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Nicolinux

Please analyze my print(s)

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Hi,

I am tuning my Ultimaker and I encountered some problems. Please take a look at the following images:

1. Blobs

I wanted to print the famous articulated trilobite:

http://www.thingiverse.com/thing:28259

When I print all elements together (it is one .stl file), I get very visible (and ugly) blobs.

Blobs

0.1 layer height, 0.6 walls, 50 speed, 220°, 20% infill

 

When I print only one single element, it is way better. The blobs are almost gone. Some are still there:

trilobite single

 

trilobite single compare

At the top, the single element, at the bottom the element printed with the others at once.

 

Those blobs seem to arise when the nozzle extrudes plastic for the outer perimeter layers. Right after the infill is done, the nozzle moves to the outer layer and sometimes extrudes too much plastic and a blob forms. I have already calibrated the extruder (E steps) so this shouldn't be a problem.

 

2. Ridges / Seams

On many objects I get those ugly seams where the outer layer starts. Call them regular blobs - but this issue is different because they are very regular.

calibration cubes

bucket

The calibration cubes feature these seems only at the front facing edge. I remember that Slic3r had a setting to "randomize starting points". Bug I guess that's only half of a solution because then those mini blobs would be scattered along the x-axis then.

3. Ugly last drop and bad underside

When a print finishes, usually the very last drop that is extruded looks big, squashed and ugly. I suspect that up until now, all my problems are related to overextrusion.

treefrog1

treefrog2

 

Don't mind the poor treefrog - he lost a leg while printing. The layers on the leg curl/warp up a bit for very small layers and have a big chance to be knocked over by the subsequent, circular layer run.

Also the underside of the frog's arm is very very ugly. Maybe the small layers didn't have time to cool and that's why the warp up (or it is overextrusion again). I have set the minimal layer time to 7s for all prints.

 

 

Sorry for the many questions. But I think I am close to a (for my actual needs) finely tuned Ultimaker.

Thanks.

 

Stefan

 

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Looks like a combination of slight over-extrusion, a slight amount of oozing from printing slower and hotter than you need to, and maybe a slightly too low amount of retraction.

It could also be too slow of a travel speed - make sure that's at 150 or higher.

 

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gr5 already posted an answer to the first issue in another thread where I posted the first image. Here it is:

 

But none of this is what you want to know!!

 

What is wrong with your print???

 

I'm not sure.

1) Was this printed by itself or with other objects at the same time? If the answer is "other objects" then almost guaranteed that is "stringing". You can verify by looking at the gcode view in Cura and there should be a blue line right at the exact same location of each blob. You can fix this by printing one object at a time. There are other ways to fix stringing but the best is method in this case is to print one object at a time.

 

2) It could possibly also be caused by over extrusion or over pressure - sometimes the pressure is too high and the UM keeps printing just fine until suddenly it all leaks out in a burst/blob. This could be caused by a bad Z movement - maybe it is sticking and some layers are less than desired so there is less space for plastic and over pressure (over extrusion).

 

3) It could be infill. This also can be checked by looking at the layer view and see if each blob lines up perfectly with the infill pattern. Even better, print it again, look at it when it is half way through and see if the blobs line up with the infill. If this is your problem, increase the shell thickness to .8 or 1.2mm to prevent the infill from reaching past the outer skin. This "extruding infill" is a problem with the latest cura (steam engine). I have some details on it here:

 

http://umforum.ultim...roblem/?p=17683

 

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@gr5: Since the object was printed together with others, I checked the layers view to look out for positioning moves. It is true that blobs form near those areas, but it is not consistent. There are not always blobs when there is a non extrusion move. But other then that, string seems to be really annoying... I have also checked if the blobs line up with the infill pattern, but that's not the case. But if those blobs are due to bad z-movement, how can I track it down?

