Welcome! Log In Create A New Profile


Hotend Stopped Working

Posted by adenton 
Hotend Stopped Working
November 09, 2017 09:03PM
Today I was printing with new filament and printed a bit too fast and jammed my machine. No biggie though, it's no like this hasn't happened before. I was disassembled the extruder and carriage to get to the thermistor so I could clear the jam. I then wanted to heat up just the thermistor using the hotebnd and push the jam out. However, when I went to heat the printer, the temperature reading never went up and it did not get hot.

I have successfully been printing and using this heating system for awhile and it has never given me any trouble. I then heated up the metal block which holds the hotend using a soldering iron, but the temperature reading in Pronterface did not change!

I checked the voltage on the RAMPS 1.4 board
Power: 12.13V
D8+: 12.13V
D9-: fluctuates between 0V-10.36V
D10+: 12.13V
D10-: 11.49V

The hotend is in D10, the fan is in D9, and I am not using a heated bed, so D8 is empty.

I'm thinking that there is either a problem with the wiring of the hotend or the RAMPS board.

I went into pins.h and changed the the pins around to do some tests.
D8- Fan works
D9- Fan works
D10- Fan turns on for a few seconds but does not stay on!...

I did the same thing for the Hot end but it did NOT heat up in any of these pins...

There's quite a bit going on...

Okay, as I was writing this, I remembered I have an old hotend that I could use to test with! AND it works! It heats up and reads just fine, however this hotend is for 3.0mm filament and I am strictly using 1.75mm so its not much use to me.

With all of that being said, would you recommend that I purchase a new hotend & thermistor? Or re-wire my current ones? Or something else?
Re: Hotend Stopped Working
November 09, 2017 10:24PM
I think you've misunderstood some terminology.

The thermistor is a little bead at the then of two thin wires that varies its resistance depending on voltage. It is normally inside the heater block, and nowhere near the extruder or carriage. The hot-end is the combination of the heatsink, heat-break, heater-block, nozzle, thermistor, and heating element. Some of these may be combined into modules by the manufacturer.

Putting the heater wires for the hotend across a low-current output (e.g. a pin intended to run a fan) could destroy that output. Don't do this!

What you should do:
1. Tell us what kind of hot-end you have. Photos are good.
2. Tell us what firmware you're using and whether you have an LCD controller on your printer, or how you're measuring temperature and controlling the printer. (You did mention Pronterface).

Some (most, all?) firmware disables the heater output if the thermistor is not connected. Similarly, if the heater is turned on and the thermistor temperature doesn't increase, the heater is also disconnected. Both of these are for safety, since otherwise that heater is completely out of control, and could cause a fire.

So... Are you seeing an actual temperature reading from the hot-end thermistor? It would normally show about room temperature (10-20 degrees C) if the heater isn't working. Holding onto the nozzle with your hand for several seconds should be enough to raise it by a couple of degrees. If it shows 0 then your thermistor is disconnected. If it shows over 250, then your thermistor is shorted out. You could also disconnect the thermistor from the RAMPS board and measure resistance across it. It should be in the region of 100K ohms.

If the thermistor is OK, then you have a problem with your heating element. Disconnect that from the RAMPS and measure resistance across the heater. It should be about 4 ohms (say 2-10 would be OK). Zero means the wires are shorted, open means they're broken.
Re: Hotend Stopped Working
November 10, 2017 05:38PM
Ah, I see. No, I definitely know that the thermistor is the tiny glass bead, just mispoke! I unclogged the heat-break.

Upon further inspection, I now see that wiring on the thermistor has come apart! Since the wire is so fine I don't think it would be worth soldering, so I'm just going to order a replacement.

I'll give an update when I replace the thermistor!
Sorry, only registered users may post in this forum.

Click here to login