I have a Prusa I3 that I built earlier this year and have running fairly well though not at the speed/quality that I am hoping to achieve. Attached is a photo of two calibration prints and the Slic3r settings for speed. The test case on the left takes almost 70% longer to print than the one on the right but the quality is obviously a lot higher.

Test Cases


Slow but Good Quality


Fast but Not so Great Quality


I have tried a lot of individual changes to the speed of printing but it seems that the whole thing needs to be SLOW to get the quality that I would like to achieve.

On the hardware side I have tried everything that I can think of but am not complete sure what knobs would drive the biggest changes.

The question is...what mechanical issues are greatest contributors to the reduction of quality as speed increase?

That looks like it's over shooting a tad. Try playing with acceleration control. For starting numbers, I have mine at 1100 for perimeters, 1800 infill.

The Doctor is in The House! Thanks for that tip as it did the trick! I am able to print at the maximum speed that I can feed plastic and the quality is fine. A little slower and it is even better...but still much faster than my test case above!

I owe you a pint!

Cheers,
Wisar

Glad I could help!
I just happened to notice that your prints are not as wide on the bottom. Have you properly adjusted your bed height? Looks like it's a little lower than it should be.

MrDoctor:

I am not sure what you mean from looking at the pictures but I do try to keep the bed level. I have adjuster knobs on each corner and have a couple of calibration prints that I use. At the moment I suspect that it is off a little but should not be much. Here is a print of a 20mm cube.



It is 'def not exactly 20mm by 20mm but it is close and the same at the top and the bottom other than the slight flare of the first two layers pressed to the bed.

Printed with .1 infill which explains the bowing of the top which would not happen at .4. This is printed reasonably fast but I still need to work on those acceleration settings. Any feedback on what you see from this test would be appreciated.

Wisar

Edited 1 time(s). Last edit at 05/06/2014 03:54AM by Wisar.

I've faced the same problem, corrected it quickly.
Try reducing the acceleration of the Z - motors, as the motors move faster than the couplers (sometimes motor shaft moves but not the coupler). This leads to skipping some steps as a result the required height of the cube is not seen.