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heater decoupled mid print

Posted by mlaustin66 
heater decoupled mid print
September 24, 2016 12:57AM
Everything with my machine was going smoothly until the other day. I was 25% through the print, and the hot end and heatbed were at 0 degrees. I happens approximately at 3mm height. I've tried 3 times and the same result. I have no idea what could be casing this. I have a temperature gun, and the heatbed heats up to temperature. Could it be a thermistor? But if so why would both hotend and heatbed heat up and print. Nothing was changed in the configuration. I'm running rewpetier .929. Any help would be appreciated.

Edited 1 time(s). Last edit at 09/24/2016 12:58AM by mlaustin66.
Re: heater decoupled mid print
September 24, 2016 12:31PM
the printer reads 0C? cause i guarantee thats not correct. Sounds like the thermistor is coming disconnected. Could be a worn out wire?

If you need some help, or don't understand what I just said, feel free to send me a PM anytime

Printer: Prusa i3, 2 E3D v6 Hotends, Arduino + RAMPS 1.4 with a Bypassed 5V Regulator, 400w Insignia ATX PSU, Custom Designed Bowden Extruders
Re: heater decoupled mid print
September 24, 2016 01:24PM
Looking at the wires, there is no visible wear either at the hotend, heatbed, or ramps board. If there was an issue, my guess is it would be up front and not 25% through a print.
Re: heater decoupled mid print
September 24, 2016 01:31PM
I found an interesting observation. I was going to plug it into my computer to do the failed print over and watch the log. This came up when plugged in.

12:26:19.536 : DebugLevel:6
12:26:19.536 : SelectExtruder:0
12:26:20.443 : DebugLevel:14
12:26:20.457 : Other:: temp sensor defect marked defect
12:26:20.457 : heated bed: working
12:26:20.457 : Error: Printer set into dry run mode until restart!
12:26:20.457 : Disabling all heaters due to detected sensor defect.
12:26:20.457 : DebugLevel:14

Does this mean the hotend thermistor has shit the bed? Why would it pas a PID autotune and work to 25% of the print?

Edited 1 time(s). Last edit at 09/24/2016 01:31PM by mlaustin66.
Re: heater decoupled mid print
September 26, 2016 02:10PM
Replace your thermistors and see if the issue clears. They're cheap.
Re: heater decoupled mid print
October 19, 2016 09:52PM
almost all intermittent heater (hot end) problems are caused by a thermistor that has a broken wire somewhere resulting in a 0 reading which terminates printing. They can be damaged by overheating above their operating range but this would be a constant failure and firmware protects against this. The best approach is to keep spare thermistors and simply change it.If it were the heater it would lose temp slowly
Re: heater decoupled mid print
December 04, 2016 11:00PM
I thought I'd post an update to this thread. It ended up being a fan control board on that particular Ramps 1.4 board. I took out the fan control board, and it ran flawlessly for a while. I had replaced the Mosfets for better Mosfets as well as I have a 200W silicone heater, and the original Fets feel like they are going to melt...super hot. Had to put in another Ramps 1.4 board for various reasons and just stuck with the original Fets. This one had a new fan control. It ran fine and then started having the issue again. So I pulled the fan control board off like before. It just had another heater decoupled message after running fine for several prints. I wonder if the Mosfets are getting too hot causing something to fail on the board temporarily, and it in turn causing the heater to decouple. Or maybe this time it is a bad thermistor (last time I replaced it with no change and then realizing it was the fan control board through trial and error). I hate these Ramps boards. I've decided to get a Smoothie board.

Edited 1 time(s). Last edit at 12/04/2016 11:01PM by mlaustin66.
Re: heater decoupled mid print
December 05, 2016 12:06AM
I have had problems with my bed heaters burning out my RAMPS Boards. What I did to prevent that was to get a Keenovo 110V (for USA Voltage) See:


This one shown is for a 230 volt System (for European voltage), but I asked the nice people from Keenovo for a 110V heater pad identical with this one and and they made me one at no extra charge. They took about two weeks before they sent the custom made heater out.

I attached the heater to the bottom of an aluminum build plate. See:


I bought a Fotek SSR-40DA 40A Solid State Relay Module. I had a mains plug to which I attached one wire of the heat pad . I attached the other heat pad wire to one of the terminals at the top of the relay. I attached a heavy wire to the other terminal on top of the relay. The other end of that wire went back to the plug. I attached the positive heat bed terminal on the RAMPS board to a wire that ran to the positive terminal on the relay and the negative terminal on the RAMPS board to a wire that ran to the negative terminal on the relay.

I have not had problems since.

Edited 1 time(s). Last edit at 12/05/2016 12:11AM by Lymphomaniac1.
Re: heater decoupled mid print
December 05, 2016 12:42AM
I have a similar heatbed and heater, butt not the same brand. When I switched out all the Mosfets to better ones on the prior Ramps, they were warm to the touch not steaming hot. The problem is it's a pain in the ass to switch Mosfets and easy to damage the conductor pads on the PCB. That board ran great until something else fried on it. So I'm over arduino/Ramps.

Edited 1 time(s). Last edit at 12/05/2016 12:42AM by mlaustin66.
Re: heater decoupled mid print
December 05, 2016 12:42PM
Even if you go to a different board you may still have the same problem. The cause of MOSFETS getting too hot is that too much current is going through them. Heat beds draw a lot of current. From what I can find on the internet, the heated bed circuit is only rated at 11A. 11A X 12V = 132W. Your heat bed runs at 200W which is an overload. Even if you put in a MOSFET that is rated for higher current, the fuse may blow. Most MK2A heater plates have a resistance of 1-2 ohm thus the power being drawn by a MK2A is between 72 and 144W which is considerably less than your 200W Silicone heater. By using a Solid State Relay and a heat bed that runs off the Mains power, the only current you need from the heat bed terminal is less than 1A that is needed to drive the relay, thus your MOSFETS will not get hot and your fuses will not blow. When I first developed this trick I thought I had a novel idea only to find that many reprappers already used this trick with silicone heaters. Do not try to run your 12V heater off a SSR-40DD solid state relay. The relay will drop your voltage and your heater will not heat up as hot as it should. Do not try to run your 12V silicone heater off of mains power, get one that is rated for the mains in your area.




Edited 2 time(s). Last edit at 12/05/2016 12:56PM by Lymphomaniac1.
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