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Top Layers not touching - UM2

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Posted · Top Layers not touching - UM2

Just wanted to let you know that we're currently playing around with measuring the actual diameters of the hotends (the two we have were 0.412 and 0.46) and slicing the files with different nozzle diameters. So far it hasn't resulted in very much, we're still getting separating lines already at the 4th or 5th layer. I should probably also mention that we've now swapped machine to another one and it unfortunately ended up having the same problems ...

 

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Posted · Top Layers not touching - UM2

I have also been having issues with underextrusion on the infill (multiple types of filament). The problem might be worse at higher speeds. It would probably be a good idea to look at how Cura handles the extrusion rate. Is there a function used to determine extrusion rate that includes any parameters other than print speed? If so, those other parameters should be removed from the function to prevent problems with both solid and nonsolid infills.

Thanks

 

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Posted · Top Layers not touching - UM2

I have found measuring nozzle diameter is very difficult. I did it by inserting a needle (with cone shaped tip as all needles have) until it stops moving inwards, then marking the needle with a marker or tape. Then removing the needle and measuring it's diameter where the needle stopped.

But it shouldn't matter much. You can print .4mm wide lines with a .35 nozzle just fine. Cura extrudes the correct amount for .4mm and puts the stripes .4mm apart. The actual nozzle diameter matters but it can be off by 25% no problem.

 

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Posted · Top Layers not touching - UM2

I will look at the .2mm layer gcodes tonight.

 

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Posted · Top Layers not touching - UM2

Ill upload some pictures tomorrow if i find enough time..

Actually im testing the new sliced cubes at my home machine and compared to the other machines prints they are again nice expect a strange other effect.

until now all new 0.2 cubes printed on the newer um2 are showing the line seperation effect

and all cubes printed on the older um2 look good so far

and 0.1 layers print well on both machines still

And because i choose half speed @ 0.2 layers it should be the same extrusion amount per time wich means not more resistance to print then the 0.1 right?

 

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Posted · Top Layers not touching - UM2

A far as I understood how UltiGcode works, the calibration_cube shows:

- 0.5 mm infill spacing

- 0.2 mm layer height

- 0.1 mm3/mm for both first and top layer infill lines

So, no underextrusion here.

 

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Posted · Top Layers not touching - UM2

Okay - I think I found the problem. I looked at the gcode. I didn't like what I saw. cura is doing everything right. You have shell thickness set to .5mm. This should almost always be a multiple of your nozzle width (.4mm) which is a major part of the problem. Changing this to .8mm (or .4mm ) should fix your cube. What is happening is it is slicing each layer for a .5mm trace which means you are sort of overextruding by 25%. That's not easy. The amount of extra energy needed to pump out that extra 25% of plastic is certainly more than 25% extra - I don't know if it's 2X or 1.5X but it's more than 1.25X. Because it has to squeeze that filament into a tiny area between the nozzle shoulder and the part.

Now Cura doesn't just make the *shell* width .5mm but also all the infill. Both the sparse infill and the top/bottom infill. Everything is .5mm traces! This is just how Cura works. I don't know why. If you change your nozzle width to .5mm it will change NOTHING in this slicing result. But don't do that because if you later change your shell to .8mm and nozzle is .5mm things will be even stranger.

Just - always make your shell width a multiple of the nozzle width. Until you are doing strange things like printing tiny text. But for a cube? Just follow that rule of thumb.

I checked the top layer traces and they are extruding exactly the right amount for .5mm wide and .2mm tall traces. I checked the spacing between traces and they are .5mm apart. So Cura did things as expected. Now how likely should this underextrude on a good UM?

Well you are printing .5 X .2 X 50mm/sec which is 5 cubic mm per second. That's pushing it - the absolute limit my machine can do is around 6 cubic mm at 220C. Thats where you expect some underextrusion. I recommend printing half that speed at 220C (3 cubic mm) so 30mm/sec. But because you are asking for an extra 25% overextrusion to fill those .5mm wide traces you might want to go slightly slower - maybe 20mm/sec. Now at 230C you should be able to go much faster. About 7 mm^3/sec so if you decide to print at half that rate that's around 35mm/sec printing speed. Again because you are trying to push .5mm wide traces through a .4mm nozzle you might want to go even a little slower.

Instead - I strongly recommend you change your wall width to .8mm (or .4mm) and then you can print at "normal" speeds. I am getting all my "max speeds" from this chart here which is designed for .4mm shell and .2mm layer thickness (dark blue line):

http://umforum.ultimaker.com/index.php?/topic/4127-um2-extrusion-rates-revisited/

So for example at 230C you can see the max speed is around 90mm/sec which is 90 X .2 X .4 or 7.2 mm^3/sec. Again I recommend printing at half that (about 3.6 mm^3/sec at 230C) for a good margin of error. You can see why I like to print hot when I print fast. I usually don't go over 240C though. If you leave PLA at 240C for too long it can turn to nozzle-clogging-gunk so you don't want to set it to 240C and walk away for 30 minutes.

Anyway this is all fine as long as you print nice and slow.

