Acrylic bed shifting during printing

[drumrboy44 0]

Hi all,

Everything has gone pretty swimmingly with my printer for awhile now, however, just recently I have had a new problem creep up. The issue is that, I suppose, a few print edges tend to warp upwards beneath the hot end (very slightly), and depending on the 3d model, contact the hot end as it passes over those warped-upwards portions. The warping is not visible in the final print, but I have returned to prints a couple times to see that the acrylic bed has shifted all the way to the wrong side, permitting the screws to escape from the holes in the bed, thus allowing the entire bed to rise a centimeter while sitting on the springs. This is not good, obviously, as now your print bed has shifted in the middle of a print. Although, I will admit that it has resulted in some pretty cool (though undesired) effects in the resulting print.

My question: Is there any way to prevent the bed from sliding out of position during a print? I'm not sure why this has become more of an issue recently, and it does only happen with certain prints (typically with moves in the X direction), but it is highly annoying.

 

[gr5 897]

Can you post a photo of the part?

This tends to happen when you have overhang slopes. The shrinkage of higher layers pulls inward and that hinges these outward facing slopes more up than in (with vertical walls it ends up more lifting the corners of the part instead).

There's lots of tricks to reducing this. For example you could include support (exterior only). In this case the support helps pull down. You can reduce the pulling forces by adding more vertical and/or horizontal holes in the walls between the lifting areas, less fan, less infill, making the part more squarish (less long and skinny), using a heated chamber, use PLA45 (less shrinkage), add support in the cad, press down on lifting parts after every 5th layer with a putty knife, and more techniques.

I'd like to see what the part looks like first.

 

[nick-foley 4]

Yeah this is a PITA.

I think I'm going to cut a new bed, using a lasercutter to etch a shallow counterbore for the head of the screw to drop in to at the end of the slots. You could probably achieve the same thing with a drill bit.

 

[drayson 62]

Hi,

before cutting the acrylic bed I would suggest to try this parts first.

http://www.thingiverse.com/thing:144421