Hi,
is there anyone that is able to print correct measures (e.g. measured size = CAD size) for cylinders ?
I discovered that even if I can print almost correct measures for squared objects, with the cylinders the diameters are wrong.
I created a test object in Thingiverse http://www.thingiverse.com/thing:120736
I tried to slice it with Skeinforge and Slic3r and both two give wrong measures, anyone with its own artifacts as you can see. The objects were printed in PLA, so even with strong cooling, that are not perfect, and the slicers create very different sized based on the cylinder type: with an hole or without. May be in ABS it would be better.
I would like to obtain perfect (almost) measures for cylinders.
Try to print yourself with your own printer and check…
Pretty much every dimension on my prints comes out to about ±0.1mm - cylinders are actually better that that since they don’t have any corners which could cause mechanical overshoot or overdeposition.
Your prints generally don’t look too pretty, I’d start with working out why that is - a nice looking print is usually accurate as well.
On a related note, did you “adjust” your steps/mm?
Yes. I played with M92 to set X,Y,and Z.
Keep in mind that I got this kind of simil-blob with object less then 7mm with PLA. Cooling may not be enough. The box and the fitting boxes seem ok.
I will do specific tests with snipped of GCODE to see the cooling effect. I forget to say that with skeinforge I used a lot of cooling plugins options that slowed the print in one and half hour. The rusults was not better than slicr3r in 15 minutes.
I had major improvements on smallish pla bits like this when I upgraded the 40mm extruder fan on my printrbot Jr. Try adding a fan and slowing printing speed?
@Roberto_Coli steps/mm should never, ever be set to a value other than the calculated, ideal one.
In my experience, PLA needs a fan - it’s not optional either, since the heat radiated from the nozzle is already enough to melt down some areas.
Your prints look like you’re extruding way too much. Part of your dimensional issue is likely caused by that. Your infill is a good indicator of that, as you shouldn’t have those ridges between passes.
It gives me the same impression, however if I print a box object it seems good.
Keep in mind that the details in the photo are REALLY, really small, and they give me the impression that a 0.5 extruder is too big for very fine details.
The zigZag vertical borders looking are tenth of millimetre.
Question:
- If the detail is 0.3 or 0.2 mm wide, how can the extrusor (0.5) be sure to deposit the melterd PLA in the correct position ?
The hole is 0.5 and the plastic could drop randomly +/- 0.1-0.2 in the vertical drop cylinder projection of the 0.5 extruder hole.
Is that the proof that objects with details less than 0.5 can’t be accurately printed ?
I printed accurately the 0.5 mm think wall box, but the whole box side was exactly 0.5 and extrusion wide was set to 0.5. I don’t think I could print correctly a 0.1 thin box object either setting the extruder wide “automatic”.
Further tests needed.
Slic3r will set the extrusion width to about 1.5*nozzle diameter, and simply skip any details that are smaller than that - so a 0.2 detail will not show up in the print at all.
@Thomas_Sanladerer , the newer versions of slic3r will compensate for small features and reduce the flow rate (and thus effective thread diameter) instead of just ignoring it now.
@ThantiK is that feature included in the stable release, and is it also trying to reproduce details that are smaller than the nozzle diameter?
Ahh, I discovered that printing circles is an issue, even with slic3r and that does not give correct measures even on correct calibrated printers. I am not alone any more … 
@Thomas_Sanladerer yeah, it’s in the stable release. Has been since 0.9.8 I think. I’ve had it just dabble tiny little dots on the top of things that were smaller than the nozzle size. Also tiny infill areas are taken care of now instead of just being skipped over.
@ThantiK that’s weird - even my 0.9.10b is not doing thin extrusions. I guess it might work under certain circumstances, but it’s obviously not a feature that instantly allows you to just ignore your nozzle size and print microscopic details.