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Cutting PETG on Zund

Discussion in 'CNC Routing & Laser Cutting' started by Marty Thompson, Jun 25, 2020.

  1. Marty Thompson

    Marty Thompson New Member

    Jun 11, 2020
    Rossville, GA
    I'm having an issue cutting .020” Printed PETG. I'm using the UCT Tool with the Zund Type 6 drag blade. It cuts perfect when it is not printed, as you can see in the photos I have provided, but as soon as it gets to the printed section, it starts to chatter. It happens if I try to cut it from the front or from the back. Brand new blade and it doesn’t matter if running it at 20 in/s or 39 in/s.

    Any suggestions?

    Attached Files:

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  2. flyplainsdrifta

    flyplainsdrifta Active Member

    Oct 13, 2017
    try a z46 blade SUPER slow. vaccum jacked. how big are those pieces. you may also want to consider layering the cut.

    edit: my operator also suggested z10 in layers. score layer, then cut layer.
  3. Bly

    Bly Very Active Member

    Mar 9, 2004
    Z10 is a stiffer blade so is worth a try. Sometimes on harder plastics we use the EOT for a cleaner cut.
  4. FireSprint.com

    FireSprint.com Trade Only Screen & Digital Sign Printing

    Uhg. Yes you wouldn't think the ink/uv light would make a difference but it sure does.
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  5. Raum Divarco

    Raum Divarco Application Specialist CWT / Amcad & Graphics

    Feb 23, 2017
    different blade choice and multi-pass cutting like mentioned above are the way to go.
    Z46 blades are nice.
    But once the tip is gone, like any blade, its done.
    The 13 blades are stronger as they are two-sided.
    you will find the extra width and contact might create more drag.

    Also you will find standard blades will leave a raised edge.
    This is particularly an issue if you are cutting from the print side.
    Cutting from the nonprint side on second surface prints is usually better.
    there are Asymmetric knife blade options that minimize this effect.

    You also may want to double-check your adhesion before getting into a big job just to be sure.
    I have seen a lot of people make "static clings" accidentally.

    You will find UV curing processes will change how material like these cuts.
    Even if you use promoters and other things you are changing the characteristics of the material.
    So on a saturated/heavy flood of color, you may be baking the material as well, and then it becomes brittle.
    Multi passes are the way to go.
    You can also adjust the angles on detailed cuts
  6. Superior_Adam

    Superior_Adam Member

    Dec 13, 2017
    Wichita, Kansas
    I would say it more of a ink adhesion issue than a cutting issue. If we are concerned with the lip from a knife blade we will route the pieces with R202 bit
  7. Grizzly

    Grizzly Member

    Sep 1, 2010
    This seems more like an ink adhesion issue than a cutting issue. What printer and inks are you using? The UV lamps could change the properties of the actual PETG causing it to cut differently. If you don't want an edge, we'd use a Z83 on our Zund and make sure you're cutting the right direction for the clean cut to be on the side you want. I'd also try the Z46 as well and as others have said the R202 as a last resort. But that can bring up another issue of hold down when routing because your piece is relatively small. Is it possible to put a 1/32 or 1/64 of either a light color or no color at all so you're not cutting on the actual ink itself? We've done that in the past. The Zund is so accurate that visually it looks like a full bleed because thickness of the blade actually removes that bleed.
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