Orcinus' Build Log (was: Thermistor insanity)

Topics Related to the ORD Bot Printer

Re: Thermistor insanity

Postby orcinus » Sun Jul 01, 2012 9:46 pm

So, anyways, apparently i didn't tighten the SS part into the nozzle tight enough (i did use two wrenches / two hands to do it, but neglected to heat the part up and retighten).

Having no other means to extract the PLA out of both parts, i've ended up torching it.
And then crap started happening, pretty much in succession...

First, the set screw that holds the other end of the SS tube in the cold end snapped in two (along the slot). I guess i'll leave it like that until i need to dismantle the hot end again, it's removable with pliers.

Then the fire cement just fell off the heater block, along with the thermistor (it cracked along the "wings" i've made to hold it on there).

Then a wrench slipped a little and dented a corner of the SS tube base. Not the tube itself, luckily, and only the part of the thread that's actually never screwed into the heater block.

Being out of fire cement and not having any high temp silicon sealant, i've glued the fire cemented thermistor back in place with some thermal epoxy (Arctic Silver). According to someone on reprap forums, it's pretty stable up to 250 deg C, despite the official page (which is actually a copy/paste of a generic text about epoxy, as i found out) vaguely claiming it goes to >150 deg C.

We'll see how that goes, i'm waiting for the epoxy to cure, it's still in gel phase.
orcinus
 
Posts: 699
Joined: Tue Feb 14, 2012 4:03 am

Re: Thermistor insanity

Postby orcinus » Thu Jul 05, 2012 5:52 pm

I've cleaned everything, tightened it up as hard as i could and it stopped flowing once again.
In the process, i've managed to dent the SS tube a tiny little bit (barely perceptible, mostly just a scuff on the finish, and no effect on the internal diameter, thankfully).

So i finally thought - maybe it's the filament.
I've switched to a different one (the first one was a sample of white PLA i've got from Ultimachine) and lo and behold - after purging the old filament, the new one started flowing just fine. It stopped after a while and when i've pulled it out and saw why - it bloated at the end due to too high temps in the SS tube and above.

I've mounted a fan on the side of the Wade's extruder (drilled and tapped a hole on the side, screwed a fan in) and - well… I finally got a successful print!

Image

I think i've ramped the temperature too high, hence the bubblyness in some places.
Plus, it's a little wobbly, because i still haven't ironed out the Z axis wobble (i'm switching to ACME rods soon anyway). But not bad for a first, i think.
orcinus
 
Posts: 699
Joined: Tue Feb 14, 2012 4:03 am

Re: Thermistor insanity

Postby Liberty4Ever » Thu Jul 05, 2012 6:30 pm

You are definitely making progress! Congratulations! :mrgreen:

I'm right behind you! I still haven't quite finished my first Hadron (life and other responsibilities intervened) but I'm about to get back to it. I ordered a Hadron kit that should be here soon, and four of the QU-BD extruders. That should be interesting. Hopefully, I'll have the first Hadron built and tested before all of the parts arrive for the second.

Thank you for your build log. I'm learning of some of the issues and potential pitfalls, and maybe I can avoid a few problems.
Apparently, I didn't build that! :-)
Liberty4Ever
 
Posts: 274
Joined: Wed May 30, 2012 1:49 am
Location: Lexington KY

Re: Thermistor insanity

Postby orcinus » Fri Jul 06, 2012 1:56 am

Thanks :)

However, it turns out that congratulations were premature.
I was done with work, got all hyped up to start calibrating the printer, then a series of screwups occurred.

First, the Z-rod unthreaded itself out of the coupler (for the umpteeth time).
While messing with the Z-rods, i've whacked them out of the somewhat de-wobbled state and into pretty nasty shakes.
Then the Z-axis got bound, due to me misaligning the left and right side while trying to get the wobbles back under control.

And then i've made a series of tiny, but crucial errors that culminated in self destruction of the hotend.

1. The Gcode i've generated with Slic3r had Cooling enabled, but with first layer cooling turned off.
2. I've set the skirt to 5 perimeters instead of 3.
3. I haven't zeroed the Z axis correctly, so the nozzle ended up squashed against the glass (not all the way, but nearly).
4. The temperature i've set before handing over the control to the Slic3r file was 175, while the temp set in Slic3r was 195.
5. I've had the Z raised to 75mm before starting the print.

All of that conspired to prolong the time before the fan went on AND increased the pressure inside the hotend by a fair amount.
The bit of filament under glass transition was right around the middle of the überthin SS tube and started to swell, eventually blocking the filament.

But that's not all - it swelled enough to DEFORM the tube. That's right, the tube bloated around the middle (where the support is thinnest), with bloated filament in it. End result - deformed tube and stuck filament.

