Almost always missing layers / underextruding

[illuminarti 18]

Also... you might want to investigate the knurled driver 'bolt' and make sure that it's firmly attached to the motor shaft - I could see how, if that was slipping slightly under higher loads, it might cause your problems.

 

[illuminarti 18]

Well, it seems that your extruder is rather weak. But if you usually print at or below 3mm³/second then you'll be ok. At that's actually pretty fast with thinner layers - 75mm/s at 0.1mm layers.

 

I guess I have a major problem then :sad:

printed with ultimaker blue at 220.

There's a hi-res here.

 

 

[illuminarti 18]

That's an important thing for everyone to bear in mind here... my test pieces deliberately use thick layers to generate lots of flow.

If you're printing thinner layers, then the corresponding print speeds get much higher. For 0.1mm layers:

3mm³/s = 75mm/s

4mm³/s = 100mm/s

5mm³ = 125mm/s

6mm³ = 150mm/s

7mm³ = 175mm/s

8mm³ = 200mm/s

9mm³ = 225mm/s

10mm³ = 250mm/s

At 0.2mm layers, halve those speeds. So if your printer can consistently print the 6mm³ band, for instance, then you should be fine - in terms of extrusion capacity, at least - printing at any speed up to 75mm/s with 0.2mm layers.

Even the best set up printer is likely to fail before 10mm³ with certain plastics, or at lower temps. The fact that the test prints fail at some point is not necessarily a problem - particularly if its a failure that happens much faster than you ever print.

It's not a case of 'it must print perfectly, or else you have major problems'... it's just a tool to help you figure out what the speed limits are for various materials and temperatures.

(But it does also demonstrate that with the right materials and temperatures, it is possible for a well-behaved UM2 to reach the sorts of extrusion speeds that were seen on the UM1).

 

[Nicolinux 288]

(Not to sound like a nag or know it all), but you guys should really try a spool roll with bearings!

My tension/friction problems with the extruder are not an issue anymore.

 

I am on it. Look what I'v got in my mailbox today

 

[Nicolinux 288]

@Chrisp: The nozzle was clean. I could see it all the way down to the tip. Besides, I think it wasn't clogged to begin with. The filament that I pulled out at 90° had a nice finish. If it were clogged the surface should have bumps and holes.

But thanks for the disassembly tip. Splitting the lower part of the head from the upper was actually the hardest step. I am glad if I can skip it.

 

Nicolinux - With the white thing at the top, that's minimum tension. When your extrusion test was failing, was the extruder clicking back (indicating that it could grip the filament, but couldn't push it fast enough), or was it seeming to turn normally, but not enough plastic came out (suggesting that it was simply slipping past the filament, and grinding it a bit).

If the latter, tightening the extruder tension a bit (moving the white indicator block down) might help. If the former, I'm not really sure... but it wouldn't hurt to try.

 

Sadly the extruder clicked right before I saw underextrusion. I also tried once to "help" him by pushing the filament in. This really seemed to help because the skipping stopped and underextrusion was gone. But when I let it go, I saw how the filament was pushed back out and the extruder started skipping again (and underextrusion occured).

By the way, the two white switches on the extruder do not move a notch. I don't want to break them, but I cant move them at all. The one next to the knurled bolt - I can't get a flat screwdriver between the switch and the black margin. It pushes very hard against it. The other switch I can move down a bit but it jumps back as soon as I remove the screwdriver.

Are these switches intended to be flipped when there is no filament in the extruder?

 

[aaronalai 2]

I just wanted to say that I have learned a lot from this thread, and that I really appreciate the hard work everyone is putting in to help out fellow Ultimakers. This forum is reason enough to purchase an Ultimaker 1 or 2.

 

[illuminarti 18]

No, no, no - that's just two views of the same indicator piece. There's a hole in the top of the extruder above the white piece. you need to put a screwdriver in through that hole, and turn a screw to change the tension (and so move the white piece). Might be easier with no filament in - I'm not sure, never done it.

 

[Nicolinux 288]

Oh and there is something else I noticed. I am printing a ball bearing filament roller right now (http://www.thingiverse.com/thing:21435). The fans on the side did not run. But as soon as I gave each a slight tug, they started turning. I've had this happen before, but only on the right fan.

Could this be an indication that there something wrong with the board? Something along the lines that it doesen't provide enough current?

 

[Nicolinux 288]

No, no, no - that's just two views of the same indicator piece. There's a hole in the top of the extruder above the white piece. you need to put a screwdriver in through that hole, and turn a screw to change the tension (and so move the white piece). Might be easier with no filament in - I'm not sure, never done it.

 

Ahh good to know. Thanks! But how do you know it? Is there any documentation on it?

