Hot End Cooling off

Having issues with my Prusa Mendle style printer . . . It was working fine for a long time, but suddenly has started acting up. I am a mechanical guy and don't know much about the electronics end of this . . . so you'll have to let me know what information you need me to find to help troubleshoot . . .

I'm using: Slic3r and pronterface. I believe it is an arduino mega board with UltiMachines RAMPS . . . not sure much aditional detail about models and versions, but I could find out if it helps, jsut tell me where to look... .

As of last week, the hot end shuts off in the middle of prints. Randomly, print will be going fine, temperature good, then for seemingly no reason, the extruder just cools down. I have sat and watched it: the temp readout on pronterface runs up, and down just as normal, I watch the LED on the RAMPS board that indicates the extruder is on, it goes on and off . . . then, at some random point, as the temp drops to the low end turn on point, the Ramps LED dosen't turn on. . . . and the extruder temp drops.

If I then click the "SET" on Pronterface to manually trigger the extruder, the LED comes on and the temp goes back up and all is fine for a while, running up and down as normal, . . . then out of the blue, it happens again . . . .

So bottom line, if I babysit the printer, and watch for the heat to drop below the call for heat threashold, I can trigger it manyally and wait again, . . .but that's silly . . .

Any advce on what or how to troubleshoot??

-Doug.

I had a similar issue on my printer, and it turned out to be a broken connection on one of the heater wires. It happened where these things usually do - right at the connector I put in so that I could easily detach the hot end.

I replaced my MOSFET, I replaced my ramps board, but what finally gave me the clue was that I noticed that it was only happening on the right side of the print bed. I was able to verify this by manually moving the carriage back and forth. As soon as the carriage pulled the wire into a certain position, the connection broke. If I moved back to home position, everything worked and it would heat up again.

Check your connections.

Hey thanks for the input . . . I wasn't feeling like this was a hardware issue, but it sounds like it might be if you had a similar problem. I'll check it out and see if I find any breaks . . . I is a reletively new J head style hotend, but you never know . . .

Any other Ideas I'm all ears while I check out this possibility!!

-Doug.

You could also check your power supply, maybe the current is dropping at some point.
Wich type of PSU are you using ?

Well . . . I think jbernardis may be a genius . . . I took the hot end apart, and noticed that the thermister was kind of touching against the aluminum block . . . didn't really think much about it but on closer inspection, it looked like a little bit of the wire insulation had warn thru. Perhaps it is shorting out against the alm and knocking out the heater cycle ?? . . . . Sooooo, I wrapped it up real good with Kaptan tape to insulate and gave it a run . . .. Rock solid for a 4 hour print . . . Knocking on wood, but it looks like the prob might be solved? . . .

THANKS!!!
Back in business for now!!

-Doug.