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Score crush cutting plastic films with rotary blade and a rotating anvil verses a hard flat plate

Score crush cutting plastic films with rotary blade and a rotating anvil verses a hard flat plate

Score crush cutting plastic films with rotary blade and a rotating anvil verses a hard flat plate

(OP)
We slit plastic film with a round slitter blade. The film is stationary and resting on a ground hardened plate. The blades are pneumatically actuated forcing them down against the film and then advanced along the film for the length of the cut, after which the blade is retracted and returns to its home position. The film is advanced and the cutting operation is repeated. This occurs multiple times per minute. We would like to improve service life of the slitter blade and associated components, The operation as designed appears to be excessively rough on the blade and associated components and we are looking into modifications to improve life and reliability.

Crush slitting plastic film is a very common operation but it usually is a continual process where the film is pulled thru a stationary slitting mechanism where the film travels over a driven and hardened roller or arbor. The score cutting blade is positioned above the film centered over the roller. The scoring blade applies pressure thru the film and to the rotating roller.

In the more common application, the score slitting blades are engaged and stay engaged. This differs from our system as our blade and its holding mechanism is moved across the stationary film as it rests on a flat hardened plate. So we still have relative motion between the rotary blade and the film and the rotary blade and the support plate. Our application also differ in that we are engaging and disengaging the blade multiple times per minute. We do however have flow controls on the air lines feeding the blade holders to soften that engagement.

My first question is, has anyone seen an application similar to what we are doing, where the the score crushing blade and its holder move as the blade runs against a flat stationary plate?

My second would be has anyone seen an application similar to what we are doing, where the the score crushing blade is engaged and disengaged multiple times per minute for an entire shift?

RE: Score crush cutting plastic films with rotary blade and a rotating anvil verses a hard flat plate

Gerber cutters are long tables that cut patterns from sheet materials that are spread over the table. They can be equipped with various types of cutters, including score cutters, although I think those are not common because that would require a large hardened table surface. Fabrics are often cut with score cutters on glass table tops, as glass is hard and flat and relatively inexpensive. But your question seems somewhat unfocused if you are trying to solve a problem with blade wear. Score blades generally last a long time without any problem. The geometry of the cutting edge is critical for this, however. Those who have no experience with score cutting often mistakenly think that the cutting edge should be razor sharp. But that results in a cutting edge that is very fragile and will be damaged by being pressed against a hardened surface. The cross-section of the cutting edge of a score cutter needs to have a radius of curvature of 0.005". This is blunt enough to be strong but sharp enough to convert the blade force into a high contact pressure that will crush through the plastic film.

RE: Score crush cutting plastic films with rotary blade and a rotating anvil verses a hard flat plate

(OP)
I appreciate your response and I'm looking into the geometry of the blade we are using. I also took a look at a Gerber cutter you mentioned. Our application doesn't require anything that fancy. We are slitting a pair of straight lines about 30 inches long. Because the slit is not continuous it requires us to lift the score blade off the web before the web is advanced a set dimension. The blade holder and blade returns to its home position in preparation for the next cut.

I expect that the repeated lifting and lowering of the blade adds to its accelerated wear. How much, I don't know, but if there were a way to mitigate the effect, I would try to do so.

Also rolling the blade over a hard flat surface rather than the more traditional arrangement where the blade holder is stationary, and the blade runs on a hardened, driven roller may create excessive loading. Maybe some side loads.

Another thing that comes to mind is maybe the hardened plate we are using is not smooth enough. The blade would cut better and see less abrasion if it were running against a polished surface.

Rather than guessing and doing a bunch of trial and error I am hoping the application looks familiar to someone who can point me in the right direction.



RE: Score crush cutting plastic films with rotary blade and a rotating anvil verses a hard flat plate

Use a microscope to examine the blade before any use and after each of the first number of individual runs to evaluate what is happening. Perhaps adding a device to hone the blade would be helpful.

It doesn't take much force on the tiny edge to do damage. Perhaps a ceramic blade would be better? They don't deform.

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