Multi-cut skewing of MAXX Air but only on long passes

Computerized Cutting Systems and Supplies – KLIC-N-KUT Forums Cutters & Equipment KNK MAXX, Groove-e & Eagle Multi-cut skewing of MAXX Air but only on long passes

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This topic contains 5 replies, has 2 voices, and was last updated by  Sandy 6 months ago.

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  • #30658

    pyates
    Participant

    Trying to decide if I just need to give up here.  I am cutting 0.02″ PETG sheet on 24″ MAXX Air with design being about 45cm x 97cm on the sheet.  I am getting terrible skewing, but only at the end of the cuts when it outlines the entire piece.  It seems mostly on the long Y axis.  As you can see in these photos for the middle of the piece cutouts it does just fine.  Using red blade, 150 force, speed 35, 10 pass cuts.  The smaller circles and rectangles are 2-5 cm in diameter.  I am not cutting thru onto mat below (another piece of 0.02″ PETG), and in fact not quite making it thru the bottom of the first sheet.  If I push I can get the cut pieces to pop out after it is cut so its pretty close.  The two PETG pieces are secured together by Krylon EasyTac.  So whats different about the small cutouts which are fine versus the large cutout which is most definitely not.  Well, the final outline (which is where all the screw ups seem to be happening) are 10 passes going around a 45 x 97 cm square essentially.  It would seem that is some positioning error that creeps in on each pass.  I do have resolution set to 1.009 Y and 1.007 X-axis since on single pass I was on getting the dimensions correct when it was just 1:1.  Any thoughts about how I fix this ?  I have read the forum and tried all the tricks, but really can’t go any lower force because already doing 10 passes and barely making it thru.  I am only using the two outside pinch rollers and they are correctly positioned.  I do not have the support tables that go with the Air, it is on a wood floor with enough space to move the large piece back and forth. My only thought is to actually create a support skeleton on the outside of the piece so that doing the final outline of the piece is a series of smaller rectangles, and then I would cut off the support structure shell around the outside (kinda like what one does for 3D printing).Oddly, at least some of the 10 passes came out OK and aligned since one doesn’t see 10 separate skew traces.IMG_0318IMG_0319IMG_0317

    #30666

    Sandy
    Moderator

    Skewing results any time a blade is being forced through a material faster than the blade can actually cut it.  “Something” has to give and it’s usually the mat.   I can suggest a few things:

    (1) At that force, you should be able to cut 0.02″ PET-G on a Maxx  Air in 2 passes.  This suggests that your blade must be really dull at this point. So, that’s the first thing I would change.

    (2) Are you removing the plastic protection layer on the top and the bottom? I have always left it on the bottom while cutting as a way of adding more stabilization.  If a material is stabilized it tends to cut clean more easily. Otherwise, the plastic can be pulled away from the adhesive on the mat and that will, for sure, keep the material from cutting.

    (3) If you WERE to use the bolt-on metal tables, then you can control skewing by buying magnets like the ones at the link below and aligning them on the left side of the cutting mat. The right side of the mat would then be aligned with the inside of the right end cap. We have customers who have successfully done this.

    https://www.harborfreight.com/retrieving-magnet-150-lb-pull-36904.html

     

     

    #31254

    pyates
    Participant

    So I went and built my own  24x 48 table extensions for each side of the printer, with guides to prevent the piece from twisting.  I absolutely positively cannot get rid of the skewing no matter what speed or cutting force.  I keep burning thru $20 PETG pieces in the process.  Any force that can actually cut thru the material on 5 passes no less ALSO causes skewing, and not just a little but alot. As in over 4 passes there is over 1 inch of vertical skewing.  If I back off on the force, use a pen, whatever, sure I can get it perfect, but it doesn’t actually cut. Hardly the point of what the machine is supposed to do.  I replaced the blade with a new one …. no go.  This is frustrating beyond belief because I bought this printer to specifically to do this task which I thought it should be capable of doing.  It just can’t keep grip on the PETG plastic if it is actually trying to cut it.  My mat is 0.03 PETC and I am cutting thru another 0.02 PETC 24 x 48 sheet that is adhered to it with Krylon Easy Tack.  I leave the plastic covering.  Right now I am finding I am having to use 225 of force on 4 passes to even get thru the 0.02 PETG.  Even this I find variable.  Sometime I can use less force and less passes (2) and get thru, other times I can’t.  This is so darn variable I am about to rip my hair out in frustration.  Can I send the file to KNK and have them try to cut on their machines.  Would pay for time and material if someone can figure this out.  Failing that its off to a laser cutter to get the job done and the Maxx Air goes on Ebay for someone else to experience frustration with.

    #31260

    Sandy
    Moderator

     

    The first time I read your post, I somehow missed the fact your overal design is so large.  The largest project I’ve personally cut from PET-G was only about 9 inches in length.  While one can easily cut large projects like that from easy materials, I don’t know how will 0.02 PET-G will track over such a long distance.

    Also, if the blade is hitting the plastic at a force of 225, then the tip of the blade is most likely being damaged immediately, thus the reason you need such aggressive settings versus what I reported in the settings table.  Whenever I replace a blade, I always start with very conservative settings for the test cut (regardless of the material) and tweak upwards until the cut is clean.  Then, over time, I will need to increase force and possibly add a pass before the blade is spent.

    It IS a good idea for you to contact someone at KNK USA to discuss your application.  I recommend starting a support ticket using this link:

    Support ticket request

     

    #31264

    pyates
    Participant

    Thank you Sandy.  Yes you are correct in that it can track  just fine when going over 3-5″ diameter cutouts.  But it fails woefully when going over long distances (12″ or more).  I will proceed with the following: 1) try new blade 2) try reduced force and speed that follow the guidelines you have provided previously 3) break these long passes into 5″ diameter cutouts so that less long distance tracking is needed.  Then I’ll get back to you if this can work.  I do realize that my use case scenario may be well outside the imagined use for the device and if it doesn’t work then it doesn’t work.  Hopeful I can find a way forward.

    #31282

    Sandy
    Moderator

    Good luck!  And definitely post back after you’ve tried again.

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