@Nick: The travel speed is at 150. I have also tuned the temperature for my filament. Just printed a high object and changed the temperature every 10mm. I have found that the lowest temperature was around 185° at 50 mm/s speed. However since the first layer won't stick at this low temperature, I changed it to 195°. The treefrog and the "good" trilobite element were printed at 195°.

How do I avoid over-extrusion? Right now I print everything at 50mm/s because I don't have a feeling yet for the connection between temperature and speed.

 

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so it's #1 above. You can have cura split the trilobyte into it's seperate pieces and it will print them all in one go but one at a time. That way there is no chancee of stringing. The old project planner in cura did this but now the project planner is built in.

I always set temp to 0 in cura and set it manually. If you try it you will see it's much nicer experience. I print hotter for first layer (usuallly 230C or 240C then as soon as first layer is done I lower the temp. You can do this with ulticontroller or cura. But never go from 230C down to 180C because it will overshoot and has a good chance of tripping the 170C minimum. So instead go to 190C first and wait until temp is stable then go lower if needed.

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so it's #1 above. You can have cura split the trilobyte into it's seperate pieces and it will print them all in one go but one at a time. That way there is no chancee of stringing. The old project planner in cura did this but now the project planner is built in.

I always set temp to 0 in cura and set it manually. If you try it you will see it's much nicer experience. I print hotter for first layer (usuallly 230C or 240C then as soon as first layer is done I lower the temp. You can do this with ulticontroller or cura. But never go from 230C down to 180C because it will overshoot and has a good chance of tripping the 170C minimum. So instead go to 190C first and wait until temp is stable then go lower if needed.

 

Oh nice, good to know about the split option...

Thanks for the tip with temp set to 0. I will try that. I guess it will also solve the issue with the skirt sometimes sticking to the nozzle and messing up the first layer. I almost always find myself trying to snatch the surplus filament strands around the nozzle.

Do you happen to have an idea about issue nr. 2? Right after those ugly blobs, that the biggest remaining thing for me (for now).

thx.

 

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I have read and understood your post (great post btw!). I have changed my z-acceleration and max speed accordingly (just took your values) but this doesn't help to avoid the z scar/seam. I have the impression that at the moment when the z stage moves there is too much filament extruded. The scar is very pronounced. I tried to print with crazy high retraction values but it didn't help.

I made a video and slowed it down at the moment of the extrusion (watch in hd):

 

And here is a picture of the seam (it is the same size on the outside too).

z scar / seam

 

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Do you have a recent firmware with the retraction bug fixed? That's the first thing to check, so that any retraction that is happening happens quickly. Although it's probably not even trying to retract on the the layer change, is it?

I think however, that mostly the issue is just that you are printing quickly, so there's a lot of pressure in the head, and when you move the head up to create space for the next layer, that helps to reduce the cap on the nozzle, and a bunch spurts out suddenly. Not sure how to fix that...

Great video btw. What did you use to film it? We need more of these sort of good quality super-slow videos to analyze a printing problems!!

 

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Do you have a recent firmware with the retraction bug fixed? That's the first thing to check, so that any retraction that is happening happens quickly. Although it's probably not even trying to retract on the the layer change, is it?

 

I don't have the firmware that fixes the retraction bug. I thought that even at half speed/distance retraction should be visible. I was planing to update the firmware later. I'll watch the extruder to see if it tries to retract. If it doesn't then I'll update the firmware immediately.

 

I think however, that mostly the issue is just that you are printing quickly, so there's a lot of pressure in the head, and when you move the head up to create space for the next layer, that helps to reduce the cap on the nozzle, and a bunch spurts out suddenly. Not sure how to fix that...

 

I am printing at 50mm/s - so pretty slow I guess.

 

Great video btw. What did you use to film it? We need more of these sort of good quality super-slow videos to analyze a printing problems!!

 

I am using the iPhone 5 to film it and Adobe After Effects to add the slowmo effect. I'll do this videos all day if it helps to get rid of this ugly seam :)

I wonder though why some objects have seams while others don't. I have printed a bunch of these end caps and there is no seam on them:

http://www.thingiverse.com/thing:56769

Oh the other hand, the calibration cubes have two seams on the front left and right edges.

