ABS printing weird

I’ve been attempting some extended prints on our Taz 5 using ABS recently. These prints are running anywhere from 8-12 hours. Just when I think I’ve got it dialed in, something weird happens.

Last night I had this happen:

I am printing between 240º and 250º C. I have typically been printing with a brim and using a glue stick to help with adhesion. I don’t have the fan kick on until 4mm and then it’s only running at 20%.

I’m using a makeshift cardboard enclosure. Perhaps it’s keeping things too hot?

Any help/suggestions are appreciated.

This does look to be the cause. The first thing I notice is how well your print is going on the lower layers. As heat builds up, it can cause your Z stepper driver to overheat. The Z driver will be the first to show signs as it is controlling two motors. When it over heats, it does not lift the head as far as intended, and you get the over extrusion “bumps” as the printer thinks there is more room for filament to be extruded.

The first thing you will want to ensure is that your controller box fan is plugged in and running. If it is not, this can cause your driver to overheat even without an enclosure.

If the fan is operational, you will want to remove the enclosure OR remove the electronics box from the enclosure. This should help prevent overheating, and allow normal Z axis movement.

+1 on getting the electronics away from the working heat of the unit. If you make your enclosure butt up against the electronics enclosure and allow it to draw in and expel air outside the enclosure.

Thank you!

The controller box is about 3 inches away from the side of the shanty enclosure and the power supply is completely outside of the setup. I opened up the front flap of the box to reveal the bottom of the printer. This helped a lot. I didn’t overheat and the 8 hour print turned out almost perfect (still had a little curling/shrinking on a couple corners even with a brim and gluestick and no fan for the first 4mm).

I appreciate your help Brent!

Thanks for the help. I opened up a flap on the box and this was enough to keep the temps adequately warm while not overheating the z stepper.