ABS print lifting

I’ve just changed to a slightly different ABS filament - white instead of orange, if that makes any difference.

After having had many successful prints, all recent ones have either aborted making a mess after part or all of the print lifted off the bed, or ended up distorted after part of the print lifted.

AFAIK the Z-offset is correct, and the first layer goes down smoothly and evenly with limited spread.

I’m trying now to print a simple angle bracket with 2mm thickness, and beside it an L-shaped piece with small upright ends, also all about 2mm thick. The previous print lifted completely after printing the base layer - as soon as it tried to print the upright parts,

I re-cleaned the bed with solvent, and started another print.

It was going well, but now the outer end of the L-piece has lifted. The print is continuing, and looks as though it may finish without self destructing.

Can this be caused by too hot a nozzle temperature? It’s set at 250C. I’ve tried changing the custom material to print at 235C but the setting doesn’t seem to stick, and once the print has started, I can’t change it manually.

The bed is set at 105C. Would hotter help?

Here’s the print nearing completion. You can see that the right hand side has lifted part way through.

Any other suggestions as to causes and possible cures?

This video helped me: 3D Printing with ABS - Tips for Success - YouTube

An enclosure is probably the right answer, Create a wall /fence around the part will deflect air from seeping under the part and bed.

A multilayer skirt will generate the wall/fence around the part. Use enough layers to get a 3-5mm tall wall at about a 3mm offset. Using 2 perimeters will help stabilize the wall and prevent collapses or splitting. A 5-10mm brim attached to the skirt/wall will help to keep it tacked down.

Reduce Z-nozzle height. If you used the paper method to get the initial height, it can be further reduced by .1-.2mm. Find a quick 10x10x1 disc/square and use the gcode start script to adjust and test.

Hope this helps.

Thanks for the link to a v useful video, and for the suggestion of a tall skirt.

Might try lowering the z-height and using hairspray first.

I’ll try again using these and the other suggestions.

Neither post nor the linked video mention reducing the hot end temperature or changing the bed temperature as having an effect.

Would temperature changes help?

Since these helpful responses, I’ve tried a few things, but none are working yet - the print keeps coming off the bed.

Lower print temperature - reduced from 250C to 230C.
Redesign part with shringage-stress-relieving holes.
Use Standard layer thickness (0.25mm) instead of previous High Definition

That almost finished, but came loose before quite finishing the lower-height part.

I’d already added a brim - still comes off the bed.

Measured the thickness of the first layer - seems to be about 0.65mm, as if no squashing is taking place.

Checked the Z-offset. At -0.9 it seems it should already be putting the nozzle more than the thickness of the washers below them, and theoretically under the level of the bed!

Tried lowering it further towards the bed, in 0.1mm steps, to -0.7.

Still not sticking well. Am I changing the Z-height in the wrong direction? IIRC the default setting is about -1.35mm.

Haven’t yet tried hairspray - maybe tomorrow as the shops are shut now.

What else could I have got wrong? Until I changed from orange to a different brand of white ABS, I’d been producing reliable prints for several months, without knowingly changing any settings on the printer.

Going from -0.9 to -0.7 is raising the Z not lowering it, since it is a negative number, more negative is lower.

I think the best way to adjust the Z offset is to just look at the “squish” of the bottom layer. You should be able to see the lines of the nozzle path. They should not be so squished together that it’s hard to see the lines. If you get that you’ve gone too low. If it’s too high you will start to see separation between the lines or even space. The proper Z offset will probably not match the thickness of the washers, even though you’d think that would be the case.

If lowering the Z doesn’t get it to stick, I’ve had good luck just putting down a thin layer of Elmer’s glue stick. Hair spray may work as well.

DoH!

I’ve been moving the Z-offset the wrong way.

What would you suggest to restart it at a better height? 1.2?

Tried again at z-offset = -1.2, with a usable print, but one corner still lifted a little. I’ll try a slightly larger negative offset tomorrow or Tuesday.

This last one was obviously better, but still not quite right.

If you want to get scientific about it, you can run your print with a skirt, and peel the skirt off and measure it with a caliper. Then raise or lower the offset until the skirt matches your first layer height. But I find it easier to just look at how the lines are squished.

If you get the Z right and still have issues with lifting try the glue stick or hairspray.

Thanks - further good advice.

I tried measuring the brim on one of the unsuccessful prints, and found it was much thicker than the layer height was supposed to be.

But I can use the ‘squish’ method to get a little further improvement, I think.

A couple of things I found useful.

  1. Printing a large disk equal in height to your first layer, using lines, and using the “tune” feature in the firmware to adjust the z-offset in real time.
  2. Printing in an enclosure while minimizing air flow. This has an additional benefit in that I can put in a small 5V powered computer fan and a filter to help reduce ABS odor.
  3. Adding disks strategically like in the video.
  4. I am thinking about getting a very tiny space heater to heat the enclosure, but this has the downside of heating the ambient temperature the electronics see. So to do this I may come up with special ventilation for the electronics.
  5. On my own designs, I break up the long outside paths after about a mm. The prints take longer but it helps. I have a flat surface for 1mm, then zig zag surface until final height - 1mm, then flat surface again.
  6. You can also play around with the default cooling settings. I think I changed mine significantly down from what the cura lulzbot edition had set for ABS. They had 40% max fan speed at layer 4, I have 30% at layer 8.

An enclosure is almost mandatory for printing ABS. With most enclosures, the bed (which is recommended to be around 110C for ABS) should provide enough heat to raise the temperature in the enclosure to an acceptable level. An extra heater is usually not needed.

If the enclosure includes the electronics, then provisions for ducting outside air into the electronics and venting the electronics exhaust may be necessary.

Thank you all for your advice. I’ve reset the Z-height to -1.3 mm and that together with stress relieving holes has resulted in prints that adhere properly and don’t lift or warp off the bed.

I’d like like next to try to improve the prints in another way - reduce stringing - but I’ll start another thread for that as it’s a different subject, unless I can find help by searching existing topics.