Shifted mid-section

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mhorton
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Shifted mid-section

Post by mhorton » Wed Oct 08, 2014 8:53 pm

OK, I gave up on my recent troubles with ABS on one of our M2 printers and shifted to PLA on our other printer. Guess what . . . it failed again and again and again. The whole print seems to shift back and forth in the mid section during printing. The object is very well connected to the glass, so it is not actually moving, it just looks like it.

Sorry if this issue has been answered before, I just didn't know what to call it and couldn't find it in a search.

Have I mentioned recently how frustrating 3D printing is???

Any ideas?
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mhorton
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Re: Shifted mid-section

Post by mhorton » Thu Oct 23, 2014 6:35 pm

This might explain it! Unfortunately, I have two of these printers and one is broken and the other cracked, so I probably cannot even print a replacement.
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insta
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Re: Shifted mid-section

Post by insta » Thu Oct 23, 2014 7:23 pm

Glue the cracked one back together with ABS cement, and get printing some replacements ;)
Custom 3D printing for you or your business -- quote [at] pingring.org

jsc
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Re: Shifted mid-section

Post by jsc » Thu Oct 23, 2014 8:13 pm

I'm not sure what ABS cement is, but you can weld a crack back together with acetone. Epoxy or your glue of choice will also work, you just need it to last for one print (the replacement).

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Tim
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Re: Shifted mid-section

Post by Tim » Thu Oct 23, 2014 8:52 pm

I assume "ABS cement" means any kind of solvent glue, like Testors model glue.

Also 2-part epoxy from the hardware store, as Jin mentioned, works decently well with ABS. That's what I used to fix my cracked motor mount, and it's still good (although eventually I printed a replacement in PET+, which is a decent alternative to ABS).

There are several threads on this forum about cracked motor mounts. Look through them for tips on printing the replacement. MakerGear prints them with a fairly low infill percentage; Jim ("jimc") recommends 100% infill; anything 70% and up should be good. Whatever you do, don't print a replacement in PLA.

The elephant print may have support issues, too, but one thing I found out is that the interfaces between support and the rest of the print, and also places where the print doesn't have much support underneath and tends to curl up (which is basically the same problems), really exacerbate the cracked motor mount problem. The nozzle hits the layer underneath, from the side, and if the motor is loose at all in the mount, it gets knocked askew.

mhorton
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Re: Shifted mid-section

Post by mhorton » Thu Oct 23, 2014 9:04 pm

Thanks, guys. I'm just worried that the solvent will turn the crack into a break. I'm going to see if I can print one the way it is and then print several more. If not, can they be purchased?

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insta
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Re: Shifted mid-section

Post by insta » Thu Oct 23, 2014 11:00 pm

Guys, ABS cement is a premade (black) slurry of acetone + MEK + ABS. It's used for joining pipes together. It will actually fill in the cracks and solvent-weld everything at the same time.

mhorton, if you break yours trying to fix it, I'll print you one for the cost of shipping, if MG won't replace it (they're awesome about replacement parts).
Custom 3D printing for you or your business -- quote [at] pingring.org

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jimc
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Re: Shifted mid-section

Post by jimc » Thu Oct 23, 2014 11:44 pm

yes print the replacement stuff a 70% or higher infill. i usually do anything extruder related at 80 or 90%. if you go on thingiverse and search "makergear m2", somewhere on there a guy took the original motor mount model and removed the hole from it. thats the weak point they always break from. you can download it. i have been using that mount for maybe 8 mos now. its rock solid. once you get that motor mount printed do yourself a favor and print spares of all the plastic parts on the machine. they do go bad from time to time as you are finding out.

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Tim
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Re: Shifted mid-section

Post by Tim » Fri Oct 24, 2014 1:13 am

jimc wrote:if you go on thingiverse and search "makergear m2", somewhere on there a guy took the original motor mount model and removed the hole from it. thats the weak point they always break from.
Well, mhorton's motor mount broke somewhere else, just to prove you wrong, Jim. Mine cracked right across the hole, but if you look back at various photos posted about cracked motor mounts, I'd say it's pretty even between cracking at the hole and cracking near the base. Not really sure why.

insta---thanks for correcting me on ABS cement. I'll remember that. . . I don't want to go around spreading misinformation.

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jimc
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Re: Shifted mid-section

Post by jimc » Fri Oct 24, 2014 1:18 am

true, i do remember yours cracking at the base now that you mention it. in any case i think these are printed a too low an infill level for the kind of stress they are on. the weight of the extruder shaking back and forth can only last so long on a part printed with 2 shells and about 25% infill not to mention the occasional collision into a part or bed.

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