 

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Posted · Top Layers not touching - UM2

OK thanks for the research but don't you forget that i printed with 25% (12.5mm/s)speed to test and i also printed cubes with 0.4 and 0.8 shells wich looked very similar.. i also printed with 240° once..

and to say this: on my other printer i print with 0.5, 0.6 and 0.9 shells with absolutely not having this problem...?

But anyway ill go to print a cube went wrong again 10% speed to see if its true..

If you would have read my posts you would know that my newly sliced cubes with 0.8 shells still looks the same on new machine and the same cube printed on my older um2 looks fine

and they have 25mm/s speed..

It must be something else i guess cause my two machines behave very differently and they can do nearly the same extrusion test result 13mm3/s and 15mm3/s

 

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Posted · Top Layers not touching - UM2

And the previous round of test cubes that went round in this thread had 0.8 mm shell as far as I remember.

 

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Posted · Top Layers not touching - UM2

Well here i got some pictures to discuss:

Orange pieces are from my older UM2 and the red ones from the new

0.2mm Layer Cura home

older UM2 0.2mm sliced on cura home

 

0.2mm Layer Cura work1

older UM2 0.2mm sliced on cura workplace1

 

0.2mm Layer Cura work2

older UM2 0.2mm sliced on cura workplace2

 

0.2mm Layer Cura home

new UM2 0.2mm sliced on cura home

 

0.2mm Layer Cura work1

new UM2 0.2mm sliced on cura workplace1

 

0.2mm Layer Cura work2

new UM2 0.2mm sliced on cura workplace2

 

0.2mm Layer different (regular) gcode

new UM2 0.2mm sliced on cura marlin/sprinter gcode

 

same other angle

new UM2 0.2mm sliced on cura marlin/sprinter gcode

 

 

0.1mm Layer Cura work1

new UM2 0.1mm sliced on cura workplace1

 

0.1mm Layer Cura work2

new UM2 0.1mm sliced on cura workplace2

 

 

Comparisons: as you can see at some angles the effect is very visible and on some not

Comparison1

Comparison2

Comparison3

closeup1

closeup2

closeup3

 

I cutted two pieces to compare the infill

Its clearly visible that the RED part show a lot stronger pipes (i know the pictures aren't very awesome^^)

CUT OLD UM2

CUT NEW UM2

 

I FINALLY i printed the 6mm/s cube to proof gr5 that it doesn't change the outcome and..:

 

It looks better! LOL that took hours to print.. sorry but no picture yet

 

What is there that i need to slow down 90% to have same quality then my older UM2??

 

And why this does not happen with 0.1mm layer at much higher extrusion rates???

 

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Posted · Top Layers not touching - UM2

I've printed the gcode files too:

calibc.gcode

Has some nice pillowing but otherwise the surface is tight.

C1

calibration_cube.gcode

Surface is not tight and the strands are evenly spanced

C2

 

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Posted · Top Layers not touching - UM2

did you use the fans on 100%? because i had to on the 0.05mm layer calibc cube

 

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Posted · Top Layers not touching - UM2

i just say because i usually set the fans in material settings in the printer and leave the cura setting default..

and for testing i set them always on 100% because that works best on the older um2 as well

 

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Posted · Top Layers not touching - UM2

Ah ok. I don't do that. It is too tedious to have to change the filament settings for every print. When I slice something I do think about it and set everything I need.

 

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Posted · Top Layers not touching - UM2

i just do as following:

large overhangs or flat surfaces-> fan100%

small overhangs or small surfaces-> fan50%

no overhangs or surfaces but some details -> fan25%

none of that stuff -> fan0%

 

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Posted · Top Layers not touching - UM2

I still think the problem is related to trying to print .5mm wide lines with a .4mm wide nozzle. It should be possible but maybe some nozzles have more trouble than others?

By the way if you ask for .7mm wide shell it will make two .35mm passes. If you ask for .9mm wide shell it will make two .45mm passes. For a .4mm nozzle I believe it will do traces .3 to .6mm wide on a single pass (75% to 150%). So .7mm is easier to extrude than .5mm. You should really stick to multiples of nozzle width if you can (0.4 0.8 1.2 1.6).

 

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Posted · Top Layers not touching - UM2

@gr5 we tested also with multiple of nozzle size why you claim on that?

i agree with you that it affects the printing but still does my older printer print all 0.5 shells fine also top infill, if you wish i could print something to show you

how can you still think it's shell related even if we printed different shell withs??

and still i wonder what difference is there to my older printer that this newer um2 prints all this 0.2 layers differently and underextrusioned if i don't lower the speed to uuuultra slow like 25% OF 25mm/s means 6.25 mm/s gives us 0.5mm3/s .. seriously???

 

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Posted · Top Layers not touching - UM2

Sorry I look at things with a microscope so to speak and only look at a tiny problem at a time.

Nicolinux printed your .5mm wide trace part and saw the same issue - "big" air gaps between traces. CLEARLY SEEN. I mean the gaps are maybe 30-50% as wide as the traces. It looks more like a screen than a flat top.

