Rotating Bed?

I have had my R1+ for a few months now and have been getting some very nice prints.

I noticed the other day, however, that the bed has a bit of horizontal "slack"...enough that when the printer is changing directions in the Y-axis, I can see the bed "rotate" very slightly. With the belt attached off center, it seems to rotate clockwise when the Y-axis is decreasing and anti-clockwise when the Y-axis is increasing.

Is this a problem that I should be concerned about? I haven't noticed any obvious problems with my prints, but I have also not printed anything very large yet, nor am I confident that I would recognize a problem caused by this in the print yet anyway...

Any insight would be appreciated!

 

Thanks for your response!

I took your advice and lifted off the glass to check for loose parts. The bearing pillow blocks were screwed in reasonably tight, the gantry frame seemed to be pretty solid as well, but pushing horizontally on the frame showed quite a lot of movement of the rods within the bearings themselves, especially when the frame was extended any real distance away from center.

So I went ahead and bit the bullet; removed and replaced the linear bearings with a new set. The new ones fit into the housing very snug and I was careful to not damage the bearings as I reinserted the rods.

After getting everything back together I did notice a marginal improvement, but the problem still persists.

Any other suggestions? Would the tension of the belt have any effect? I checked for alignment of the stepper pulley and idlers, but they seem to be pretty straight and didn't ride up or down during full motion of the bed. (I also made sure that the glass magnets were all sitting properly in their recesses)

I do admit that I forgot to check for alignment of the ball bearing channels in the lm8uu's... perhaps this is the problem? Unfortunately I am too tired tonight to go back in and check that, but perhaps I will do that tomorrow... (I'm also hoping that I didn't replace crappy bearings with another set of crappy bearings)

 

TL;DR: I fixed it by throwing out the junk bearings that came with the printer and then properly orienting the replacement bearings.

This has been an interesting learning experience. I ended up taking everything apart again and tried just about every orientation of the bearings that I could, reassembling and testing each configuration.

While I thought that the correct/perfect alignment would be a 45 degree angle for all bearings, it turned out that the best was to use 45 degrees on the belt-side, and 90 degrees on the opposite side; a very counter-intuitive setup to me!

Once assembled again, the bed is now rock solid and all chatter is gone. Even tugging on the gantry frame side to side results in very little movement. Normal operation of the bed yields no movement that I can discern.

My prints are also now dead on! A slight problem that I was convinced was ribbing and/or bad extrusion rates completely vanished.

I'm now completely in love with this printer!