Rostock Max V2 unable to hold temperature during raft

[sithslayer78]

So I manage 3 Rostock max V2s and one of them has been giving me problems for about a month now. It heats up to temperature OK and completes the first layer of the raft but as soon as it starts printing layers 2-4 of the raft the temperature plummets and the raft looks like garbage before I get "def" for both thermistors.

At first I thought the problem was with the stock heater resistors, so I swapped the extruder with a HE280 hotend. Same problem, even after many PID autocalibrate attempts (It just gave me values close to default). I thought that I might have built the hotend incorrectly so I swapped the hotend with a different HE280 hotend. Still the same problem. At this point I'm at a complete loss. I've checked all the wiring on the RAMBO and it seems fine. Should the layer fans be off while the raft is printing? I can't find where to configure this for the HE280 other than the front panel (Using Mattercontrol). I guess I should outline a bit about the printer's history.

• -The kit sat around for about a year waiting to get built (shipped Nov. 2015)
  -Once assembled, the RAMBO was found to be faulty and was replaced (August 2016)
  -After replacement, the printer experienced repeated heater decoupling errors. It was found that the hotend thermistor was pulled out. We are curious if this failure damaged the power supply due to overheating, but the printer does not seem to be currently browning out. It does share an outlet with two other V2s.(Sept. 2016)
  -The printer in its stock configuration worked well enough for a while but experienced heating issues about 3 weeks ago (Oct. 2016)
  -Hotend was replaced twice with HE280. Both HE280s tried shipped in the same package. The first one tried to run itself through the build plate on leveling calibration, but the second did not. (Nov 2016)

Any help anyone can provide would be much appreciated!

[morgandc]

Is that when the fans turn on?

[sithslayer78]

Is that when the fans turn on?

Yeah. I've tried printing with and without fans on and with fans off it gets past the raft but fails once it gets to the part. It looks like it's just jamming because there's inadequate heat, but I just can't explain why the printer refuses to provide the heat required to the hotend.

[Xenocrates]

I have a slight suspicion that the PID loop is unable to provide enough heat to the hotend as flow rate increases (As the raft first layer speed is a fraction of the rest of the part's time). I would increase your PID drive max, and then tuning the PID loop (autotune works, but not really well, I would autotune and then manually tune it to achieve the proper results). It's the only way I can think of reasonably, as the power supply would not allow it to reach temperature if it were failing (The PID however only cuts in within a distance of the set point IIRC, which would with the inertia of the system, should allow it to reach and hold temperature even with a bad tune).

[sithslayer78]

Sorry if I am necro-ing an old thread. Printer is finally up, almost a year and a half after ordering. We suspect that the incorrectly set power supply fried some power delivery or control capacity on the RAMBO. Anyway, we replaced it with a smoothieboard, and a different power supply. I do have to note that the autoPID didn't work at all, and I had to manually tune it, which resulted in an abnormally high P factor, but it holds temperature well now. As for the bed leveling, we've jury-rigged a nano to translate the accelerometer input to the Z endstop, but we're still working on figuring out the multi point leveling in smoothieware. Thanks for all of your help!

[img]http://i.imgur.com/VVFPdMG.jpg[/img]