First time using my LR3 in several months, couldn’t figure out why my jobs were coming out so poorly.
Then I noticed that the core assembly is loose on the beam assembly. I’m quite certain it wasn’t like that previously, and I’ve been unable to deduce what must have shifted to cause this issue.
The rear lower bearings don’t even touch the rail and I can move the whole assembly by probably 3/32" back and forth. If I lift the assembly, I’ve got more than .020" clearance between the rail and the top bearings.
Any ideas what the problem is and how I might go about fixing it?
The first photo is just a shot of the core assembly on the beam. Pretty ordinary.
In the second photo, you can see daylight under the top bearing when I lift the core assembly.
Ok - next time, I’ll search before posting… Turns out it was just the bottom bearings, though I had to tighten both of them by more than half a turn. No idea why or how they got loose.
No I think it got figured out in another thread. I wound up completely rebuilding the machine in that thread, and while it was down I had the same problem with my smaller LR3, talked with Ryan and took the core off and that one had a massive crack right through the middle. Went and looked at the old core off the full sheet machine and that’s when I found that crack
I discovered a similar problem today, however I could practically pull my core off the rails. I thought loose bearing as well, or missing with the amount of play. Turns out I had a cracked core. I should have suspected - I’ve been slowly printing and replacing parts as they’ve been suspiciously cracking here and there. Turns out either matte PLA doesn’t hold up over time or I got a bad batch. I’ve had more than just LR3 parts failing with matte. They look good coming off the printer but aren’t meant for the long haul.
Consider even the optimum strength of printed PLA, and the amount of torque that an M5 screw/bolt can exert, and of course you can crack it with those screws. It gets even more ridiculous with the M8 or 5/16" bolts.
PLA is chosen for rigidity, not tensile strength. Because PLA is more rigid, when forced, it cracks. ABS or PETg is more likely to flex, but… well, more likely to flex. Thus it can take a bit more abuse that way and survive, but it is less rigid.
PLA is within the envelope, so long as you don’t overtorque things. My LR3 core was among the first printed, and has seen a lot of use, and 2 different spindles, plus a couple of pen and lasers mounted, and the core is fine, but I don’t put much torque into those screws at all.
Now I didn’t use a matte plastic, just basic black Overture PLA. So maybe the matte stuff is different. Different colours seem to make a difference, too. I know I often have difficulty with printing white filaments, though they seem to last OK. Maybe just my imagination but I seem to have more difficulty with greens warping…
Personally had Overture Black Matte PLA delaminate too easily. Like the color and finish, but observed same behavior with multiple rolls. Am reluctant to use that particular brand-color combination for structural parts, I tried raising temp but couldn’t get satisfactory results. Am not hating on Overture, I mostly buy their filament and am usually happy with results.
So, I’ve limited Overture Matte Black PLA use for aesthetic/toy stuff, e.g. train tracks around, and under the christmas tree…
I agree. Compared to my Primo, which is much older and has seen many more jobs, All of its parts printed in standard PLA have held up perfectly well. Whereas a matte black dinosaur sitting on my desk has had his head fall off. I’m sure something’s getting added to the mix that influences adhesion and strength. Lesson learned now I’m 10 hours out from a new core.
Wonder if LR3 Core Cracks #CrackedCore occur in similar spots? Pics of cracked cores are useful feedback for where to add more material/infill? Guessing Ryan already closely analyzes pics like this.
Wonder if a few indents/marks on the model could help people double check dimension/skew before they assemble self printed parts?
Docs could explicitly call out checking/verifying before assembly. Would help with build confidence, or help catch problems sooner. Something like…
I’d 100% chalk this failure up to the matte PLA. Like I said other unrelated prints with no stess whatsoever just fell apart. The upside is I was able to tear down the LR3 and swap cores in about 30 minutes. 3D printing still amazes me in that way. You can go from broken to new part in relatively short order and inexpensively. We once had a piece of equipment break at work, trivial plastic part, but a whole new replacement component was $3500. Can’t order just the plastic part. A little measuring, some CAD and eight cents later we saved $3500.
