[Resolved] Think I need to re-build my hotend...

[PhoenixNZ]

First machine. Completed the build this weekend.
When running the calibration scripts I noticed that my hotend wouldn't stop heating up.

Seems to be when the wires move a certain way. If I hold them just right, Repetier-Host picks up the temperature signal again and goes back to controlling it

I'll pull it out and re-build it. Hope to god I have a spare thermistor somewhere. Can anyone confirm it's the thermistor that's the problem? Any way to tell if I've broken the thermistor or is it just dodgy wiring?

[img]http://i.imgur.com/odQxwuo.png[/img]

[Eric]

I'd bet the thermistor itself is fine, unless you've actually broken the glass bead somehow. Of course, then it probably wouldn't work at all. To test one, measure its resistance. A 100K thermistor should measure 100K at 25C, so if it's close to that at room temperature, it's likely working.

From what you say about moving wires, I'd say it's more likely a wiring issue or a mechanical issue. Wiring could be a poor connection or an unwanted connection between wires and/or the metal of the hotend. Mechanical movement pulling the thermistor in/out of the hotend hole would produce similar symptoms.

[PhoenixNZ]

Definitely the wiring. Thermistor came out anyway as I was disassembling and I tested it - was about 100K.

Going to allow more slack in the connection this time and hopefully avoid it happening again.

[Eric]

Use some of that slack to provide a strain relief by strapping the wires down on the effector. Then there will be no movement-related tugging on the hotend itself.

[PhoenixNZ]

So... I re-discovered one of those cool little threaded thermistors you can buy on ebay which I believed I had mistakenly thrown in the trash. Awesome, thought I - now I can make a better hot end.

I merrily tapped the thermistor hole on the hotend and started screwing the thermistor in. Hmm... must be getting to a point where the thread hasn't been tapped in properly. it's less than 0.1mm to go, I'll just do the last half turn with a wrench...


[img]http://i.imgur.com/e8ic4mF.jpg[/img]

Sigh....
SS/Aluminium/Whatever the Hotend is > Brass

Advice? I'm thinking a 1mm drill bit and maybe an easy-out,then buying a new thermistor and waiting 3 weeks while it makes it's way across multiple bodies of water to where I live in Tasmania.

I'm more mad at myself than anything else. Shouldn't have tried to do this on a few hours sleep after a full day at work

[Jimustanguitar]

Use a cutoff wheel in a dremel tool and cut a slot for a flat blade screwdriver in it. It shouldn't matter if you put a little bit of a line in the aluminum, just be conscious of how deep the resistor hole is.

[Eric]

Or you can leave it like that and use the hole on the other side for a fresh start.

[PhoenixNZ]

Or you can leave it like that and use the hole on the other side for a fresh start.

Unfortunately this is one of the newer hotends and doesn't have a second hole. Not that I couldn't drill one of course.

Use a cutoff wheel in a dremel tool and cut a slot for a flat blade screwdriver in it. It shouldn't matter if you put a little bit of a line in the aluminum, just be conscious of how deep the resistor hole is.

That's not a bad idea. I do have a Dremel.

[PhoenixNZ]

Dremel didn't work and couldn't find an easy-out small enough so just drilled a hole in the other side of the hotend instead.

The stars aligned somewhat and found a fast local supplier for a new screw-in thermistor. My Rostock Max v2 is now alive and kicking . The PEEK shroud is printing as I sit here typing.