Ball screw preload & proper setup

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RJS100
Posts: 380
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Location: Arizona

Ball screw preload & proper setup

Post by RJS100 »

I am almost done converting a PM833 to CNC. While all the Centroid directions and materials have been fantastic, I had purchased a conversion kit from Heavy Metal CNC just as the owner (Bruce Nelson) suddenly and sadly passed away. The business was permanently closed. Somehow, I this kit was shipped to me by accident and was never supposed to be shipped. I have had to remake all of brackets and have two of the ball nuts repaired. They also shipped me deep grove bearings instead of angular contact bearings for the ball screws.

While waiting for angular contact bearings to arrive I started doing a trial fit up using the deep groove bearings (temporarily). I have two quick questions:

1. Image (Washer 1) shows the stepper motor, helical coupling and the top of the ball screw after it has passed through two bearings. I understand that I need to tighten the nuts to apply a preload on the bearings. How tight to they have to be? Also, should there be a washer between the bearing and the preload nuts?

2. Image (Washer 2) shows the ball screw with one bearing on it for illustration. Should there be a washer between top of the threads and the bearing?
Attachments
Washer 2.JPG
Washer 1.JPG
suntravel
Posts: 1967
Joined: Thu Sep 23, 2021 3:49 pm
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Location: Germany

Re: Ball screw preload & proper setup

Post by suntravel »

This is not looking like a proper fixed bearing construction....

Also adjusting preload with two nuts is, well difficult. Better is a nut with a setscrew for fixing position after adjustment.

Here is a std. construction with angular bearings, adjustable preload and seals:

https://www.upload.sorotec.de/doku/manu ... 9_soro.pdf

Uwe
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