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tool head rotation about Y-Axis
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Description

As the tool head changes directions I am seeing some twisting.
Is this the scenario in which the tool head must be removed in order to tighten the compression on the X-Axis bushings?

Event Timeline

logan created this task.Fri, Dec 28, 7:48 AM
logan created this object with edit policy "LulzBot Hardware Products (Project)".
tutley added a subscriber: tutley.Fri, Dec 28, 7:59 AM

@logan yea i saw this a long time ago with an early quiver prototype, and i had to tighten the bushings on the x carriage. I think this is due to the 3 bushing design with the self aligner being the isolated bushing

i feel that the self aligner should be paired with another bushing and not be isolated

logan added a comment.Fri, Dec 28, 8:10 AM

@tutley There aren't any self aligning bushings on the X-carriage, at least not on Alpha

@logan ah thanks for clarifying that. Sorry i havent had a quiver in a while. Anyways i corrected it by tightening the bushings adjustment screws

logan added a comment.Fri, Dec 28, 8:13 AM

Ok I will do that before my next print

logan added a comment.Fri, Dec 28, 9:01 AM

@tutley No improvement after tightening. I tightened until I could not twist the x-carriage about the Y axis by hand but the tool head still has a very obvious rotation.

@logan is it the entire toolhead moving?

@tutley Yes it is quite noticeable, I think it may've gotten worse after I tightened the compression also. But without a video for reference or measurements I can't say for certain. Is it possible we're compressing these bushings in the wrong direction?
Looking at the assembly, the bushings are compressed front and back which should cause an oval shape, giving the tool head more room to rock rather than less.

@logan well i think you would have seen the x carriage rock without the toolhead if that were the case

@tutley To clarify, it was still rocking a little by hand but it is much less pronounced without the tool head. I was afraid to tighten any further as drag was already approaching what I would perceive to be too tight.
But if you think about the arrangement of the compression, how would it not oval the bushing elongated vertically causing more rotation?
The fact that ALL parts must be removed from the x carriage in order to adjust (tool head, cap/board cover, interface board, board mount) makes this arrangement far less than ideal.

It is printing one of your vernier scales right now, feel free to come take a look if you like.

@logan the betas wont need all those parts removed to adjust this. it is just removing the toolhead and the screws are right there

For betas could we try compressing the bushings in a direction that would be helpful? By doing so we could likely make the screws accessible from above and below without removing anything.

tutley added a subscriber: west.Fri, Dec 28, 12:15 PM

@logan yea that is definitely the whole tool head. I honestly think it is from having 3 bushings instead of 4, or that the 2 are on bottom and 1 up top with the belt mounting close to the top single bushing. Ben Baldwin ran into this when he tried to convert a gladiola to a 3 bushing set up on the x axis. Id like to come take a look at this machine at some point today.

@west do you think we can easily change the bushings to compress from top and bottom instead of front to back?

FWIW i dont think that rocking is any worse than the Taz6 chevron mount gets but i still think it needs corrected

west added a comment.Wed, Jan 2, 7:24 AM

The new part for betas seems to work, it also moves the tension screw to the from so the only thing you have to remove is the toolhead T4833. I dont see what changing the tension screws from front and back to top and bottom would do. The belt is mounted closer to the top rather than center is because of how close the rods are

logan added a comment.Wed, Jan 2, 7:26 AM

@west Because we're compressing the bushings into an oval shape. Doing so from front and rear elongates the bore vertically, whereas doing so from top and bottom would elongate the bore horizontally. We want to avoid vertical elongation of the inner bore as it will increase the motion seen in the video above.

logan added a comment.Thu, Jan 3, 8:46 AM

After loosening the compression bushings, the rotation is still there but less pronounced based off of observation alone, in my opinion. I cant think of an easy/quick way to measure that.

logan triaged this task as High priority.Thu, Jan 3, 10:01 AM

This causes a failure of circular dimensional accuracy because lumps are created at the X axis direction changes.