Wednesday, March 31, 2010

Kiss Die Cutting

Written By Mark Batson Baril

We started with this Question:

We are a small Die cutting shop that produces flat labels and decals. For years now we have run kiss cut jobs. The problem we have run into is on the more intricate, and complex jobs. In some areas we will produce a perfect cut and in other areas our cut will only dent the surface without even penetrating the label material. We consistently use the same backer or liner which is a 90 lb stock, approx. .010" (.254 mm) thick. We have been told by some industry people that we would get better results cutting into a thinner backer for these complex Kiss cut jobs. Is there any truth to this and do you have any other suggestions for us?

There are many potential problems and/or combinations of problems that an cause uneven cutting, especially when Kiss cutting.

Possible Problem: Not enough tonnage on your press.

Check: Have you run larger dies (with more lineal inches of cutting) on your press without problems? If so, then this is not the problem. Note that a great deal of cutting in a very small area requires a larger amount of tonnage to cut. Also, a dull knife requires more tonnage to cut.
Solution: If a lack of proper tonnage is the problem, then reduce the number of cavities in the die, spread out the cavities, use a larger press or reknife the die.

Possible Problem: Your Press is not level.

Check: When one side/section of the die is not cutting deep enough, rotate the die 180 degrees in the press. If the problem area follows the die, it is generally a die problem. If the problem area does not follow the die, then it will be a press problem.
Solution: Die problem - have diemaker correct the die. Press problem - level the press or replace the cutting plate. Also the use of "stop blocks" in the die will help and sometimes eliminate this problem.

Possible Problem: Diecutting pressure is not centered in the press.

Solution: Make sure the cut to cut area is centered on the press. The exception is when the die has a large amount of cutting concentrated in a smaller area, move this area closer to the center of the press. Balancing the press is key in every situation. A rocking press will never Kiss well.

Possible Problem: Cutting rule in die is not level.

Check: Make sure the back of the die is level. You may not be able to notice .003 to .006" offset in the knife. The knife may be too tight in the diebase and cannot be leveled correctly. Check for any debris under the back of the knives. Wood or other material may have worked its way under the back of the tool.
Solution: Send die back to diemaker for inspection and/or correction along with a couple sheets of your material and sample die cuts.

Possible Problem: Cutting rule is dull or just not sharp enough.

Check: Check to see if you can see shiny areas on the cutting edge of the knife. This may be caused by (1) The diemaker's bending dies not being squared up which will flatten the edge during the bend; (2) improper handling of the knife during the cutting, mitering, bending and/or insertion of knife into the diebase; (3) the knife was dull to start with; (4) the knives were damaged after the tool was made.
Solution: Again, ask your diemaker to check the die (send sample cuts with returned die). Also check incoming tools and just off the press tools for wear spots. Remember, that first impression can be a killer. Ask your diemaker these same questions and make sure he is confident that he is supplying you with a flat tool/ ± .0005 flatness in the rule is fast becoming the industry standard. In some cases the radius areas will need to be broached (steel removed) prior to bending the knife. This results in a flatter rule at radiused areas.

The question at hand: Yes, you may get better results cutting into a thinner/harder backer material. Your .010" (.254 mm) thick liner material will cause you problems when the cutting edge of the knife is not sharp or when the material being cut is a thin mylar or vinyl. These materials have a tendency to stretch not cut especially when the liner us softer. Many times you can go with a thicker liner which will allow for more slop in the cut and still allow for a partial cut that looks good. Just remember that you always want to cut into the softer material first.

Before you reach any conclusions on the backer material it would be worth going through the above problem solving areas to try and find the real cause. The cause may be in the die, the press, the operator, the material, or perhaps in a combination of two or more.

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