Torgeir

Hi JJB, This driver is in the "Pololu" family, and have the same feature of configuration (as we name it) as the one used in Ultimakers late family 3D printers (as far as I'll know). Actually your "hack" is just the same thing as I did with my printer, that is using "PoLolu A4988". You said it improved your print about 80%, yes that was missing step, -but then there is some sign of it still, right. When things improve like this, we might wonder; is there still some missing steps? No there is not! So what could it be then, the answer is "production tolerances". It is maybe a cheap (Chinese?) stepper motor. The truth is; those steppers might not stop at the "exact" same position when the current is reduced. This is actually true for every stepper motor, if we go "deep" enough into it... This is why we still may have sign of those stripes, if we look close enough into it. You can have a better stepper motor, or you can gear down the speed by 2 (sure using belt for this), in order to improve the print further. All this said, however, most of the steppers today is made in China. So, if you like to have “real good” quality, the stepper motors used here for X/Y play an important role. Thanks. Torgeir.

Aha, of course you're right here (as well) , I was thinking of using every step as a value as we does in some cases. Thanks. Torgeir.

Hi coolm8, When it fluctuated "before", did you have the old thermocouple as a temperature sensor, or did you use the same PT100 sensor there as well? Does your PT100 thermistor have a loose fit before you lock it? What happen if you print without the heating on the bed? If you have a loose fit of the PT100, then this prevent proper thermal conductance between the aluminum block and the stainless steel housing of the PT100. This will create such fluctuation, because the thermal properties between the aluminum block and the stainless steel housing of the PT100 is not like what the firmware is tuned for. To cure this, you may use “copper paste”, the one that can stand 1100 deg. Celsius! Check the properties of the one you find before buying/using it! This stuff is used on cars, for brake pads, exhaust pipes and spark plug. Etc. It has very good thermal conductance and prevent parts to burn stuck. One of the best thing with this copper paste is, that the thermal properties is best around (200-300) deg. Celsius. One thing more, when adding copper paste, add it to the hole's in the aluminum block (yes it can be used for the heater as well). Don't overdue it, you should just fill the open space around the PT100/heater. Have a rag ready to wipe off any excess copper paste. Also, when doing this be very careful and do not bend/straiten out those wire going into this two elements. They are to easy to break... Note: When you heat this up first time, you sould be able to see the two “elements”, cause it will oze out some exsess of the copper paste here and smoke a litlle, so have good ventilation. Rise the temperature slowly and use this rag. When you reach max, temperature and there is no oze or smoke, -you are ready. And yes, this was one of the first thing I did on my 3D printer. This setup require a power supply that's delivering enough power without any fluctuating voltage during any part of 3D printing. Should be able to deliver about 30% more amps than needed. Good luck. Thanks. Torgeir.

Hi David, Been a little on/off lately. First; use 5V/1024 (0-1023) remember zero count one in this world... Then, use the max temp 275 (or even 300) to have better resolution in temp range we're interested in. Edit: Maybe they use a standard sub. here so, look around. 1100 deg. makes sense for thermocouple (as K element), only! I'll think someone “messed” with the table used for compilation in this web software. Just a hint... Well, I'll know you're on the track, but as Gr5 said the one recommended (firmware) should work for the thermistor PT100. Use this firmware to check out the PT100. You can compare etc... OK. Good luck in hunting for the offset and the correct hi(gain) setting. Thanks. Torgeir.

Hi DrR1pper, Ok. You have the problem even if you printed this object 90 deg different (rotated) from this position. The conclution is then; both X and Y steppers suffer of this problem. If you try to print at 45 deg angle different from previous print, there should be an improvement in this print. Is it? Why not try? Also, if you look closer to your print (in the area I've marked), you'll find tree different lenght in a row over the step down point. Those plastic treads tend go a little on the side, either outer or inner side of the previouse tread (hmm line). Remember, both X and Y can be one step more or less! This is the phenomen creating lines located over or under the predicted surface height in your special test print. If there's a problem with the Z-axe, well this axe cannot create this short or long lines! Z-axe failure; two thing, step too far down or miss steps, I.E. no step. If it dont step, next extruder round will prob. ruin your print. Too far down, opening in between lines. Many things can be said here I'm sure. But; is there any slack in the Z-screw? Can you feel any slack when liftig/pushing down (at both sides of the two 12 mm shafts) the bed a litle? Does the stepper sound «heavy» loaded when going up and down, or at any place along the lenght of the shafts, is there any different there? If no on all this questions, forget about the Z-axe. A litle bit skeptic does no harm. Well, I do hope my explanation here helps in understanding how missed steps «can» modify our 3D prints. You know, when we come to this level of 3D printing we will see other problem, small details really counts here. Thanks. Torgeir.

