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  1. No I have almost never seen private sellers accept returns, however in case something is not right or was not described appropriately, honest buyer/parties work out a solution. If you sell via PayPal, I as a buyer would only purchase via PayPal Goods and Services. That means, you should take good pictures and list the details as accurately as possible. On receiving, if I as a buyer find discrepancies, I can open a dispute with Paypal and the resolution would likely result in the buyer sending the printer back and getting their money. As a seller, you can protect against fraudulent Paypal disputes by taking lots of pictures and describing the printer in detail.
  2. Aah!Sorry I misinterpreted your question. Very good question indeed. One hypothesis I had was the PSU could be 'faulty'. If you look at the derating due to temperature for the powersupply, it could underperform (and result in voltage sag) in warmer climates. Temperature wasn't an issue for my PSU. So it could be 1) I genuinely had a faulty/non-optimal power supply or 2) 220W is just isn't enough. I suspected the latter (could be wrong) because at its peak the printer consumes about 220-230W (190 peak heating, 35W peak extruder, 20-50W transients from motor). As far as the board traces, I do not think. It is really well made. It looks like 4Oz copper with pretty wide traces that power the heater and other power hungry aspects. Plus, when I looked at it with a thermal camera, it did not show any 'hot spots'.
  3. @geert_2: I measured it at the 24V connector: You are right about voltage drop over significant distances or over thin traces. With a high-impedance measurement (a voltmeter or oscilloscope) that is not an issue. The voltage drop over thin traces or long distances (aka high resistance) is V_drop = I*R. When making a high impendance measurement the I is very small and such drops are negligible (not zero). Second, it is irrelevant. Let's say I measure 23.5V instead of actual 24V. Goal of my measurement is not to measure exact voltage, but to measure the change in voltage. The step change in voltage was exactly lined up in my scope experiments to the exact timing of bed heater. That is all I needed to know. In a well designed circuit (or one resilient to the drop), respectively, there should be no drop or the performance should not be affected. Could the minute drop in voltage affect my exact measurement of the delta change in voltage drop? Yes. But again, for the purposes of the issue at hand it does not matter. The drop due to heater is ~400mV and with a 1M-Ohm probe at 24 V we are talking about a measurement drop of 0.000024‬V. I did keep ALL the current circuitry intact. All I did was disconnect the heater wires and connected them to my "external heater controller". A mechanical relay is a pretty bad idea due to how often it will be turned on/off. This would also preclude anyone from using PWM control. It will wear out quickly. A Solid State relay is better. I highly recommend a ultra-low Rds MOSFET as the right mechanism. No heating of the MOSFTET, no heat sink needed and that's how its actually done on even the Ultimaker board. One alternative for non-EE folks would be to use a product like these: Amazon Link. I am not a big fan of these. You will see how all the MOSFETs have a big heat sink. This is because these are cheap MOSFETS with high Rds and dissipate heat. I could not find something else. I will look for an alternative and post here. If folks could afford it, Pololu G2 (or anything that series of devices) is ideal. They are robust, engineered to perform, and top of all, SAFE!
  4. The source files for the firmware are here: Ultimaker2 source is here: https://github.com/Ultimaker/Ultimaker2Marlin Ultimaker2 plus is here: https://github.com/Ultimaker/UM2.1-Firmware You just need to download Arduino IDE, open the Marlin.ino file, and compile. To upload, connect printer to PC, select the right COM port, select Mega2560 as the board, and hit upload.
  5. Only one component is something I built/soldered. I am happy to make one for you at cost (I ended up with parts for several because of minimum PCB/Digikey/Mouser orders). That component is the PSU breakout board. If you don't mind a bit of a hack, you could literally cut the connector off a new power supply and just wire it to the rest -- you don't need it. I wanted the connector to look like factory installed at the back so I went the route of making a PCB. The Pololu G2 is something you can buy on Amazon (LINK to exact item I got). Again, this is a bit pricey but I over-engineered. You can get the lower current ones or a different MOSFET/controller. You will note that the G2 is actually a poor choice since it is a H-bridge motor controller which means you are paying for 4 MOSFETS! This is pretty stupid, and I bought it because I know Pololu engineers stuff really well for *high* current and did not mind paying extra to save myself time in looking for an alternative. The cut-off TE relay is also from Amazon - here. Again, same reasoning, I wanted to keep everything safe so opted for a very high quality relay. Rest was simple firmware tweaks and a 3D printer mounting plate.
