Minimum layer thickness relative to nozzle?

DocTrucker

Morning,

I've thought about the maximum layer thickness for a given nozzle size but what about the smallest for good (/slow!) builds? I heard yesterday that ultimakers often run at 0.06 for. 4mm nozzles?

DocTrucker

Largely material dependant? ABS flows well but not sure PETG would like thin layers? Bridging different or just more aparrent?

deckingman

@doctrucker

Hi Wes,
I think you may run into issues, especially with short moves, where the amount of material to be extruded is actually less than 1 micro-step of the extruder. I recently realised that this can be a problem when using a mixing hot end with "normal" layer heights but with mixing ratios that include low values for one of the filaments. One way to get around it is to use high micro-stepping for the extruder. But, then you can run into the step pulse frequency limit of 200,000 hz. You won't see that with normal print moves but you might with retraction so then you need to run lower retraction speed (if you can).

DocTrucker

I hadn't considered that, thanks for highlighting it. Is that 200kHz figure for the Duet 2 rather than 0.6/0.8.5? I've potentially got a double whammy of only 16 microsteps and slower processor.

Really must get around to having a crack at my g-code parser. I'd like to have something flag potential issues with slow jerk etc at least for a few trials.

deckingman

@doctrucker said in Minimum layer thickness relative to nozzle?:

Is that 200kHz figure for the Duet 2 rather than 0.6/0.8.5?

Yes. I've no idea what the maximum step pulse rate is for the 0.6 and 0.85 but I'd guess it will be lower. DC will no doubt step in and tell us.

dc42

I haven't measured the maximum step rate on the older Duets, but I suggest you keep it below 120kHz.

DocTrucker

Thanks. So that's the total number of steps to all drives?

dc42

@doctrucker said in Minimum layer thickness relative to nozzle?:

Thanks. So that's the total number of steps to all drives?

It's probably capable of a higher total number of steps to all drives, but I suggest you keep each individual motor below 120kHz. if the MaxReps value reported by M122 goes above about 50, then reduce microstepping to reduce the maximum step pulse frequency.