Thermal Runaway

[Cedrik4995]

Hi,

I have recently finished assembling (started 4 days ago) a "Prusa i3 Pro C Dual Extruder" printer and I am trying to make my first prints. So far there are a few Issues that I can't solve on my own, so I turn to smarter people on forums.

1. (It may be how it works but) a part right above the heatbed connector (Grey cooling metal cover part on a black diode, probably related to bed heating) on the Arduino board gets really hot to the touch, nothing melts but compared to the two other (same metal bits) for the hot end heaters (that are cold) the hotbed one is really hot. Is that normal? I read somewhere that the bed uses more power, that could be the reason.
Also, the hot bed heats up to 50 deg. in a minute but then slowly creeps up to 60 deg. in over 10 minutes. If I raise the temp to 70 deg. , it will go fast to 60 deg. and then creep slowly to 70 deg. . Is that supposed to do it so slow or is there something wrong in the configuration? How to fix it?
My current workaround is to raise the temp 10 deg. higher and then back to the needed one once it has reached it, but I doubt it is supposed to work that way.

2. (Worst problem, can't finish prints longer than 5 min) I get a Thermal Runaway error after about 5 min into a print, the heat graph is stable but just randomly gives error, then cools down. The error has also appeared while heating up all parts in the beginning not even printing. The error in Repetier also indicates a part ID of 9, I found from Google that Marlin refers to Bed using ID 9, so could issue nr 1 be causing issue number nr 2 (number game ) ?
Possibly related:
One of the hotends thermal sensors pin broke (was bent too sharp during assembly and reassembly due to leveling and such). To fix it I had to remove some of the white cable cover for the connection part between the wire and the sensor pin, I then removed the broken part of the pin from the clamp that holds it together and connected the wire to the rest of the pin that is still with the sensor (but shorter). I also swapped the heads and I have only used the left extruder, right now I am using the head with the sensor that did not break.When the hotends are turned of, the once broken sensor shows 23 deg. and the other 24 deg. , the bed is also 24 deg.
I did however get the Thermal Runaway error before the sensor was broken as well, at that time all was working.
How to figure out what is causing the Thermal Runaway and depending on the issue, how to fix it?

If you need any more info, please let me know what and I will try to provide it. It is sad that the device is new and It has these issues preventing me from doing what it is supposed to do. Hope I can find a quick solution.

Thanks in advance.
Cedrik K.

[Cup]

Hi,Cedrik
The grey metal part mentioned is used to cool for the corresponding mosfet(which controls the bed heating),so you'll feel heat when you touch it.
But it is abnormal if it is extremely hot...
You can refer to the following post to check your mosfet:
http://www.geeetech.com/forum/viewtopic ... 19&t=17039
And maybe some pictures or videos are better to diagnose the exact issue.

[Cedrik4995]

Thanks Cup, for the response and the article reference.

And thanks for the new vocabulary "Mosfet" (I'm Estonian so I have still a lot to learn ).

I had a little time to only take measurements of the mosfet, I will be able to possibly add pictures or videos in a few days.

What I did was measure the whole process of heating up the bed (only) and here is the result:

Power on but no heating: 12.31 V
Set to 60 deg.
from 23 deg. to 35 deg.: 2 - 4 V (oscillated between those voltages)
from 40 to 55: 5 - 7 V
on 58 deg.: 7 - 9 V
on 60/61 deg. : 6 – 9 V and stayed like that never going 0V.

The article explained that when heating is off it should be 12V, which it is basically and when it reaches the temp, it’s supposed to go 0V but it did not do that for me.
What I can guess is that I was on 60 deg. which is not the possible max for the bed, so the Mosfet has to hold some of the 12 volts so that the bed would stay 60 deg. not higher and if I would set the desired temperature to 100 deg. it would be closer to 0V once it reaches it. Am I close with that thought?

Does that info seem normal so far or is anything wrong with the Mosfet, again, the temperature of the mosfet’s heat-sink (aluminium part) gets hot to the touch but that may be normal for the bed heating.
If the Mosfet is fine, why do I still get a “Thermal Runaway” error during prints stopping the print process (wasting plastic each time)?

I will try to print again and perhaps film the process to catch the issue happening (once I have the time).

If you have any more info, I would be very grateful.

Cedrik K.

[Cedrik4995]

An update on the situation:

I have changed the settings in the firmware for the Thermal Runaway protection, I noticed that for the Extruder hotend the temperature was set to 4 deg. allowed change and 40 sec until the Thermal Runaway is initiated. The heatbed had 2 deg. and 20 sec of reaction time. I change the bed to the same as the Extruder hotend and I then was able to finish a smaller print and then when it finished the print, the heatbed was turned off, it dropped a few degrees, I turned it back on for a second print and in about a minute (most likely the 40 seconds) I got the Thermal Runaway.
I reset and started over and have not had any errors so far after 3 more prints. Seems that the error is less frequent.

So the issue seems to be that the Thermal Runaway check does not reset after the bed is turned off, which hopefully would get a fix with an update cause the Thermal Runaway check would turn into an issue rather than a helpful safety feature.

Anyway, once I get more filament I will try longer prints and post here if it helped (for anyone who has the same issue).

[bang]

Hi,
I found this when i search with "Thermal Runaway":

QQ截图20170104174110.jpg (30.12 KiB) Viewed 12077 times

[Cedrik4995]

HI bang,

I did notice those articles here but they did not seem related to my issue as I don't have bed auto leveling. I did read through the articles but they seemed irrelevant, so I created a new thread. But thanks anyway