  6. Hah, thank you for your kind words. I think, much like yourself, more than 3D printing, I enjoy perfecting it 😉
  7. This is super interesting. The image on the right looks very close to the issue I just resolved, however I would not suggest that is the cause because you had the printer working fine before you identified mechanical issues. My cause for prints like that was electrical and it would not just solve itself. It had to be there all along -- unless, power supply is degrading or is now being operated in much warmer ambient temperatures (causing wattage derating). Just for the heck of science.. can you reprint the same but with NO bed heat? Use Blue Tape to have the part stick.
  8. To bring closure to this thread, I have solved this issue for at least my printer. I tried several different software fixes such as PWM vs. Bang-Bang control of heat bed etc, and none were helpful for me. The issue as @Torgeir has pointed out is that there is a significant voltage drop. In the (poor) screenshot of the oscilloscope you can see the drop in the 24V line when the heat bed turns ON/OFF. The drop is around 400mV. With more time (and will) I wanted to figure out what subsystems are susceptible to this voltage drop (is it the ADC for temp sensors?, is it the change in temp for hotend? etc.) but instead I chose the easy route and just modded my printer as follows. It seems like a bit heavyweight mod, but at the end of the day, this substantial drop in voltage suggested to me at least one of the following if not all: The power supply is under powered Lack of resiliency in circuit design to cope with 1.5% 24V drop This could be as simple as filter caps Or better Vref for ADCs and such Or need for better PID/temp control of hotend I don't know which of the above it is. Here is what I did. I made custom circuitry and mods to support an independent heater power supply and control. To (over) engineer it for safety and spec, I went with high quality power control modules. For example, instead of rolling my own MOSFET board, I chose to use the ever popular and reliable Pololu G2 which is designed for 24V 21 AMP continuous draw and still be warm to touch! Items Needed: I had to design a simple little board to breakout the KPJX power supply. This was the only custom electronics component. Again, I chose high quality high amperage rated connectors (TDPT 2,5/ 2-SP-5,08 - 1017503) and good quality electrolytic caps. 24 V Cutoff relay. If you look at the UM2 Mainboard, there is a 555 timer that brings up the 24V supply once the input is stable. I did not want a scenario where a floating PWM pin or some other mistake on my part could ever turn the heater ON if the power to the printer is off or the mainboard is in-operational. As such, the main power is cutoff from rest of circuitry is there is no 24V on UM2+ Mainboard. Pololu G2 21Amp version. This board uses really good MOSFETS with very low Rds and excellent perfomance. They are an overkill for our 7 to 8 amp application, but this means, I do not require any active cooling. Under a thermal camera I found the MOSFETs to only get upto about 35-40 deg C. A 120W 24V Meanwell PSU. Again, a bit over powered since the printer barely uses 60W (without heater) but the price difference was negligible and I took into account temperature related derating. Changed the heater control PIN in firmware to use an unused pin on EXP3 header. This pin is then connected to the MOSFET board (PWM on Pololu G2) to turn the heater ON/OFF. Designed a Mounting Plate (my first CAD where it had to fit an existing part [UM2] 🙂 ) Made sure it looks like factory fitted and modeled it after the original way the connector is cutout at back. I think it came out really well. Mounting plate uses unused screw holes in UM2 to securely stay in place (not happy with tape.. but had to move on :-)). The original heater wires are connected to the new circuitry using a high ameprage WAGO connector for easy removal. All wires have ferrules attached. Reverting this mod to original printer will take ~10 minutes with only permanent mod being the connector hole. Summary: My prints now have no bumps/lines and look like they did in my experiments with heater OFF. My next improvement is that the 24V still has high frequency ripple from the motor controllers. I hypothesize that the really fine lines on print (variations, not layer lines) are a result of that. I have to decide whether I figure out what the underlying problem is (why extrusion changes?) or filter out that motor noise.
  9. Sorry to hear. Same here. My money is gone but at least here, the FBI case is still open. I also provided them with his TWO IP addresses that I was able to gather on my own accord. Those IPs are traceable to a unique mobile network subscriber and I am hoping someone does. If I do hear back, I will ping you so that you could have your police involved as well.
  10. Dear @rcfocus: Thank you so much for the detailed and elaborate response. I completely understand what you mean by a non-optimal grounding path. I think it does have to do something with noise (as @Torgeir also alluded to). See one more data point below. I turned the bed heater ON exactly in middle of the cube (so it was ON at 100% from middle to almost 3/4th way complete). No impact on quality, but as soon as the bed reaches it set_point of 60C and starts modulating ON/OFF, we see extrusion variations that correlate with the ON/OFF almost perfectly.
