Converting to Ball Screws

[indy4x]

Just toying with the idea of converting to ball screws on my mill but I know nothing about this kind of conversion

The currently has 28mm dia feed screws on the X and Y axis, would I need to be getting ball screws with a similar dia screw?

Mill is an old Warco WM-20 or similar, table size is approx 900mm x 225mm

Warco WM 20 Milling Machine - Very High Specification Mill

Highly accurate precision mill Includes 3-axis DRO with glass optical scales Includes power feed & coolant system Operates safely from a single phase (240v) supply Tested for Accuracy - Report Supplied Excellent Spare-Parts Availability 12-Month Warranty Fast Delivery to UK mainland - call for a...

www.warco.co.uk

Thanks

 

[striker]

I believe that ball screws are only suitable for CNC. There isn't enough friction for them to hold position unless attached to a stepper motor. At least this is what I was advised when I asked about doing it for my z axis on my mill.

 

[fizzy]

Yes only for use with stepper/servo motors really. They are so free turning they will almost move under their own weight.
Mind you why not do a CNC conversion. Not so difficult or expensive these days.
You can get a paddle to control by hand if you wish.
As it is a Bridgeport style mill you will need some pretty hefty ball screws and nuts. Also some half tidy servos etc.

 

[m_c]

What @striker says, but on that size of mill you could drop to 20mm or possibly even 16mm.
20mm would be better, but the limitation would be around how much room there is to fit the ballnuts in under the table.

 

[Robotstar5]

I believe that ball screws are only suitable for CNC. There isn't enough friction for them to hold position unless attached to a stepper motor. At least this is what I was advised when I asked about doing it for my z axis on my mill.

Some early electric robots used ball screw drives, if they weren't parked in a certain "balanced" position they would fold under their own weight, later models had brakes on the drive motors to hold them in position.

 

[Erie Fred]

Yes only for use with stepper/servo motors really. They are so free turning they will almost move under their own weight.
Mind you why not do a CNC conversion. Not so difficult or expensive these days.
You can get a paddle to control by hand if you wish.
As it is a Bridgeport style mill you will need some pretty hefty ball screws and nuts. Also some half tidy servos etc.

...and then put it online so we can drive it live on the internet....

 

[indy4x]

Thanks for all the replies, guess it's a no then

 

[minimutly]

Yes only for use with stepper/servo motors really. They are so free turning they will almost move under their own weight.
Mind you why not do a CNC conversion. Not so difficult or expensive these days.
You can get a paddle to control by hand if you wish.
As it is a Bridgeport style mill you will need some pretty hefty ball screws and nuts. Also some half tidy servos etc.

Ah, and hefty is expensive, so I would suggest against it. Expect to spend £1500 on a Bridgeport diy, maybe more.

 

[Shox Dr]

I fitted 1605 (16mm dia 5mm Pitch) ballscrew with an anti-backlash nut, to my M300. I can confidently state its a mith.

They do NOT move. i have a 5mu resolution magnetic reader fitted the DRO doesn't flicker. even on the heaviest of cuts.

 

[m_c]

I fitted 1605 (16mm dia 5mm Pitch) ballscrew with an anti-backlash nut, to my M300. I can confidently state its a mith.

They do NOT move. i have a 5mu resolution magnetic reader fitted the DRO doesn't flicker. even on the heaviest of cuts.

It's definitely not a myth.
The spindle on my big mill will drive the Z screw and servo if I pull it down with the power off.
I should really have bought a braked motor for it, but didn't really think about it at the time.

Whether they self-drive or lock depends on how much friction/stiction is in the system.
Something like a horizontal dovetail/box way could probably maintain enough friction to avoid being pushed, but something vertical or with some low friction slides is not likely to stay in position.

 

[Pete.]

The lead angle of the screw is also a factor. Ballscrews with high leads will back-drive much more readily than those with smaller leads.

 

[pressbrake1]

I believe that ball screws are only suitable for CNC. There isn't enough friction for them to hold position unless attached to a stepper motor. At least this is what I was advised when I asked about doing it for my z axis on my mill.

Depends upon lead that is all
It’s the other way around cnc are only suitable for ballscrews

 

[pressbrake1]

You can by ball screw conversion kits for Bridgeport

 

[pressbrake1]

 

[Brad93]

Was just about to say many rebuilt bridgeports use ball screws

 

[Brad93]

that looks like a first class rebuild

 

[pressbrake1]

that looks like a first class rebuild

They’re not silly boys

 

[Agroshield]

This might be useful if anyone wants to do some calculations:

How to determine if a screw will back drive

Lead screws typically have a very low chance of back driving, whereas ball screws are more likely to allow the load to fall.

www.linearmotiontips.com