Written By Mark Batson Baril
Recently a question came to us from a diecutter that was having problems with stripping some intricate designs. The information contained in the answer is quite generic and we hope it helps you as well!
What resources are available for stripping complex diecutting jobs? We are becoming more involved with diecutting jobs which involve intricate stripping designs. An example might be a 26" x 40" (660mm x 1,016mm) sheet that has 100 holes 1/4" (6.35mm) that have to be diecut and stripped. We find that most diemakers are not very versed in how to supply male and female stripping boards. The other big problem is putting together the bottom pin assembly. Typically we will use spring loaded bottom pins to help remove stripping waste. When the stripped pieces are too close together or too numerous then we cannot get the bottom pins close enough. Are there any devices available to help work around the problem or any other alternatives available in place of bottom stripping pins?
Indeed there are many diemakers that are not versed in the most advanced techniques of high speed stripping. Most do not need to know as they may not have customers demanding the type of product you need. On the other hand there are many die shops around the world that are very well versed in how to make jobs strip well on press no matter how complex. Most of them belong to the IADD and their numbers are growing all the time! Keep looking and you'll find one that has the experience and skills to do what we'll outline in this answer.
The particular job you describe in your question is a tough one. Especially if you have a very picky customer that will freak-out with even one slug left in the product. When you get into very small intricate cut-outs that must be stripped it is critical that the stripping boards be made as precisely as the die is and in some cases better than the die. Laser cutting of all the parts from die to strippers to blankers, from the same exact computer design, is a requirement due to the accuracy and repeatability it provides.
On less complex jobs, a well made female stripping board can be used in combination with top and bottom pins to do a good job. When you hit the slightly more complex jobs or those that repeat often, it is smart to purchase both male and female strippers. Most of the time these can be made as you would in the first case where the openings in the female are slightly larger than the waste to be pushed through. With the right placement of the male pins, the job will strip well.
In the most complex of jobs, as you have described, bottom pins are impossible to use because of their shear size. There are companies that make specialty pins and assemblies to get as close as you can. They can work well yet with the right die maker at the helm a stripping tool can be made to strip these complex jobs. Making the opening in the female board slightly smaller than the waste (or at least several corners of the opening) combined with the right placement and type of male pin will force the waste through without the use of bottom pins. When you get into situations where you have hundreds of pieces to strip, the male pins should be varied in height to reduce pressure and increase performance. On the job you have described we would split the number of holes into thirds and reduce each section of these male pins by approx. 1/8" (3mm). Some companies will actually angle the male board slightly 2-3 degrees to accomplish this same scissoring effect. The newest systems actually place the pins at varied heights to accomplish the same thing.
Alternative methods are available. Of course there are many other ways to strip waste away from parts that may involve different types of presses and stripping tools. Feed-thru punches, side eject punches, matched metal tooling, air assists, post cutting bending of parts, stripping wedges, stripping fingers, etc... in both flat and rotary configurations are just a few alternative approaches to similar problems.
Whatever the complexities of your job, don't give up on the diemakers you have at your disposal. Although we are all learning more and more everyday and are constantly making improvements, the problems you describe are ones that have been solved many times before.
We hope you enjoyed the article. Please contact Cut Smart if you would like more information on this subject.
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