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saulbass1

Cura XY resolution

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Hi,

I'm printing some objects using flexible PLA (@ 15mm/s) and the prints corners look a bit rounded in the XY axis. Is there any way I can adjust my Cura settings to sharpen the XY resolution of my 3D prints?

Cheers,

Selected

 

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Do you have a photo? The default UM extruder nozzle size is .4mm diameter so I would expect corners to have a radius of at least .2mm. Are you seeing more than that? If so try more cooling maybe? Or printing slower and fan on 100%. Perhaps 20mm/sec.

 

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2s0e51h.jpg

The picture above shows my flexible PLA print in comparison to my original data file. As you can see the corner radius of the 3D print is approx 0.8mm rather than the 0.2mm suggested. I have pasted my Cura settings. (The printer is a recent factory built machine in conjunction with Cura 13.06.4.) Does anyone have any ideas how to improve the quality of the print - which is a decal project?

Cheers,

 

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Is this the bottom most layer? The bottom most layer is the hardest to do. The thicker the easier so a .1 bottom layer would be very hard. So for example if the bottom layer is .3mm (default I think?) and the bed is .1mm high then you are squirting enough plastic for .3mm in a vertical gap of .2mm and much will leak out beyond the intended location.

So if you want the bottom most layer with .2mm rounded corners then your levelling technique needs to be accurate within maybe 1/4 the height of the bottom layer thickness.

Also I haven't looked into this thoroughly but if the layer height is set to .2 but the bottom layer is set to .3mm it seems like (I could be wrong) the z axis is set to .2mm instead of .3mm for the first printed layer. Perhaps a bug in the latest cura? I really haven't paid much attention. However, by the time you are printing the 4th layer or so I would expect it to agree to your expected XY tolerances of .2mm radius much better.

 

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14ub3fs.jpg

Hi,

Thanks for the quick responses.

I reprinted the object using 'normal' non flexible Ultimaker PLA at 0.1mm layer thickness and as you can see from the attached image the corners are tighter in comparison with the flexible PLA. In both cases the interior corners are sharper than the exterior corners.

I've uploaded the source file to thingiverse for reference if anyone is interested: http://www.thingiverse.com/thing:139777

Owen - good idea - once I reload the flexible PLA I will try some lower temperatures...

gr5 - the test piece is only 1mm thick and as this new image shows, the top and bottom layers look similar in terms of profile.

As for my leveling technique - I normally stick a thin sheet of paper under the nozzle and shift the printhead from corner to corner until it just grips the paper in all four positions. I then check this by watching how thick the filament lines are as the brim is printed - making fine adjustments on the fly so that the PLA just 'digs' into the blue tape. I think this technique is a good one as you have time to see how the PLA squishes out or begins to lift if the bed is uneven.

While I'm not surprised the normal PLA prints tighter than the flexible PLA, overall I was expecting the Ultimaker prints to be a little 'sharper'. Is there anything I need to adjust? Everything feels pretty tight and the calibration Robots look good to me.

 

 

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.4mm diameter is the best you can expect for outside corners as this is the diameter of the nozzle. You can go lower nozzle size if you need to do this a lot. Some people have reported good success with .25mm nozzles. You wouldn't want to print anything larger this way as you will need to lower your extrusion volume dramatically.

If you only ever want to print square outlines like this you could in theory have a square nozzle tip. It would decrease accuracy on curves but increase accuracy on things like this particular print. However I don't have any idea how one would build a square hole that small. With a laser maybe?

This is very good results with .1mm layer. You will get slightly better results with .2mm or .3mm bottom layer as the leveling doesn't have to be quite as precise.

Higher temp makes the plastic flow more like honey. Lower temps more like toothpaste. For super high precision you want lower temps.

 

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His leveling is excellent. If he was too close to the bed by just .1mm (thickness of sheet of paper) the PLA would have been noticeably squished and he would have had corners with a radius of more than just .2mm.

But with a round nozzle producing filament .2mm in radius you can't get tighter outside corners than that. That's the radius of the filament coming out of the nozzle. I believe you that positioning is 12.5 micron but outside corners can't be better than your nozzle size.

 

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Guys, thanks for the replies which have helped me understand some of the operating tolerances of my printer - I wasn't sure if it was operating to specification. I'd previously thought that the Z axis would be the limiting resolution of the Ultimaker but gr5's explanation about the 0.2mm radiusing makes perfect sense, not withstanding the 12.5 micron positioning. The suggestion to print a raft is good except I'm not wanting to have a raft in this case.

Cheers.

 

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I'll give a shot to a possible improvement. I would suggest to increase the temperature. The flexible PLA probably has a longer melting-traject and will be more sticky at the transitiontemperature. Therefore it will stick more to the nozzle and will be dragged along with it. So it could create the rounded corners. Compare it to dragging a stretchy rubber hose over the floor while walking the same path of the nozzle. It will bend at the corners because its more connected to the part which you are still holding. I hope you get my idea haha.

With a higher temperature it will be more fluid and wont stick to the nozzle so much.

Just try and share the results please!

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