A couple years ago I wrote a blog post on dies, technical and informative but deadly boring. The topic does need some expansion, especially with multiple shapes on a laser sheet label set as well as the intricate back and front cuts on a variety of multiple purpose TTR label sets and closure / tear strips. Not only adhesion and legibility but in the case of closure strips and tear seals the function also needs to be tested. Cutting dies are normally the most expensive part of the one time set up charges and invariably the one with the longest lead time. What I want to do is present a logical progression for simulating die cut parts as well as a method for creating first article and qual / validation parts without breaking the bank.
When a new label is being designed the first question we ask is whether it’s a geometric shape or a special shape. We literally have thousands of standing dies in rectangles, squares, circles, ellipses, and other shapes. Our policy is that those dies are available for use by all customers. Proprietary shapes of course, are limited to the customer that purchased them. Don’t ask to make you some die strikes of that cool tear strip you saw on the Acme Medical Spineatron package, we just ain’t gonna do it. I will make you a die that’s slightly different (if there are no patents involved) and we could do that with one of three methods.
The first method would be wielding the trusty Exacto knife. We can make up some rough cut shapes here or send you the raw material to make your own shape. This has been very successful in evaluating and reducing the number of label options in the mix. A couple things need to be taken into consideration however. If it’s a paper label stock the grain needs to be oriented the same way on the paper that it will be for the actual press run. Paper is much stronger with the grain than it is going against the grain, as we see from the different tear strength numbers for machine direction, MD, and cross direction, CD. It is also critical to note that on complex shapes the Exacto is not quite exacto enough. Small nicks and tears can compromise the shapes. Still it is a very effective way to begin the design and testing phase.
The next logical step is to create some product using a ‘real’ die. The choice here would be flexible or ‘mag’ tooling. We purchase magnetic cylinders of fixed repeat length, the circumference of the die and actual size of the finished label. These tools run from about $275 to $400 and are very good for accurate prototyping and short runs. The cutting is very precise but the die life is much shorter than engraved tooling. Typically we use a larger repeat and put several permutations of the desired shape on the tool, different perfs, shape angles, tear strip configurations, etc. A number of options can be tested for the relatively inexpensive cost of one mag die.
Once the shape is approved we can move to long lasting, precise, and efficient engraved rotary tooling. BUT be advised that if you did your quals and validation on the flexible / mag tooling and want to switch to the production tooling for production runs, more than a few companies regard this as a process change and reams of paperwork, delays, and multiple redundant activities will almost assuredly ensue. Time seems to stand still once these changes are submitted. My advice, learned painfully from years of experience, is to get as far as you based upon your internal change control processes and then buy the damn production tool. It will save lots of time and aggravation for everyone.
When ordering rotary tooling we need to know the material we will be cutting, whether we will be cutting against liner or a steel base roller, estimated run quantity and based on that info which press we want to run it on. Larger presses have a higher hourly rate and take more expensive tooling but can make up for it with the reduced run time from running more parts across on the equipment. The more information we have the better we can dial in on which direction we need to go to get your label qualified, validated, through the FAI process, and into production.