Orcinus' Build Log (was: Thermistor insanity)

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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby orcinus » Tue Jul 17, 2012 7:02 pm

I was too impatient to wait for the replacement parts from Arcol/Laszlo, so i ended up buying an e-bay hotend from a local reprapper.
It does have a week point (PTFE is a load-bearing component, so it's bound to fail at some point, event though there's a beefy heatsink acting as a barrier right beneath it), but has been working so far. And it's of a lower power than Arcol, so i had to do a lot of experimentation to figure out a way to cool the prints without cooling the hotend too much (if i direct a 50mm fan anywhere near the hotend, it can't keep up and starts cooling down to 100 deg C). I've insulated the side facing the fan with some ceramic (alumina, actually) cloth-tape-thing from Ultimachine.

Anyways, printed this today while i was working:

Image

Image

An even smaller one i've printed before that one, with translucent yellow/green filament turned out much better (without support, sans the tail).
But i ran out of that filament and accidentally splashed that print with acetone while cleaning the heatbed.

This was printed with a PLA sample i got from 2printbeta with an order. It's much much more stringy and the supports (at least slic3r's) are nearly impossible to separate from the object. I've actually cracked the legs on the lion while cleaning support and had to glue them back. Not sure why it's so stringy, especially considering it was printed at 175 deg C (which in itself means nothing, because i think my temps are off by 5 deg C or so, but i *normally* print at 185).

I'm out of that sample too, i think i'll try and calibrate for the black PLA next, then give printing out a set of herringbone gears a go...
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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby orcinus » Wed Jul 18, 2012 12:14 pm

Argh. This is so frustrating.
First i've had everything tuned in perfectly for the translucent green filament and then, just as i was about to start printing "seriously", ran out of it. Then i've switched to green, retuned, ironed out the kinks i've noticed while printing the lion and ran out of that filament. (both from 2printbeta.de, if anyone's curious)

Now i'm running Ultimachine's black PLA and, for the life of me, can't tune the hotend for it.

The difference between UM and the filaments i've used previously is huge. Ultimachine's acts more like a weird hybrid between PLA and ABS. It's not brittle and whitens when bent, instead of snapping cleanly in half. I could extrude the 2printbeta PLA as low as 170-175. I have to extrude UM PLA at 195 minimum. It's also much much more viscous and sticks less well.

The weirdest thing about it is, i've got it to print the single-wall object relatively nicely (some random, slight Z striations here and there, but nice and even) but the moment i try printing something with infill, everything goes crazy. The first three layers get wider than the ones above, the ones above don't even have straight walls (they're wobbly as hell) and about the only thing that looks good is the actual infill, which is nearly perfect. Too bizarre.
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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby orcinus » Wed Jul 18, 2012 1:13 pm

Some photos of the above...

Image

Image

Image

Oh, and yes, i've had the fan on.
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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby Medel » Wed Jul 18, 2012 2:20 pm

That's exactly my experience. I was using some garbage red PLA from an amazon seller (I assume straight from china) that I would print at 170-175, switch to UM and can't get consistent flow until 185 minimum and it doesn't stick to the build platform as well... I thought it was just me!
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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby Enraged » Wed Jul 18, 2012 5:39 pm

I think it's tuning as well, but I'm using UM PLA and I have issues getting the first layer to stick, even on blue painters tape. It seems I either have the hot end too far away, so I add a layer of blue tape, then it's too close and plows through things its already printed? However, once the first layer sticks, everything seems to work fine.
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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby orcinus » Wed Jul 18, 2012 9:27 pm

I need to keep my bed at 55-60 for the first layer of UM PLA to stick. And it has to be absolutely pristinely clean.
And the parts pop off the bed the moment i touch them. Printing on glass, BTW.

For the 2printbeta PLA, 40 degrees was enough and the parts would stick so well i'd have to pry them off with a knife.
I actually managed to unclip the glass from the hotbed once while trying to pry it off!

Weird, weird stuff.

Also, i keep getting odd yellowish (not brown) residue here and there while printing and the flow is horribly uneven.
Plus, the pressures are so high i'm getting some black PLA ooze between the PTFE insulator and the heatsink, which in this particular hotend's case means PLA oozed all the way up between the barrel and the PTFE (the barrel goes about half way up the PTFE insulator) and then back down the insulator to the joint with the heatsink. Pretty bizarre.

Also, apart from horribly uneven flow, i've got no explanation for the spaghetti look of the perimeter walls. The cube i've posted above is relatively mild case. I've tried printing the companion cube thing (this one, i think: http://www.thingiverse.com/thing:13588) and it turned out horribly. The first 3-4 layers are perfect. After that, it's a complete mess. There's not a single clean corner, all of them either have blobs or dents and some layers look like they're completely missing, because they turned out too small. And no, it's not a Z wobble, neither of those artifacts was present when i was printing with other PLA.
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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby orcinus » Wed Jul 18, 2012 9:29 pm

One other thing i've noticed is that the black UM PLA seems to harden almost directly, with minimum time spent between the glass transition and melting point. It's as if its glass transition has been nudged from 55 degrees up to something like 100 or even higher.
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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby orcinus » Thu Jul 19, 2012 2:19 am

I did some testing with free air extrusions and came to the conclusion the issue is viscosity.
There's a noticeable pause between the extruder going off and the extrusion actually coming through the nozzle.

It's even worse when you extrude for a while then stop.
The extrusion just keeps on going out for a pretty significant amount of time. And i don't just mean regular ooze - it's a clean extrusion.

That even makes sense w/ regards to the leakage i'm seeing - the pressure in the hotend is consistently extremely high.
I had absolutely no leakage with any filament till now.
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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby Enraged » Thu Jul 19, 2012 2:35 am

probably a stupid question, but have you calibrated your extruder properly? I had a few issues with mine when it wasn't properly calibrated.

also, you can add retraction in Slic3r, it might help relieve the pressure in the hot end during moves when no extrusion should be happening.
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Re: Orcinus' Build Log (was: Thermistor insanity)

Postby orcinus » Thu Jul 19, 2012 10:16 am

Yup, that was one of the first things i've checked.
It was off by a little so i've corrected it, but it didn't change anything.

Oh, and i've got retraction on, but had to actually reduce it a little (both acceleration and amount) because it was causing gaps near retraction points (for the exact reason i've mentioned, i assume - the plastic being too viscous and taking too much time to start flowing again after a retract).
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