Yes, I printed them as you say here; bottom at right side.

Hi DrR1pper, Not a problem, but I'll think it would look even better with 0.15, at last in the foto. Thank you for the flowers! Why not, I'm just as interested in this cause as you are. Of corse, no problem, but how do we handle /share files in here. Aha, s3d, this explain why I got the message like this when I tried to open your Gcode file in Cura: «No file found in Gcode file. This feature only work with Gcodes made by Cura 12.7 or newer.» I used Cura 15.04.3 ! -Well, I printed it as is, and it started printing from the inner left corner. No, I'm using the first filament I ever own; the Verbatim PLA gray(kind of transparent), black and white. But I like it like that, as it is very nice to see how the infill work in "test print" etc. Thanks. Torgeir.

Hi DrR1pper, I've printed your "drr1pperprintsurfacetest.gcode and drr1pperprintsurfacetest.stl". Your file was h: 0.1 and double wall plus 10% infill... I used temp: 192 deg. Celsius and no heat bed, just glue stick. Do you use Cura slicer? I made a second print with the stl file with settings: height 0.06, single wall and infill 20% the other parameter as above. As I do not have a good macro camera, I used a USB microscope to evaluate. I've a little ringing in the prints, but that's prob. a little slack in the X/Y motor belts and a shaky table. The print is as good as your m200 and maybe a little better. There will be a few pictures here. First picture is from a high res. print h: 0.06 mm picture from flat side. Edit: The wide parallell "dark gray" lines is infill (20%), due to one layer of transparent gray filament (Verbatim PLA gray). Second picture is done with a microscope of the area indicated in the first picture. Note the notch in the upper left corner caused by glue and cold bed... Third picture is the same as above from the other side, the angled stair side. Fourth picture is done with a microscope of the area indicated in the third picture. Then the picture of your gcode file with your setting height: 0.1mm, double wall, 10% infill and 192 deg. C hot end (by me). Your gcode file print, flat side first. Funny how this color change, it is gray! Hmm. This picture is done with a microscope of the area indicated in the previous picture. Then the steps side. And the microscope view as indicated in the picture above. Yes the above picture is upside down... Then we have a look at one of your pictures. Here is The magnified area as shown in the previous picture. This should be enough to make a final conclution in this matter, you have the missed step syndrome in your printer... Thanks. Torgeir.

Hi cloackfiend, Yes, the standard originally delivered with UM2. I've read it in here some place: A very good place to use for testing purposes. http://www.3dbenchy.com The OB will be my next to learn and test out, as the 0.25 that will be very interesting. I'll think this is a game changer... So when the budget allows... Yes! A slimmer OB, not for me to answer. But if you like 0.8, -it might have to be of that size in order to cope with the need of heath capacity and at least a 40w heath element. Thanks. Torgeir.

Hi folks, Just made some prints after all this adjustments and thoughts... I'll kind of like this one: They said it could be done, but none of my boats come close to this - before... This little other object is ment as a calibration tools for those "chemical printers", I could not resist. All is printed with Verbatim (transparent) PLA. Height: 0.1, extruder temp: 192 deg. Celsius No heat bed (just glue stick), infill: 20%. The "chemical printer" calibration tool; height 0.06 and other as above. Edit: And only using the "old" standard nozzle 0.4 mm. Thanks. Torgeir.

