Solved - Excessive Whipping on XR Ballscrews

Seeing excessive whipping on the Y1 ballscrew when operating the break-in routine (400 IPM). The Y2 side is fine. Tension seems consistent between the two sides and is within spec (3/8" movement by hand). In fact, I’ve got noticeable deflection in both of the far side mounting brackets - don’t want to get past some yield point…maybe I’m paranoid. Reset the ball screw end bearing mounts using the bar holding tool and reset the motor assembly alignment to the ball screw. Made no difference. Pretty frustrated at this point. Will try to measure sag at a set weight to better calibrate.

Link to video: https://drive.google.com/file/d/1tnkO5QEpTe2pUo2QiQiFrkNNuqmCuiHM/view?usp=sharing

This is a square up against the frame and against the bracket holding the ball screw mount. About 1/8" deflection.

I think this one is solved. Worked through all the possibilities and landed on a problem with either the ball screw or the hub it is mounted in. Indexed both. The hub is definitely not concentric to the ball screw (.075" TIR). The resulting vibration seems to set up a harmonic thing causing the whipping. Langmuir support is calling tomorrow. Should be an easy fix.

Langmuir is sending replacement part. They were great to work with.

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glad to hear…you can change the title and add “solved” to it

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I’m glad to hear someone else experienced this problem, however both sides of mine are doing it although not as severe as yours. I haven’t checked the runout on the hubs yet. I’m more curious to know how much load did you put on the screws to acheive the proper deflection? I was going to use a fish scale for loading them but it would be helpful to know how much pressure is needed.

I was very deliberate about the 3/8" deflection specified in the manual. Used a ruler and careful eyeballing using “reasonable” downforce by hand. Likely about 10 lbs of down force. I do wish Langmuir provided a more objective measure - fish scale sounds like a good solution actually. Here is a link to indexing the parts (ball nut and ball nut hub: https://drive.google.com/file/d/1JCx_JsElTKiscQdSCib7rFOb2NdQoc7Z/view?usp=sharing). There will be some vibration inherent in this setup. The TIR I’m seeing produced a LOT of vibration and was clearly out of spec. New ball nut hub will be here Monday and I’ll update the forum.

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Replacement part took about 20 minutes to install. MUCH better performance - vibration is way less. Very happy with the table at this point. For anyone in the same position, the gantry should be at the far (not home) end of the table so you can remove the ball screw from the hub without the ball nut coming off. That’s the only catch. Make sure the ball screw is inside the belt on install and the rest is super easy.

I’m glad to hear that solved your problem. When unique situations like this occur we always appreciate the feedback so we can tailor solutions for future customers who may encounter a similar situation. Thank you for being so thorough with your investigation and prognosis. That would have been a tough one for me resolve from my office chair. Thanks for making my job easy. Happy cutting and Merry Christmas to you all.

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I wish they would have included a torque number when adjusting the deflection , and maybe they will eventually, a dial torque wrench would work perfectly if they only provided a number as the force by hand is very subjective to each person

Deflection will get you a more direct measurement vs torque (grease and lube on those ball screws can mess with a torque setting).

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I didn’t think about it till reading through the post but a trigger pull gauge (like used in measuring lbs of pull on a gun trigger) measuring ball screw deflection seems to be an ideal way to get repeatable results.

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A trigger pull gauge would work if you were hanging a calibrated weight but not if you are just pulling on the ball screw.

If they instructed ex. “Given 5-7lbs of force, the ball screw should not deflect more than 3/8” then it would. Granted, as long it the weight profiles were something like 2.5lbs, 5lbs, 10lbs one could simply use a standard free weight.