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3D Printing For Tabletop

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A forum Dedicated to 3D Printing primarily for Tabletop

Print sticking too hard to bed problems (10 posts)

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  • Avatar Image maledrakh515p said 2 months ago:

    I just changed the nozzle and teflon tube on my flashforge finder, and have had a total of 4 prints since then.
    My problem is one I have not encountered before.

    The prints a fine, but stick hard to the unheated print bed (glass with a special blue sticker-layer on to keep the prints in place.) I have printed tons of stuff without problems with this set up.
    I have had similar prints sticking hard to the bed before, and use a blunted flat knife to get the off. no problems there.

    but after I changed the nozzle, the prints (large, flat bases for miniatiures) look fine when finished, but stick really hard to the bed, so hard that they are shredding/cracking up instead of seperating from the print bed. Bits of the bases are so stuck to the layer I can’t get them off at all. I have replaced the bed layer-sticker thinking maybe that was the problem, but the exact same happened again. I relevelled the thing after changing the top layerstickerthing.

    Has anybody experienced something similar to this, and what was done about it?

    The infrequent blog: At the Mountains of Minis
  • Avatar Image stvitusdancern689p said 2 months ago:

    A couple of options. 1. Place your glass bed in the freezer for about 10 minutes or so and then try removing them. 2. You don’t need blue sticker? (Painters tape?) Use a simple elmers glue stick. What type of filament are you using?

    BoW Gianna spreading gaming love one continent at a time.
  • Avatar Image monkeysloth30p said 2 months ago:

    Printing at a lower temp as well as raising the print head when leveling can also help against it sticking. However if it’s breaking apart a higher print temp may be needed.

  • Avatar Image maledrakh515p said 2 months ago:

    The Flashforge Finder only takes PLA. It is a new roll, so there might also be a problem there.

    The prints loook fine, but when I look closer at themm It seems that the bottom part is much thinner than usual,
    Maybe it is not printing the first layer properly? If the nozzle is to close to the bed, would that not cause problems with burns or clogging? I will check to see if the nozzle is fastened as high as it goes and recalibrate it before doing anything else.

    since this is on the exact same settings as before I changed the nozzle, and it is not the first time I change the nozzle either. If the nozzle thing does not make any difference, I will try printing at a lower temperature, and later a different roll of PLA.

  • Avatar Image maledrakh515p said 2 months ago:

    right. some frustrating hours later…after checking the nozzle assembly was in the correct position, the printer’s level assist went on the fritz, demanding to lower the bed until no linger possible. The sensor thingy that drops down seems to be slightly askew so that probably is the reason for that.
    so, manual levelling is the order of the day.

    the first test print gave nothing at all, just a strand. this was a flat object with a 25mm diameter footprint. Next I checked that the PLA was feeding properly and tried again with another object (a small gravestone, much smaller footprint). This printed.

    After pulling the piece (hard!) off the print bed, I noticed that the bottom mm or so was missing completely, and checking the earlier broken prints, they do seem to have really thin bottom layers.

    So, I surmise that the printer is simply not printing the first (or first few) layer(s), which is causing the sticking problems.WTF?!?
    Does this mean that the print head for the first few layers is actually hitting the bed and not extruding anything because there is no room for the PLA to get out the nozzle? Can it be the motor that pulls the PLA into the print head does not kick in before the subsequent layers? How can that even happen?

    The print bed does not show any signs of being scorched or even melted and there is no stringing, lumps of PLA or even clogging in the nozzle as the print prints perfectly apart from the very bottom.

    This occurs after leveling both assisted and manually.The nozzle is a paper’s width from the bed.

    Anybody have any experience or thoughts about what causes this an dhow to fix it?

    The files I have used are both first -time prints and older files that earlier have been printed properly. All look OK in the slicer.

  • Avatar Image nakchak4214p said 2 months ago:

    first of all are you sure that the “blue sticker” isnt transit packaging for your glass sheet to keep it free from scratches, when i was extruding plain glass with no special coating or stickers was one printbed that i used with quite a bit of sucess…
    Most tack sheets have a limited shelf life as the tack wears away with use and you could be finding that its bonding to plain paper now…
    If you dont want to print directly onto glass try a small square of baking parchment (same stuff you would use for a DIY wet pallet) shiny side up tacked down with some blobs of hot melt glue (glue gun sticks, if you dont have a glue gun you can heat it with a lighter or candle to blob it on the glass then stick the paper down corner by corner), or spray some hairspray onto the glass then stick the baking parchment to it and trim to size with a hobby knife once dry.