Hi David, I've been looking into this many times and think that it is the look up table for the thermistors that's in error. This table shall contain the "offset value" (the value at zero deg. Celsius, water with ice cubes that's stirred to keep mixture at zero) and the "gain value" (boiling water 100 deg. Celsius at sea level). PT100 offset value (at zero deg.) is 100 ohm, will give 1.111 volt output from the extra PCB in your heat bed kit. Actually, this table (in C) might be around some place I'm sure. OK. Good Luck. Torgeir.

Hi Torgeir, Please correct me if i am wrong but if the problem in the photo's i provided (on the um2+ vs m200) were caused by the missing steps issue that is causing zebra stripes, wouldn't one expect there to be a repeating pattern in the layer misalignment in my um2+ print? It's just that i've tried printing different objects multiple times in a row with the same g-code and cannot see a repeating pattern. I do not see the layer line misalignment's occurring in the same places. For all intensive purposes, they look rather random. Hi DrR1pper, This is interesting I may say. Try to turn your print object 90 Deg and make another print. To me it looks like one of your axis (X or Y) have an offset problem. The missed step may also be in here, but may be hard to visualize. If you give us the file.gcode of the picture below, I'll give it a try with my printer. SandervG, As firmware is a software to control the hardware, many thing can be done with firmware. Even the “configuration change” I did can be done by the firmware IF the designer made it possible. By using the firmware to increase the current to the actual stepper motor (that's have a missing step) may cure this problem, also by increasing the voltage to the stepper motor “can” do the same. There is not much talk about another important parameter when we discuss stepper motors. I'm thinking about the impedance (resistance) of the actual stepper we're using. The impedance and ampere tell us a lot more about how “strong” this stepper “can” be. What we do here is to increase the energy to the stepper motor (make it stronger – a little more torque), we remember that the reduced current for micro stepping is about (10-12)% of max current. I've also read the link you refereed to here: This guy changed the firmware to: “repetier firmware “. How do they handle this problem I do not know, but if there was a rounding error, as he asumed, would not the error still be present on my printer then? Thanks. Torgeir.

Hmm., maybe another one, find the X thermistor (the thermistor supposed to be used on your UMO back then) by using a resistance bridge to find zero deg. Celsius, then same method to find the resistance for the 100 deg. Celsius value. Those two temperatures are good calibration points to use when setting up your system. Armed with this numbers it might be easy to adjust the Rg "gain resistor" in order to match the actual value the firmware use for the key temperatures. Edit: You might need to adjust the offset for zero and the gain for 100 deg. Celsius. Should be possible as an alternative solution? Thanks Torgeir.

If you just swap two of the wires for one of the phases on the feeder stepper, it will change direction and the number of steps might be an easy one to handle in the firmware... or? Just a suggestion. Thanks. Torgeir.

Hi David, Great info. here! This mean the signal is going straight to the A/D converter, so it could(must) be a firmware issue. Cause here, R4 and the old type of thermistor is sending a voltage that is across of the thermistor directly to the A/D converter. Good investigation! Thanks. Torgeir.

Hi dbotos, You did your calculation right... Next question, what is on the input side of the UMO board? If there have been just a thermistor input(no thermocouple), then this is even more interesting to investigate. Good job. Thanks Torgeir.

Hi, Great info in here, yes I understand the problem here, -I'll think... The A4988 differ from the A4983 that's have no current control. In the UM2 the current is controlled by firmware (the controllers "op" system). For the UMO you have to set the current limiting (current increase, will increase the temperature). As the driver PCB is set to a low level (current) state, this might be the reason your stepper motor do not move, -you need to adjust the current setting yourself. Go to this page: https://www.pololu.com/product/1182 Go all the way down to the current setting. Here you'll find all the information of how to adjust your driver PCB. Sure you'll need a multimeter in order to adjust this Vref voltage. (I did not find the Vref marked on the PCB, but it should be at the potentiometer (metallic plate) where you do the adjustment.) Based on your stepper motor type, you'll need to calculate the Vref setting. Clockwise decrease the current and counter clockwise increase current. Check out the video of what to do. Yes, this turn out to be a little more than that, but this is not as complicated as seems. Just takes a little more time. Well, good luck. Thanks. Torgeir Edit: I'm still wondering about the faulty PCB that's start working for a minute...

