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  1. #61
    Maybe not. Over night i had the octopus running on a double thick raft with a more than doubled from default airgap value of .39mm (parameter cura describes as facilitating raft removal from the print...not the bed) and a 66c bed temperature on a thoroughly cleaned and dried bed. As i watched to ensure the entire raft completed normally and the first layer finished successfully i left thinking to myself that maybe now i had opened myself up to the risk that the octopus parts would simply get dislodged from the raft mid print and fail the print.

    This morning i found a perfectly formed 4 to 6 layer octopus partial print on the floor solidly super welded at each and every point onto the perfectly intact raft and a huge spaghetti mess being piled up on the print bed. Apparently the entire raft had been totally displaced at high bed temp.

    I think i even had a z hop turned on for this print.

    What the hell? Rafts can't be separated from the print at all but can't remain in place on the bed for even the duration of the print?

    Something is very wrong. This should not be this difficult.

  2. #62
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    Actually there's a lot of useful information here. Can you take a photo of the base of your print, and, while you've got the camera, the top surface as well and post them up.

    Couple of quick questions. Have you done an e-steps and/or flow calibration?
    What filament are you using?
    What infill and perimeters?

  3. #63
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    I've just performed a quick scan of this entire thread. It's interesting to see how it's progressed from one problem and solution to the next. Nowhere did I see the information that comes to mind with this latest description.

    What print speed and temperature are you using? The description is consistent with slower speeds for earlier layers, then faster ones. In this type of printing, the heater block has to heat more filament per unit time than on the slower layers, often causing underextrusion failures.

    The slicer will often have predetermined reduction of speed for the base (raft) and first x number of layers, then move on to one hundred percent for the speed. If the temperature is too low, perhaps borderline okay for the first layers, it's going to be too cold for later, higher layers.

    Post your print speed and temp and we'll pick it apart.

  4. #64

    Unhappy

    Thanks guys! I took a picture before i left for work. But didn't realize how blurry it was until i tried to upload it. Now i realize i should have also attempted to export a profile from cura since between the mysteries of what was defined in the profile i downloaded from tenlog, and my own imperfectly recalled modifications i suppose ive made it much more difficult to troubleshoot the print.

    I do recall that after spending the day printing a few dozen of these things

    https://www.thingiverse.com/thing:909901

    and eliminating massive stringing just by upping retraction from 2.0mm to 5.0mm I also found the things printing fine and adhered fine (without a raft!) at 0.1 mm resolution even at 100 mm/s so I decided to try the octopus at that speed and same overall settings except with the addition of a raft for good measure, and yes i remember by default the raft was set at an independent lower speed setting, 60 mm/s.

    Is there any use in having 150mm/s capable printers if everything just gets whacked off the bed at speeds only 2/3s that high?
    Attached Images Attached Images
    Last edited by minneapolis-matt; 05-14-2021 at 08:40 AM.

  5. #65
    Super Moderator curious aardvark's Avatar
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    right - absolutely NO brim on that octopus - It will weld all the links together.
    And yes - rafts on a longish print will pretty much always weld themselves to the print.
    Just plain avoid rafts.

    and it is actually a bit of a sod to print.
    The tiny little links between the sections are really narrow and lift fairly easily.

    Like everything else, the sapphire laughed at such things and I knocked out a re-mix of it with the same legs but a spiders body :-)

    Okay - so we need some print setings.

    what is your extrusion ratio ?
    speed of first layer
    z axis offset
    bed temp
    print temp
    print speed.
    Retraction settings

    And what is your objection to decent print glue ?
    Great stuff.
    Unless you have PEI or printbite (and often even then) a decent print glue that sticks when hot and releases when cold - is the answer to a lot of problems.
    To be fair PEI also does that quite well.

    Me I'd order a sheet of self adhesive PEI. It's about 0.2mm thick - get the cheap stuff, so has no effect on bedtemp and all calibrations can be dealt with simply by adding +0.2 to the z-axis offset.
    It should be around $15 for your bed size.

