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  1. #1

    Persistent Warping with PETG

    I am printing very dense brackets to use as part of a CNC. I chose PETG for its resiliency and stiffness, but no matter what I try, the corners warp upward and the part curls up. I have tried different printing surfaces like kapton tape and masking tape. I've tried with the bed heated at many different temps all the way to 110C, but the problem is that when the part cools it starts to curl. So even if it stays relatively flat during printing, it curls when the heat turns off. I recently tried printing with a brim and a raft, but it's curling right off of the 10-layer raft like it's nothing. I've included my settings in Slic3r for reference.
    Capture3.jpgCapture4.jpgCapture.jpgCapture1.jpgCapture2.jpg

  2. #2
    Here's a link to the settings/pictures because there is a five picture limit, and I think they may be compressed because I couldn't read the text when I looked at the preview.

    https://drive.google.com/open?id=1Jt...NkTZEcO9h6HNWA

  3. #3
    Engineer-in-Training
    Join Date
    May 2018
    Posts
    304
    PETG need to have the starting height set correctly. What this means is for whatever layer height you are using, you must adjust the Z offset so the part comes out the correct height. When set correctly and the PETG is a quality product and dry, and your starting offset is correct it sticks like glue and does not warp. I am currently printing some finger gards which are 7" long and 4 inches wide and 1.5mm thick using PETG with not warping. One thing to note when designing part for 3d printing, using fillets to round corners and edges is really helpful to stop warping.
    If you tell me your nozzle size I will upload a model that is 3mm tall, that you can print and measure the height of the walls with an accurate digital caliper. They should be 3mm tall +- .02mm
    If not adjust with the z offset in your slicer or within the firmware depending on your experience level.
    Hope this helps
    PS PETG is not stiff it is very flexible, for parts that need to be accurate and stiff I typically use ABS which is a bigger can of works with warping and difficulty in printing.

  4. #4
    Quote Originally Posted by airscapes View Post
    PETG need to have the starting height set correctly. What this means is for whatever layer height you are using, you must adjust the Z offset so the part comes out the correct height. When set correctly and the PETG is a quality product and dry, and your starting offset is correct it sticks like glue and does not warp. I am currently printing some finger gards which are 7" long and 4 inches wide and 1.5mm thick using PETG with not warping. One thing to note when designing part for 3d printing, using fillets to round corners and edges is really helpful to stop warping.
    If you tell me your nozzle size I will upload a model that is 3mm tall, that you can print and measure the height of the walls with an accurate digital caliper. They should be 3mm tall +- .02mm
    If not adjust with the z offset in your slicer or within the firmware depending on your experience level.
    Hope this helps
    PS PETG is not stiff it is very flexible, for parts that need to be accurate and stiff I typically use ABS which is a bigger can of works with warping and difficulty in printing.
    Thank you. my nozzle is .4mm, and I set my first layer height to .4mm, but then switch to .1mm on the subsequent layers. This is a 12 mm plate, so hopefully it will still work the same as the 3mm ones you are working on. What do you mean about the Z offset? I level my bed manually, and I can get the first few layers to look excellent, but no matter what the corners always bend upwards as the print progresses. I even tried super 77 adhesive on painters tape. It's so frustrating. You are right about the flexibility. PLA is stiffer, but it seems like it snaps easily (brittle).PETG still feels pretty stiff to me though. I can't even bend the 12mm plate more then the tiniest flex, even if I try my hardest.

  5. #5
    Engineer-in-Training
    Join Date
    May 2018
    Posts
    304
    with a 4mm nozzle I would be printing the part at a .3mm height and and extrusion width of .4mm
    your first layer should be .3 just like every other layer when the staring height is correct.
    Your bed should be 70 C
    If using eSun petg the nozzle should be 230- 235C
    Not knowing your part size speed should be slower than what you would print PLA

    When you set up your printer there is probably some point when they tell you to put paper under the nozzle.. that would be manually setting you Z offset or starting height.

    Within most slicers is a place where you can insert a Z offset positive and negative. Not sure which move the nozzle away from the bed and which moves it closer you will have to experiment of find documentation on the setting. I use a different method using the firmware M206 command.

    What you will do is set your slicer as i suggested above with starting layer just like all the rest of the layers .3mm extrusion width .4mm if that is something that get set within your slicer.

    Print the square and it should be 3mm +- .02mm so 2.98 - 3.02 mm tall
    If not use that Z offset and make small adjustments until you achieve the proper height
    Than print you part.

    Also if you designed the part, go back and round the sharp edges, sharp corners increase the warping.
    Attached Files Attached Files

  6. #6
    Quote Originally Posted by airscapes View Post
    with a 4mm nozzle I would be printing the part at a .3mm height and and extrusion width of .4mm
    your first layer should be .3 just like every other layer when the staring height is correct.
    Your bed should be 70 C
    If using eSun petg the nozzle should be 230- 235C
    Not knowing your part size speed should be slower than what you would print PLA

    When you set up your printer there is probably some point when they tell you to put paper under the nozzle.. that would be manually setting you Z offset or starting height.

    Within most slicers is a place where you can insert a Z offset positive and negative. Not sure which move the nozzle away from the bed and which moves it closer you will have to experiment of find documentation on the setting. I use a different method using the firmware M206 command.

    What you will do is set your slicer as i suggested above with starting layer just like all the rest of the layers .3mm extrusion width .4mm if that is something that get set within your slicer.

    Print the square and it should be 3mm +- .02mm so 2.98 - 3.02 mm tall
    If not use that Z offset and make small adjustments until you achieve the proper height
    Than print you part.

    Also if you designed the part, go back and round the sharp edges, sharp corners increase the warping.
    Thanks, I've been using the paper method. I looked for a Z offset on the stock firmware of the Maker Select v2 but not seeing it. I noticed my bed might be warped because I can't get all four corners leveled. Two of the opposing corners will be too low, and the other two are too high, which is impossible to fix. I got it as close as I can, and I also bought mirror tiles from Home Depot and used the hairspray method to stick to it better. I re-designed my part with 1mm discs around the corners and I am going to put a radius on the corners next time. It doesn't appear to be warping very much, but sometimes it doesn't happen until the end, and I still have about 40% to go, so I will check back afterwards. I can't find the setting for extrusion width in Slic3r. I will try 70C for the bed. I've been setting it to 100 and extruding at 250.

  7. #7
    I can't believe how perfect this thing came out (relatively speaking). The radius on the corners was the last piece of the puzzle. That, combined with the glass surface and the helper discs on the corners was enough to produce a half inch thick plate with a flat surface and zero warping. Thanks for all the help!!!

    20200129_091145.jpg

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