Filament setttings (Slic3r)

[ZS6HDV]

Hi Quentin

I must admit, I find PLA to be much more difficult to set up for neat printing than ABS. Maybe I was lucky to stumble upon good settings with ABS early on, or maybe my PLA is the problem, but I find the print quality to vary a lot.

My specific problem is that I set up the printer to give a beautiful part, say the extruder motor spacer. Nice solid fill, not oozing etc.

When I then print another part, in my case a high part like the Z rear brackets (Lego hands) or even the Hall effect mounts, the higher layers (after about 2mm) start extruding thin beads (unlike the lower layers).

I can physically see how thin the beads become (half the low layers?). But not always – sometimes it lays down a nice fat bead. When the extrusion width thins out, the fill becomes sparse (you can see the layer below through the top layer where it doesn’t touch).

I suspected variation in the PLA filament diameter, but every single time I have measured it, I get a consistent reading (actually on 1.75 mm on my standard (not digital or dial) vernier). It is “Reprapper” filament.

Another side effect is that on high parts, the wall is not smooth, as the outer perimeter extrusion varies in width from layer to layer. It’s not too bad but not as good as the parts I got from you.

The Theta and Psi motors both run 1/32 and 0.9 degrees so it’s not limited by printer resolution. I also had better results with ABS, even when running 1/16 microstepping.

Any suggestions where to look? I have mostly played with extrusion multiplier and hot-end temperature.

Thanks
Hein

[ZS6HDV]

The thinning of the extrusion width with height seems to be repeatable, and not random. If I re-print parts they suffer at approximately the same level, never at the bottom.

What I have done is to stop a print when it is extruding very thinly or in one case almost none at all, and immediately press the “Extrude” button on Pronterface (set at 10mm at 100 mm/s). There does not seem to be any problem like a blockage in the hot-end, it pours filament as expected.

This was done because I thought there could be something like a heat build-up over time in the hot-end causing the extrusion characteristic to change. But as I said it extrudes normally when manually initiating extrusion.

My only other thoughts are either the heat in the workpiece, which I don’t see how it could impact the plastic delivered by the hot-end. I could understand if it did not adhere to the workpiece well or something like that. My last suspect is Slic3r.

However, in software, if your software is not doing what you expect, and you start suspecting a compiler bug, you need someone else to look at your code. Unlikely to be the compiler (but not impossible), you’re missing the bug in your s/w. Same here. Unlikely to be Slic3r but if all else fails I will try another slicer.

[ZS6HDV]

I built the latest Slic3r from source, and although it now slices the small extruder gear without the “not manifold” error message, the extrusion width looks similar to before at high layers. My test print is the Hall holder as it prints reasonably fast.

Next I will try running everything under Windows (all my ABS prints ran under Windows).

[ZS6HDV]

I am not too keen on things that fix themselves, but at this stage I’m happy to report that PLA printing is looking good on my printer.

I theorised that my Z offset might cause the bottom few layers to be “squished”, and me calibrating extruder multiplier on these layers (incorrectly). Once the print gets to higher layers I then see the actual extrusion width.

I lowered the bed in 0.2mm steps reprinting first layers, expecting to see thinner extrusions nd having to up the multiplier to compensate. But at 0.5mm lower the printer started producing good prints.

Any ideas, anybody?

[ZS6HDV]

Oh, and I still have not been able to print a good gear (either small or large) for the extruder.

I have got a good set of calibration settings, though. Circles are round and pretty much on size.

My large extruder gear slices very differently to yours – did you use Slic3r? I can see the direction of filling being different, but the main problem is the teeth – they just do not look good.

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