Extruder not heating

Hello,

I recently build my first Prusa i2. It uses Ramps 1.4 and Jhead hotend.

After some of its most successful prints so far, the extruder refuses to heat up. The bed works fine and the thermistor reads room temperature. When I measure the voltage from the board to the wires it reads 12v. When I measure the resistance of the heating element itself, it reads between 4 and 7 Ohms. There is no wire obstruction, nor breaks in the wire. When I removed the heat element resistor it was an intact cylinder, white in color, and wrapped in thin black wires.

Any ideas why it wouldn't heat correctly?

Update;

I found a guide suggesting wrapping tin foil around the heating resistor in the hot end in order to make it fit snuggly. I tried that and now when my printer goes to heat the hot end it restarts.

you have probbly shorted the heater with the tinfoil

Well the problem occured before I attempted the tinfoil method. Once I tried the tinfoil and it reset I removed most of it, leaving only a little wrapped around the center. This worked and the hotend heated until I turned the printer off again- then it went back to not working. Unfortunatly, in an attempt to tinker with the foil again, I broke the arms of the resistor so I've had to order another one. Hopefully a new resistor will fix the issues. :/

I have received a new heating resistor that I purchased from Amazon.

[www.amazon.com]

I plan on removing the legs of the old resistor from the wires, placing the new resistor in the hotend block's hole and re-crimping the new legs onto the wires.

Any hints on how to avoid the same problems as before? or was it just likely a crummy part?

You could try a cartridge heater instead.

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Waitaki 3D Printer

With a name like JarlSagan I would almost expect you to be able to solve these problems by yourself

Soldering the parts is usually much better than crimping, you get much better contact between the two surfaces. Crimping can work loose especially if the wires are moving backwards and forwards, that could be what caused the problem in the first place. Use flux to make sure you don't get a dry joint.

Quote
ksk
Soldering the parts is usually much better than crimping, you get much better contact between the two surfaces. Crimping can work loose especially if the wires are moving backwards and forwards, that could be what caused the problem in the first place. Use flux to make sure you don't get a dry joint.

Not in this case. The temps too close to the melting point of solder and it will oxidize it and may fall apart

It sounds like your heater isn't stable.
Try putting a new one in, they're only a few pounds, if you look on ebay there are some with longer wires attached, keep some length on the wires. Solder any joints and insulate with heatshrink tubing.
If you also use new wires if you need to extend them, then it should work.
If you still have the same problem you'll know that the fault lies somewhere else, the ramp, transformer or software.
Sometimes you have to eliminate things one at a time.

Edited 1 time(s). Last edit at 05/02/2014 01:24PM by ksk.