aaronalai

I had a couple of questions about the hardware on the UM2 board. It took a little searching but I think the stepper controller chips are A4983 controller chips. I was reading the datasheet for it because I was curious as to how the current for the extruder stepper could be controlled by the firmware and/or Gcode, but is not being fed back into the computer code. It looks like current is controlled as a function of the VREF pin 17, and the two Rsense resistors placed inline on pins 27 and 23 of the A4983 chip. I can't quite seem to figure out the values of these resistors, I think they are 0.05 ohm precision resistors, but there is only the letter E after the 0.05 value, so I can't figure out the tolerance. The VREF signal looks like it is coming from pin 38 of the ATMEGA2560 chip. So this explains why the amount of current cannot be fed back into the computer code, the current control is a one way street with the A4983 chip doing the real current monitoring. My questions are these: 1. If we know the value of the resistors emanating form sense 1 (pin 23) and sense 2 (pin 27) would it be possible to feed the voltage drop across those resistors back into the main computer so it knew that it was skipping steps and moving backwards? Calculations indicate an estimated voltage drop across those sense resistors of around 62.5 mV when 1.25 amps are flowing through the motor (assuming 2 ohms of motor winding resistance), so any deviation from this could indicate that the stepper is missing steps or grinding filament. 2. Has anyone tried this already? 3. Has it already been established that monitoring what the extruder motor does is irrelevant? I hope this is not the case, I think it would be a real benefit. 4. Are there simply not enough extra pins on the main Atmega chip? From the PDF of the schematics it looks like there would be ample room. 5. Am I completely off base and just jabbering about nothing?

Shoot! It's hard to tell who has what type of exact problem; perhaps most of the under-extrusion problems are a function of settings but you have a somewhat different problem. When are you suppose to get that teflon coupler?

Definitely interested to see the results of such a test, a 10% reduction in the flow rate from other peoples print seems reasonable; the difference could easily be from the summation of assembly/parts tolerances. I hope the problem is as simple as this :mrgreen:

Yeah, I did notice the jumps were not all of the same rotational distance; I understood this to help prove the teflon hypothesis though; as putty like filament gets crammed into any interior deformations at higher pressures/flow rates (the temperature and nozzle diameter cannot change so the only thing that can change is the pressure inside the nozzle) I wouldn't expect to see the extrusion motor spin backwards until the material stretched to a certain extent which would have some variability to it because of the constant release and build up of pressure from the extrusion motor. I can also see it being a function of a defective stepper motor as well. I think until I get a datasheet for the controller chip of the feeder stepper, I can conclude that the circuitry is pretty sound; leaving the motor as the next suspect. I wouldn't expect the motor to be allowed to rotate that far backwards; the folks at Ultimaker would have to know that it would cause an extreme release of pressure in the nozzle causing under extrusion while the head built up pressure again. I believe it was their intent to have the motor stall but still apply a load to the filament until the motor could spin again. I see what you are saying, if the motor itself if faulty then it could explain why the backwards spin is so great resulting in under-extrusion. It's like once the stored potential energy (from wherever it is stored) is released the motor just gives up and takes too long to move the filament again. It's just a thought, and admittedly one that just came to me so I haven't had much time to really think it though. But when the filament is at room temperature, I think it would be rational to conclude that it wouldn't have much of a capacity to build up potential energy, it's too stiff. If you could hold a very short segment of the filament at the very exit of the extruder (take off the bowden tube and hold the filament in your hand very tightly, I really don't know how feasible this is) you could see if the motor just sits idle trying to move the filament (I wouldn't expect any springy action to push the knurled wheel in reverse), or if it just gives up when it reaches it's current limit and you can move the move the filament freely for an instant. If the ladder happens I would guess the motor is missing steps (something I don't think it should do), potentially being a way to test your hypothesis. Essentially this would tell you if the motor was always applying a load to the filament but the filament pushes back too much, or if the motor simply looses power momentarily.

Sigi, great post! I hope that the next generation grows up with 3D printing a regular part of their lives. I love seeing stuff like this!!

Hmm, interesting. I'm not abandoning the teflon coupler explanation just yet; even with your reported observations the sequence of events may be too close to identify causality. There is a chance that potential energy stored in the head (as a function of a teflon deformation) is reaching a critical point, but the stepper yields and spins in reverse before under-extrusion can be observed at the head. But your observation has lead me to think about the problem a bit differently nonetheless. Let's see if we can rule out the stepper controller circuitry. I'm looking at the board schematics found here: https://github.com/U...aker/Ultimaker2 mnis suggested through our communications that he thought the chips were too small to not be actively cooled, I've also seen others question if not having an active cooling system on the board can cause any problems. So I thought I would look at the schematics to find the chip type (I agree they do look too small to not be actively cooled); but without a data sheet I can't do any calculations that could tell me anything conclusive. The pdf of the board does not specify the chip model, if someone could post a chip model number, I'll see if I can find the datasheet and do some calculations using the thermal resistance information. After doing some calculations with the default current allowance of 1.25 amps Ultimaker sets in the firmware, and some assumed thermal resistance and RDS(on) values; I don't think those chips can overheat very easily. Even if the thing had a Junction-to-ambient temperature of something like 80 C/W (just making up numbers here, a pretty large value nonetheless), an RDS(on) value of 0.04 ohms, and it was suspended in free air, the thing would probably rise only 5C in temperature. Without anything more to go on then estimations, I can't follow this line of rational to it's conclusion though. Edit: This is an image of the board: If someone could tell me what the chip labeled U12 under the E1 interface is, I'll do my best to do some worse case scenario thermal calculations.

