Strong vibrations in ball screw linear actuator - is it normal

**mbridge87** · 05-01-2021

Ha ha ha! That's some pretty good stress testing!

Good to hear that I wouldn't have caused the damage. In my initial test when I was setting current etc. for the first time I remember the marked performance increase when going to the higher current so clearly it's been like this since day 1.

One other very quick question, I have a job next week which I want to use this on. It won't be very taxing, slow moves, nothing crazy, and it still works fine just makes noise at that speed. Do you guys think it's still ok to use this? I'm not going to cause further damage? Hard to say I know.

**JAZZCNC** · 05-01-2021

Originally Posted by mbridge87

One other very quick question, I have a job next week which I want to use this on. It won't be very taxing, slow moves, nothing crazy, and it still works fine just makes noise at that speed. Do you guys think it's still ok to use this? I'm not going to cause further damage? Hard to say I know.

I can't imagine it will do much damage provided it's not working for a long period, but like you say it's hard to know. Please if it's anything that is bent then the damage is done already.

**mbridge87** · 05-01-2021

Thanks Jazz. It would be working for two days but on a video shoot so nothing like being used for CNC. Most of the time it won't be doing anything. Cheers for giving your opinion.

I've just had a reply from the manufacturer and I'm waiting to see if it's ok for me to take it apart. Fingers crossed I hear from them tonight and then I can investigate this tomorrow.

**mbridge87** · 08-01-2021

Hey everyone,

So I've started investigating things today. I need to read through the thread again and see all the suggested things to test but so far I have:

1) Taken off the motor and tested it on it's own. It was fine. This was the loudest it got:

https://drive.google.com/file/d/18nG...ew?usp=sharing

2) Removed the top and tried moving it by hand and visually inspecting. Moving it by hand seems to suggest to me that there is a problem. I recorded another video to show you all:

https://drive.google.com/file/d/18mv...ew?usp=sharing

What do you all think?

**m_c** · 08-01-2021

There's definitely something wrong with that. Sounds like some contamination.

How does the ballscrew feel when you turn it by hand through the sticky section?
If the ballscrew feels notchy/gritty when turned by hand, it's likely to be something ballscrew related, but if the ballscrew just goes a bit tight, it's more likely to be something to do with the linear guides.

What are the coloured sections on the ballscrew? Grease?

Any chance of a couple photos showing the carriage assembly?

**JAZZCNC** · 08-01-2021

There's only one word for that noise.!!. .Grrrrrrrrriiiitttttyyyyyy bad. It should be more Swissssssshhhhhhh than growwwwllllllll.

It's not unusual to feel resistance in the movement because that's the preload in the linear bearings and ball-nut, however, the sound should be more of a Swish than a growl.
So absolutely got something going in there and I'd tip it's the ball nut doing most of the growling.

I would remove the bolts that attach the carriage to the ball-nut and move the linear guides on their own. This will identify the bad guy.

I can't quite see on the video but do the rails have bolts holding them down in every hole.? If not then you could also have an alignment issue which is compounding the issue. Linear guides are great when set up correctly but unfortunately because they are precision components they don't accept sloppy fastening or poor alignment very well and will binding and can growl if the alignment or parallelism is out.

Time to move onto the next phase and take those bolts out of the ball-nut. It should soon become clear where the problem lies.

**mbridge87** · 09-01-2021

What are the coloured sections on the ballscrew? Grease? - Yes they are

Any chance of a couple photos showing the carriage assembly? - I've taken a few photos this morning, lots of the ball screw in the area where it gets stuck. Hopefully these will be helpful:

https://drive.google.com/drive/folde...AM?usp=sharing

I just started to remove the bolts then realised I need to take the whole thing apart (the metal surround/case). Sadly, I've got way too much prep to do for this job next week so I've not got the time right now. I'll have to come back to this after the job is complete.

Thanks everyone. I'll post more once I have time again

**mbridge87** · 09-01-2021

Strange development. Having put it back together, it's now running even worse. I say strange as I barely did anything. All I did was decouple the motor, remove the top part of the carriage and then begin to remove a few other screws until I realised it was going to take too long. Then I put it all back together...

I've tried coupling the motor again a few times but it's not helping. I also took the carriage off and am running it like that but the problem is still there...I'm not really sure how this is happening but it's definitely struggling in that same place. The place it gets stuck

**mbridge87** · 22-01-2021

Hey everyone.

So I've finally finished my shoot, it was a very busy ten day shoot but glad to be working given how things have been this year.

Now I've got time to investigate a bit further, I removed the ballnut from the carriage and moved each component individually. The carriage moved perfectly on the linear rails, no sticking, juddering etc. Moving the ballnut by hand it did feel as though it was oscillating a little rather than moving perfectly on axis but it's hard to say if what I felt is normal given I have so little experience with these machines.

When I put the ballnut and carriage back together the problem returned. This suggests to me that the issue resides with the ballnut + ballscrew but I'd love to hear opinions. As usual I recorded a couple videos so you guys can see what's going on.

https://drive.google.com/file/d/1EfN...ew?usp=sharing

https://drive.google.com/file/d/1Ele...ew?usp=sharing

In the meantime, the Chinese company have asked me to locate the issue and then they will send replacement parts. As such I'd really love to hear what you all think. Am I right in thinking the cause is the ball screw? If so, is it difficult to replace this part?

Thanks!

**Gary** · 22-01-2021

As Dean pointed out, this sounds like a bent screw.
if you can remove the screw and the stage moves freely, this will be a good indication where the trouble lies.