Setting Heat Bed Height Manually Mid-Print?

Question

So, I've gotten the G-code to work regarding the waiting 10 seconds as I wanted it to. However, does anyone know if there is any G-code that exists that will allow me to manually set the height of the heatbed? I'm trying to find out after each layer if I give it 10 seconds to fully 'cure' or 'cool' to see if the results will be better. But I need to move the bed down away from the extruder.

Answer 1

The way to do this is something like:

G91     ; Relative coordinates mode
G0 Z5   ; Move +5 on Z axis
G4 S10  ; Dwell for 10 seconds
G0 Z-5  ; Move -5 on Z axis
G90     ; (Return to) absolute coordinates mode

You can of course insert this manually in the gcode between layers, but most slicers have functionality (built-in or as plugins) to let you do that automatically, or of course you could use a text-processing utility like sed, awk, or perl to do the insertions automatically if you're familiar with something like that and it's more to your liking.

In a since-deleted answer, Trish raised some reasons you might not want to do this, including significantly increasing the time your print takes and possible difficulties getting the next layer to adhere to a fully cooled layer. I'm not convinced the latter is a real problem, but these concerns are worth considering. Some other reasons not to do what you're asking about include:

• Even with perfectly dialed-in retraction, a hot nozzle dwelling for 10 seconds will almost certainly start to ooze, giving underextrusion and poor surface quality right after restarting.

• Most cooling occurs via the part cooling fan. If you move it away from the part, it won't do much. So you might find even after wasting 10 seconds per layer, your layers still aren't cool.

If you want to cool the entire layer effectively before the next layer goes down, I would recommend "side fan" setups that produce a thin layer of airflow (ideally laminar) at the current Z height. You can find examples of this in lots of the #speedboatrace speed Benchy entries on YouTube, especially on Vorons and other CoreXY machines since it's the easiest to setup on a printer where the bed moves down (like yours) rather than the nozzle moving up, being that you can just mount the fans and ducts at fixed height.

If you want to experiment with this without actually making fancy fan ducts and mounts, just get a desk fan or box fan and point it at your printer. This works surprisingly well.