I have been trying my first multi-filament print on the H2D today.
Right nozzle from the AMS a PETG spool, left nozzle, directly fed Bambu support for PLA and PETG.
I was printing a simple item with horizontal support where I did the support base with the main material (PETG, right nozzle via AMS) and support interface with the support material (left nozzle)
Now since it was “our first time” I walked to the printer and watched the procedure and I was also curious how long it would take.
For switching from PETG to the support material it took 193 seconds - more than three minutes - before it continued printing with the support material.
Heating, purging (poop shoot), wiping, cooling, purging (poop shoot) again, and a lot on the prime tower.
Is that normal? I saw YouTube videos where the change was a lot faster and also no poop. Isn’t that the whole point of a dual-nozzle printer that changes are fast and waste is low? Am I doing something wrong?
Also, I thought the double poop with the support material was b/c it was the first time this support material was used in this print print but when changing back to PETG it pooped again (only once though) and also the change time was faster (didn’t check the time).
I mean, it puts a lot material on the prime tower. There should be really no need to additionally poop. And while the material consumption is hardly my concern here really, it’s the long time it takes for changing and the print cooling in the meantime.
Anyway, there must be something I’m doing wrong why YouTube videos showed fast changes and no poop where mine is both the opposite. Any guidance or gentle nudge in the right direction would be appreciated.
being the support filament which seems to wipe/poop/flush extensively
and
the filament being used for the first time in the current print
The first point I can’t change but for the second - is there a setting somewhere to prime/flush filaments before the actual print starts?
Of course this would only make sense for one filament on each nozzle (which it is in my case, main material (right nozzle) + support material (left nozzle))
Alternatively I would draw a single line on the build plate, assign the support material to this line, and change the filament order for the first layer so the support material is printed (and therefore prepared) before anything else so it’s ready when it is to be used in higher layers.
But to be honest, that seems quite cumbersome to me and I am hoping for something easier.
Looks like you’ve got it nailed down. I was going to mention that the first time it uses the filament it’s likely purging and doing the flow dynamics calibration. Every switch after that should only be a few seconds and then priming on the tower.
That only changes when the wait happens, not whether it happens. The delay will either appear at the very beginning or the moment the filament is first required. I don’t see any advantage in that. Instead, it forces a priming line every time, which becomes unnecessary filament waste if you run multiple prints.
I rather like that delay in the beginning since I mainly print technical/functional parts with engineering materials in many cases where layer bonding is crucial and correct measurements are important.
Stopping a print for three minutes (waiting for the initial preparation of a support material) somewhere in the middle of a print can weaken the bonding or can cause the material already printed shrinking more than usual before the next layer is applied.
So better to keep the print interruptions as short as possible.
I agree, for simple PLA multi-color prints I can’t see an advantage, either.
I get your point, but I don’t think the preload changes the behaviour you want to avoid.
If the printer environment is stable (chamber temp, nozzle temp, material path), the printed layers won’t cool down or shrink just because the support material is introduced later. The switch behaves the same either way — the only difference is when the wait happens.
I mostly print engineering materials, and I’ve never seen any improvement from preloading support at the start.
Thank you for that information.
Probably I’ll do a compare between both options (fast support material load and slow material load) and see what the difference ist.
Btw, I like printing rather warm (nozzle and chamber), I even print PETG in a heated chamber and most of the time with fan off so I agree, this environment does the extend the time of the print cooling but still, three minutes is a long time.
Anyway, once I tested it, I’ll update this thread here.
Would love to hear your experience.
When I print PETG, I keep things as cool as possible — the chamber stays well under 40°C — but then I crank up the bed temp like it owes me money