I took it all apart, heated up the SS tube, pulled the filament out when it softened enough to get squeezed back through the tube, then torched the remains of PLA in the tube. I think the hotend's pretty much busted now, because whenever the pressure and temperature in the SS tube rise enough, it's going to happen all over again, except much more easily this time, because the tube's already deformed.

I'll take some post mortem photos tomorrow...
orcinus
 
Posts: 699
Joined: Tue Feb 14, 2012 4:03 am

Re: Thermistor insanity

Postby Liberty4Ever » Fri Jul 06, 2012 2:45 am

On the plus side, that stainless tube should be relatively easy and inexpensive to replace?

I wish you the best of luck. You should run out of things to do wrong soon. I can sympathize, as I'm doing my first LinuxCNC retrofit of a large gantry machine, and I'm learning a lot of things not to do... one at a time.

However, please don't stop posting. Describing your problems can help the rest of us avoid them.

Good luck!
Apparently, I didn't build that! :-)
Liberty4Ever
 
Posts: 274
Joined: Wed May 30, 2012 1:49 am
Location: Lexington KY

Re: Thermistor insanity

Postby orcinus » Fri Jul 06, 2012 12:52 pm

The SS tube is actually not that easy to replace, because it's a lathed single-piece consisting of the tube and two screw blocks on the ends that go into the heat sync and the nozzle. Plus, it's really, really, REALLY thin. In fact, it's so thin that, after having the wrench slip again last night, i've destroyed it (bent it).

So it's gonna be another wait for a replacement... Oh well, it's not like i'm in a hurry.
orcinus
 
Posts: 699
Joined: Tue Feb 14, 2012 4:03 am

Re: Thermistor insanity

Postby Medel » Fri Jul 06, 2012 2:01 pm

orcinus wrote:The SS tube is actually not that easy to replace, because it's a lathed single-piece consisting of the tube and two screw blocks on the ends that go into the heat sync and the nozzle. Plus, it's really, really, REALLY thin. In fact, it's so thin that, after having the wrench slip again last night, i've destroyed it (bent it).

So it's gonna be another wait for a replacement... Oh well, it's not like i'm in a hurry.

That's the worst. I had a similar issue a few months ago (tightening backed-up nuts and sheared it). On the up side, the new one will be nice and clean! :D
Medel
 
Posts: 34
Joined: Thu May 24, 2012 6:39 pm

Re: Thermistor insanity

Postby orcinus » Fri Jul 06, 2012 7:14 pm

I'm sorta used to it, all my pet projects have "bumps" like that, all the time :D

The funniest one was with my quadcopter. Everyone claimed that there's absolutely no harm in having all the spinner nuts with the normal threads (instead of 2 right and 2 left handed threads, which would make sense since two of the props spin CW and two CCW). I kept thinking i should threadlock them (which i desperately wanted to avoid, since props are broken & replaced often), or replace the two with left handed nuts, but left them as is with only a tiny bit of threadlocker.

The first run went okay, just a short hover, everything doing fine.

The second failed hilariously - one of the props went BROP-ZOING! and flew its own trajectory somewhere in the air, while the nut went BZING by my ear and hit the wall nearby. I reacted reflexively and killed throttle, so the quadcopter went down (it was just 10cm above the ground) without flipping. As it hit the ground, another prop went-a-flying on its own. Never found the second nut :lol:

The first one was under a dent in the wall.

At least with 3D printers and tiny CNCs there's nothing flying about and all the spinning objects are tiny and with not that much momentum.
orcinus
 
Posts: 699
Joined: Tue Feb 14, 2012 4:03 am

Re: Thermistor insanity

Postby Liberty4Ever » Fri Jul 06, 2012 7:24 pm

It sounds like the small R/C copters have the same problems as big helicopters. Too many essential parts! Not enough redundancy!

It also sounds like you should wear eye protection when flying your quad copters. :shock:
Apparently, I didn't build that! :-)
Liberty4Ever
 
Posts: 274
Joined: Wed May 30, 2012 1:49 am
Location: Lexington KY

Re: Thermistor insanity

Postby Medel » Fri Jul 06, 2012 8:38 pm

Liberty4Ever wrote:It sounds like the small R/C copters have the same problems as big helicopters. Too many essential parts! Not enough redundancy!

It also sounds like you should wear eye protection when flying your quad copters. :shock:


All the microcopters are getting a lot simpler quickly thanks to MEMS gyros and accelerometers. Such simpler rotor heads and repairs.

I was playing with one of my micro CP birds and tried to flip it indoors. Hit a chair rotor-first, and nothing broke except the canopy..which I stepped on by accident leaning over the chair to grab it....

Back on track: hope your printer is back online soon!
Medel
 
Posts: 34
Joined: Thu May 24, 2012 6:39 pm

PreviousNext

Return to ORD Bot

Who is online

Users browsing this forum: Google [Bot] and 4 guests