by orcinus » Fri Jul 20, 2012 12:54 am
Fingers crossed it's the filament for ya.
So far, the white UM PLA is behaving much better. It extrudes at 185 and doesn't generate gaps and holes like the black.
I'm getting no weird residue nor leakage either.
However, i'm getting a whole 'nother set of problems. As long as i extrude thin walls or perimeters only, everything's fine. The moment i start extruding something with infill everything goes pear-shaped. I've been printing myself some angle brackets (35 degrees) so i can mount the fan pointed towards the bed instead of blowing directly at the hotend. I've been tweaking the width-over-height manually in Slic3r and when i increase width to 2.5-3.0 times the height, i get nice clean M3 holes in the brackets and relatively even walls. But no infill - it doesn't fit, because i've made the brackets 2mm thick. If i decrease WoH to 1.5-2.0, i get nicely filled out insides but the walls look like a wobbly mess.
The thing i've noticed is this - as long as i extrude long straight wall sections, the layers are almost perfectly even. I get just a little wobble from the threaded rods, but that's expected. The moment it gets more complicated than that, the layers become totally irregular.
I'm sort of guessing it might be the hotend. In particular, i think i've screwed it up with the black filament and now the pressure is high enough and the wooden clamp cracked and weak enough that the whole hotend floats up and down as the pressure rises and falls, perpetually changing the distance from the nozzle to the previous layer.
'Cause the thing is, i've noticed that irregularities in layer height vary with extrusion demand for that layer - if there are holes in the current layer, causing the extrusion to stop and start, i get wider layers (meaning more squashed, meaning higher pressure). If there's a lot of fill in the current layer, reducing the pressure in the hotend, i get narrower layers (less squashed). There are irregularities, of course, but the fact remains that long straight continuous extrusion sections end up perfectly, while anything with starts and stops and retractions is a mess.