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Recently got a Creator 3 (v2) and single-colour prints are great, but dual colour Benchies are coming out quite bad. Initially, I thought it was X/Y calibration as when I printed a dual-colour cube, I could feel a slight bump as I ran my fingernail across the joins. I tweaked that and the cube now seems good (pics attached), but the Benchy came out the same, with a lot of scruffy plastic in several places.

I had the same with some old Balco filament and now with Technology Outlet filament (all four reels have printed fine on their own, the prints are really good).

I'm using Flashprint 5.1 for slicing, with mostly default settings (though infill reduced to 10 % and temp increased from 200 °C to 210 °C for the Technology Outlet filament). I'm using an Ooze Shield and a brim. Stock 0.4 mm nozzles.

Any suggestions on what the issue might be or what I can do to improve it some? The dual-colour pic on the Benchy website looks way better, so I don't think it's just that these parts of the models are difficult to print.

Thanks!

Dual-colour Benchy highlighting printing errors

Another dual-colour Benchy with printing errors

A dual-colour cube showing good X/Y alignment

Another side of a dual-colour cube showing good X/Y alignment

agarza
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Danny Tuppeny
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2 Answers2

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You have a problem with retraction or more broadly with what happens to the material in the inactive extruder while it's waiting to be used again. I'm not sure what your printer does, but there are various strategies for how to handle this, which can possibly be mixed:

  • doing nothing and letting it make a mess
  • a large amount of extra retraction to get the filament entirely out of the heated zone, followed by a slow unretract into the heated zone when the extruder becomes active again
  • using a priming tower (sacrificial junk part) to re-prime the inactive nozzle when it's activated again
  • priming in thin air and using a wiping brush to clean the inactive nozzle when it's activated again
  • maybe others

You need to figure out what options are available for your printer and how to tune them to get results you're happy with.

R.. GitHub STOP HELPING ICE
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  • Thanks! I was using an Ooze Shield for these prints, but someone else suggested they had better results using a wiping tower so I'm going to try that. I did try increasing retration from 1mm to 5mm and it made a significant difference, so I think you're right this is the problem (for some reason I was thinking it was something like calibration of the two nozzles positions). Thanks! – Danny Tuppeny Aug 21 '21 at 18:55
  • Using the towers was worse, so likely will stick to the ooze shield. Thinking about this more though, I'm surprised changing retraction helped so much, since the ooze shield is printed first on each layer, so I'm surprised it doesn't take all the stringing/oozing and prime the nozzle ready for printing on the part. Maybe I should try and get a good recording of a print to see exactly what's going on. – Danny Tuppeny Aug 21 '21 at 20:52
  • I watched some prints more closely and realised me issue is actually _not_ when the nozzle comes back after being parked - that works fine (the ooze shield correctly primes the nozzle). It's when it lifts away from the part (to go back and park) that it's actually oozing out string. So oozeshield/tower/etc. are not going to fix this - I was mostly messing with the wrong settings! – Danny Tuppeny Aug 22 '21 at 10:33
  • In that case it's probably just wrong retraction settings. Don't use zhop. Nozzle needs to move purely horizontally immediately after retraction or the extrusion won't be cut off but will pull from the nozzle. In theory zhop might be great if slicers would emit a 1 mm horizontal move first, but I don't know of any that support that. – R.. GitHub STOP HELPING ICE Aug 22 '21 at 13:49
  • The only z-hop option is disabled. It seems there's a _forced_ hop during nozzle change. I found a possible workaround - I've added two sacraficial columns/cylinders (one for each nozzle) and ensured they're positioned so that they're printed last. The nozzle now travels without a hop to them, then the hop is after the cylinder, so it should get the stringing. If the print comes out well (looks good so far), I might see if I can convince FlashForce to add some setting or something to fix this - seems like a rather silly issue with a slicer for a fairly expensive printer. – Danny Tuppeny Aug 22 '21 at 14:25
  • Yes, great printers (even inexpensive ones) are so limited by all the slicers doing really stupid things, and it's perpetually frustrating... – R.. GitHub STOP HELPING ICE Aug 22 '21 at 14:40
  • By the way, the stringing looks worse with one of your materials than the other. You might also try drying them both, especially the one stringing worse. Drying cannot make the issue go away entirely when there's another cause (like the hop here) but moisture-contaminated filament does string **a lot** worse. – R.. GitHub STOP HELPING ICE Aug 22 '21 at 14:41
  • They're both brand new filaments I just opened because I had the issue with some older filament, so I don't think it's likely there's any moisture in it. I actually reversed the colours in the last print, and the opposite one seemed worse (in the same places), so I think it might just be the way the model is - something about that point seems to be worse (less filament is used on that layer, so maybe there's more molten plastic left at the end of the layer to pull out than if it had been feeding more cold filament into the top?). Will try some lower temps shortly too. Thanks! – Danny Tuppeny Aug 22 '21 at 14:45
  • Perhaps something else that isn't helping, is that FlashPrint is showing red lines in some areas (at least for my curent test print), and I'm not sure why - my feelins is maybe it thinks the models are overlapping? But I used "Align Models" to align their origins, so I'm not sure why that would be the case https://imgur.com/a/0ZMO35C – Danny Tuppeny Aug 22 '21 at 14:48
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I've tracked down the cause of this, although I don't yet know a solution. It only occurs with dual-colour prints and I noticed the stringing is coming from when the nozzle moves away from the print, not from the new nozzle coming towards it.

After watching some prints, I realised what it is. After finishing with a nozzle, the bed is lowered (like a z-hop), and it's thta action that is pulling filament out of the nozzle causing the string. For a standard single-nozzle print, this action does not occur, and no filament is pulled out.

The only z-hop option in Flashprint is disabled, so I'm not hopeful I can fix it here though. Perhaps other slices may do better (I'm going to try Cura next).

Danny Tuppeny
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