Yes, it seems that the current system may just be operating very close to its limits: for many people it works fine; for others having problems it's not clear to me that there is one particular cause - it seems to be a combination of small effects: perhaps the solution is as you say to simply move the envelope, rather than trying to reliably eek out the last 10% of performance in each of half-a-dozen areas?
Yes, I see many people putting at lot of effort in this issue and developing brilliant ideas but the room for improvement seems to be rather limited.
Fortunately UM doesn't follow the trend to proprietary filament. But this approach requires a robust feeder and extruder design with some performance reserves. And unfortunately, due to the automatic filament loading you get no idea about the amount of friction a certain type of filament creates in the feeder - bowden - extruder system.
Maybe we'll see the comeback of two little gear wheels ... :wink:
Hi all, just did my first cylinder to be in the community of cylinder fanatics ^^
I had a little underextrusion at 7mm3/s and a little a 8mm3/s just a little line nothing more at 9mm3/s it begins underextruding a lot and the last one it's a complete mess.
A little picture or two:
And a little timelapse that i did (just for fun):
The temperature is the default temp for PLA (210°C) is it better to put the temp at 230°c like said? Or doesn't it change anything?
:s
Temperature will change a lot. It decreases viscosity and makes it easier to extrude.
Okay then i'll try again with 220°c or should i directly change to 230°C? It's my second day with the UM2 i'm mainly doing stuff with the recommended settings.
I'd try it with 230°.
That result at 210C is very good, just to put your mind at ease in case you were disappointed. Looks like your printer is doing just fine.
No no i was pretty happy with the result 
I will try with higher temp to see how it goes after my current print.
I just have a "problem" i have a really hard time taking the pieces from the buildplate... the buildplate temp is 60°c and i have applied a little glue on the first print nothing since then.
Just let the bed cool to about 40° or less, and then the parts should lift or twist off quite easily.
It's what i do but i really have to battle to get the piece off...
I level the temperature up to 230°c and i got no underextrusion at all:
Does this mean that i should put 230°c for all my prints?
I'm pretty happy of the result for the moment it's running very good.
I print everything at 230 unless I find a good reason to go cooler on a particular print.
Awesome Didier, you have a perfect UM2
My first test had pretty good results, since then I have done a couple more but results were not as good. I think under extrusion is a real mystery and can be effected by so many tiny things, its difficult to put a finger on it! I am sure I could manage a full 10 if i really needed it to 
I recently visited my parents who are 84 years old. The topic of my 3D printer came up. They had no idea what I was describing to them so I showed them the youtube video where the orange halloween jack-o-lantern was being printed. Still nothing. That video is in real-time so you can't really notice that anything is happening. I should have shown them something else. They wanted to know what the waffle shape inside had to do with a pumpkin. "It's the support structure." Nothing.
What will the technology be when I am 84 years old, about 40 years from now, that I can't even comprehend what I am seeing?
In other news, my printer is now skipping with the printbl PLA at 4.8mm3/sec. I'll have to see if someone has declared victory in the feeder design contest.
In other news, my printer is now skipping with the printbl PLA at 4.8mm3/sec.
At what temp? What color?
Does this mean that i should put 230°c for all my prints?
If you are printing at 10mm^3/sec then yes. But that's damn fast. For .2mm layers that is 125mm/sec. For .1mm layers that is 250mm/sec. So if you are printing that fast, then definitely - go 230C or even 240C.
It depends on the filament color. I think this gold color doesn't need as high a temp.
If you are getting stringing then consider going cooler:
http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/
Well for my first prints i used the default settings for PLA which is 210°c bed temp 75°c.
All of the prints went pretty well with these settings.
When i tried the extrusion test it failed a little at 7mm3/s and 8mm3/s and a lot at 9mm3/s and 10mm3/s was a complete failure.
Raising the temperature helped a lot at 230°c the cylinder was perfect.
I've found an interesting post on the forum with the speeds and temperature but for the moment i didn't really experiment a lot with speed.
Most of the prints i do keep the default 50mm/s speed that works good with 0.2 layers and 0.1 layers. I tried 80mm/s with 0.1 layers and it looks ok too.
Is it safe to put a speed of let's say 150mm/s for 0.1 layers?
