Perform mesh bed level during heating?
I have a setup using Cura and Octoprint with a start G-code for my MK3s+ that involves waiting for hotend to heat before mesh bed leveling. I'm not sure where I got the G-code from, but I didn't write it myself:
G21 ; set units to millimeters
G90 ; use absolute positioning
M82 ; absolute extrusion mode
M104 S{material_print_temperature_layer_0} ; set extruder temp
M140 S{material_bed_temperature_layer_0} ; set bed temp
M190 S{material_bed_temperature_layer_0} ; wait for bed temp
M109 S{material_print_temperature_layer_0} ; wait for extruder temp
G28 W ; home all without mesh bed level
G80 ; mesh bed leveling
G92 E0.0 ; reset extruder distance position
I'm thinking about changing this G-code; it seems like moving the "home all" G28 and "mesh bed leveling" G80 before the wait for bed M190 and extruder M109 temp would parallelize the two slow operations that happen before each print.
Is there any reason this is a bad idea? Could the bed possibly change shape after being heated? This seems like a fairly obvious optimization (since even I can think of it!), so I'm suspicious I'm missing something.
RE: Perform mesh bed level during heating?
The are a couple of reasons it is done after, one is to allow thermal expansion to occur of the bed and get everything to a working temp. The other issue with mesh levelling is that the pinda probe is temperature dependent, no matter which one you have. Super pinda is supposed to be 'better' but any of them will vary with the probes temperature.
The closer you do a mesh level to a set temp the more repeatable it is. Its why I prefer my old non super pinda that has its own thermistor, I can measure the temp and not start levelling until it reaches a specific value. Yes it takes longer on a cold day. However what's a few extra minutes on a prints that are usually multi hour. Especially when it gets me perfect first layers. I'd rather have rock solid adhesion than lose a print after a few hours. Thats a bigger waste of time as well as material. Subsequent prints start faster as everything is already warmed up.
RE: Perform mesh bed level during heating?
Aha, that means my other modification to G-code (let bed preheat to 50º before starting to preheat extruder to minimize "leakage") is also a bad idea because it means less time for the super PINDA to warm up.
Thanks!
RE: Perform mesh bed level during heating?
That depends. On where your extruder is parked doesn’t it. One of the techniques to preheat the pinda is to park it about 5mm up in the middle of the bed while the extruder heats to a no ooze temp of 160-170 and also use the bed preheat to help warm the pinda up. That’s essentially what the bobstro type start up codes do with the older pinda.
You leave it parked until the temp reaches your desired value and then you level. As the bed by that point is nicely equalised thermally, the extruder is mostly all the way there and won’t ooze and leave spots of filament when levelling and the pinda is at the same exact temp every time then when it’s finished mesh level it only takes a short time to bring the extruder up to full printing temp.
It’s why I prefer the older non super pinda as you can’t do this with the super as it doesn’t have a built in thermistor any more. Personally I think it was a step back. The downside is that in winter it can take a lot longer to get to that desired temp, which is where an enclosure helps as well as the parking position. But as I mentioned a few minutes extra is a small price to pay. And after a first print everything is warmed up anyway so it takes less time after that.
Have a read through https://projects.ttlexceeded.com/3dprinting_prusaslicer_start_gcode_mk3.html bobs site and some of the ideas behind what it does. There’s lots of useful info there, nicely arranged with notes. Kind of miss him posting here like he used to.