Hot and Bothered

March 4, 2013

Finally got round to fitting a new heater to the Huxley today, not as easy a task as I had anticipated. I removed the hot-end from the X carriage yesterday only to find that the old resistor was stuck fast in it’s hole. I also had problems un-picking the crimps that I used to join the resistor to it’s wires.

In the end I had to cut the crimp in half; place the nozzle block in a vice and have at the old resistor with a hammer and a dowel. When it came out I could see that the enamel around the wire-wound resistor had worn off and probably shorted out on the block causing the burn-out.

Next challenge was getting the new resistor in, very tight and I hope that I won’t run into the same problem again in another few months. If I do need to replace the resistor again I may look at either rebuilding the whole hot-end or finding an alternative, see below. I did put a new crimp on the wire end only and slid the resistor lead into the crimp end so should be simpler to replace next time, but I do need to check the insulation around the crimp does not slip over time.

After re-fitting the hot-end to it’s carriage and re-levelling the X-Axis I fired up Pronterface and warmed up the resistor, starting from 50°C and going up to 200°C in steps of 50°C. All was well ’till I checked the Z-Axis end-stop! There was a clunk and the Extruder side Z-Axis threaded rod fell off it’s stepper motor.

So, dismantled the clamp; re-set the rod; re-re-level the X-Axis wind up for a test print and hit PRINT… Quarter of way through I notice that I probably don’t have enough PLA loaded. Stop the print; back up the PLA; load a new reel; let the partial print cool; remove from the bed; start again. Finally, I have a working printer again!

This has made me realise that I ought to make a list of things that I’d like to improve. Top five are:

  1. Power supply loom is messy – I’d like to add a 12v supply for the extruder fan; add an ON/OFF switch and shroud the inlet a bit more.
  2. Remove and re-build the bed. I’ve never been happy with it at it’s a pain to level and a pain to clean between prints.
  3. Add an out-of-filament alarm, or, if possible an out-of-filament emergency stop.
  4. Checking out some X-Carriage mounted Extruder as these will cut down on wasted filament. As it is, unless someone can tell me otherwise, once the filament goes past the hobbed bolt in the Extruder then it’s wasted as there’s nothing to push it into the hot-end or pull it back out again.
  5. Redo the hot-end wiring as it’s a pain to replace, as I know from today’s little demonstration! Whilst waiting for my test print to complete I saw a “J” hot-end which looked very neat and compact: might be worth a further look (

Anyway, end of this week I hope to clean and level the bed and apply some of the Kapton tape I got to see what the results are like.