I am sory for the delay, but my print tests were interrupted by a thief in my garden. Not a joke!
I was drinking a beer and smoke a cigarette on my garden when I saw one guy and one girl inside my garden. Still a bit nervous and adrenaline is kicking right here but i will finish the tests today.
Were they looking for a quiet place or were they trying to steal stuff from your garden? (or break in?).
Hi Nico,
Steal and break in...
Have to go to the door... i think its the police.
Bastards...
Next time have this thing ready (print it in parts/BIG) and swing it while screaming like a mad man 
Oh, didn't read the entire post (damn mail preview).
Well, if it's the police, continue swinging and screaming while also employing typical medieval action moves hoping they will identify you as one of those crazy LARP dudes :mrgreen:
Ok I am back.
Like always portuguese police are a piece of.... dont care about it...
So... I will start the test with the ventilation now...
Hey, I am glad Ultimaker and my bad smoker habits prevented a robbery.
Second extrusion test at 230ºC and 22,0ºC room temperature with ventilation and without the board cover
Board temps (measured as close to behind the chip and resistors as possible)
Start (idle) 22,0ºC
In the end of heating up process: 26,0ºC
1º Layer 3mm3/s: 27,5ºC
1ª layer 4mm3/s: 27,5ºC
1º layer 5mm3/s: 27,5ºC
1º layer 6mm3/s: 27,6ºC
Failed at 6,5mm3/s: 28,1ºC
Made the test twice and they failed in the same way.
Tomorow I will check my nozzle for any clogs just to be sure
I forgot to mention that I am using a half empty spool. It seems that with empty spools it fails at 6,5mm3/s and with a new filament spool sometimes fails at 9,5mm3/s and sometimes can make the 10mm3/s. After checking the nozzle I want to repeat the same tests with a new filament spool and maybe with a litle higher extrusion rate to understand if there is diferences with the board ventilation and this way we can exclude bended filament from the equation.
Edited: These tests means nothing, I may have permanent damage resistors. It seems to me that the temperature near the extruder stepper is too hot. I can´t complain a lot because I can achieve the 10 mm3/s (after a few changes) and maybe with less bended filament and with board ventilation its possible to reach the 12mm3/s. My real problem here it's just filament bended due to radius of an empty spool. The spool should be changed for a bigger radius to avoid so much bended filament.
It should be great if others users could do the same tests because is not enough data to take any conclusions. I think that Nico's printer board after being inspected by Ultimaker team, can give some anwsers. (or the stepper motor)
Shoot, I knew it seemed to good to be true; the temp on the board increasing to the exact stated Absolute Max Ratings Ambient Temp, then failing. I wanted to believe, oh well; it is still curious though that the chip is clearly being exposed to temps larger than what can be tolerated according to the datasheet I still don't think this can be a good thing for that specific component. I wonder what Cohen's thoughts are on this?
Regardless, still interested to see the results of you next print; maybe it's simply a combination of the filament spool diameter and the chip as you are suggesting. It's been a long day at work, and I need to get some sleep and a clear head to think about this with a fresh perspective.
Edit:
At least we solved one thing this evening; what those damn kids were doing in your garden. I lived in a bad neighborhood once before and got stuff stolen from me, that really shot my nerves as well. Just a side note investing in an IP surveillance camera really helped put my mind at ease.
One more Edit:
I totally fell asleep earlier and woke up to respond, and didn't do those calculations I promised, I haven't forgotten about them and will get to them tomorrow.
Shoot, I knew it seemed to good to be true; the temp on the board increasing to the exact stated Absolute Max Ratings Ambient Temp, then failing.
In the exact some milisecond when the temp changed from 85,0ºC to 85,1ºC the underextrusion occurs. I really have to repeat this test because its a very big coincidence...
It's certainly interesting to understand the precise causes of the problems, in terms of any thermal effects/damage that may be done to the board components, so that they can be mitigated in the long run through better design or active cooling (although the current design is specifically intended not to need active cooling - compare to the Original ultimaker electronics that DID need active cooling).
However, ultimately all that matters is the current that's actually going to the extruder motor. Not sure how easy that is to measure directly, but measuring the temperature of the motor might be a reasonable proxy.
The current that goes to the motor determines the torque that the motor delivers (and the heat given off as a side effect). It needs to be enough to give sufficient torque to move the filament at a reasonable speed, but not enough that it causes the knurled bolt to chew up the filament, or the motor to overheat.
In the original Ultimaker, the current was set quite crudely, via a mini pot on the stepper drivers. Now it is precisely and digitally controlled. On the old electronics, if there wasn't enough torque, you just turned the pot up a bit. On the new version, that is harder to do, but it should be possible via gcode.
So, if the reference resistance is off on some machines, for whatever reason, or some other effect is causing the effective current to the stepper to be less than the nominal value, all that needs to happen is just to increase the requested current to the stepper, in order to get the current that was originally intended. Rather than worrying about getting the electronics back to the right temperature/resistance, just calibrate the stepper current rather than assuming one size fits all.