I'm a bit afraid to clog the extruder ^^ i'm a newbie
Do the math and you'll have your answer. 150*0,4*0,1 = 6mm3/s. So it should be fine on the throughput but you might not like the quality. And don't be afraid of failure, it's how you learn to fix it so you're no longer a newbie 
okay then 6mm3/s is fully doable if i look at my cylinder test... but this will decrease quality... whats the purpose of increasing the speed?
I guess it's okay to increase the speed if you want to have a quicker result of what you print (if you want to see how it goes but don't care of the quality).
By the way if i put 100mm/s can i still increase it with the tune menu on the controller?
Yes, exactly. All printing is a trade-off between print speed and quality (primarily the quality of the finished surface) - the aim for every print is to find the settings that provide exactly the quality that you need (no more, no less), while minimizing the time take to print the piece.
If you print slower, or with more infill etc, and get a part with a higher quality finish than you need for the application in which it will be used, then you are simply wasting time. On the other hand, if you print too fast or make the part too weak, then it will no longer be suitable for your application - and you will end up with a part that is defective and probably has to be redone anyway.
The tune menu on the ulticontroller is a percentage speed, compared to the speeds entered in Cura during slicing. So the actual speeds that the printer tries to move will be that percentage of the speed hard coded into the gcode. So percentages under 100 slow it down: percentages over 100 speed it up.
So long as you don't violate the cubic-mm-per-second limit, you should be able to increase the head travel speed up to 250mm/s or 300mm/s - maybe more. But at high speeds, prints tend to look under-extruded, because it's hard to get the fresh plastic to stick to the layer below when the head is moving that fast, and the slightest vibrations can cause major problems.
100mm/sec is a reasonable print speed for parts that don't need to be perfect but you can definitely go faster. I recommend higher nozzle temps for higher print speeds. Setting feed rate to 200% won't print twice as fast because the acceleration and "jerk" settings aren't affected by feed rate.
You mentioned you use "the default of 75C" bed temp for PLA. This is a horrible default and results in uglier parts for the bottom 10mm due to the filament having trouble cooling down between layers. Typically the parts bow inward in the bottom 5mm. I recommend no higher than 70C. I've printed many excellent parts at 70C bed temp and at 60C bed temp and see no difference so I usually print at 65C. Most people on the forums seem to use 60C. For very large parts that are likely to warp/lift at the corners I like 70C which keeps the part in the glass state where it is soft enough that it can't lift the corners.
If you try to remove a part from the bed when the temp is 70C it will be like clay and get all bent and destroyed so you have to wait longer for it to cool before removing.
Has anyone found a good source for the SY42STH47-1684MA stepper motor? All of the vendors I've found won't sell less than 50 units. :sad:
Sorry, I was "away" for a few days. You miss a few days you miss a lot.
The printbl filament I was using was cherry red. I was printing a C-130 section programmed in Cura at 4.8mm3/sec at 230C.
Speaking of the printbl filament, they use cardboard cylinders and cardboard sides which are held together by plastic inserts that are pressed into the cylinder. Nice and recycleable. Problem is the plastic inserts can work loose over time. Of course this happened when I started an 8 hour print before work. When the plastic insert comes loose it allows the cardboard sides to fall away and no longer hold the filament on the cylinder/spool. When this happens the filament explodes off of the spool and becomes a tangled mess. This results in a knot that eventually gets drawn up to the feeder. Eventually, the knot jams and the filament stops. The printer keeps going along completely unaware of the mess hanging below. 8 hours gone.
I had an almost full spool of filament that was an unuseable tangled mess. I decided to unspool the entire thing and wind it up again. This was a very bad idea. I was dealing with a very large slinky that hated me and refused to wind up again. I ended up winding up the filament until it twisted into a mess and then cut it off. I untangled the mess and wound again, several times. I will have to use the amount of filament required and make sure I have that amount before I start a print.
In other news, I tried geeks feeder design. It did not help.
My printbl spools have held together so far but I know what you are talking about. I had to make my own spool holder because the innermost diameter is too small.
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I've been following this discussion since the beginning. If I would own a UM2 and think about changing the extrusion stepper motor and the feeder design I would go for a NEMA 23. In the reprap community it seems to be common sense that a direct driven 3 mm bowden extruder pushes even a high-torque NEMA 17 to its limits. It's a deadlock: limited motor torque asks for a knurled wheel as small as possible but its minimum size is limited due to the increasing risk of slipping and grinding.
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