  11. Yeah I think this is some sort of stepping issue as well that happens as a result of current deficit. Maybe. I will look into ROSC, thank you for all those pointers! Edit: @Torgeir: I just read through that discussion about missed microstep. That is very interesting. I will try out the ROSC mod.
  12. Hi rcfocus, that is a great point, and I will measure the V rails to make sure. BTW, I am not sure what you mean by "ground level shifting". That is a term I've never come across and unfortunately unable to interpret. GND is simply a label reference for measurement purposes. In such a floating circuit what matters is the net potential difference, which should be 24V. Maybe what I interpret by ground level shifting is that when the power budget is exceeded, the power supply becomes current limited and is compensated by a reduction in voltage (i.e. 24V drooping). Even if that is the case, I am not sure how it affects the PT100 measurement (it might but seems unlikely to my brain). The PT100 temperature sensor is a differential sensor that is being amplified by the INA826, whose output is then sensed by the ATMEGA ADC. All of these are running off a +5V supply which is generated by the buck converter. Droop in +24V should not affect the 5V supply (unless supply falls below 18V -- A4403GEUTR has an input operating range of 9 to 46V). So two things: 1. Check how much the 24V power supply, if any is changing 2. Measure EMI noise or such on 5V rails
  13. Okay, so I went with the hypothesis: that the bed takes up plenty of power and that causes temperature variations in the extruder. As a result we see micro extrusion variations. Experiment The idea was to run a print job with and without BED_HEAT and conclude if there difference in quality and; if it can be attributed to temperature variations in extruder I edited my Gcode for Cube test such that mid-way into the print it would turn the BED_HEATER to OFF. I I collected temperature data as frequently as Marlin would print to Serial. I wrote a quick analysis script to collect results from multiple runs and compute stats. See below. Conclusion: There is basically no measurable difference in extruder temperature whether bed is ON or OFF. There is a significant difference in quality of surface finish when BED_HEAT is OFF. Figure below shows exactly when the bed turns off half-way into printing (as programmed). # HOTEND TEMP ANALYSYS Average difference from set point (all range): -0.045 degC [BED ON] Average difference from set point: -0.054 degC STD 0.757 VAR 0.572 [BED OFF] Average difference from set point: -0.036 degC STD 0.524 VAR 0.275 Dammit. 😞🙁 New Hypothesis: BED_HEAT is causing motion artifacts, position inaccuracy or extruder motor motion artifacts. It could also be an issue only on Z-axis? Cause that moves infrequently and when it does needs inrush current. There also seems to be a 'pattern' that likely mimics the ON/OFF of BED_HEAT. Few ideas to test this: Measure motor currents Measure and log any droop in +24V supply voltage (could be the motor inrush currents) Reduce bed power (takes longer to heat up.. but meh, I can live with it) EMI from bed heating (highly unlikely.. its resistive and switched ON/OFF at Marlin bang-bang rate, which I don;t know what it is..) See if the fat/vs thin layers seem shifted or consistent all around? Could be overshoot as well in motor position. Most likely candidate is that the tuned accelerations and peak velocity need to come down -- they could have been tuned with bed heater off and a bit lower current on motors is mucking it up. Any other ideas why bed heater could be causing the lines in print?
  14. That's right, but I think the PID loop is pretty slow, of around 7 Hz, so EMI isn't an issue as much. If really, I can shield the cables. Fortunately, electronics is in my wheelhouse so I will figure this out and report back for posterity in case someone has these issues.
  15. Okay friends, it looks like I am a LOT clsoer to the source of the problem. 😄 I think this is it!! Although I did not follow the floating ground aspect, my guess is that the PID needs better tuning. When the bed fluctuates power, it is causing micro-variations in the nozzle temperature. What bothers me is that such a minor temperature variation can cause this. I am in process of running an extensive log of temperatures and will report back. Thank you @geert_2 for bringing this on my radar! @Torgeir, so yes, it is not related to ground, but looks like it is dependent on the heated bed being operational or not. Note how much cleaner the edge is with bed heat OFF. Also note, the surface when reflecting light is a lot more consistent. When looking in person (sorry hard to capture in photos), there is about 70-80% improvement in surface quality and the micro-extrusion variation. This also explains why I saw slightly less of such variation on higher speeds (70-80 mm/sec), the reason being, the temperature variations are happening at a certain slow rate. When the print is sped up, the printer goes through many more layers before the temperature variation (or whatever the heated bed causes) has a change to impact it. I am going to monitor and log detailed temperatures and try and tune the PID. If that doesn't help, I am gonna see what the underlying reason is and make a modified circuit possibly to separate any power impact of heated bed on rest of circuitry. I might run a separate power supply or add filtering circuitry.
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