Out of control hot end temperatures

Hi Everyone,

A friend of mine is learning to use the last Prusa i3 I just built, and he is having a hard time with the hot end temp. On my big old Mac, hot end temps were very steady. He is seeing fluctuations from 185 up to 250°C. As you can imagine, it is not good for the J-Head with its PEEK and PTFE parts. He is suspecting all sorts of things from Windows, to the USB implimentation, Java ect.

He is using Pronterface, and Marlin firmware uploaded to the Adruino/RAMPS 1.4 electronics.

Any clues?

Edited 1 time(s). Last edit at 12/12/2013 05:40PM by Yvan.

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Yvan

Singularity Machine

Is the thermistor firmly fixed in the hotend? I ended up squirting some spare Arctic silver thermal paste I had in to hold it firmly and give it a constant temperature reading.

Good point, but I had no problems here and he had no problems when he tested on another machine. It's just when he goes back to his computer that it goes up above the set temp. I -think- I seated that one in exhaust cement....

I'll ask him to check that anyway. Who knows at this point?

Edited 2 time(s). Last edit at 12/13/2013 03:26PM by Yvan.

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Yvan

Singularity Machine

I'd bet his thermistor wiring is loose and it's shorting to something.

.

Edited 1 time(s). Last edit at 12/13/2013 05:48PM by waitaki.

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Waitaki 3D Printer

Well it seems something is wrong on the software side, or with the USB connection. He can get it to work reliably now by setting and resetting the temp in Pronterface 3 or 4 times. Print quality is bad for the first 6 or 7 layers which print very slowly, and then speed and quality pick up!

I have no idea what could be causing such silliness!

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Yvan

Singularity Machine

Does he get errors in Pronterface? It waits for an "ok" on each command. You can turn on debugging to see what all it's saying back and forth.

If you do not have the Mega set up to power from +12 via the magic diode, and the USB power cuts out (as in can with a laptop) odd things might be happening. I would expect a reset / reboot rather than garbage prints.

Does he have a whole ton of stuff going on in the background on his machine? Is it a very old computer? If so it might get a bit slow. It should not reset any temperatures.

Is all his software installed correctly and are all the configuration things done correctly? Half of the printer is really in the configuration settings in Slic3r.

Has he dropped the compeer a couple of times and broken the USB connector? Is it loose / does it wiggle?

Thanks for those suggestions. I think his computer is one of those small form factor jobs, he is not too impressed with its performance overall. Slow and limited RAM might be part of the issue. I'll ask him more questions...

At the moment he is very pleased, he managed to print a replacement gear for a milling machine.

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Yvan

Singularity Machine

My guess is that he's running a bunch of "surf" under Windows in the background. If it's a small footprint machine, the stuff will stop things dead for a while. That still should not create the issues he was seeing. He may also have a flakey USB port.

More updates...

Seems as a rule he is making sure there is little else running in the background. One long print started off fine, and then the temp jumped to 247°C or so mid way! It still managed to finish the part, but you can see a clear transition half way up.

He's also switched back to another machine once more to check things out, and the problem followed. He has to set the temp 3 or 4 times for it to "stick". Sometimes it will jump up anyways part way.

This issue is threatening to fry another nice J-Head...

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Yvan

Singularity Machine

Without seeing what's happening this is sort of a monster guessing game.

1) Are the jumps instantaneous?
2) Does anything else ever go wrong with the print?
3) Will the printer hold temperature with nothing going on?
4) Do you have an LCD on the printer? Does it agree with Pronterface?
5) Have you checked the thermistor mounting on the hot end?
6) What sort of power supply is it?
7) Have you checked all the grounds on the Ramps board to be sure they are tight?
8) Does he run a radio transmitter?
9) Is the temperature reading stable with the hot end turned off?
10) Is the temperature reading stable with the hot end turned off and the printer moving around?
11) Does he run anti-virus software and is it up to date?
12) Do the temp jumps always happen at the same point in a gcode file? If so have you looked at the file?


At some point you are going to have to start swapping parts. I'd start with the Mega board.

Okay just an update to close this issue.

My friend worked through the 12 questions above, and then took a peek at the g-code. Turns out 248°C was being set by slicer. He is having problems running it properly and adjusting settings in it.

We are glad to find it is not the Arduino. Saves us having to return it!

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Yvan

Singularity Machine

What slicer are you using that's randomly putting temperature change commands into the gcode without being told to do so?

He is using Slic3r, but he says it is not running properly on his machine. Seems he can export g-code but he can't adjust most or any of the parameters...?

Have not seen the situation on his machine myself, only trouble shooting over the phone!

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Yvan

Singularity Machine