A simpler solution then might be to try printing the calibration test piece after increasing the requested stepper current somewhat, and see whether the print can now complete without the motor getting too hot, or the filament stripping. If that solves the problem, then hopefully the issues of resistors and stepper drivers won't really matter much and any weakness can just be designed away in later iterations.
(I'm not clear whether the current electronics are able to detect when they've skipped a step - if so, then it would be fairly easy to add a self-calibration routine that just extrudes at a target speed, and lowers the current repeatedly until it starts to skip. Even without that, it could still be semi-automated, just invoking the user's assistance to push the button when skipping starts).
All that said, I can't help much with this testing, as I've yet to find a printer that couldn't deliver 10mm³/s at 230º, and I've now tested about 10 UM2's.
Just one final thought before I go to bed, else it will be going through my mind and I won't be able to sleep. The ambient temp of the air around the chip may be cooler than 85C, the thermal transmission properties of the solid material that comprises the chips and pcb is going to be more efficient than those of the air around the chip.
And another final thought before I go to bed, thank you for your post illuminarti. Woah, I didn't realize you have tried this on 10 machines without any problems. This is something to digest for sure. I also like your suggestion for the user intervention to tell the machine the motor is stalling, I asked myself the same question you did as to weather or not current monitoring could be used to detect stalls and the short answer is yes it's possible, but not as straight forward as just measuring the current here is the thread if you are interested: http://umforum.ultimaker.com/index.php?/topic/4466-monitoring-current-from-extruder-motor-for-feedback/.
Just in case someone has a weak extruder due to heat (I don't know if this is a problem or not), to increase the current as Illuminarti suggests do this:
M907 E500 - sets extruder current to 500ms. Default is 1250ma. Max is 2000ma.
You can do the command using prontrface or just insert this command into your gcode. More info here about how I tested that this command really works and how strong the extruder is at various currents (post #19 with the graph):
http://umforum.ultimaker.com/index.php?/topic/4222-pulling-force-of-um-extruder/?p=35887
Hey guys, before I go jabbering on again I just wanted to say I view this thread as a casual conversation with ya'll, and that I'm not trying to spam it with ideas or cause confusion. I hope you view it likewise 
. We have meetings at work where we try to figure stuff out and all types of ideas are thrown around, I think it really helps to see things from many different points of view.
Has anyone downloaded the datasheet for the precision resistors gr5 posted?
I thought the Derating Curve on page two of the resistor datasheet was interesting. If the ambient temp get's above 70C the rated power of the resistor plummets; perhaps heating up the resistor and then running 0.078 watts through it is slowly damaging the thing.
Up to 70C the resistors can facilitate 0.125 watts; with 1.25 Amps going through them at a nominal resistance of 0.05 ohms they are only facilitating 0.0781 watts. But if they are heated up too much and the power rating starts to drop off, perhaps trying to pump 0.078 watts through them is slowly killing them. It's hard to tell from the graph but it looks like at about 80C the resistors are only at 60% their power rating, which would be 0.075 watts.
Edit:
Regarding illuminarti's suggestion of increasing the current; I don't know if this would be the best idea if the resistors really starting to drift out of spec. Increasing the current may make the problem worse over time to the point where increasing the current won't work anymore and parts need to be replaced.
Hey guys, before I go jabbering on again I just wanted to say I view this thread as a casual conversation with ya'll, and that I'm not trying to spam it with ideas or cause confusion. I hope you view it likewise
. We have meetings at work where we try to figure stuff out and all types of ideas are thrown around, I think it really helps to see things from many different points of view.
I consider your comments as a casual conversation, we just discuss possible scenarios and possible culprits. This is very usefull, please keep the "jabbering".
Has anyone downloaded the datasheet for the precision resistors gr5 posted?
I thought the Derating Curve on page two of the resistor datasheet was interesting. If the ambient temp get's above 70C the rated power of the resistor plummets; perhaps heating up the resistor and then running 0.078 watts through it is slowly damaging the thing.
Up to 70C the resistors can facilitate 0.125 watts; with 1.25 Amps going through them at a nominal resistance of 0.05 ohms they are only facilitating 0.0781 watts. But if they are heated up too much and the power rating starts to drop off, perhaps trying to pump 0.078 watts through them is slowly killing them. It's hard to tell from the graph but it looks like at about 80C the resistors are only at 60% their power rating, which would be 0.075 watts.
I downloaded the resistors datasheet and I totally agree with your thoughts and I also agree that increasing the current may worse the problem
Today I can't make more tests because I have to finish some "homework", but tommorow I will return to the attack
So Aaron keep the jabbering comming because they are very smart deductions.
Yes, but if the resistors are out of spec for whatever reason, then that's causing the actual current delivered to the motor to be less than the intended amount, because the control circuitry is misreading the current. So asking the firmware for more current isn't pushing anything beyond its intended spec, it's just making up for a miscalibrated current scale, and operating the motor at the original design spec.
