Strong vibrations in ball screw linear actuator - is it normal

**Gary** · 22-01-2021

Move the stage to the end, and remove the four bolts holding the ball nut in place, then slide the stage back, and the nut should come away from the stage.
you can then see if the issue is the screw and nut.
I think the issue is more than just a dirty nut, this really points to a screw that is bent in a number of places.

**mbridge87** · 22-01-2021

Hi Gary,

Thanks for the reply,

Dean thought it may either be the linear rails or the screw. It seems obvious to me, given the quick investigation shown in the videos, that it's the screw. I just wanted to confirm that before I ask the company to send a replacement screw. As they're in China I'd hate to have them send the wrong part.

Would you agree then? Based on the videos in my post earlier that it definitely seems to be the screw?

**JAZZCNC** · 22-01-2021

I'd say it's the screw for sure, Like Gary I think it's got several issues with being bent and it also sounds gritty but that could just be the camera making it sound worse than it really is. I get this all the time on videos, the mic seems to applify the slightest noises and makes them sound much worse than reality.

If they are prepared to send you another I would take it without hesitation. But it could easily arrive in exactly the same state because Chinese ballscrews are ok for hobby routers etc, but not the best for precision stuff like this which you need to be super smooth.

**mbridge87** · 23-01-2021

Audio quality on phones is not the best but it definitely does sound gritty.

Like you said, I may as well get them to send me another but in the meantime it seems sensible to explore other options. This machine was a bit of a headache on the shoot. It was really good, software worked well, the camera moves I was able to accomplish were great but the vibrations ruined shots. Everything would look fine until I got into the edit and noticed these violent vibrations which would cause the lettering on the pen we were shooting to almost buzz for a moment.

In other words, still really interested in what you can put together Dean.

Shall I ask them to send another ball screw and ball nut? From what I understand it's hard to put those two elements together so I'd be a little concerned if I needed to put the new ball screw on the old ball nut.

**Gary** · 25-01-2021

Personally, i would get them to send both. especially if the ballscrew and nut are Chinese, Replacing a nut was always an issue, because the Chinese buy the reject screws from the big factories like TBI in Taiwan and then make their own nuts to suit the screw. But they get rejected for a number of issues like the root diameter is not within specification.
So you end up getting a replacement nut and it does not fit correctly on the screw and is either too loose or too tight.
Get them to match the nut to the screw and test its straightness prior to sending.