Mat slipping on return.

[lexcut]

Hi all,

I've searched the forums and have found a couple instances of mats slipping and we have tried those fixes. For example, it was suggested that the pinch wheels be cleaned so we cleaned ours. We've also tried slowing down the cuts, a larger mat, a new mat, rearranging the order of the pinch wheels (in case one was bad), etc.

This is where we are at. We have a 13 inch Silver Bullet and the “13 and 15 in Mat�. We are trying to cut 0.01 in (0.25 mm) polycarbonate sheets. The sheets are 12x16 inches and take up most of the area of the mat. We first cut the sheet into strips with a cut all the way through using a force 170-190 grams at a speed of 60 mm/s. The cross cuts (only the blade carriage moves) work very well. When the long cuts are made (using the rollers) the mat slips when the mat reverses direction in the cutter. This slip is consistent to one side and only by a few millimeters. When the mat is loaded, I use the lines on the mat to run it parallel to the pinch roller. After the slip, that line is no longer parallel, it starts where it was originally but as the mat is fed through, the line displaces by 2-3 mm. This is an issue because it changes the size/shape of the pieces we are cutting.

The slipping also occurs with the second set of lines we cut, which are partial cuts using 90 grams and run the full length of the sheet. When the mat feeds to the end and reverses direction, the mat slips.

The slipping seems to occur when the mat reverses after being fed most of the way through the cutter (to within an inch of the edge). We do have a longer mat so we tried cutting the sheets on the longer mat but the slipping still occurs. I’ve also decreased the speed to 10 mm/s but it did not fix the issue.

Is there any advice or changes we could make to end the slippage? We have ordered new pinch rollers to see if they are not gripping enough. I was also planning to remove the roller assembly to make sure one was not loose.

Thanks in advance.

[Gigi]

How thick are the polycarbonate sheets that you are cutting and which blade are you using? Are you sure that the pinch wheels are over the grit shaft as they will not slip if they are. Are you placing the pinch wheels on the material you are cutting or to the side of it on the bare mat. Depending on the thickness of the material, the pinch wheels should almost always be on the mat, not the material you are cutting. Are you sure the mat is slipping and not the material? How many pinch wheels are you using. Again, the mat won't slip if the rollers are clean and they are properly placed over the grit shaft.

The force you are using to cut is very high and I think you would get better results at a lower force with a multi-cut. And I would want to be sure you are using the correct blade given the material you are cutting - again need to know the depth of the material. Did you perform a test cut?

You are also cutting at a very low speed and you will find in almost all instances that the Silver Bullet performs better at a higher speed, but first we need to figure out some of the other issues you are having.

[lexcut]

Gigi,

Thanks for the reply, I'll try to answer all your questions.

The thickness is 0.01 in (0.25 mm). The blade used is a 45 degree blade. I tried a 60 degree blade but it did not cut through the material and the slipping still occurred.

The pinch wheels are over the grit shaft. All 4 pinch wheels are being used, all centered over the grit shaft. One pinch wheel is off the material, the other three are on the material. The material is wide enough only one pinch wheel misses the material.

The material is not slipping. The mat is sticky and the material is stuck down sufficiently.

I haven't tried multiple passes yet but it was avoided because it is necessary that the repeat cut do not miss the previous cut. I realize the force used is high but at 90 grams, the mat also slips.

[Gigi]

Something really doesn't make any sense to me. There is no reason for the 60 degree blade not to cut .01 plastic unless it is chipped, nicked or set too high in the blade holder.

You do not need to use all 4 pinch wheels. I cut almost everything with 2, placed on the mat directly. I understand that with your material 12 " wide it might be difficult, but theoretically you could position the material so that the pinch wheels are on either side. I don't have my 13" machine anymore so I cannot test that to see if they line up, but at least keep one on the mat.

Are you cutting into the mat as that would certainly cause it to move, and at that force with that material, it would not surprise me.

Ok, I Just found sheets of .01 plastic that I have had for a while. Now keep in mind that every plastic can be different (manufacturer variables) and cutting a lot of plastic does wear the blades down faster than usual. I had little luck with the 45 or 60 degree blade, but the 60 degree plus cut it beautifully at 98 - one pass. I was working on an old mat so a new mat could probably result in needing a lower pressure.

Based on what I have done, I would definitely use a 60 degree plus blade when cutting. Have you done test cuts with just regular lightweight card stock to see if the mat shifts at all with the outside pinch wheels down. Since I believe you recently joined the forum, are you a new machine owner? Have you gone through the learning center classroom? Just trying to determine at what point problems occur as it is very rare for the pinch wheels to malfunction. So I would like to know if you can successfully cut a regular piece of cardstock with no issue.

What happens if you put just the mat in with outside pinch wheels on it and run it forward and backward? It should feed evenly in both directions. LMK.

[NewMan]

As regards the mat slipping I think this is normal and can not be avoided, I would suggest that for each material you are using to measure the distance which the cutter is losing and then calculate it as a percentage, for example if you draw a square 100mm x100mm then cut or draw it and it is 100mm width but 101 length then reduce you drawings length by 99% or until when you draw or cut it is 100mm x 100mm. then use this reduction for all other drawing of the same material.

[mmhockeyfan]

Hi, Is is possible you are starting and/or ending your cuts at the very edge of the mat? I'd recommend starting your cuts a little further away from the top and bottom edges.
Good luck!