    The last sheet I bought was £7 and that was 250x250 and trimmed it to size.
    So yours shouldn't be that much more

    In the meantime try some PVA gluestick from a buckstore.
    heat the bed to 60c.
    And run the gluestick over it lightly - you don't need to press down.
    do it a couple of times - leaving about 5 minutes between layers. It forms a thin plastic layer.
    Pla love it.
    I've never bothered trying to print on glass and none of my printers have use their original print surface.
    'cos basically until manufacturers start using PEI - I'll keep sticking PEI on top of whatever crap the printer come with :-)

  6. #66
    Quote Originally Posted by curious aardvark View Post
    right - absolutely NO brim on that octopus - It will weld all the links together.
    And yes - rafts on a longish print will pretty much always weld themselves to the print.
    Just plain avoid rafts.

    and it is actually a bit of a sod to print.
    The tiny little links between the sections are really narrow and lift fairly easily.

    Like everything else, the sapphire laughed at such things and I knocked out a re-mix of it with the same legs but a spiders body :-)

    Okay - so we need some print setings.

    what is your extrusion ratio ?
    speed of first layer
    z axis offset
    bed temp
    print temp
    print speed.
    Retraction settings

    And what is your objection to decent print glue ?
    Great stuff.
    Unless you have PEI or printbite (and often even then) a decent print glue that sticks when hot and releases when cold - is the answer to a lot of problems.
    To be fair PEI also does that quite well.

    Me I'd order a sheet of self adhesive PEI. It's about 0.2mm thick - get the cheap stuff, so has no effect on bedtemp and all calibrations can be dealt with simply by adding +0.2 to the z-axis offset.
    It should be around $15 for your bed size.

    The last sheet I bought was £7 and that was 250x250 and trimmed it to size.
    So yours shouldn't be that much more

    In the meantime try some PVA gluestick from a buckstore.
    heat the bed to 60c.
    And run the gluestick over it lightly - you don't need to press down.
    do it a couple of times - leaving about 5 minutes between layers. It forms a thin plastic layer.
    Pla love it.
    I've never bothered trying to print on glass and none of my printers have use their original print surface.
    'cos basically until manufacturers start using PEI - I'll keep sticking PEI on top of whatever crap the printer come with :-)
    Thanks Aardvark,

    For what it is worth, the Voxel would print for hours and the rafts came away easily every single time, even on large time consuming prints. I suspect the slicer did its' rafts quite differently.

    I hope I can open my cura profile files when i get home from work and dump the contents here. I think given my schedule this weekend that might be the only way to be sure I am answering the questions correctly.

    what is your extrusion ratio ? - no clue...probably never modified after downloading tenlog profile
    speed of first layer - probably same as speed of the rest of the print. I remember finding an option to change the speed for the raft but not one to change the speed for particular layers of the print itself.
    z axis offset - no clue...probably never modified after downloading tenlog profile
    bed temp - I've been gradually increasing as build come loose and no build shows signs of warping or melting. I've been trying 68C lately. nothing higher yet.
    print temp - 200C
    print speed. - 100mm/s but I believe the raft was only 60mm/s - supposedly the printer can handle 150 mm/s
    Retraction settings - until yesterday I had left it at 2mm retraction and 60 rate for everything but my prints were too stringy for my tastes. I printed 4 post retraction test prints and increased these until the strings no longer concerned me. finally setting was 5mm retraction at a rate of 65

    I have nothing against gluestick but I got the impression here that if prints succeed due to use of a gluestick the operator is doing something wrong and the glue should not be necessary so I stopped using glue as I never needed it on the voxel and as I was worried it would mask deficiencies in my technique. my prints are failing even with the use of glue at this point however.

    I would love to have a PEI sheet. I just wish I had bought one with the other new items. I'm sure my timing would be poor to add another $20 3d printer related purchase. too bad they don't appear to be sold at any brick and mortar.