 

[illuminarti 18]

The way I know most of this stuff - I spend a lot of time trying to remember what everyone else posts :-D

See these photos:

http://umforum.ultimaker.com/index.php?/topic/3046-i-have-an-ultimaker-2-for-a-week-what-do-you-want-to-know/?p=22592

 

[Nicolinux 288]

Ha ha, ok. Thank you master Yoda. I'll start lifting stones and remembering posts right away :mrgreen:

 

[chrisp 10]

Nicolinux

"By the way, the two white switches on the extruder do not move a notch. I don't want to break them, but I cant move them at all. The one next to the knurled bolt - I can't get a flat screwdriver between the switch and the black margin. It pushes very hard against it. The other switch I can move down a bit but it jumps back as soon as I remove the screwdriver.

Are these switches intended to be flipped when there is no filament in the extruder?"

Those two white switches only move by turning the screw that is located inside the top of the extruder case, next to where the Bowden tube goes in. "Don't use a screwdriver to push against the white tabs! When you turn the screw righty, it loosens the bearing up against the filament. When you turn the screw lefty, it tightens the bearing against the filament and the white tabs will move down following the indicated lines on the extruder case.

[illuminarti 18]

The fans come on slowly - over the course of the first few layers to avoid over cooling the nozzle at first with blown air bouncing off the bed. When the fans are running at a slow speed, they can struggle to overcome the friction in the bearings, so getting them started with a push can help. But by the time they are running at full power (5mm into the print, by default, I think) then they should be turning freely by themselves.

Another oddity to watch out for... if you're printing mostly by the light of the built-in LEDS (and especially when the LEDS are not at full power), then you can get a stop-motion strobe effect where the fans appear to be turning slowly, but are actually running at full speed, and are just being lit by the (very fast) flashes of the LEDS in positions where the blades almost line up between flashes. Freaked me out the first time it happened... at night in the middle of a long print... go to check printer, and the side fan looks like its sort of wobbling back and forth... went to poke it with my finger, and it about took my finger tip off, lol!!

 

[takei-naodar 0]

Ok i have done the flow test and had allready problems with 4mm³/sec.... guess i have to check some things...

 

[Nicolinux 288]

Or maybe illuminarti just got a special printer. You know, something like an Ultimaker 3 prototype disguised as an UM2 that was wrongly delivered to him (just like Apple likes to disguise their iPhone prototypes). And now the Ultimaker crew is all skittish and nervous and try to lure his printer back to the UM HQ for "routine inspection" :-P

 

[Nicolinux 288]

Man this printer drives me crazy. Printed another piece and it came out flawlessly (retraction on, filament on the floor). This printer must be a girl because she features interesting but inconsistent behavior...

 

[takei-naodar 0]

btw you are also printing on the raw glass?#

pro-tip:

if you make the model and dont want that edge at the bottom of the print add a 0.5mm radius to the bottom

 

[Nicolinux 288]

I am printing on glass. But right now I am printing a model from someone else. But thanks for the tip.

 

[illuminarti 18]

Hmmm from your results i would take both feeder and spool need to be repositioned to improve quality and quantity.

 

Maybe on the side?

 

I think ideally the extruder should be above the printer so the Bowden goes straight down. Probably not very aesthetically pleasing, but that minimizes the stress on the filament. With the current arrangement you have to bend the filament 90° one way to enter the extruder and then 180 degrees the other to pass through the Bowden - all the while overcoming whatever natural curl is on the filament.

[illuminarti 18]

In all my testing, the problem ended up being that the extruder clicked back, not that it ate the filament up. So simply increasing the stepper current might be an ok solution: that's controlled in software now, so perhaps we can get an option in Marlin to be able to tune it.

On the subject of how to measure them... here's a review of several types of drive gears that presents one way of doing it:

http://airtripper.com/1676/3d-printer-extruder-filament-drive-gear-review-benchmark/

 

Excellent testing and very useful information. I guess that in order to have a good extrusion, the feeding mechanism should be even stronger/better than currently in UM2. I wonder which one is considered the best on the market?

And how to measure it?

It needs to handle all kinds of filament, both hard and flexible (though the UM2 feeding mechanism does already handle rubbery filament pretty well, we've tried NinjaFlex as well as FlexPolyester 45D and 40D).

Now with these models you designed it should be possible also to establish a temperature baseline and see what temperature offset is needed for each color. At least within a manufacturers line, for example Colorfabbs PLA/PHA line.

 

[takei-naodar 0]

Ok i took the printerhead and the feeder apart.... now i can print to the 10th layer without fails, though that one gives me headaches. That one was a complete desaster. Though i can atleast do it with the spool on the filament holder and i dont need to straighten it ^^

Laziness for the Win. YAY!

 

[illuminarti 18]

You may just need to bump the temperature up a bit.

 

[takei-naodar 0]

Well... i will test that when i got some new filament..... i am nearly out right now

 

[gr5 2,167]

Well after Illuminarti's test, I decided to create my own - at different temperatures - and I created a graph showing max print speeds for various temps for my UM2 using ultimaker light blue PLA filament. I also included data for nylon pa6 and some "printing in air" tests. The graph is here along with how I did it (it's pretty easy!) and other info:

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

Actually publishing my data took twice as long as collecting it.

 

[Nicolinux 288]

Thanks for the tests George. I guess that settles it that the UM2 should be fast enough to print fast at 0.2 layher height.