Thanks for the video upload Mr. Waldorf, I have a rather specific question for you or anyone that has uploaded a similar video and I hope it comes across clear enough. Alright, I've been watching a lot of videos where these extrusion motors "JUMP" backwards. It was my belief that the motor current circuitry was designed in such a way that if the motor did not have enough current to facilitate the displacement of the filament, the motor would stall but keep it's approximate location with respect to the rotational motion it provides, and to not jump backwards loosing stored pressure in the nozzle causing under-extrusion. These jumps backwards indicate to me that there is the storage of potential energy inline with the filament somewhere, or potentially the bowden tube; upon the motor stalling the filament pushes back against the knurled wheel spinning it in reverse. I think this is quite clear; the question is though, where the potential energy is stored within the filament or filament encasement. I think it can be stored in several locations, but currently I believe it is the result of a deformation in the teflon coupler; I'm very willing to concede that there are other locations of potential energy storage though. So the question I have for you or others is this, do you observe under-extrusion before or after the knurled wheel spins in reverse? If under-extrusion happens before the motor spins backwards, I would be more incline to believe it is a problem with the nozzle head, and potentially the teflon coupler. Imagine the extruder motor trying to push the filament, but the filament not being able to flow out of the nozzle creating more back pressure (potential energy) than the system was designed to handle, and bam the motor spins in reverse. If under-extrusion happens after the motor spins backwards, I would be more incline to believe it is a problem with the circuitry that controls the motor. Imagine the motor trying to keep an almost static load applied to the filament while pressure is being released from the nozzle end, but due to an electrical problem the motor looses all capacity to hold a static load on the filament and spins in reverse as a function of the release of stored potential energy somewhere in the filament or filament encasement system. I don't think answering the question will yield a definitive conclusion, but I believe it will help the UM community home in on the problem because of the more detailed cause and effect relationships between the nozzle dispensing material and the feeder feeding material. This relationship is unclear, to me at least. I also understand that my question may be difficult to answer, you can't watch both the nozzle and the extruder motor at the same time; but I'm hoping that the sound the extruder motor makes is clear enough to note the exact time it occurs with respect to the nozzle depositing material. Edits; grammar and clarity.

A pretty interesting idea indeed, given that it's some type of polymer that is repeatedly heated to print on, and flexed to remove the print, I wonder what type of life expectancy the plate has. Very cool idea though, it looks like it mitigates the need for brim as well. It looks like the qestion is already in their FAQ: https://3dprinterninja.com/ninja-printer-plate/

Thanks for the answers guys :smile: It's something to keep an eye out for I suppose when priming the nozzle. From what I understand now though, it isn't a very big deal.

Thanks for posting the images and video, I can barely see that really thin strand but the calipers help. I would think the texturing from the knurled wheel would help in gripping any excess material that might be located inside the bowden tube. Any thoughts? Also, how do you think the thin filaments are generated? Do you think the filament is getting snagged on a deformation to the interior of the hot-end, from the filament as a whole naturally stretching, or something else?

Whom made such an offer? I am not privy to the specifics of your seller, but I would watch out for stolen UM2s. There is a thread about it here: http://umforum.ultimaker.com/index.php?/topic/4247-ultimaker-2-local-pick-up-at-night/

I'm a little confused by the data sheet, it's been a long day :wacko:, is the "P" identifier indicative of a PCB style with the No tab terminal form factor? If so, I would buy a tabbed terminal relay, especially with your implementation of it.

Yeah, Lennart, the cat looks really good for a first try and on a model not intended for printing. Did the supports break away pretty easily? Thanks for the post, you are a very quick learner grasshopper!

Owen is right, and I don't see any mention of a diode in the datasheet I linked to. I would ask your colleague to test for a 12 VDC output at the terminal screw interface.

Woah! How did I miss those gears last time I checked this thread? Your case looks fantastic! I hope prospective UM2 buyers come across images like the ones in this thread; this is enough alone to sell the printer. This forum is much more active than the MakerBot forum, with many more great examples of how well the Ultimaker product really works.

Noooooooooooo! Those pictures make me very sad :shock:, I would have at least cannibalized the pieces :( Thanks for the suggestions and the cool video link! I really like just watching the printers print and I like your experimental setup :smile:. I definitely have the patience to overcome any obstacles I might face when learning the nuances of the UM2, plus using your cool program I can test out different printing schemes I hypothesize to be helpful!!

