Extrusion Multiplier Calibration and actual dimensions of printed parts
I did the extrusion multiplier calibration for my MINI now several times, always using the "precise method". I get now very close to the 450µm thickness - with some systematic deviations on the fours sides of the cube. I thought so far so good... I tested also if the weight of the part that is as specified by Slicer is the same as the actual weight and that is the case. So I thought that I have a proper extrusion going on.
However, when I print parts now, the overall dimensions do not fit and the parts are usually slightly too large. When I print again with 100% flow, everything fits and the dimensions are correct - but I can see signs of underextrusion in the first/top layers.
Was I doing something wrong for the calibration? I measured with a proper micrometer and on multiple places on each surface. I even printed on different positions of the bed... How can it be, that a single wall is "exact" while the overall part then gets too large?
Do I miss some setting in slicer to compensate for something?
RE: Extrusion Multiplier Calibration and actual dimensions of printed parts
You didn't indicate the typical size of your objects and what you consider slightly too large. It's quite possible that you're simply running into the limitations of FDM printing. A tiny error on a 450µm wall that you can'r measure easily can multiply across a 20 cm object and lead to some measurable differences. That's why it's really hard to make snap-fits etc work for everyone as different printers will have different precision. You can try to adjust for that in your design (by designing slightly larger or smaller parts and/or add more tolerances and/or try a material with greater dimensional stability.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Extrusion Multiplier Calibration and actual dimensions of printed parts
sorry, yes the length scale is important. Most parts I printed so far were <50mm and would not fit when printed with the calibrated settings. These were typically models from printables with lots of makes.
I found out that the four sides of the calibration cube would have a systematic error. For example, on average I get to 451,25µm but the front is 440µm, the back 460µm, left 460µm and right 445µm. I thought that maybe some of the problems I see comes from this deviation and that parts on the back-side are maybe just a bit too thick. Thus maybe it is better to calibrate for the maximum of the four sides rather than the average?
RE: Extrusion Multiplier Calibration and actual dimensions of printed parts
I also think you are just running into the limitations of FDM printing
I did the extrusion multiplier calibration escape road 2 for my MINI now several times, always using the "precise method". I get now very close to the 450µm thickness - with some systematic deviations on the fours sides of the cube. I thought so far so good... I tested also if the weight of the part that is as specified by Slicer is the same as the actual weight and that is the case. So I thought that I have a proper extrusion going on.
However, when I print parts now, the overall dimensions do not fit and the parts are usually slightly too large. When I print again with 100% flow, everything fits and the dimensions are correct - but I can see signs of underextrusion in the first/top layers.
Was I doing something wrong for the calibration? I measured with a proper micrometer and on multiple places on each surface. I even printed on different positions of the bed... How can it be, that a single wall is "exact" while the overall part then gets too large?
Do I miss some setting in slicer to compensate for something?
I also think you are just running into the limitations of FDM printing
RE: Extrusion Multiplier Calibration and actual dimensions of printed parts
There are two calibrations in the latest slicer that affect the print. As you stated, you did the wall calibration for extrusion at 0.45mm. In my case, for PETG that said I needed to change the extrusion to 1.07 from 1.00. I made a little six sided object to test with. Average of three measurements on all sides. I use the test object to mix epoxies.
There is also a shrinkage adjustment to compensate for filament shrinkage. This is relatively new in the slicer and it works quite well. Print a 50mmX50mmX50mm cube and enter the values into the filament settings. Test again. I am not at the computer with the slicer so I cannot tell you the exact setting. There are settings for X, Y and Z compensation.
I am now within 0.2mm across 150mm in all directions.
RE: Extrusion Multiplier Calibration and actual dimensions of printed parts
I played around with the calibration even more... So far I'm at this stage: If I apply the calibration for wall thickness, I get the exact wall thickness (with some systematic deviations for the four faces) but on subsequent prints, I see signs of overextrusion in the layers. Thus, I reduced the flow multiplier again by 2-3% - which leads to smaller walls but good optical print quality. So far, I get the impression it is better to calibrate by eye and by measurement, rather than relying on the measurements...
Thanks for the hint, I haven't looked at the shrinkage yet.