Dual extruder thermal runaway

[kcramp]

Hey guys, I am new here, and I just completed my first build a few days ago.

Attached are my calibration cubes, possibly out of order -- but I figured I had it calibrated pretty well. (I got impatient and stopped halfway through on a lot of them.)

I am stock everything (minus the LCD, botched solder job), and I have the tricklaser ball joint/CF arms.

I decided that since it was calibrated pretty well, I would install my add-a-struder kit. However, I find a few things:
I was able to run PID on each of them seperately at first, but now I cannot run a PID control on extruder 2. It only wants to work with extruder 1. (Have tried M303 E1 S200, M303 P1 S200, M303 E0 S200 and they all only do ext1)
Extruder 2 wont heat up unless Extruder 1 is heating up
Extruder 2 has catastrophic thermal runaway - after doing a heat to 200C (I print ABS), before extruder 1 even reached 200C, extruder 2 reached ~380C. Lots of smoking and emergency air conditioning followed.

I cannot get them to work together, but I have a feeling it has something to do with the PID settings -- I could bust out my old controls book and solve it by hand, or maybe try matlab/COMSOL... but I would rather have the firmware do it for me.

Attached are my calibration cubes, firmware settings, and a picture of a vase I did in which I varied the print speed from 100-150-200-250.

Cheers,
Kevin

https://www.dropbox.com/s/0g1a2flf3tgyc2p/firmware.rtf
[img]http://i.imgur.com/4GIei1vh.jpg[/img]
[img]http://i.imgur.com/jE9l8iAh.jpg[/img]
[img]http://i.imgur.com/r8nj6BPh.jpg[/img]
[img]http://i.imgur.com/LwEDXCkh.jpg[/img]


-edit: As per (http://forum.seemecnc.com/viewtopic.php ... 2&start=10), I changed the num extruders down to 1, and now I appear to have control back. I am going to bed because I have to wake up for work in 5 hours, but maybe that one small change will assist with my runaway. What I really need is PID control for both extruders at the same time, as with the dual mount mine are essentially touching.

[kcramp]

After disassembling the hotends to rebuild them with a little more clean RTV job, I found out that the radiating heat melted my mounting plate and somehow caused the offending hotend to split down the middle. Sad day

Going back to one it is, it would seem -- Unless you guys think that this is still usable?

[img]http://i.imgur.com/UyDWq01.jpg[/img]
[img]http://i.imgur.com/80CXEt6.jpg[/img]
[img]http://i.imgur.com/DMQBqnX.jpg[/img]

[Flateric]

To me it looks as if you may have either bent your thermistor over the top of the fat aluminium hotend which could have A, caused it to pull out during the heatup and read a much lower value than the hotend was actually getting leading to a "runaway" melt down, or B you may have shorted you resistor leads out against the tip during heat up which, is well, to be honest very bad for your rambo's thermistor ports, often fatal in fact.

I encourage you to switch over to heater cart's as they are very difficult to short, easy to handle and perform better and last longer. Seeme sell them.


Carefully check through the melted mess for any potential shorts that may have occured with the leads and/or the bare or possibly melted thermistor leads. Keep in mind that you kind of have to speculate these shorts as if the hotend were hot. They may have moved away or not be shorting after it cooled enough.

Can you please tell me what you bed temp and hotend1 temps are without any power other than the usb cord plugged into the Rambo? Are the readings normal?

[kcramp]

I was at the gym and read this and you scared me!

I actually hooked everything back up, minus the faulty hotend, and started a large print and left my apartment. It is currently printing like a champ at 235C hotend and 80C bed.

You could be right, I do not know why it would get so hot, but it looks like the tubing I put on the resistor melted through. Maybe I accidentally punctured it during the install and it shorted out on the hotend? My thermistor was fine, I believe, as when I actually glanced back at my other monitor it said extruder 0 - 180C, extruder 1 - 340C, that was then I emergency shut-downed and put it in front of a fan.

In its current state, assuming all is right with the hotend other than that plastic part being melted out of place, will I be able to extrude? I am not quite too sure on the makeup of a hotend, or what the point of that plastic piece in the center is.

[Flateric]

I am not trying to scare ya, LOL! I melted my hotend after printing exactly 3cm of filament when I first got my machine. It really sucked...ALOT.

I would recommend NOT leaving your printer running un-watched CLOSELY yet. You are not anywhere near being able to trust it not to do bad things as soon as you walk away yet. Even though you may think you are close. Lots to learn just yet.

I asked you to tell me your thermistor readings with them plugged in at room temp with only the usb cord powering you rambo for a reason. Since you have melted through the thermistor leads as you say there is a small chance of badness, don't panic yet ok though, these are steps we gotta go through to check everything out and also find out the cause of your "hot little issue oopsie"

So I need ya to tell me what your thermistors are reading out in repetier when they are at room temp with no external power applied. So we can start eliminating current and future concerns.