Solid layers aren't solid

My apologies if this has been covered elsewhere, but I'm having a heck of a time finding an answer. Every model I make has this same problem - the solid layers aren't. I've tried slowing down, re-measuring that 100mm extruded moves the filament 100mm... nothing.

What am I doing wrong? I've got a Prusa Mendel with a Steve's Bowden Extruder, Slic3r, 0.35mm nozle and 1.75mm filament (measured at 1.6mm with cheap digital calipers), no measurable oval shape, and printing at 0.2mm layer height, 40-55mm/sec move rates, 20% infill, and 235 degree extruder. And a frosty homebrewed pumpkin beer for anyone in the Davenport, Iowa area that can help.


Thanks!

You just need to increase the amount of material extruded in the solid layers, or the filament is being laid down too far apart..

In the print settings tab find the 'Infill' entry in the extrusion width box. If it is not zero reduce the number by perhaps 20% for a start and see how it goes. The smaller you make the number the closer the strands will be laid down in the solid infill, eliminating the gaps you are getting. You will need to do this by some trial and error. If you reduce it too much the printer will try to stuff too much material into a small space and make a mess, so you have to look for the optimum number.

If the number is zero then it is setting this automatically, and probably incorrectly. Try staring with 0.4, which is a bit more than the nozzle width. If there are still gaps decrease it. If there seems to be too much plastic being extruded then increase it.

Here I am assuming that only the solid infill is too thin. If even the side walls (perimeters) seem weak then perhaps you need to tweak the overall flow rate rather than just that of the solid layers.

To do this go to the filament settings, where I am assuming you have entered the measured diameter of 1.6mm in the 'Diameter' box. Just below it there is 'Extrusion multiplier' which is usually set to 1. Tweak this number, perhaps starting in steps of 10%. AFAIK increasing the number extrudes more material, decreasing the number extrudes less.

Have you checked you have set the correct nozzle width in slic3r ?
It looks like its slicing with the lines too far apart, as if it thinks the nozzle is wider.

I tried the suggestions, no luck. In fact, not change at all. I couldn't tell for sure, but it looked like the filament was slipping a bit. I took apart the extruder and pushed the filament as hard as I could. I got ~100mm/minute, a bit slower than I expected. I took apart the hot end & it seems the short PTFE tube segment had shrunk & was really gripping the filament. I plan to give the nozzle a good soak in acetone & replace the PTFE, and try again.

I really like the design on the SeeMeCNC extruder & hot end, but they just don't work very well for me.

I tried just about every combination of settings I could think of tonight - nothing worked. Adjusting tension, temperatures, bowden length... nothing. Then I found something surprising (to me). I shot the bed with an IR thermometer & came back with a range of temperatures from 105-111 (it was set to 110). Then I shot the hot end set to 230 & got ~135c. Hmmm.... I think the thermistor is set incorrectly in firmware. I'll try that next.

Have you tried a different slicer? Just to see if ther are som setting error somwhere or an extruder problem.

An IR thermometer will not measure the extruder temperature. It is too small and not emissive enough unless you paint it black.

Also low temperatures do not in themselves change the flow rate. Only if the plastic becomes to viscous and then the extruder skips or slips. It just looks like incorrect slicer settings or E step calibration to me.

Edited 1 time(s). Last edit at 10/19/2013 06:55PM by nophead.

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OK, I fixed it completely by accident. I turned on the ceiling fan. That was enough airflow against the cold end of the hot end to make a drastic difference. I'll be mounting a 40mm fan on it ASAP. In the mean time, I've printed half a dozen items without issue since, so I'm declaring it a success. Thanks for all the suggestions, and I take back half the nasty things I've said about the SeeMeCNC bowden setup.

Quote
lister6520
You just need to increase the amount of material extruded in the solid layers, or the filament is being laid down too far apart..

In the print settings tab find the 'Infill' entry in the extrusion width box. If it is not zero reduce the number by perhaps 20% for a start and see how it goes. The smaller you make the number the closer the strands will be laid down in the solid infill, eliminating the gaps you are getting. You will need to do this by some trial and error. If you reduce it too much the printer will try to stuff too much material into a small space and make a mess, so you have to look for the optimum number.

If the number is zero then it is setting this automatically, and probably incorrectly. Try staring with 0.4, which is a bit more than the nozzle width. If there are still gaps decrease it. If there seems to be too much plastic being extruded then increase it.

Here I am assuming that only the solid infill is too thin. If even the side walls (perimeters) seem weak then perhaps you need to tweak the overall flow rate rather than just that of the solid layers.

To do this go to the filament settings, where I am assuming you have entered the measured diameter of 1.6mm in the 'Diameter' box. Just below it there is 'Extrusion multiplier' which is usually set to 1. Tweak this number, perhaps starting in steps of 10%. AFAIK increasing the number extrudes more material, decreasing the number extrudes less.

I'm not understanding what the infill percentage has to do with the solid layers like the bottom and top of a part? I'm getting gaps between the perimeter and solid part of the tops and bottoms, the infill part of a solid seems to be fine....

Jeff.

Edited 1 time(s). Last edit at 11/25/2013 12:08AM by jeffegg2.

If the problem was that the top layers were sagging or not bridging over the infill properly, increasing the infill density could help. In this case, though, that wasn't the issue.

Are your gaps consistent all the way around the part, or just on two sides per layer? If it's on two sides, you might have a belt tension issue. I got a couple belt tension springs off eBay that really helped.

.... is your printer correctly calibrated mechanicaly? Do 100mm moves in X,Y, and Z moves come out close to those numbers?

Slic3r has settings for fill percentage by layer type. Make sure they are all at 100%. You can set that more than one way...