However in all your orange/red cubes above they don't seem to have these air gaps. I don't see the same problem. Instead I see melted plastic pushed around by the nozzle. It all looks normal and typical quality to me. I didn't see *any* bad cubes in the red and orange recent posts. If you consider these bad then I think it's a different problem.

Even in your cutaways the infill looks about the same to me. I don't know why you think one is better than the other. So I'm confused about that.

The only clear problem I see is in a single print that nicolinux was able to repeat and with the .5mm shell width.

Or maybe I'm just too impatient to look carefully? Instead of posting about 20 cube pictures how about just 2. A "good one" and a "bad one" with complete settings (ini file) for each and what % speed you printed at. I feel like you did that and I claim it is probably the .5mm issue.

Maybe you should post a single picture of a cube with (.4 or .8) walls and .4 nozzle and .2mm height at 230C and 40mm/sec that has the same issue and as bad as Nicolinux photo. Also you could link to the gcode.

 

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Posted · Top Layers not touching - UM2

I cannot stay aside :)

There is one clear difference between "blue" and "orange". While blue is equally spaced, meaning a well calibrated XY gantry, the orange shows signs of backlash or whatever causes the lines to come in couples. This is also visible on 0.1 mm print, but since the plastic is more squished, it almost look as normal, but it is not.

I fully disagree that you cannot print traces that are larger than the hole diameter of the nozzle, except maybe if the nozzle is so sharp that there is very little metal around the hole so that extruding more plastic will make it curling around the nozzle tip, eventually leaving a space between traces. This definitely depends on the geometry of the nozzle tip, but I doubt that UM has no flat around the hole, at least some 0.1 mm that will allow for a 0.6 mm trace width anyway.

Also, if the extruder could note cope with the actual extrusion rate the result will not be a trace of constant thickness for as long as the extrusion goes, but will start printing interrupted lines due to skipping steps.

A constant width underextruded line could be produced only by a constantly insufficient extrusion rate.

Since there is no proof in the Gcode that this happens, I cannot thing of anything else than the machine itself is... guilty.

Assuming the mechanical calibration is correct concerning axes parameters (which has to be checked, not just admitting cannot be), the only other reason is the firmware. If the machine receives the instruction to extrude 1 mm3 to print a straight line 10 mm long, 0.5 mm wide and 0.2 mm high, but it is executing just 0.5 mm3, over the same distance, and at the same height, resulting in narrower 0.25 mm wide trace, how the helll this could happen if the "brain" of the machine is not somehow ill, 'cause the "body" is presumably healthy - forget about the backlash story for now :)

 

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Posted · Top Layers not touching - UM2

Bear in mind that these extruders all suffer from back-pressure related under-extrusion to some extent. Given that the Ultimaker² design is fundamentally the same as the Ultimaker Original design in the most important aspects of the physical drive mechanism, I imagine that the Ultimaker² has similar issues - maybe even more so - than the Ultimaker Original did.

See my findings with the Ultimaker Original here:

http://www.extrudable.me/2013/04/18/exploring-extrusion-variability-and-limits/

Given this, I think it would be interesting to see if extruder tension affects the perceived infill under extrusion, and also whether temperature affects the problem.

Also, I wonder whether, for instance, the knurling on the machines that have this problem is noticeably different/worse than that on machines that don't have the issue.

 

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Posted · Top Layers not touching - UM2

@gr5 no, these parts are nearly perfect but i see this constant effect that makes a difference on 0.2 layers if i compare all this prints from my two UM2's.

..i believe that on the 0.5mm shell sliced cubes the effect is just stronger but i clearly see it (even in the pictures) that there's missing material even on 12.5mm/s what doesn't happen on my other machine.. i want to find out why because all prints without that effect look perfectly awesome and there is this layer dependencie still why..?

i mean why can underextrusion happen on 0.2mm layer but not on 0.1mm layer with even higher extrusion rates?!

 

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Posted · Top Layers not touching - UM2

but i clearly see it (even in the pictures) that there's missing material even on 12.5mm/s what doesn't h

 

Can you post just one picture that shows this? And zoom way in on the picture and recrop please so that it's obvious.

What *I* see on these pictures is that the shape of the tip of the nozzle is kind of pushing the plastic around like a plow. Not a lack of material.

 

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Posted · Top Layers not touching - UM2

Also, if the extruder could note cope with the actual extrusion rate the result will not be a trace of constant thickness for as long as the extrusion goes, but will start printing interrupted lines due to skipping steps.

 

This is mostly true for some filaments and for some printers (like mine). When I print too fast the feeder skips back. But for many other people (I don't know why!) they get no skipping and instead the filament actuall slips in the feeder. So it's not obvious.

Even on my printer (but only at high speeds - > 75mm/sec) I can get zero skip backs but still obvious signs of underextrusion. I don't know why this is more likely to happen at high speeds.

The problem seems that as the feeder turns the teeth slip backwards just a little bit. You get a different pattern in the filament - the holes are longer along the axis of the filament. This of course is much more common with UMO where the stepper motor has much more torque.

 

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