Skeinforge 40 and sparse infill

Hi,

I'm having trouble making airtight/watertight infill. I initially tried to make a whistle I got on thingiverse, but it didn't work because air flows right through the walls (base layer and top layer). I've been tuning the infill, but when I ended up on a skeinforge setting of Fill -> Infill width over thickness: 1.05, and still got sparse infill, I figure something must be wrong. If I print with width/thickness of 1.5, the infill lines barely touch. I've also tried increasing my temperature to try to get the plastic to "flow" better, but that didn't seem to help. I've also tried increasing feed rate (though that probably screws up the math with volumetric 5d), but still no luck.

What settings are you using to get solid infill with skeinforge 40?

Hmm, I just noticed something very odd. When printing infill, every other line is printed right on top of the previous one. So watching the print closely, I see one line being put down, then the next line in the opposite direction is put right on top of the previous one (extruder feeds all the time). The the nozzle shifts to the side, and the next line is printed next to the first one, but so far away that the lines don't touch. I verifed this by stopping a print after the first layer was done and counting distinct lines of infill. On this first layer, I counted 20 distinct lines of infill. However, looking at Skeinforge's view of the generated gcode, I see 41 distinct lines. My conclusion is that every other line is "missing" from my print, because it's on top of the previous one.

This isn't happening because I'm skipping steps, though. If my printer was skipping steps for every other line, the infill would only reach halfway through the object. But it fills the complete perimeter. So this appears to be some form of aliasing, where one move "sideways" (perpendicular to the infill direction) doesn't move, and then the next sideways move shifts twice the distance it should.

I'll be working on trying to figure this out, but any tips would be much appreciated.

It may be mechanical backlash. When the extruder is cool, if you put your finger in the tip, will it wiggle back and forth any?

fdavies

You need to change the fill settings, not the width over thickness. I use a width over thickness value of about 1.6 and get watertight layers.

Edited 1 time(s). Last edit at 04/17/2011 07:16PM by NewPerfection.

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@fdavies My X carriage does shift a bit, actually, but I'm not sure what I can do to avoid that. The nozzle seems well stuck in the carriage.

@NewPerfection I agree, width over height is wrong, as I figured out when I'm only getting half the lines I ought to have for each layer.

Here's a picture of a small coin sized object, together with the second try that I interrupted after the first layer was printed. On the first layer, it's clear that the lines are only attached on one side, and are not held together at all on the other side.

[dl.dropbox.com]

Edit: And here's the first layer as Skeinforge visualises it, with 41 lines instead of 20:

[dl.dropbox.com]

Another stupid issue I have that is visible on the first layer is the off-center perimeter. That happens because it is printed starting at home position, so while trying to print a circle it reaches home on the X axis and I get a flat side. This probably helps my object stick together for now, but I should fix this as well somehow.

Edited 1 time(s). Last edit at 04/17/2011 07:34PM by ketil.

There's a discussion in the Skeinforge forum, [forums.reprap.org], on this subject. The bottom line is that you need to do the following:

• Set the extruder steps per mm of feed instead of extruded filament in the firmware based on your extruder design,
• Set the flow rate equal to the feed rate,
• Set the filament diameter to the actual diameter of the feed,
• Adjust the Filament Packing Density Ratio.

You should also turn on Multiply and set the object to print centered at 100,100 so you don't go over the limits in the x-y direction.

In addition, you probably have to adjust your belt tension to eliminate backlash.