Hmm, an interesting suggestion; I download this image Nicolinux posted eairler in this theread: blew it up really large and tried to measure the inner tip by assuming the larger opening was exactly 3mm. If this is a correct assumption, I get something like the nozzle diameter is around 0.35mm; although without some exact measurements my assumptions leave me dead in the water, and I would be surprised to see this much variability in the nozzle tip size; if it's smaller than yours I don't think the difference is as large as my measurements suggest.

Oooo man, this thing is getting sexier and sexier! I'm new the Ultimaker environment and am still waiting for my printer, but this thing looks sooooo useful. I like the absolute control it gives you, I can totally see changing these settings to print out very specific parts of things I've already designed. Thanks again!

Hey Roald, I messaged you in a chat window but misunderstood the problem. I downloaded the .brd files for the 1.5.7v build of the Ultimaker Shield, and I would have to say wiring wise everything looks good. I don't think you could have ruined your relay coil by putting it a the Hot Bed terminal output, even at 20 volts that's only 72mA going through your coil. If you hooked it up to a functioning 12 volt battery and you still don't get the device to turn on, I would check the model number again against the data sheet. I downloaded this datasheet: http://www.omron.com/ecb/products/pdf/en-g2r.pdf and it looks like coil excitation with AC current is a very popular item, do you think it's possible you simply purchased the wrong relay. Edit: Also, if you look at page 4 of the datasheet, it indicates that the coil can be supplied with voltages 170% larger than the nominal value, so if it really is a 12 DC coil then it should be able to withstand 20.4 volts. Edit2: Also, like gr5 said I wouldn't worry about the diode, from both your drawings and the photographs of your installation, the diode is facing the correct direction and would have only been in parallel with the existing diode on the board, essentially doing nothing.

The remainder of the information can be disregarded, but may be helpful as yellowshark seems like he/she may be new to Meshmixer and the links I supplied helped me significantly.

Also, what's different in your version than in illminarti's?

Go to Edit>Transform Here is a list of useful Meshmixer sources: I found this video to be very helpful in actually constructing the supports: illuminarti's thread about meshmixer is very useful: http://umforum.ultim...nerate-support/ These two blog posts of illuminarti's, directly address meshmixer usage and tips. http://www.extrudabl...upporting-role/ http://www.extrudabl...-dragon-part-2/ There is also the meshmixer forum: http://meshmixer.com/forum/index.php I also have a couple of tips, garnered from the forum and just messing around with the program. 1. If you don't get enough support contact locations, check to see that your tip diameter is not too large as a function of the number of layers used to generate the tip, as this will prevent neighboring tips from being generated. 2. To make supports that contact the build surface, you have to click an existing support structure or support node generally where you want a support structure on the build surface, and hope the program generates the right support structure in approximately the right place on the build surface; then you can delete all your failed attempts :???: , and build upon the support structure that approximated what you wanted. The auto support function is a little buggy, but the workaround may be worth it. The last time I downloaded the software was around late December, and "v9001" was in the name as well.

A little handheld pressure transducer of a known thickness with a light that blinks when it's being squeezed. Think about slipping one of these under the head; https://www.sparkfun.com/products/8713. Heck, it doesn't have to be handheld; it could just plug directly into the main board, assuming enough pins, with a long wire and could sit attached to the side of the printer. You know I have one sitting around, it's 0.19 mm thick, each sensor could be calibrated to each printer.... anyway; yeah I really can't wait for my printer.

Hey Daid, could you explain exactly what happened to the teflon? Did it melt or deform a little? Also, for my notes, can you you recall the approximate length of time you had the heater powered on for? And another also, did you have all the fans running? Thanks!

I've got a couple good meshmixer links for you: I found this video to be very helpful in actually constructing the supports: illuminarti's thread about meshmixer is very useful: http://umforum.ultimaker.com/index.php?/topic/3880-meshmixer-20-a-better-way-to-generate-support/ These two blog posts of illuminarti's, directly address meshmixer usage and tips. http://www.extrudable.me/2013/12/28/meshmixer-2-0-best-newcomer-in-a-supporting-role/ http://www.extrudable.me/2014/01/02/the-guy-with-the-dragon-part-2/ There is also the meshmixer forum: http://meshmixer.com/forum/index.php I also have a couple of tips, garnered from the forum and just messing around with the program. 1. If you don't get enough support contact locations, check to see that your tip diameter is not too large as a function of the number of layers used to generate the tip, as this will prevent neighboring tips from being generated. 2. And probably the most applicable to you Lennart, is that to make supports that contact the build surface, you have to click an existing support structure or support node generally where you want a support structure on the build surface, and hope the program generates the right support structure in approximately the right place on the build surface; then you can delete all your failed attempts :???: , and build upon the support structure that approximated what you wanted. The auto support function is a little buggy, but the workaround may be worth it.