremendous amount of tonnage and inertia to snap through. The result: the higher the shear strength of the material, the further you have to close your press to cut the material, the harder you hit the cutting plate, the faster your tool becomes dull. If you can eliminate this, the battle is half over.
Leveling the Playing Field
Most diecutting presses have peaks and valleys on their cutting surfaces and also lack having "perfectly" parallel cutting surfaces on impression. The press stops tend to help equalize these variations and thus the rule in your die is not required to act as the leveling agent during impression phase. Without stops, the rule tends to dull very quickly where the "peaks" are and the makeready becomes very cumbersome.
Controlling Part Tolerance
Maintaining tolerance throughout the run of your job is critical. By keeping the rule sharp, we can better predict rule deflection and thus better anticipate growth and shrinkage factors that occur during diecutting. When the rule becomes dull, you begin to crush the material even more, which causes a whole list of problems, including poor edge quality of the part, uncontrollable rule deflection, puckering of parts, wandering part dimensions, poor or failing performance of ejection rubber in the dies, etc. When you begin to control your tool wear, we as diemakers may be capable of developing further advances toward holding even closer tolerances than we are now.
Solving the problems of seating
We go through the tedious process of hand leveling the rule in each die we build. Many diemakers do not. In either case, steel rule will move and seat itself during the first several impressions made on your diecutting press. If there is debris stuck in a rule slot, the joints/miters are too tight, or if the rule is not level for any reason, the first few impressions made against the steel bed of your press can do irreparable damage to your die, sacrificing the quality of your finished part. An outstanding benefit that comes with utilizing the "Pad and Stop System" is the fact that any unusual or severe seating problems will show up on the pad surface and can be corrected without permanent damage to the die.
Personally, I have seen and/or tried them all when it comes to using pad systems; Phenolic, Formica (countertop), brass, aluminum, galvanized steel, nylon, polypropylene, cardboard, styrene, etc. None provide the features of accuracy, consistency, low cost and efficiency of use, as this one does.
Remember that the last thing you want to cut against is the steel plate on your press. Yes, there are times when this may be your only option, but exhaust all other alternatives first! If the material you are cutting is softer or as hard as the polyester pad, the process will work!
Setting up the polyester pad and press stops
Materials needed:
By following these steps you will dramatically reduce re-knifing costs and set up times while enhancing the quality of your finished die cut parts—even on the toughest-to-cut materials.
Note: It is important to state that this combination may not be the answer to all types of diecutting problems you may encounter. However, it has solved the majority of issues we were dealing with. This system is designed to work best on newly constructed dies. Depending on the condition of your existing tooling, the "Press Stop and Pad System" may or may not be effective. It's worth a try!