Heat creep

I have to confess that I’ve been lately not contributing here as I would like to – mainly because I’ve hit several obstacles in our project and I didn’t want to report failure without having a solution in my hands. So – this is a story with a happy ending!

2-3 months back, our 3D printer started suddenly mysteriously malfunctioning. To provide you with some idea on this, see pictures below, but beware those are pretty creepy, so if you are afraid of rabbits missing ears, their heads being chopped off and missing body halves – don’t look! 😉

Yep – out of nowhere – all prints failed. Here comes brief list of things I did to find solution.

  • Got very grumpy – for weeks, still trying to resolve that.
  • Got filament stacked in a feeding bowden and tried to clean that bowden in our oven which let to melting a clamp which holds bowden in the nozzle – making me even more grumpy.
  • Ordered replacement bowden made from PTFE
  • Installed new bowden, failed another set of prints and got it clogged again, cleaned it in the oven and cut mangled end in a way that it was useless
  • Ordered another 2 replacement bowdens made from PTFE
  • Ordered hardened-steel nozzle to prevent clogging
  • Installed replacement bowden + hardened-steel nozzle -> another fail
  • Dried filament in the oven for 8+hrs to rule out it is all just a moisture
  • Sort of gave up here as being seriously depressed about how the heck I can’t solve this and went radical – bought a direct filament drive to replace that bowden drive!

Following picture (borrowed from here) demonstrates that difference. The idea here is that with that bowden drive flexibility of filament and bowden somehow creates a problem in a nozzle, which leads into a clog.

It wasn’t cheap, but I was convinced to do anything!

Whole thing came in couple weeks and I started eagerly unpacking and mounting.

Whole operation took couple hours, but it was a real fun. Minutes later after taking that last picture I’ve been getting in a situation where I needed to Google to actually tell me how I feel – problem persisted – dead rabbits everywhere! Actually having all those crippled rabbit bodies, I made a Halloween scary-story about all that and played my boys a little bed-time story about how important is to eat carrot. Not sure about boys, but that cheered me up a bit.

Banging my head like this for more then a month already – I reverted to the last resort option and reached to the original seller’s support. Support page seemed to be strangely non-responsive, but still there was an email from them in my mailbox next day already!

Couple calls + chain of emails + many pictures later – Al suggested that one of the problems could be mysterious “Heat creep”. I started reading all about it, from all the sources and while playing with some parameters + doing some test prints I noticed that fans cooling the nozzle are not running! Bit of review of all connections and stuff revealed that few months back a bit of melted filament ended up in between blades and fan wasn’t probably running since – quick fix turned into a major one when I accidentally hit already-rotating blades with a screwdriver and broke one of the blades. Couple hours/days later after the fan replacement I was eager to give it another go! … which suddenly worked out! Anyway another consequent print failed again. 🙁

So a tiny recap of the situation – not printing for months, printer practically new, several expensive upgrades, multiple support calls and I had a single successful print out of … 20? Still revolving that “Heat creep” mantra in my head I kept failing, while I still had that single successful print. How come it worked out, when even an instantly following print failed?

Dear Holmes, … while cleaning that clogged nozzle after 10000x failed print … I’ve accidentally touched the light bar I mounted roughly 2-3 months back to see how those prints are going well … it was hot, not too much, but it was hotter than I expected. Can it be? I sort of remembered that I turned off light before for that print which worked out, because we’ve been going out.

Another test print with the light turned off revealed that it was not a coincidence and all started working like before. I am still feeling super-charged while writing this post and while it was again typical PEBCAK solution, I am happy we can progress on this field again!

EDF unit case prototype – bit hairy as printed with wrong retraction settings

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