Right. The guinea pig butt-warmer build is complete;
Seems a bit over-engineered to me but they're pleased with it.
The rest of the assembly went smoothly. My label maker got a proper workout. The commissioning of the software went very smoothly (though MatterControl seems to be buggy as all _getout_ on both PC and Mac) with one notable exception; PID loop tuning would _not_ give consistent results. We'll revisit this later.
Printed out my PEEK fan shroud like a frickin' HERO. I get the impression that I could take an empty cornflakes box, write "Fancy Three Dee Printer" on it, copy the fan shroud onto an SD card and drop that, along with a couple meters of ABS, into my new 'printer' and it would still successfully produce a fan shroud.
I installed the TrickLaser LED ring at build time so I knew the layer fan part wouldn't fit, but I printed it anyway as a matter of principle. Came out pretty much flawless. Does anybody have a conveniently modified version of the layer fan shroud that _doesn't_ interfere with the LED ring that I can use until my 3d modelling chops are up to doing it myself? Ideally one that mounts to the same tabs and uses the same little squirrel cage fan (of which I own three)?
So I meant to write this post and ask these questions this morning but instead I got carried away printing gear bearings (multiple) and nautilus-shaped gear sculptures and Marvins and my kid's names and their teachers names and and and. I'm particularly impressed with how the geared bearings turned out. Video below;https://www.youtube.com/watch?v=6M2I3jFBr9w
Also amazed at how _fast_ the thing is. https://www.youtube.com/watch?v=kwA7KR0RQN4
I've completely fallen in love with it already, and i'm only 63.5M of filiment in
I am going to need to buy shares in the glue stick people though, didn't realize how much of that I'd be going through.
However (and there is a slight however) there's _something_ not quite right about my thermistor behavior.
I've got jumpy readings from both probes, even down around room temperature, consistent with each other, but not all the time.
Sunday afternoon, immediately following the completion of the build and initial power up was the worst thermistor behavior, reported temperatures jumping around all over the place (+/- 3 degrees at ~24 degrees) for both the bed and the extruder. Calibration was impossible, I got figures like the following (sorry, don't think I can make tables in this BBS software);
Run Kp Ki Kd
1 29.77 7.94 37.13
1 20.48 1.71 61.27
1 29.1 7.76 27.29
2 27.14 2.9 63.53
2 37.37 9.96 35.04
2 31.92 3.55 71.73
3 30.25 8.01 28.58
3 15.93 1.07 59.08
3 25.78 6.87 24.18
4 21.37 1.92 59.51
4 26.94 7.16 25.34
4 14.19 0.81 62.44
What appeared to be happening was that the temperature reading was so unstable, the reported temperature effectively jumped above 200, then back below, then back above, all in a matter of a second or two, and not in a true response to the heater, thereby greatly confusing the calibration routine which was trying to cross the 200 degree threshold in a nice controlled fashion. In the end I averaged the numbers from Gene's example screenshot in the instructions and used that, which worked well enough. When I tried running _my_ calculated values (even averaging out all 12 entries the 4 complete runs above) yielded a printer with at +/- 8 degree temperature swing (220-236*) at ABS temperatures.
Cut to Monday morning, after a night of being turned off, I turn the machine on and both bed and extruder temperatures are dead stable, varying +/- 0.1 degrees at room temperature. 'Whoopee!' sez I, 'it's fixed itself!' (though I was deeply suspicious) and I set about running the calibration procedure again. This time it worked flawlessly, here's two runs worth of data from that;
Run Kp Ki Kd
1 14.78 0.88 62.2
1 15.59 0.94 64.31
1 15.17 0.92 62.6
2 15.31 0.93 63
2 15.59 0.95 64.1
2 15.59 0.95 64.03
I ran it a third time but the numbers were near as dammit identical so I didn't bother recording them.
I averaged and plugged those numbers in and got printing. Initially it seemed to be flawless, maintaining target temperature to within small fractions of a degree. But after a few minutes of printing it seemed to lose accuracy again and the swings started to creep back in. But I wasn't having serious print quality problems so I kept going until Monday night when I just re-ran the calibration routine a couple of times and am getting much the same nonsense results I was on Sunday, and the ambient temperature swing has returned as well, though not as pronounced, about a degree total variance at room temp, though _occasionally_ 2 degrees. See video;https://www.youtube.com/watch?v=cTNuTY4c41k
So, I don't have an o-scope to hand, I'll have to borrow one from a mate, but based on the behavior I'm seeing I have to suspect that there's either a problem with the ADC resistance measurement circuitry on the RAMBo, or the nifty new industrial-style PSU is feeding me dirty dirty current and throwing everything else off. Or possible something else that I haven't considered. The fact that both thermistors are experiencing the same behavior suggests it's not a wiring issue, nor cross-talk in the columns, but that doesn't get me much close to knowing what it _is_.
To, Brain Trust, a penny for your thoughts? How did I manage to screw this up? What's considered the 'normal' thermistor jitter? Clue me in!