X Axis Bearing Upgrade

Next on my agenda was to upgrade the X-Axis bearings from LM8UU to the same Self-Aligning, Self-Lubricating Sintered Bronze Bearings that I used in the Y-Axis. After printing out a bunch of X carriages, I decided I didn't like any of the designs for various reasons, not even the ones I designed myself, so I decided to modify the existing carriage.

Please note that is you do this, you cannot go back to the LM8UU as the bearing outside diameters are different (15 mm vs. 15.9 mm).

After disassembly of the X-Axis Carriage this is where things get interesting. Took my carriage to the drill press, but any drill can work with some care. Chucked up a high speed steel (it's what I had) 5/8" drill bit. A 5/8" drill bit is 15.82 mm so it is close enough to get a snug fit on the bearings. Drilled out the two holes that hold the LM8UU bearings. Then used a few Q-Tips soaked in acetone to smooth out the surface of the the holes on the inside and to gain the few hundredths of a mm I needed. The new bearings then just press in. Used the same technique to "pre break-in" the bearings once installed (outlined and video link in Y-Axis Upgrade thread). Had to use the same Q-Tip / acetone trick on the left X-Axis Idler Arm as there was a small discrepancy in the width of the two X-Axis rails (measured exactly 83 mm c-to-c on the right, but 82.7 mm c-to-c on the left) which caused the X-Carriage to bind near the X-Axis home position. Reassembled.

Here is a video after installation. It demonstrates how much less noise there is with these bearings over LM8UU's. The first few seconds are with no movement so you can get a base reading on just how noisy the fans are. The video shows a Auto Home sequence (need to tune the speed and retune the stepper drivers since the bearings are a bit snugger) there is a very slight shudder which will smooth out as the bearings are broken in. Following this was an Auto Bed Level Sequence.



Y Axis bearing replacement thread located here.

 

Yeah, there is a trick, you need to follow the video in my Y Axis thread. It shows how to break the bearings in, the heat produced help set the bearings in place. The bearings can adjust for as much as 5% mis-alignment.

 

I cracked on of my X Idler Arms (the left side), when the Robo replacement gets here I will take a video of the run around the bed 100 times gcode file I wrote, so you can see just how quiet it is. You will be very surprised.

 

@danzca6 That is a great way to implement this upgrade. Thanks for the work.

 

Fusion 360 is the way to go for free to use programs, don't care much for the web based stuff, and can't afford Solidworks, but Fusion 360 does nearly everything Solidworks does anyway, at least for my needs.

So I have had this upgrade installed about a month now, and the only issue I ran into was the need to retune my stepper driver for the X axis, it was stuttering at startup, so I tuned it to just below the maximum stepper input and now it is working perfectly.

 

I think I had a bit of binding, but after breaking it in it is much smoother now and of course quieter, I have not revisited the stepper driver.

 

Answered in Shoutbox.

 

Yeah tried to make the description as complete as possible. These two upgrades have made a world of difference to my Robo, it's not quiet, but it doesn't sound near as bad as it did before, and maintenance is easier too since I don't really need to lubricate the rails. Just a quick wipe with a dry cloth and it's good to go.

 

Most slicers have an adjustment value used for inside perimeters, Slic3r calls theirs XY Size Compensation and it is under Print Settings >> Advanced. They define it as

@KTMDirtFace I sent you solid models.

 

I may try these next time I need to deal with bearings:

http://www.igus.com/wpck/3637/drylin_r