Z axis threaded rod and smooth rod not parallel  

RE: Z axis threaded rod and smooth rod not parallel

I thought the images in the post above would be clickable, opening the full resolution ones, but looks like that's not the case. Re-posting them here:

RE: Z axis threaded rod and smooth rod not parallel

If you look carefully, you should notice that the threaded rod isn't actually captured in the top bracket, only the smooth rod. Actually, with the z-axis all the way down you should notice that the top of the threaded rod has a little play. The threaded rod's only function is to move the z-axis up and down. The smooth rod does all the work of making sure that the carriage is stable in the x and y directions.

Also, your measurements are all suspect. You are using your calipers wrong.

RE: Z axis threaded rod and smooth rod not parallel

Does loosening the screws in the trapezoidal nuts affect your readings?

RE: Z axis threaded rod and smooth rod not parallel

If you look carefully, you should notice that the threaded rod isn't actually captured in the top bracket, only the smooth rod. 

Does loosening the screws in the trapezoidal nuts affect your readings?

RE: Z axis threaded rod and smooth rod not parallel

The calipers are not designed to be used that way. 

Use the interior jaws, (smaller pointy ends), one jaw against the smooth rod, one jaw at the top (major radius) OR bottom (minor radius) of one of the threads on the lead screw. 

Or, use the exterior jaws to measure the outer side of the smooth rod to the outer major radius of the lead screw.

RE: Z axis threaded rod and smooth rod not parallel

Actually, with the z-axis all the way down you should notice that the top of the threaded rod has a little play

I can push the rod over with some force, but it springs right back to the inside edge of top bracket.

RE: Z axis threaded rod and smooth rod not parallel

Try loosening the screws which locate the Black POM nuts (Trapezoidal nuts) on the lead screw, then drive your X carriage UP and DOWN the Z axis a couple of times, then re tighten the screws holding the POM nuts in place, this may resolve your issue. 

regards Joan

RE: Z axis threaded rod and smooth rod not parallel

The calipers are not designed to be used that way. 

Use the interior jaws, (smaller pointy ends), one jaw against the smooth rod, one jaw at the top (major radius) OR bottom (minor radius) of one of the threads on the lead screw. 

Or, use the exterior jaws to measure the outer side of the smooth rod to the outer major radius of the lead screw.

That's precisely what I'm doing. I took each measurement like so:

But for the sake of everyone reading this post, I flipped the calipers around before taking the picture:

So each picture above is just intended to convey what the reading, not show that I know how to use the calipers correctly. That's what I meant when I wrote:

Note that I did use my caliper correctly; I've just flipped it around for the sake of showing the readings in the correct orientation for the photos.

"Correct orientation for the photo" was intended to mean "oriented so that readers don't have to read the numbers upside down". I have practical reasons that I couldn't take the inner distance (due to my cramped work space) which would have otherwise had the digital display upright, and I really didn't want to use an image editor to add text labels showing the measurements, and I didn't want to flip the image (because the printer being upside down probably would have confused people, and again, I really don't want to deal with image software), so I just pulled the calipers away, flipped them around -- while still holding them at the right height -- and took the picture. That was the most practical approach given my constraints. Sorry for the confusion.

RE: Z axis threaded rod and smooth rod not parallel

Try loosening the screws which locate the Black POM nuts (Trapezoidal nuts) on the lead screw, then drive your X carriage UP and DOWN the Z axis a couple of times, then re tighten the screws holding the POM nuts in place, this may resolve your issue. 

Thank you for the suggestion. Unfortunately, I did just as suggested, but there isn't any change.

Here's a video showing just how bad the offset from center is; if I lift up the top brackets to free the threaded rod, it swings quite a bit:

RE: Z axis threaded rod and smooth rod not parallel

So, I might have an idea about why this is happening. I noticed a small crack on the right side, so I pried back the thin piece of plastic to look inside the print:

My guess is that the infill to the right collapsed, and that the smooth rod has now pushed too far into the printed part, causing the X-axis width to shorten. This theory is consistent with the fact that the tilt is almost perfectly identical on both sides of the printer. Also, when I remove the top brackets, the smooth rod and threaded rod both lean in towards the center of the printer.

I'll try reprinting this part, and see if that resolves the issues I'm seeing.

Thanks for your help thus far, everyone!

RE: Z axis threaded rod and smooth rod not parallel

When you get it back together, the Z-rods fit tight into the upper supports, and the Z-lead screws fit into wells in the top supports: they really can't be that far out of adjustment without grinding the supports.

Also - as you reassemble the X-Axis - test fit each rod by itself in each part. Wouldn't hurt to mark the depth of the holes on the rods so you know when they are "home" ... I found tamping the rods into the right bearing guide first, then using a very slight twisting motion helps move the rods into place in the motor end.  Your mileage may vary.  A few people recommend using an 8 mm drill bit to ensure the rods will fit without breaking the plastic.