Hi, Did you actually swap the two drivers? An important question for fault finding here. You said you pulled it out, then installed it again... As you have an UMO, I'll think the one (driver) used there is A4983. I know the UMO can be upgraded to use same driver as UM2 and maybe is delivered with (A4988) on later model. You can check the P/N on top of the (Integrated Circuit) IC mounted on the driver PCB. I'll think there is some pin issue between those board, but I'm sure anyone in here have the answer about this matter. Good Luck. Torgeir.

Hi neotko, No question is silly... To remove a surface mounted component, -even a resistor, can be risky. So the best way to do this is to short the resistor, use two cord of 0.1 mm twisted copper wire. You'll never know a proper ground on such a PCB, as there may be several points that seems to be ground, but are not! Remember the size of the soldering tip, if you want to see what tip I'm using I can make a picture. You'll solder one leg first, then make a short loop to the other side of the resistor, cut the twisted wire here and make the (solder) the other side. Then the resistor is 0 ohm. Do not use to much solder, as it may float around and short something nearby. Remove/clean the flux(solder paste) by using reed spirit and inspect to see there is no bridging to other components near by. It's always smart to study the PCB and the place you want to solder before any work here. Also use a good magnifier glass, 5 to 10 X. OK. Good Luck. Thanks. Torgeir

Hi Chri, I've added pictures and details about this previous in this tread, have a look at topics on 27 of May. I did not go externally to ground, but just made a jumper across the actual resistor on all the driver IC's. Thanks. Torgeir.

Thanks for the reply Torgeir. I have a limited understanding/knowledge of electronics in general let alone of stepper drivers. When you say "having installed this (A498X) series of stepper drivers" it sounds like you are saying that you installed a new physical stepper driver onto the printer. Is that correct or am i misunderstanding something. And just to confirm, you are saying this mod should work with any other 3d printer using different electronics than the um2? Thank you. Hi. The stepper driver I've been talking about is the one currently installed into the UM2 and this part number P/N is; A4988. I never changed this driver on my printer, just changed a resistor from "10 000 ohm" to "0 ohm". I have described this in detail previous in this tread. When I talked about other 3d printers with this problem, they might have the A4988 installed or can also have a driver belonging to the "same family of drivers", meaning starting with the P/N; A498X, where X can be other number than 9. As an example, UMO are using A4983 (if I'm right here) and later model/upgrade may have A4988 as the latest. Thanks. Torgeir.

Just my Expierience with the so called Decay Hack (ROSC pin to ground), that is alreaday known to the A4988 drivers since some time. I did the hack for over a year on my other printers, with success on all steppers /printers i have. I also discussed that issue also with valcrow since long time. so i finally tried the decay-hack on the UM board 2.1.1 , with bad results. (i`m skilled at soldering so no problem from this side ) first i did the hack on X and Y axis on the board, resulting that the X driver instantly burned after powering it up, Y axis is still okay. after that i reconfigured E1 to be the new X axis, and printing was well with that "decay" lines also dissapearing on the Y axis, so its definitly the cause of the effect. Here a picture of the comparison, before and after: Ignore that X, its Y axis ^^ Unfortunatlye i then did the hack on the E1 driver, resulting in also a burned driver after powering up. Normally setting ROSC to ground should not be an issue there, but maybe some UM engineers ma have a look on it why steppers altough tend to burn up when do the hack. So far, now i have a bricked UM2 standing here :( Chri Hi Chri, Sorry to hear that. I've got the same version V2.1.1. as you have. I studied the data sheet and the original drawing "from github" for some time before this modification, just to make sure there was no issues... However, I made all drivers at once as I would like to have same configuration to all drivers. The current during micro stepping at 100% should be like 500 mA max. each coil., so no problem. Anyway, glad you solved it. Thanks. Torgeir.

Hi Cohen, It was actually MartijnvG in your team that goggled the link to nophead's article. Thanks Torgeir.

Hi DrR1pper, I'll think such a reconfiguration of the driver can improve all printers "with this problem" having installed this (A498X) series of stepper drivers from the manufacturer “Allegro micro system”. Thanks Torgeir.

Ok, I see... Maybe we could start a new tread about vibration, ringing etc. Have no idea about this nozzle? Torgeir