Z-Ribbing/waviness on TAZ 4

Any thoughts on what is causing it and how to fix it?

That’s definitely something out of alignment / bent / misconfigured. For starters, is this an upgrade from a 3.2 to a 4, or a stock factory 4? I’m going to assume it’s a stock one for the moment, and that you have the default factory configuration and firmware and are using a default lulzbot printing profile.

On a Taz 4, the rods and leadscrews are constrained at both ends, so they can’t “flex” to accommodate missallignment. IN your case, the issue goes all the way up, so it’s not likely that it is the endpoints of the Z axis assembly itself. Without a picture of the printer to take a look at, I’m guessing you have something loose at the Z to X axis mounting points that is allowing the X axis to shift more than it should.

With a good set of calipers, levels and gauges, work from the bottom of your printer up to the top and verify that everything is in alignment, all the bolts are tight, the leadscrews are lubricated, the leadscrew to motor couplers are tight and locked down, etc. Make sure the distance between the leadscrews themselves at the top and the bottom of the assembly is identical, and the distance from each leadscrew to each bearing rod is correct. You may want to pay special attention to the leadscrew interface to the X axis, ensure that all the bolts there are correct. It doesn’t take being off very far to show up as a fairly major issue. You also might try swapping out the bearings if this machine has seen a lot of use.

Whats odd in this case is that it looks like every other layer is too narrow across the board front and back. Z wobble usally shows up as an every other layer slight offset in one direction. Yours looks like each other layer is just smaller than it should be. Maybe underextrusion? maybe printing in a layer height that isn’t a multiple of the leadscrew height?

A high resolution picture of the machine itself might be helpful if you can upload one.

This is a stock factory TAZ 4. Firmware is pretty much stock. I had to do a PID autotune and set the values in firmware, then re-flash.

Everything seems to be in alignment, though I’ll admit, I’m not the best at knowing what proper alignment is.

I’ve attached some pictures of my TAZ 4.
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2015-03-11 08.08.31.jpg
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2015-03-11 08.07.59.jpg

Have you emailed support? You will most likely get a better response there.

Hmm. Everything looks correct from the pictures. You might want to try removing some of the grease from the leadscrew, it is a little thick. It also looks like the bushings themselves might be a little worn or out of round. I can’t tell if it’s just reflection or not there. Might be worth a shot trying a different set of those bushings inside the bushing holder. You also might try loosening the mounting bolts for one of the two Z axis motors and see if that makes an improvement. If it does, run the carriage up and down a few times, then lock it in where it centers.

Support may have other ideas as well.

I’ll give that a shot! Will report back if it fixes the issue.

In the meantime, here’s a short video of the z-screws while lowering the gantry and me doing a belt tension test. https://www.youtube.com/watch?v=SCSoLTNjyus