  7. #67
    Staff Engineer
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    100 millimeters per second is screaming fast, especially at 200 °C for the nozzle. At that temperature, 60 mm per second is pretty quick.

    You have to keep your problems and symptoms distinct. Your prints are failing above the first few layers, which has nothing to do with the bed temperature. A bed temp of 60 °C is likely sufficient, anything higher is just throwing away electrons.

    I think you should slow the print speed down a good bit and you'll get good results.

  8. #68

    Question

    Quote Originally Posted by fred_dot_u View Post
    100 millimeters per second is screaming fast, especially at 200 °C for the nozzle. At that temperature, 60 mm per second is pretty quick.You have to keep your problems and symptoms distinct. Your prints are failing above the first few layers, which has nothing to do with the bed temperature. A bed temp of 60 °C is likely sufficient, anything higher is just throwing away electrons. I think you should slow the print speed down a good bit and you'll get good results.
    Long term I've always felt slow prints should be fine...if everything works. That said I am disappointed that the high 100 mm/s was way too fast. Would the vendor quoted 150mm/s ever be good for anything at all? Maybe the simpler the print the faster the speed or something? how does it work? I'd like to dial in the speed in the future without just guessing or always defaulting to slow.

  9. #69
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    Quote Originally Posted by minneapolis-matt View Post
    Long term I've always felt slow prints should be fine...if everything works. That said I am disappointed that the high 100 mm/s was way too fast. Would the vendor quoted 150mm/s ever be good for anything at all? Maybe the simpler the print the faster the speed or something? how does it work? I'd like to dial in the speed in the future without just guessing or always defaulting to slow.
    Yes, it will be useful, but troubleshoot first, then ramp up speed once everything is dialled in. There will also be some prints that just do not warrant that sort of speed. I've got machines that will hit 300mm/s without blinking, but there's still a whole bunch of situations where that is a bad idea, particularly with small, fiddly, prints.

  10. #70
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    Quote Originally Posted by minneapolis-matt View Post
    Thanks Aardvark,For what it is worth, the Voxel would print for hours and the rafts came away easily every single time, even on large time consuming prints. I suspect the slicer did its' rafts quite differently.I hope I can open my cura profile files when i get home from work and dump the contents here. I think given my schedule this weekend that might be the only way to be sure I am answering the questions correctly.what is your extrusion ratio ? - no clue...probably never modified after downloading tenlog profilespeed of first layer - probably same as speed of the rest of the print. I remember finding an option to change the speed for the raft but not one to change the speed for particular layers of the print itself.z axis offset - no clue...probably never modified after downloading tenlog profilebed temp - I've been gradually increasing as build come loose and no build shows signs of warping or melting. I've been trying 68C lately. nothing higher yet.print temp - 200Cprint speed. - 100mm/s but I believe the raft was only 60mm/s - supposedly the printer can handle 150 mm/sRetraction settings - until yesterday I had left it at 2mm retraction and 60 rate for everything but my prints were too stringy for my tastes. I printed 4 post retraction test prints and increased these until the strings no longer concerned me. finally setting was 5mm retraction at a rate of 65I have nothing against gluestick but I got the impression here that if prints succeed due to use of a gluestick the operator is doing something wrong and the glue should not be necessary so I stopped using glue as I never needed it on the voxel and as I was worried it would mask deficiencies in my technique. my prints are failing even with the use of glue at this point however.I would love to have a PEI sheet. I just wish I had bought one with the other new items. I'm sure my timing would be poor to add another $20 3d printer related purchase. too bad they don't appear to be sold at any brick and mortar.
    I just printed the model. Printed it with a brim and had no issues removing it. Those smaller pieces are going to be a challenge to print without brims/rafts/etc. If the nozzle hits them on the way past it's pretty likely they'll pop off.

    Got any photos of the underside of that raft and top surface of the print from a few posts back?
    While we're troubleshooting, spend a few minutes printing this and see what your results are. https://www.thingiverse.com/thing:1622868

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