 

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If it doesn't try to retract, then the firmware change won't make any difference - it affects the speed that the retraction happens at, but if the gcode doesn't try to retract, it won't help.

When you print things with infill, then the height change is happening during the move at the end of printing the infill, so the excess plastic is inside, and spread out. When printing thin walled things with no infill, then the height change has to happen on the outside, and so is very visible.

 

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Oh man, that's so weird. I started another print of the exact same object (in fact same .gcode file since I was printing from sdcard) and now the seam is nearly invisible. I printed it at 190° and about 10mm in I switched to 220°. No difference so it is not the temperature. I have no idea why it is different now...

No seam

https://www.dropbox.com/s/6i29hrhyp6tdq5i/Thin_wall_test.gcode

 

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If it doesn't try to retract, then the firmware change won't make any difference - it affects the speed that the retraction happens at, but if the gcode doesn't try to retract, it won't help.

 

Retraction is always enabled so I guess it should have tried to retract. As you explained in another post, the bug means that the retraction speed isn't right so I thought that it would at least move a bit. But it doesn't.

 

When you print things with infill, then the height change is happening during the move at the end of printing the infill, so the excess plastic is inside, and spread out. When printing thin walled things with no infill, then the height change has to happen on the outside, and so is very visible.

 

But then why do the the cubes have to seams? They are printed with infill.

 

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Love the video. Clearly there is still pressure built up before the Z moves up. Reduce this by slowing down the print speed or raising the temp. If you cut speed in half I would expect half the size of a blob.

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Retraction may be enabled, but Cura is picky about when it actually uses retraction. I don't think it's triggering it in the case of this thin wall object for the z-height change.

If you don't have recent firmware, and you changed the z-acceleration settings using the Ulticontroller, it probably wouldn't start using them until you restarted the printer.... (that's another bug that is also fixed along with the retraction one). So it you power-cycled the printer in between tests, that might explain why the z-seam issue is less now...

As to the cubes having seams... maybe it's just bad luck that with cubes, the infill pattern starts ends back at the layer start, maybe... I dunno.

 

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@gr5: Thanks :) But should I go slower than 50mm/s? I have also tried to print at the lowest temperature possible (190° for this filament). I have read so many posts about temperature vs. speed - I guess too many. And there is no "if this than that" kind of guide when chosing one over the other. Need experience - fast! I will try going slower and check the seam size.

@illuminarti: Oh that makes sense. I definitelly power-cycled the printer. Regarding the cubes - I printed another without top/bottom and 0 infill. The seam is still there but only on one side. So it is related. But I will keep testing. The last print of the thin walled object with almost no seam gave me hope.

 

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The object in your video is perfect to test with. It doesn't matter if you have an ulticontroller or use cura, in either case there is a setting to control the print speed (%). If you use cura, set all speeds to the same % because for this test you don't want pressure build up caused by infill speed.

I usually set my mm/sec to 100 so that the percentage equals print speed. So 50% would be 50mm/sec. I would do 10 layers at 70mm/sec, then 10 layers at 50mm/sec then 10 layers at 20mm/sec then 10 layers at 10mm/sec.

Use a permanent marker pen to indicate where you changed speeds. Keep good notes on paper while you do this.

 

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@gr5: I will definitely do this soon. But in the mean time, with my endless z-stage pains I wanted to print some tall objects. While testing I thought it'd be cool to print the Stratum vase. But although I printed at a fairly high speed and realatively hot, the object shows some serious blobbing. How can I avoid it?

