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gr5

Pulling force of UM Extruder

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gr5 um2: 4.9-5.5 Kg   (48-54 N)

IRobertI um2: 4.5-5.75 Kg (44-56 N)

Nicolinux um2: 5.7 Kg +/- 5% (52-62 N)

(Bertho's UM Original can pull about 4.8Kg)

I will update the above values if people post more data below.  Here is my test setup:

20140127_121331.jpg

I used prontrface to slowly extrude the filament.  The weight on the scale slowly decreased until suddenly the extruder stepper slips backwards ZIP!  I repeated the test several times at different points of the filament and things were repeatable within 1%.  I extruded about 50mm at a time at 200mm/min (3.3mm/sec).  Pronterface is the perfect utility for tests like this and a very easy to use GUI.  It gives you much more control over your printer (although you have to heat the nozzle to 170C for the extruder to run).

Originally I got 5.5kg very repeateable.  But I repeated this test a week later and wasn't able to get more than 4.9kg force because the filament would grind up.  See graph in post much further down.

printrun/pronterface download:

http://koti.kapsi.fi/~kliment/printrun/

Nicolinux data from this post:

nicolinux post #26 below

IRobertI data from this post:

http://umforum.ultimaker.com/index.php?/topic/3976-almost-always-missing-layers-underextruding/?p=34885

Bertho UM Original data came from here:

http://vinland.com/Extruder_Drive_Force.html

Edited by Guest

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The spring is overly strong in the extruder so everyone is supposed to loosen the screw as much as possible so the sprint is compressed as little as possible. People who have tightened this spring had problems with grinding filament.

I posted elsewhere how to modify the current to the extruder but I haven't messed with that for this particular test. I doubt anyone has.

Supposedly if you increase the current much more to the extruder it will grind the filament instead of slip (skip steps). Slipping is strongly preferred. Although the alternate story I heard is that increasing the current any more doesn't make much difference. I kind of doubt that.

 

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Thinking about this some more I'd like to see someone do one more quick test. I'd do it myself but I don't have the tool needed. If anyone has a fairly sensitive pull scale it would be very interesting to see how much friction there is in the bowden with straightened vs coiled/tightly coiled filament. Insert the filament all the way to the extruder head and then pull it out and see what it takes. You'd of course have to either remove the bowden from the feeder (but keep the same bend!) or find some other way to make the filament run through the extruder without friction.

 

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From experience this force is tiny compared to 1kg. However when there is already 3Kg of force on the filament in the bowden, now I expect some significant resistance. I'm not sure how to measure that. I guess if I completely disassembled the bowden and put it in a jig and put force meters on both ends and tried to see how much gets lost in the bowden. When under 5kg of pressure at one end - how much force is received at the other end? Test both static and dynamic friction under those conditions.

Variations: with and against curvature of filament. With and without oil. Nylon versus PLA. flexible pla versus regular pla.

 

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... Pronterface is the perfect utility for tests like this and a very easy to use GUI. It gives you much more control over your printer (although you have to heat the nozzle to 170C for the extruder to run)...

 

Or you may manually issue a M302 command thru the terminal, to allow for cold extrusion.

 

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Hi,

I have repeated the weight test. This time I tried to emulate gr5's test conditions as best as I could.

extruder test

It looks like my extruder can pull less weight than the others. It jumps/skips at 3.75 kg.

edit by gr: with more accurate scale (post below) nicolinux got to 5.7kg

 

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You forgot the pillow! :) I'm sure it doesn't matter. Wow - you really did copy it right down to the vice grips. My scale only goes to 13.6 Kg so I got it a little more accurate but this is a good test. So you have 70% as much pulling force as I do. That could just be normal variation in UM2's - I might just have an above average UM2. You should be able to print something like 70% as fast as me also. Besides when you print near the limit of what the UM2 can do you will get worse quality because of the pressure in the head and the springiness of the bowden.

 

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You forgot the pillow! :) I'm sure it doesn't matter. Wow - you really did copy it right down to the vice grips. My scale only goes to 13.6 Kg so I got it a little more accurate but this is a good test. So you have 70% as much pulling force as I do. That could just be normal variation in UM2's - I might just have an above average UM2. You should be able to print something like 70% as fast as me also. Besides when you print near the limit of what the UM2 can do you will get worse quality because of the pressure in the head and the springiness of the bowden.

 

Damn, the pillow was it. And I used a cheap analog scale that I bought today (because my stupid high end, internet enabled digital scale can't hold it's shi* together for more than a few seconds...).

I hope more people will do this test. Then we would have more data. But even with 70% of you extruder's power, my tests shouldn't fail at 5mm^3/s. Now whenever I hear the skipping, underextrusion occurs instantaneously. I remember this was different before.

 

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I had a few layers of under extrusion a couple of days ago when printing the spoolholder upgrade while using another idea I had which also offered little resistance. (You can see it in the background of the video I posted). That was a print at 235C x 40mm/s x 0.2layers = 3.2mm3/s... I reaaally don't want to pull the head apart but I guess I'm going to have to.

