Avoid printed layer (drags) [slic3r]

I'm trying to print this piece that has a weird pattern on the top layer using slic3r, and I'm having issues with it:



The issue I have is that when it tries to print the last layer it moves like this:


This causes the nozzle to print one of the elements in the pattern, and then move back to the corner, where it goes on to print a different one, but on the space it travels through, the nozzle drags, destroying the printed parts of this layer. I have tried a few different things, but nothing seems to solve this issue. If I could somehow tell the nozzle to lift in the z axis for those movements (lift z on retract doesn't seem to lift when the movement is in the same layer) or tell it to move from one of the elements of the pattern to the next without going to the corner, I think this would print nicely but I haven't been able to find options to achieve that.

Does anyone know of any options to be able to do this?
Thanks!

Edited 1 time(s). Last edit at 06/15/2016 10:22AM by uorbe001.

Slicer does have a "Lift Z" option, it's in the retraction settings for the extruder. I use it all the time on my delta printer.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
Slicer does have a "Lift Z" option, it's in the retraction settings for the extruder. I use it all the time on my delta printer.

Yes, but the retraction (and thus the lift) is only triggered when it changes from one layer/piece to another doesn't it? I have it setup to lift .2mm with a .15mm layer height, and I am still seeing it drag for this piece.

Quote
uorbe001

Quote
dc42
Slicer does have a "Lift Z" option, it's in the retraction settings for the extruder. I use it all the time on my delta printer.

Yes, but the retraction (and thus the lift) is only triggered when it changes from one layer/piece to another doesn't it? I have it setup to lift .2mm with a .15mm layer height, and I am still seeing it drag for this piece.

No, retraction occurs for any travel move whose length exceeds the "Minimum travel after retraction" setting.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
No, retraction occurs for any travel move whose length exceeds the "Minimum travel after retraction" setting.

Ah, you are right. I increased the amount of lift from .2mm to .3mm and I watched it while it was printing these layers, and it did in fact lift the nozzle on those movements. It went from this (where the movement lines are pretty obvious, although the picture might not show it):



To this:


There is still some drags on that one so I tried increasing it to .35mm and adding a retraction of 11mm, but that made it even worse:


It looks to me like an oozing problem, I'm thinking maybe my extruder can't handle this, as the 11mm retraction is quite a lot.

Are you sure it's not a stringing problem? Retraction won't cure that, but reducing the temperature might.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Try slicing in Cura. Tool paths often makes more sense in Cura. Turning on "combing" will reduce the 'border crossings", I think.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
dc42
Are you sure it's not a stringing problem? Retraction won't cure that, but reducing the temperature might.

Not sure, I tried decreasing the temperature 15 degrees (that's about 20 degrees below the manufacturer's recommended temp!) and the result seems to be similar to the second picture I posted above, maybe slightly better:

Quote
the_digital_dentist
Try slicing in Cura. Tool paths often makes more sense in Cura. Turning on "combing" will reduce the 'border crossings", I think.

Cura does indeed print on a path that makes more sense for this piece, I have tried with the original temperature I was printing at (230C) and the result wasn't very good (it was better than slic3r though), so I tried a second print with the decreased temperature (215C) and the result is a lot better:


I would like to get this to print nicely on slic3r because I hate Cura's UI, but at least I can print it decently even if I can't get nice results with slic3r yet, thanks!

I like Slic3r because of the control it allows, but some things are better done with other slicers.

I recently printed some stretchlets at a public demo. I was getting some weird artifacts when I sliced with Slic3r, so I tried reslicing with Cura, keeping the settings as close to identical as possible. The prints came out perfect. I regularly inspect prints under a microscope to try to spot problems in the printer, but when stuff like that happens, it makes me feel like the printer is about as good as it can get because I can no longer tell the difference between printer and slicer problems just by looking at the prints.

Now I'm building up a mental catalog of which slicers work better for which type of prints, frequently by comparing slicing results displayed on the computer and then comparing the prints to those results. For some reason Slic3r comes up with weird tool paths on certain types of prints such as yours. If you want to make spiral vase prints, Slic3r is "da bomb". If your prints need a lot of support material, Cura or S3D (still testing) seem to be a better choice. I've also played with a couple other slicers. There's one called Voxelizer that is looking forward to improved printer technology where print materials and colors can be varied voxel by voxel. It doesn't use STL as input.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

It makes sense that some slicers generate a better path than others for certain prints, but the one generated by slic3r seems to make sense (in an strangely dumb kind of way). It feels like there is something wrong with my extruder (or config) that causes those 'nozzle holes' in the slic3r version and maybe a better extruder wouldn't have this issue. In any case, I have tried other prints and this is not happening with Cura, so I suppose that gcode is better suited to deal with my extruder on these prints lol. I will make sure to check other slicers the next time I have similar issues ;-)

What filament are you using, that the manufacturer recommends a minimum temperature of 230C for but still works OK at 215C?

Are you certain that your firmware is correctly configured for your hot end thermistor?

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
What filament are you using, that the manufacturer recommends a minimum temperature of 230C for but still works OK at 215C?

Are you certain that your firmware is correctly configured for your hot end thermistor?

I just downloaded the technical sheet from the manufacturer's website (for abs: [smartmaterials3d.com]) and it says the hotend should be around 240C for printing, I have been printing at 230 for a few months with this same spool (my extruder doesn't go higher than 235C before 'heating failed' errors happen). I only just noticed the 'oozing'/stringing with this print, but it might be related to the fact that I changed the hotend nozzle last week from a .2mm to a .4mm one. I tried extruding with repetier-host at lower temperatures when you mentioned lowering the temperature, and I was able to extrude properly at 215C, although I've been printing at 220C after that.

My thermistor has been working without noticeable issues since I set it up. I've had issues when I accidentally pulled it out of the extruder block and it was reading the wrong temperature, which quickly lead to 'heating failed' errors but that's a pretty obvious 'user mistake'. I wouldn't rule out the thermistor giving me the wrong temperature within a margin of error, but I don't think it is incorrectly configured. (haven't actually measured the temperature at the hotend with a different sensor though)

Edited 1 time(s). Last edit at 06/20/2016 04:16AM by uorbe001.

Maybe check the actual temperature - most printers are not that accurate. Get a thermocouple type digital thermometer with a long wire-ended thermocouple. Remove the filament and feed the thermocouple into the nozzle in place of the filament until it bottoms out. Heat the nozzle to your normal set temperature and see what the actual temperature is on your thermometer.

Dave