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ekh

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  1. Thank you for helping :-) The BANG_MAX is in use when the reguation (e.g. during initial heating) is not used or outside bounds if I got it right, while PID_MAX is the max PID output during regulation. So you are right that both values must be changed, if I will use the (weak) original power supply again. But because the PWM frequency is so low, maybe the power supply will fail anyway within the time the PWM pulse is on.
  2. You are right. Somehow I wanted to multiply before summation, but the official formula sums the error and multiplies afterwards. I suffered from the end of life heater and "now it works" syndrome, instead of going more thorougly through the code. Please acceept my apologies for having wasted your time. By the way the 4ohm heater element draws too much current for the power supply, it resets randomly within the first few minutes of a print. I also added the suggested change to the FET driver circuit, to avoid problems with the FET driving the low ohmage. After replacing the power supply w
  3. Let me quote myself: This was correct, but it was not the supply woltage, but the nozzle heater element that was worn out. The resistance was 10ohm I checked that even when the FET was on all the time the temperature was too low. The printer has for long periods worked 24/7 and the heater element has been worn out. In another post I blamed the FET because it has failed once before, but not this time. Another heating element I bought for making my own printer is only 4ohm. So the loop amplification was more than halved (10/4 = 2.5 times assuming the original heater also was 4ohm). T
  4. One more thing caught my eye. The 3 instrumentation amplifiers ( INA826 ) for the PT100 sensors are loaded too much capacitively. The datasheet says: Any amplifier with feedback is a regulating system in itself, where the bandwith and loop gain must be designed to have a sufficient phase margin at gain = 1 to avoid noise, or worse that the amplifier acts as an oscillator. The ouput are loaded with 100ohm in series and 10nF in parallel. 10nF = 10000 pF. Even with 100 ohms in series, the instrumental amplifier is loaded too much and challenged to keep stable. The ADC input on the ATm
  5. One more idea. If all the linear bearings were adjustable, then we can minimize free play and get a better print quality. It can be made as an upgrade. New bearings and plastic parts for the printhead, and replacement bearings for the buildplate.
  6. Thank you for your thoughts :-) I have not thought of uneven lowering, as I expected the vertical linear bearings to be OK. So I tried the free play on both my machines, and there was a free play sufficiently large to be a factor in the print quality. I do not agree that 2 spindles will be the solution, because the angle precision of a motor step and uneven spindle picth could be a problem in itself. I think the solution is adjustable linear bearings like this example: http://www.ebay.de/itm/x4pcs-ID16mm-Adjustable-Linear-Bearing-LME16UUAJ-CNC-/221455576263?pt=LH_DefaultDomain_3&
  7. Hi again, Every bird signs with its own voice. Maybe I'm not the most diplomatic guy, I focus on the possible solutions. Please read the following in the positive spirit it has been written. I got triggered to make this post because my UMO does not regulate again, this time it is not the "UMO PID formula error" but the FET transistor driving the heater. So it will be the second time I have to change this FET. I looked into the diagram of the UM2 to see if the cause of the failing FET has been corrected there. It was unfortunately made the same way. The curcuit is an AVR uC pin driving the
  8. You can check if the fans cool sufficiently. Make a tweak to pause the print and park the head so the nozzle is free of the part but a fan sends air over the part to cool it. Wait half a minute then resume printing. Try 3 tweaks for each 2mm print height, if cooling is the problem then it will look better in that area. I have printed small buttons, and they easily looks like your print wihout reducing nozzle temperature and increasing min. layer time. It can also be a bad quality filament, or the filament contains water that makes the plastic expand after being printed due to many small
  9. I have designed a product with 13 pcs 3D printed parts taking 60 hours to print. Several of the parts are not economically feasible for me cast in plastic, as the molds will be much too expensive. As I want to "mass produce" the product I need many printers in our newly started company. So I bought 3 pcs of this as a start: http://www.ebay.de/itm/SainSmart-Ultimaker-Mega2560-R3-LCD-12864-Controller-Similar-With-Ramps-1-4-/231172221638?pt=LH_DefaultDomain_77&hash=item35d2f02ac6 I have looked into config.h but there are so many options that I gave up after an hour where the best attempt
  10. Thank you all for many insights, I have this problem on both the UMO and the UM2. Thinner layers increase the problem. As I see it gr5 is right: "Your z movement is not linear." The result is both under and over extrusion. When you have a sledge, there will always be some friction resisting the movement of the sledge. When you have a screw and a nut, you must have some free play, else the nut is stuck on the screw. When the buildplate is lifted, the direction of movement is always against the friction, so the play does not disturb accuracy. The vertical arrangement has two possibiliti
  11. It seems to me that the cooling is not sufficient. Maybe the nozzle temperature is too high, Also consider the minimum layer time in Cura
  12. I have had an UM2 for 2 months now, I have some suggestions to the production of the UM2. But first I have to say that you guys at Ultimaker do a great job IMHO. It is no easy task to start a company and grow as fast as you have and keep everything perfect. Also the way you selected for your busyness model is very positive and along what is suggested here: http://www.thrivemovement.com/the_movie I recommend you watch the Thrive movie. If you have no knowledge of the issues the movie puts light on, watching the movie can change the life quality for yourself and others in a positive way. Th
  13. I can't say, sometimes you are fighting more than one error at a time. But adding noise near the amplifier can be the problem. What I can say is, that when operated within specifications, parts from Analog Devices do an excellent job. It is one of the most skilled producers of analog IC's. I have added a picture showing the pcb on the UMO printhead, where an extra 1uF ceramic capacitor has been added upon the original C1. On my UMO I have seen no temperature noise since this addition.
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