Bumpy Prints

I've just started having a problem with bumpy prints on my Prusa i3 clone. I've been using more or less the defaults in Slic3r to print. I've moved the print temperature around a bit, but this does not seem to be the problem. The attached picture shows two printouts. The red one is PLA, and the white one is ABS. Both exhibit the bumpy texture. I see the bumps on all four sides, so I don't think it's a problem with the X or Y axis having backlash.

Possibilities:
- moisture in filament. It's only a few months old, so I don't think this is the case.
- overextrusion. Multiplier verified at 1.0. Measured filament with caliper at 1.75 +/-0.05 mm. Since I see the problem with different filaments, I don't think this is the problem.
- thin wall prints. Wall thickness is supposed to be 0.10. Measured thickness in bumpy section about .12" Maybe there's some problem in printing thin walls? See note below about white print triangular section, though. Again, I don't think this is the problem.
- printing speed. Set at default of 60. I have not tried slower speeds yet.

When watching the print, the only think that I've noticed is that when a layer is deposited, it seems to "bow up" slightly, like it's not adhering. Then later on that layer, the print head passes over that area again, and seems to smooth it out.

The white print has some odd things displayed. Near the bottom, to the left and right of the hole, the print looks OK. The roughness stops before the slotted hole, and starts again after the hole. If you look closely, you can see that the left edge shows bulges above and below the layers where the hole is. This section is supposed to be 0.100", and I measured it at exactly 0.100" around the hole.
There's also a smooth print on the triangular section near the top where the bumps stop. This section is designed at 0.062" thick, and I measured it at 0.070.

Thanks!

Do you have the same problem if you print a standard test cube. If not then I would say that the way you have designed your model is asking too much of both the slicer and the printer. Side wall thicknesses should be a multiple of the nozzle diameter, top and bottom thicknesses should be a multiple of the layer thicknesses. Layer thickness should not excede about 3/4 of the nozzle diameter. Holes mean that the extruder has to stop extrusion momentarily and the re-start, do you have retraction turned on ? and is is set correctly. If I had nothing else to go on from the appearance I would have said over extrusion.

Try another slicer like Cura and see. Sometimes Slic3r just doesnt work well with some files.

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When watching the print, the only think that I've noticed is that when a layer is deposited, it seems to "bow up" slightly, like it's not adhering. Then later on that layer, the print head passes over that area again, and seems to smooth it out.

!

I think your problem could be one of two things (or both)

First I would look at your starting z height, it might be too high, start a print and when it is about to start printing check the height. Also check your z steps / mm, set them to the calculated valve for your motor step size, micro steps and pitch of lead screw. [www.prusaprinters.org]

If the z height and steps are fine, and you are still having issues, then it could be a temperature related issue, follow the nozzle temperature setup on the wiki to find what temp you should be printing at for that material.

[reprap.org]

Success!

Thanks for all the suggestions. The one that sounded the most promising was the one about trying another slicer. I got the Cura slicer configured for ABS and made another print. This is using the same roll of ABS as before. All of the bumpy stuff went away! See attached. So the problem was the algorithm in slic3r. Incidentally, I had this bumpy problem on an earlier print I made of a phone dock. It was not as bumpy, but the walls were 0.20" instead of 0.10".

In answer to one of the questions asked, yes, I did make a standard print of a cube using slic3r, and it was fine. So I don't think that the problem was caused by some odd thing set in the slic3r configuration.