Do couplings provide any advantage over the standard plastic tubing in terms of z ribbing?
In certain configurations, the metal spiral-cut couplings can actually introduce ribbing. If your carriage has too much friction, it’ll “pop” up every couple of layers, and you don’t want to put them on machines with top motors hanging down and supporting the X axis (like the prusa mendel)
What about in an i3? Specifically a makerfarm kit.
i3 is fine to use them on. They’re not really any better as far as I can tell. That’s because the i3 uses M5/M6 rods which have plenty of give to them so they won’t overpower the 8mm rods…even with a rigid connection.
Hmm, in that case what would you suggest? I’m getting a little bit of ribbing
I may be a little evangelical about Oldham couplers right now, but the improvement they made for my printrbot GO is huge. I suspect that the threaded rods may need to be constrained at the top to make this kind of coupling effective, but I can’t say for sure as I haven’t tried.
Take a look at the before and after pic at the end of the post.
Does the ribbing match the threaded rod? If not, then you may be experiencing an incorrect layer height setting. Odd layer heights (those not divisible by the full step length of the Z motor) can cause some inaccuracy which results in the plastic “smooshing” (scientific term I swear! :D) out more on some layers and less on others.
If it does match the threaded rod, then you need to look for places where your X axis gantry is connected, make sure things are tightened up.
Thanks, I’ll give that a try. What’s weird is that these issues are new. I’ve never noticed it before this print. It may even be the new filament I’m trying with this print, although I doubt it since the ribbing is so consistent.
The metal spiral cut couplings are not intended to bear thrust loads at all, just torque. And then only to absorb minor offset and angular differences between motors and driven elements. Any use beyond that essentially guarantees eventual failure.
Turns out it was a loose hobbed bolt causing me patterned problems. I still have some ribbing but it’s very slight.