hot end problems

Hi,

I built a Ormerod 2 earlier this year, i'm 16 and this is the first printer I've ever made and incidentally this is also the first forum post I've had.

I'm having some major problems with the hot end.
Primarily the fact that it's temperature control has gone majorly strange.
The problem aroused when printing a small object the temperature of the hot end started plummeting and the filament got stuck.
When i stopped the print and manually set the hot end to 200 degrees it wouldn't reach or even change value on the screen. However it was getting hotter and the light indicated
current was flowing so the value reported on the web didn't seem to reflect the actual temperature in real life.
I assumed the thermistor was broken but after a day i re did the hot end wires came back and it had fixed itself and i was able to get a successful print out of it.
However now the problem has come back and even after re wiring it the hot end won't get hot and the reported value either stays at the value on start up (which incidentally is usually about right to room temperature) or fluctuates between 2 about 2 degrees apart) even when i set it to heat up.

I don't know if this is a short, a software issue or something else?

Thank you for taking the time to read.

Oliver

I suspect that you have a bad connection in one of the wires in the hot end loom or associated wiring that feeds current from the Duet to the hot end heater. The LED on the Duet shows that at the Duet end there is voltage available to drive current through the hot end, but not that current is actually flowing. I suggest you de-mate the 6 pin connector, look for signs of charring, and check that all 6 pins in each half are pushed all the way home and so level with each other. If the pins are OK then the problem could be a bad crimp connection, a failed cartridge heater, or just possibly a bad connection on the Duet.

If you have a multimeter, you could disconnect the hot end loom at the Duet end and measure the resistance netween one of the yellow wires and one of the brown or orange wires. It should be about 3 or 4 ohms.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].