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Strange diversion at bottom of left 3d object


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Posted · Strange diversion at bottom of left 3d object

Hi,

 

While printing a cube (Petg Ultimaker with my S3) the first 3 a 4 mm’s differ from the last ones. (Left model). Somekind of step is made, although it’s not designed. 
 

Could this be due to the printing of the lid at the right (comparable height), the model looks almost like modified by heat. 
 

I am a beginner. 
 

 

08194DBA-783A-4F43-94BA-C23031A92EBF.thumb.jpeg.cc4c06e6d6c37c237584fecd60b7bbd0.jpeg

 

AF3A8650-F81B-4953-B430-5B50878DB621.thumb.jpeg.701850ade8b72912781c800f579e42e9.jpeg

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    Posted · Strange diversion at bottom of left 3d object

    With the models loaded in Cura and the settings the way you want - use the "File | Save Project" command and post the 3mf file here.  It's tough trying to figure things out from photos only.

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    Posted · Strange diversion at bottom of left 3d object

    That is odd.  The box bottom in your images doesn't match either your slice preview, or my slice preview.

    I tried to force the issue by playing with different settings, but I couldn't get the problem to show up (in the preview).

    Maybe @gr5 has a take on this?

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    Posted · Strange diversion at bottom of left 3d object

    I'm not sure.  I've seen that pattern a lot - it's usually caused by heat.  It goes away as you get farther from the heated bed.  But why doesn't the lid do it?  Well it does.  It's just not as obvious.  But for many materials you need the heated bed above the softening temp of the material being printed (not sure if I ever printed ASA) so that it won't warp off the print bed.  I'm not sure if I remember right but I think UM recommends print sheets for ASA?  Or am I confusing with some other material.  If you use print sheets you can probably lower the bed temp by 10 or 20C to see if that pattern goes away.

     

    I guess I would print a small test cube.  Smaller models don't have as serious problems warping/lifting off the bed.  Maybe 10mm cube.  Print with existing settings and then lower print bed by 10C and try again and then lower another 10C and try again.  That pattern should go away if it is heat related.

     

    Do your side fans work okay at 50% (that's your cura fan setting)?  Maybe they don't work when lowered to 50%?  On my printer the fans are still at 100% power when you set them to 50% so I'm not sure what the person who designed this profile was thinking.  On my printers you have to go down to 10% before the RPMs start slowing but your print needs more fan if anything.  not less fan.

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    Posted · Strange diversion at bottom of left 3d object

    By the way you should change support placement from "everywhere" to "touching buildplate.  You don't need any support on all the "windows".  You only need it in these 4 holes shown below.  This will save you material, time, and cleanup, and reduce ugliness.

     

    582638253_Screenshotfrom2022-03-1309-57-11.png.166830c55a08dd3406fdeac2f2bb241c.png

     

     

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    Posted (edited) · Strange diversion at bottom of left 3d object
    3 hours ago, gr5 said:

    I'm not sure.  I've seen that pattern a lot - it's usually caused by heat.  It goes away as you get farther from the heated bed.  But why doesn't the lid do it?  Well it does.  It's just not as obvious.  But for many materials you need the heated bed above the softening temp of the material being printed (not sure if I ever printed ASA) so that it won't warp off the print bed.  I'm not sure if I remember right but I think UM recommends print sheets for ASA?  Or am I confusing with some other material.  If you use print sheets you can probably lower the bed temp by 10 or 20C to see if that pattern goes away.

     

    I guess I would print a small test cube.  Smaller models don't have as serious problems warping/lifting off the bed.  Maybe 10mm cube.  Print with existing settings and then lower print bed by 10C and try again and then lower another 10C and try again.  That pattern should go away if it is heat related.

     

    Do your side fans work okay at 50% (that's your cura fan setting)?  Maybe they don't work when lowered to 50%?  On my printer the fans are still at 100% power when you set them to 50% so I'm not sure what the person who designed this profile was thinking.  On my printers you have to go down to 10% before the RPMs start slowing but your print needs more fan if anything.  not less fan.

     

    GregValiant and gr5 many thx for the answers!

     

    As proposed by gr5 I just changed support placement, put ventilation on 100% and lowered the bed temp to 70 degrees. Within 2 hours the calibration cube should be finished with these settings (based on the first one, but with these changes).

     

    Thinking of heat: I use a cover to maintain heat and reduce particulate matter:

     

     IMG_2173.thumb.jpg.1276b3d5372a7971d6d092aa5631df48.jpg

     

    Maybe that wasn't a wise decision, although I thought it would also benefit because of stability in temperature.

     

    And gr5: you mentioned the deformation of the lid, it was also deformed in the same way:

     

    IMG_2172.thumb.jpg.c660420b7fcedcc9dee6f0fee0636240.jpg

     

    Up is the lid, little bit warping(?) at the upper left and the same smaller aspect of the cube.

     

    Will post the result of the next print in a couple of hours 🙂

     

    cal.3mf

    Edited by remyhx
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    Posted · Strange diversion at bottom of left 3d object

    I wouldn't call it warping.  That term is used to describe so many things.

     

    So here is what happens.

     

    When you melt plastics such as PLA and other plastics, most of them (especially PLA) stick to themselves even when liquid.  Like snot.  Like mucus.  All of these materials shrink a little when they cool and they cool in the first few milliseconds as they exit the nozzle.  Fast!  At least initially.  And so the liquid filament is under tension.  Like a stretched liquid rubber band.

     

    As this snot like plastic goes down it is pulling inwards so outside corners especially get pulled inwards.  This is also the reason why vertical holes are always smaller than in the CAD model.

     

    The problem is worse near a heated bed.  As it gets to cooler air it slowly recovers.  That's where the wall is angling back out.

     

    I would enclose the front but not the top.  And for PLA don't even enclose the front.  PETG is relatively safe.  Safer than say being in a mcdonalds with all those fryer fumes.  Which is also pretty safe.

     

    Now as far as tests.  You don't need to print a 2 hour print!  Try to find tests that only take 10 minutes.  The longer a test takes, the fewer you are going to print.  If you can make 5 tests in 2 hours think of how much more valuable that is!

     

    That's why I said 10mm cube and not a 30mm test cube (9 times more volume, 9 times slower).

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