Making Your Die Cutting Operation Run Smoothly
Editor’s Note: This is the third in a series of articles about how to set up an efficient die-cutting press system. Following are excerpts of a presentation made by Randy Norman, Preco Applications Specialist, at the 2007 Odyssey Exposition. You can see the first article here, and the second here.
Standardize your cutting plates
When standardizing cutting equipment plates, the feed line height on an automatic press needs to always be the same. For example, if you change your cutting plates to a 1⁄8" (3.17mm) bar plate and then go back to a spring steel cutting plate, it results in 1⁄16" (1.58mm) difference in height. That may not seem like a lot until you're trying to run something flat, but when it’s cut, it starts potato chipping up or coming out of the web because it's off by that 1⁄16" (1.58mm). It is imperative that the feed line height is all the same.
Typically recommended on the Preco is a blue tempered spring steel because it’s inexpensive, approximately 1⁄16" (1.58mm) thick, features a 48-51 Rockwell hardness and is lightweight, so when you use it, you can make a makeready and store it with the die for the next time it’s used. If everything is flat, a makeready may not be necessary. However, if you’re working in an area with varying climate conditions (raining one day and dry the next), patch ups may be needed as the dieboard wood expands, shrinks and swells. In theory, most applications require a makeready. Variations exist even with coated boards. Humid conditions can make working with coated boards difficult as well.
Maintain your equipment
Poor maintenance of equipment is another problem seen in the industry. If diecut slugs are all over the clamshell or diecut slugs get into the gearing, they will create problems such as deflection issues. Consider the following example that shows how easy it is to run into problems if equipment is not maintained. During the first Odyssey, I was working on a clamshell. I pulled a cutting plate out and was showing people how the die worked, put it back in and proceeded to crush my die. I had unknowingly left a slug underneath the cutting plate. Thank goodness they had a die shop onsite and could immediately make me another one, because I didn't have an extra.
Let's consider plate stack up and the importance of maintenance on the plates. A ram is in the press and sometimes a spacer, in our case it's usually an aluminum spacer. There’s a die mounting plate which is usually steel and then a die that goes up against the die mounting plate. Oxidation can occur when an aluminum plate is next to a steel plate, so be sure to clean between your press spacer plates. The plates need to be taken out and washed with a 3M penetrate or WD40, scrubbed and put back in.
A good point to remember: when the plates are pulled, mark them so they are put back in exactly the same way they were removed. If a plate is accidentally spun 180 degrees and then put back in, all of the makereadies stored are going to be off by 180 degrees. Make sure when a plate is pulled out, it is put back in exactly the same way on any press, because if it isn’t, setting up a preset job will be much more difficult than it has to be.
Preco cutting equipment plates feature four posts and inserts that should be greased every day. If one post dries out, the ram platen will stick on that post and then the cutting plates will not be parallel with the die. A maintenance program is a must, no matter what type of press you have. At Preco, we constructed a simple micrometer adjustor that allows us to check and make sure the plates are parallel in our system. Nine points are measured inside the press before it ships out: three on one side, three in the center, and three on the other side. These have to be within three thousandths before they ship out. Anyone can perform this test with a micrometer that will fit inside the press area.
Preco equipment also has feed systems with rollers that have to be cleaned. Like anything else, if they're not cleaned, the rollers are going to get contaminate on them and the diameters will change. If the diameter of the roller changes, the feed lengths of the material will be affected. Soap and water is recommended to clean the rollers. If using alcohol to clean the rollers, use 90% denatured alcohol as the 70% alcohol will dry out the rollers and cause them to crack. Be sure to wipe off all alcohol.
Another item to consider on roll feeds is the pressure. You want to maintain constant pressure on the rollers. If this does not happen and one roller has more pressure on one side than the other side of the roller, the surface diameter increases with greater pressure which increases your feed length on that side and causes tracking issues with the material. If you're going to have roll feeds, make sure they're all gapped and have the same pressure on them at the same time. It is also very important that the rollers are parallel within .003" (.076mm) of each other. Anything greater will cause tracking problems. At Preco, we typically test these with a micrometer and measure left and right on the roller, spin around the roller and get a measurement within .003" (.076mm), to ensure the rollers are all the same, in parallel with each other.
Proper set-up tools and other tips