Furthermore, its very standard practice on most other 3D printers to tweak the stepper-drivers reference voltage settings, I'm not sure this is vastly different.
hypothetically speaking that the problem were the resistors out of spec due to heat, increase the motor current should be a temporary fix, this will generate more heat and eventually will damage the resistors permanently to the point where increasing the current won't work anymore. If the problem is a weaker stepper motor, increasing the current could solve the problem.
Hey guys, I've calculated a worse case scenario if we make the following assumptions, WoofysPlace's trace assumptions (pretty reasonable, http://umforum.ultimaker.com/index.php?/topic/4542-comedoone-for-ultimaker2/?p=39341), a change in temp from 25 C to 100 C, and a resistor that is at it's full 1% error and it's full TC of 200 ppm/C as per specified by it's data sheet. The motor will receive 1.194 Amps of current, or a 55.4 mA reduction in current.
According to gr5's graph http://umforum.ultimaker.com/index.php?/topic/4222-pulling-force-of-um-extruder/?p=35887it should still be able to pull approximately 5 kg of mass, although his tests indirectly measured current as a function of the firmware.
Is there anyone out there with something like this: http://www.robotshop.com/en/pololu-5a-acs715-current-sensor.html and can actually measure the current over long durations of time? I have one but don't have the printer yet, but will definitely be interfacing it with my printer almost as soon as it arrives just to monitor the current over time. I can make a pig tail connector so I don't have to cut any wires and make any permanent alterations to the printer.
This document will help provide some insight into how I am looking at things and why I brought this resistor thing up in the first place, it is a general overview of how resistors drift out of spec. http://www.vishaypg.com/docs/49865/selresis.pdf It's pretty interesting even if you don't have much of a technical background.
Edit:
Yeah, Mr. Waldorf has accurately summarized what I was trying to say earlier in post #41.
Also, where did Cohen go? I hope he brings some news to the thread, even if he thinks it has nothing to do with the resistors; I would be very interested to hear what he has to say about this hypothesis either way.
Oh, I have difficulties to follow the entire discussion. In addition, I am only at the beginning of learning to communicate in your preferred language, and much more about electronics.
Policy discussions are very important , I am sure. But I miss the simplicity of curious experimentation with possible alternatives.
I say by myself:
- I have a good sense of clean running processes in machines, which helps me a lot in finding errors. So I've found after low usage time, the material-feed of the UM2 has definitely more than a mechanical trouble. But also a massive additional electrical problem. And a well-functioning solution in relation to the problem I have also been offered. The implementation requires a low price and low risk. I'm wondering something, why so far no one yet has its own experimental daring.
- I am ready to take risks, and have the will to pay the price for it.
- This time I was lucky and was apparently successful quickly.
- I made sure to deliver a few more proves what I'll try also this weekend.
- I need to learn how to make simple and almost correct tests, has anyone have suggestions? What should I start? I am looking for a brief explanation and a test file.
- I can not fast enough absorb and understand information because I am occupationally very busy.
- Of course I will tell also about failures, if there are any and I also know this.
Sorry, maybe I'm having a bad day today, but:
- Why not a small additional active cooling in thermally sensitive areas?
- Why not just use a drive with a higher efficiency in power and energy requirements, if it already exists?
- The new engine requires de facto much less phase current in contrast to the regularly used. There are whole 0.68 amps less. More holding torque and torque comes free.
My logic tells me, take it, try it.
Phew ... I get dizzy ... tired ... and a little frustrated for today ...
Markus
Ha Ha!! Mr Waldorf said "comfort beer." One of my favorite quotes, "Beer. It helps things not suck."
I sure do hope this gets solved soon. I'm trying to design a plane that will actually fly. I'm losing time reading all the theories people are looking into. I thought I was pretty good. Compared to you folks working on this I'm just so average. All I can offer is "Go team. Go."
I'll have some comfort beer tonight and ponder my averageness.
hypothetically speaking that the problem were the resistors out of spec due to heat, increase the motor current should be a temporary fix, this will generate more heat and eventually will damage the resistors permanently to the point where increasing the current won't work anymore
I seriously doubt this is a problem. For one thing, the other steppers all run at a higher current. The feeder is at the lowest setting. For another, resistors tend to be pretty tough. We are running them at .078 watts max typically but in reality if the feeder is moving then the current goes up and down depending on the current step and so on average should be at half that power. And it's rated to .125 watts.
It's possible but it just doesn't seem likely. Eventually I plan to spray cold spray and heat gun on those 2 resistors and repeat my "pull test".
Ha Ha!! Mr Waldorf said "comfort beer." One of my favorite quotes, "Beer. It helps things not suck."
Speaking in my official capacity as a natural cenosillicaphobia sufferer: I concur! :lol: :lol: :lol:
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You already treat us like kings. You don't have to thank, the pleasure is all mine.
I will take pictures of the sensor position
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