Stratum vase

 

  • Layer height: 0.2
  • Shell: 0.8
  • Bottom: 1.2
  • Speed: 100
  • Temp 225

I printed at 100mm/s and the print took 6 hours to complete. Illuminarti says that printing faster and hotter does not necessarily reduces blobbing, but going slower was not an option here because it already took so very long. I doubled the shell thickness because I printed another vase before that with only 0.4 walls. While it looked ok, there were some holes and I thought that doubling the wall thickness would avoid it. Which in retrospect was stupid for the Stratum vase. It is not possible to make out holes on this object anyway.

Here is a pic from the twisted gear vase. Looks alright on the outside, but seems to be a nice home for spiders on the inside :)

Twisted gear vase side

Twisted gear vase home For spieders

 

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I consider 225C to be medium. I often print at 190C which I consider cool. And I often print at 240C which I consider hot. 225C is just normal for me.

 

seems to be a nice home for spiders on the inside

 

Oh! I laughed at that one! :)

Well if you want to avoid "spiders" print cooler. And if you want to avoid blobs print slower. If you aren't picky about quality you can print very fast but if you want very very good quality there is no substitute for printing nice and slow. I would have printed both of these objects at .2mm layer and either 100mm/sec at 240C (or 50mm/sec at 190C if I don't want the spiders). But if I want it to look even better I would print 70mm/sec at 240C or 40mm/sec at 190C. And as you go slower and slower it will look better (less blobs) and as you go cooler and slower you get less stringing.

 

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I consider 225C to be medium. I often print at 190C which I consider cool. And I often print at 240C which I consider hot. 225C is just normal for me.

Oh! I laughed at that one! :)

Well if you want to avoid "spiders" print cooler. And if you want to avoid blobs print slower. If you aren't picky about quality you can print very fast but if you want very very good quality there is no substitute for printing nice and slow. I would have printed both of these objects at .2mm layer and either 100mm/sec at 240C (or 50mm/sec at 190C if I don't want the spiders). But if I want it to look even better I would print 70mm/sec at 240C or 40mm/sec at 190C. And as you go slower and slower it will look better (less blobs) and as you go cooler and slower you get less stringing.

 

Thanks for the pointers (more content for the cheat sheet btw.) :) I will try and print hotter.

The stratum vase is really nice and has a nice tune while printing. I found about it here on the forums: post. I would also recommend to scale it up a bit. As it stands it looks very elaborate but the vase is fairly small.

 

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I guess there are 3 things going on. If you are printing high volume of PLA you need to increase temperature to get that much to flow through the nozzle. The max you can do with a .4mm nozzle is around 10 mm^3 which works out to around 120mm/sec at .2mm layers. But you need it hot to get those speeds.

But when you are at these limits of printing speed (whether hot and fast or colder and medium speed) results in high pressures of PLA in the nozzle. This can result in underextrusion. Also issues where you can get blobs or leaking when the head slows down for a corner as there is still high pressure in the nozzle (so over and under extrusion at the same time).

The 3rd issue is stringing which is also worse at higher pressures, but even at low pressures stringing is better the lower the temp (I like 190C to get rid of all stringing).

So there will always be a tradeoff between printing speed and quality. The UM has fantastic design and can move the head at 300mm/sec very accurately but for excellent quality you need to print more like 50mm/sec or 20mm/sec. I usually prefer to print fast and don't care about quality as much.

Note however! That if you are printing .1mm layers you can print twice as fast and get the same quality regarding blobs and stringing and still avoid underextrusion as well.

 

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But when you are at these limits of printing speed (whether hot and fast or colder and medium speed) results in high pressures of PLA in the nozzle. This can result in underextrusion. Also issues where you can get blobs or leaking when the head slows down for a corner as there is still high pressure in the nozzle (so over and under extrusion at the same time).

 

Ahh slowly - George you are overloading my tender mind. How can over- and under-extrusion happen at the same time? Maybe I don't understand underextrusion. I thought that's the case when less than expected PLA is extruded wich results in crappy infill - like strands that are too thin and do not touch each other. I do get the part with blobs when the head slows down - we discussed this in my other thread with the slowmo video.

 

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