Printed objects too thick

Hi all,

I'm using an Eventorbot, which is technically a repstrap I guess. I'm having issues getting parts to print to the correct dimensions. My Z axis is calibrated spot on and I can hold the dial calipers and tell pronterface to move 10mm and it goes 10mm +/- 0.1mm (because it's just a plain old threaded rod). However, when I print something that I have modeled in Inventor that is supposed to be say 5.6mm high, it measures out to be in the neighborhood of 6.1mm. Also, in my X and Y directions, slots are coming out slightly undersized and exterior dimensions are coming out slightly oversized. It's very frustrating trying to get slotted pieces to fit together and what to change in the model to make it happen. Is Slic3r calculating something incorrectly, or am I expecting too much from hobby type printer.

I'm using:
Slic3r 0.9.10b
Pronterface/PrintRun newest version
Sanguinololu w/ Sprinter firmware

Sounds like your extrusion rate may be too high. In Pronterface, you can experiment with changes to your extrusion rate using either M92 Ennn or M221 Snn.

Since you may not know your starting steps per unit (usually in Configuration.h), you may want to try using M221 first, as it lets you input a percentage. Start the print, then type M221 S95, then M221 S90 (5% reductions in extrusion) on smaller parts until you get the dims you want. Then you can go into configuration.h and set the proper extrusion steps by taking you final % and multiplying it what exists in firmware. Or, I suppose you can always add it to your "Start Print" gcode.

Normally you can run these commands live as you're printing, but I'm not sure changing the extrusion rate will be noticeable for you unless you are printing solid layers. See the calibration guide for setting your extrusion steps for better info. In short, you want to print a near solid layer (0.95 infill) and adjust the extrusion rate until you can just barely see gaps between the infill lines.

Edited 2 time(s). Last edit at 08/19/2013 06:49PM by Filip.

I think the extrusion rate is ok. I calibrated the steps per mm in Sprinter and if I tell it to extrude 100mm of filament it measures 100mm. The prints look great quality wise, there's no gaps, it's just that it comes out 0.5 to 1.5mm too thick.