 

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I was thinking I should at least check the teflon part and see that it was ok, haven't done that yet. And no, I printed that holder while using a different spool holder design I had made earlier (also with very low resistance but less practical).

 

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If you want to avoid taking the head apart, you could take the bowden tube out (at the head) and slide filament by hand (while the nozzle is hot). You don't need to go all the way in, just test the passage in the teflon coupler. If it slides without resistance, then you are fine.

Regarding the spool holder. I mean now, with the new one - did you print illuminarti's test objects?

 

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Because of the gear reduction of the old design which gives the original a lot more torque with a weaker motor and possibly not being current limited as much as the new one (speculation on my part). I've had the UM1 get a tangle on the spool, rip the whole spool off the holder and keep printing like nothing happened (scared the shit out of me though as I was in the other room when it happened). On the UM2 a bend in the filament means I can only print at 3-4mm3/s...

 

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I repeated this test with different current settings to the extruder.

M302 - allows cold extrusions

M907 E500 - sets extruder current to 500ms. Default is 1250ma. Max is 2000ma.

I repeated this test several times and an hour later got results as much as 7% different (although repeating immediately I typically got the exact same result. I did all tests slower than last time - at 50mm/min or .83 mm/sec.

Filament got ground up/stripped at 4.9 kg. This was repeatable on different sections of the filament and an hour later. I don't understand how I got 5.5 kg a week ago. This is the same filament. Although the room is slightly warmer (73F versus 70F) and humidity is higher today. Don't see how this would matter. More likely something changed in the extruder while printing stuff. Or the filament is slightly different diameter from the piece used the other day.

So higher currents did not yield any greater pull because the filament ground up every time.

gallery_1527_132_2827.png

 

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I haven't been keeping tabs on this thread, but it seems like a lot of continual discussion on the same issues that were established weeks ago. Has Ultimaker BV chimed in on this officially? it's a problem not only affecting all current UM2 owners, but unless it's resolved, will also affect each new unit sold.

I have a new bowden tube and collet I'm yet to install, but I don't see this preventing the problem occuring again.

Sander has been very helpful, and active on this thread, but I'm wondering what plans, if any Ultimaker have to improve the issue?

 

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@gr5: Thanks for the effort, I'll repeat the test. Though I have a digital scale that can handle only 5kg. I'll try it - don't trust that analog scale that much.

@braddock: I think the reason is because there aren't many users with this issue. Or at least they may not be aware of it because they print slow.

Maybe one of the forum admins could make a sticky post about underextrusion and redirect people here and to my underextrusion monster thread.

 

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I actually meant to post this in the monster thread! my mistake, there's a few similar cross over threads.

 

 

@gr5: Thanks for the effort, I'll repeat the test. Though I have a digital scale that can handle only 5kg. I'll try it - don't trust that analog scale that much.

@braddock: I think the reason is because there aren't many users with this issue. Or at least they may not be aware of it because they print slow.

Maybe one of the forum admins could make a sticky post about underextrusion and redirect people here and to my underextrusion monster thread.

 

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Sander is very aware of whats going on and Harma - head of engineering I think - is also very aware. This issue has Harma's attention and they are spending time on this although if you are trying to print beautiful things, in my opinion having an extruder with half the power of the UM Original isn't an issue because neither printers will print very well when you have over 5kg of force on the filament. I think people are much pickier about surface quality than a few years ago and for them, this isn't an issue.

But some people don't care how pretty their print is. They just want functional and ugly is fine and they want it fast. So for them - it would be nice to understand what's going on.

 

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Sander is very aware of whats going on and Harma - head of engineering I think - is also very aware. This issue has Harma's attention and they are spending time on this although if you are trying to print beautiful things, in my opinion having an extruder with half the power of the UM Original isn't an issue because neither printers will print very well when you have over 5kg of force on the filament. I think people are much pickier about surface quality than a few years ago and for them, this isn't an issue.

But some people don't care how pretty their print is. They just want functional and ugly is fine and they want it fast. So for them - it would be nice to understand what's going on.

 

I'll speak for myself and bounce in the say GR5. :)

 

I am aware that you may print defects. Everything depends on the area of default.

 

If the fault is on a layer and that in this place there, the function provided must support a large force, then it will break and this is what I want to avoid at all costs. :roll:

 

For pure design without mechanical stress, there is some fault does not bother me. :wink:

 

Hoping that it illuminates why and how questions about the expected quality. :D

 

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Sander is very aware of whats going on and Harma - head of engineering I think - is also very aware. This issue has Harma's attention and they are spending time on this although if you are trying to print beautiful things, in my opinion having an extruder with half the power of the UM Original isn't an issue because neither printers will print very well when you have over 5kg of force on the filament. I think people are much pickier about surface quality than a few years ago and for them, this isn't an issue.

But some people don't care how pretty their print is. They just want functional and ugly is fine and they want it fast. So for them - it would be nice to understand what's going on.

 

I'd say there are different issues then. I do get underextrusion even at relatively low speeds. But my issue might not be related to the extruder after all. Can't wait to test the new teflon coupler.

By the way, I ordered a digital scale that can take up to 10kg. My next test should be way more accurate.

 

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