Trying to print multiple copies of the same object simultaneously gave me some insights into what might go wrong with that approach…
So wrong
At least kind of.
It’s true multiple objects means more time between each objects layer, however with a properly heated and treated bed you shouldn’t get any peel up.
As for the blobbing, you just haven’t tuned your retraction settings
And as for the top layer porosity, sounds like you’re under-extruding, at least slightly - this would be masked when you print a single part because of the shorter layer times / higher flow?
In all, there’s absolutely nothing preventing a properly tuned machine from printing as many perfect duplicates as you have room for on the build plate. Don’t give up so easy!
I had the exact same issue, though not quite as bad.
I’m working on something which requires 30 identical pieces, and my build volume can hold 4 at a time. But the quality of the 4x versions is clearly much worse than doing it single.
My problem seems to be more related to how much the printer is moving around, I get alignment issues and rough edges when trying multiple objects.
@Tom_Nardi alignment issues suggest your axis are binding perhaps? if you’r using nearly the complete xy build area,missed steps could also be your issue. Check your current limit settings.
Rough edges are likely from retraction not perfectly tuned - an annoying process.
@Anthony_White Are you suggesting I should have a lower retraction setting? For top layer under-extruding, does that mean I should put a lower filament diameter so it feeds more?
THANKS for the super helpful comments!
I’ve been looking for some feedback on the @LulzBot forum, but got none so far. It was the pure comparison between the multiple and single quality that drove me to that conclusion - but your points make sense as to why the single may have had higher quality.
I’m not sure on the retraction, but I would try increasing retraction speed a fair amount, and length just .1mm at a time (until blobs go away.)
As for the top layer, I would either print a thicker top shell (when doing 0.2mm I’ve only ever managed consistent “water tight” with 4 solid layers, minimum), or increase flow% by 0.1 until the issue goes away. You can also decrease filament diameter to have the same affect - my suspicion is the flow % fudge factor value in most slicers is jut modifying the filament diameter appropriately (and across the board.) @Whosa_whatsis - is this true?
I assume they apply the multiplier to the filament length after doing volumetric calculations, but the result is the same.
If you’re seeing gaps in top surfaces when printing multiples, but not with singles, it’s probably a speed issue. A single piece is probably dropping the layer time below the minimum in your cooling settings, making the whole layer print more slowly. This allows the plastic to more thoroughly heat and reduces back pressure, which could result in more plastic being extruded if your extruder’s grip is marginal. It could also just be that bridging over infill more slowly results in less drooping (or more likely, fewer broken threads) which will allow the surface to seal up in fewer layers. Either way, more top surface layers should help somewhat.
Great advice - will try all… I also switched from Slic3r to Cura - so a whole new set of parm starting values to play with.