Diecutting – Keeping the Process Simple
by Nick Crabtree, president
N & J Training, LLC
Whether the parts are folding cartons, plastic clamshell covers for electronic products, gaskets, shoe leather, pocket folders or POP displays, the principles of diecutting remain the same. As a colleague of mine once stated, “We are creating nothing more than a giant cookie cutter.” This is true, but that simplifies the manufacturing of diecut parts a little too much. Once we start to throw things into the mix, such as creasing, perforating and 50 percent partial cuts, these additions start to make the part production a little more complicated. Or, do they?
If we approach these mixtures in the same fashion that we would if we were cutting only, then it should not add an exceptional amount of additional work. To keep the process simple, there are a number of steps that should be taken before each diecutting project.
The first step should be to clearly identify the product or stock being diecut. This is a very important step because it will dictate the tooling and materials needed to successfully cut the product. For example, we would not use 3 point cut rule on 100lb. cover stock. It is overkill and, in fact, would jeopardize the opportunity to cut the material cleanly.
Step two would be to make sure the cutting surfaces and plates are in good condition and, above all, the cutting surface and the tooling holder are parallel to each other. Make sure all old tape, rust and general dirt is removed from the front and back of the cutting plate. Clean the backing plate supporting the die. By doing these two simple cleaning processes, we are already 50 percent of the way to a quality diecutting job. I am amazed at the number of times I have been called into plants to solve a problem, and the simple solution to a good makeready and diecutting job is to clean the equipment.
We now have a nice, clean piece of equipment ready to receive the tooling for the diecutting. One of the most amazing things I have observed over the years is that most companies will not spend 10 minutes to clean up the last diecut job, but they will allow three- to four-hour makereadies, when the makeready should take no more than 30 to 45 minutes. I call this a violation of the step-by-step approach to diecutting – and, of course, we all know it is false economy. That false economy very often is caused by not allowing time in the schedule for cleaning. An unskilled scheduling department can cause untold losses in profit and communication barriers with production.
Let’s take the next step and look closely at the right tooling and the correct materials built into that tooling for the optimal diecut part with the highest quality finish.
Twenty-five years ago, there were only a few manufacturers and types of steel rule in the US. Now, there are many manufacturers from around the world, many types of rule, with many bevels and many gimmicks. Twenty-five years ago most diecutting operators knew how to diecut, but today, in our fast-paced world, we have let go of the focus on basic training.
A number of years ago, the only thing to worry about with the rule was whether one could bend a 90° angle with a 1/32 radius and the rule would not crack. The bevel angle is mostly decided upon by the equipment in the dieshop. If the diemaker has a miter machine that is set for 42 to 45°, that is the angle of the rule that he orders. If it is 54°, he has limited himself to that support on his miter machine.
What the diemaker must focus on is where the majority of his business lies. If it is in folding carton, then 42 to 45° is probably best – that is, if his customer protects the cutting edge on press. If his customer cannot protect the cutting edge, then 54° is the best. It is a little more robust and, if the diecutter cannot protect the edge, hairing on the carton is not an issue.
These are the three simplest ways to look at rule requirements:
- edge angle
- diecut material
If the product to diecut is plastics, things become a little more complex. As materials have developed, rule manufacturers have risen to the occasion. For example, Poly-Ethyl-Toluene (PET), which is mostly used to protect electronic products against theft, requires sophisticated bevel angles and special edge hardening. Choosing the correct type of rule for the job being cut should be kept very simple.
In many cases there are a number of flaws in the rubbering process, and I see them like this:
- Training of the person applying the rubber. Many diecutting operations take the least experienced person in the plant and give him rubber, glue and a pair of scissors. His complete training is summed up in a few words, “Just put rubber on both sides of the sharp bits.”
- Too much rubber being used. Systems using waterjet cut rubber are very spectacular, and the die looks very pretty. But, if we look carefully at a job that is covered in waterjet rubber, take note how much rubber contacts the cutting plate, causing additional pressure on the material. The amount of surface area of rubber on the dies has increased significantly using this process. So, when designing the rubbering pattern, use caution in how much rubber is used. The high-speed diecutting presses rely on using the least amount of tonnage, preventing distortion in the sheet and thereby allowing the operator to “fly” the sheets at high-speed. From the benefit side, waterjet rubber does allow for an even distribution of pressure throughout the sheet.
Steel, phenolic counters and creasing matrix
This is where it can get a bit more complicated. Fortunately, the International Association of Diecutting and Diemaking (IADD) has helped organize formulated charts for calculating the channel widths and depths. These figures are used as guidelines when producing phenolic counterplates. The organization also has charts for the production of steel counters.
As we had indicated with steel rule, there now are a number of worldwide manufacturers for creasing matrix. Whether the matrix is manufactured domestically or from abroad, each supplier has its own way of calculating the two most critical dimensions. These dimensions are the matrix thickness and the channel width. Matrix height is calculated by simply using the material thickness that is being diecut. That is how it used to be when cutting the crease by hand. Now, it varies from material thickness plus 0.010" (0.254mm) for a backer, to 1.5 times the thickness, etc.
The channel width is calculated using all kinds of formulas from 1.5x to 1.75x or even 2x material thickness plus the thickness of the crease rule. The formulas themselves are very simple if we choose one and stick with it, but if we want to change, then what happens? It is difficult to understand, from my perspective, why there is not more control and standardization as there is in Europe – but, it is something diecutters here in the US must deal with.
The point is, look at different matrix products and see how many variations there are available. Years ago, when we used to cut our creasing matrix grid by hand, we never had these problems. It is a simple process, and there is no need to overcomplicate it.
The message here is to try to keep the diecutting process as simple as possible. Study the process carefully, and choose the rule that works best for the diecutting job. Choose the creasing product and formula that works, then stick with it and learn from it. Diecutting and finishing life, in general, will become much easier to work with.
Nick Crabtree is president of N & J Training, LLC, Hagerstown, Maryland. To contact Crabtree, call 240.313.8598.
This article is reprinted with permission from the International Association of Diecutting and Diemaking’s monthly magazine, The Cutting Edge, June 2007.