    Try printing some “waffle” raft patterns and see if they stick and print well, generally you want some wastage print layers before the main item as it gives a chance for the extruder(s) to heat up and stabilize temperature. It sounds like to me that the extruder is possibly cold for the first few layers hence the missing mm, can you preheat the extruder for 5-10 mins before you begin printing? if not, add some wastage layers to your design for the initial few layers, (i used to print a raft double the foot print of what ever i was printing to get around the lack of preheat on my last extruder) and that consistently got me acceptable results at the expense of additional clean up (i printed a holder for a flexi shaft on my dremal which made clean up a doddle with a mini desk grinder/sander :D ).

    The third thing it could be as you identified is your new roll of PLA, this was perhaps the main thing which made me abandon home extruding was inconsistencies between rolls of filament, even when sticking to the same suppliers there was no guarantee that roll a and roll b came from the same upstream supplier, each with slightly different thermal properties leading to a lot of frustration when switching to a new roll and what was printing fine suddenly misprinting, drifting, clogging or just not extruding cleanly, the remedy was to tweak the extruders temperature, but that was a series of misprints and wasted time until i got it dialed back in, only way i got around that was to bulk buy rolls of filamament at a time which then caused issues in cashflow and storage lol…

    As a side note thats one reason why i take exception with the term “3d printer” as it implies you can treat replacement filament like you would a printer cartridge plug it in and off you go, not quite in my experience….

    There is no ignominy, there is glory,
    There is no servitude, there is dominance,
    There is no defeat, there is victory… victory eternal!
  • Avatar Image maledrakh515p said 2 months ago:

    Thank you for excellent pointers and suggestions!

    The bed-sticker is a purpose-sold original piece of kit for this printer. Used in much the same manner as blue tape, but fits the print bed exactly.

    The nozzle seems to heat up fine, there is a bit of pre-printing plastic melt thread coming out before it starts the actual print.

    Further experimentation has led me to believe that this is about the distance of the nozzle from the bed and not other things. I have tried levelling manually with a thicker piece of card and then later with a (much) thicker piece of cardboard, and each print is actually taller the the last.
    I belive my theory about the nozzle scraping the bed and therefore not having space to extrude the PLA.

    It seems this type og printer defaults to needing a larger space between the nozzle and the bed then other types, I notice when the level assist sensor pops down, there are several mms from the nozzle to the bed.

    now for the tedious task of determining the right thickness for levelling… rinse and repeat.

    at least I am gettin a whole bunch of little gravestones I can use for some terrain.

  • Avatar Image nakchak4214p said 2 months ago:

    @maledrakh i would try finding the largest workable gap you can have i.e. start at 3mm and work downwards until you start hitting the bed and losing layers.

    Rather than use card i would invest in some aluminium or brass sheet, like this stuff:
    http://www.ebay.co.uk/itm/Aluminium-Sheet-0-5mm-thick-various-sizes-1050A-H14-cutting-service-available-/161058396343?var=460186678499&hash=item257fd418b7:m:mNL1f729WK1HD7xRqecXF_Q

    That way you can be pretty confident on the thickness, buy it in peices approx same size as your bed, then add or remove in 0.5mm increments, so for a 3mm gap you would want a 6 sheet ply (stack), if your bed is unheated you could use plasticard as well, the main thing is to be scientific and work with known thicknesses, the more you can put your self in an engineering mindset the easier the levelling and printing in general will be.

  • Avatar Image maledrakh515p said 2 months ago:

    just a quick update here if anybody is interested: The height of the nozzle on the bed was definately the problem, the assist leveller was on the fritz causing it do be 2.1 millimeters too close… which would mean that it has been digging up to 2.1 mm into the bed sticker moving about.

    Frankly, I am amazed that it still went throught the motions and even continued to print the rest of the model perfectly!

    must have been the printbed sticker that was flexible and deep enough to allow the printhead to actually move around, and still bounce back when the printhead has passed. or the printers z-axis motor not pushing all that hard to get to the correct position. Likely a combination.

    At any rate, after printing out 7 or 8 little 5 minute gravestones I have at last got it levelled properly and the printer is happily back to printing near-perfect models as before.

    So, now that the prints are proper again, they stick to the bed properly, loosening with applied pressure like before the problems, and not sticking like sh*t to velcro which was ruining both the models and the bed sticker.

    It might be that the extra heating of the bed sticker caused by contact with the print head made the PLA to partly fuse to it.
    Or the fusing of the PLA when printing is different in the bottom/top layers than in the inside layers,Or both, or something else entirely. I can only speculate.

    At any rate, thank you @nakchak and @stvitusdancern for your input and suggestions! Much appreciated.

  • Avatar Image nakchak4214p said 2 months ago:

    @maledrakh glad you got it sorted in the end :)

    Sounds plausible that the PLA was melting the glue on the tack sheet and printing onto paper or plastic backing.