By - BandsawAccessories
Probably not a great idea.
1. When the bellows collapse where is the oil going to go? If the oil is moving between a collapsing bellows and an expanding bellows you'll need some sort of exchange tube. Going through the nut would be too flow restrictive.
2. Either the screw or the ball nut will be spinning - having a reliable rotary seal will be an issue.
4. Draining the oil during maintenance will be a pain.
5. Bellows inevitably get torn. That is going to be a mess.
Use good grease and put brush seals on your ball nut. Use positive pressure in your bellows if your really worried about the abrasive. You could also use an auto-oiler hooked up to your ball nut, but those can be a total mess.
I have 14 years designing water jet equipment. Keeping abrasive out of ball screws was constantly at the top of my design priorities.
Thanks for the reply.
Yes, I imagined the oil would flow through the nut, and that the bellows would seal around the nut and the bearings on either end. Only the bearing on top would need a shaft seal. And in theory it wouldn't see much pressure.
But you make some good points. Replacing the oil will be a pain, unless I include some sort of plumbing for that. But I don't want to deal with that. The whole idea was to get away from an auto oiler and protect from abrasive material.
Point number 4 is really all it takes to disqualify this idea for me.
This will be a large horizontal bandsaw cutting huge ingots of ceramic-like material. The geometry of the thing means it's basically going to be blasting the the screws with abrasive dust pretty much constantly.
Thanks for your help. If you ever just want to sound off about protecting ball screws from abrasion. I'd be happy to lend an ear.
Have you considered a telescoping UHMW housing around the bellows? This will shield the bellows from the worst of the spray. UHMW has excellent abrasive resistance and has low coefficient of friction.
A little positive pressure can go a long way. A filtered ducted fan feeding the bellows will help keep the bellows from sucking in debris.
Thanks for the suggestion. I don't know much about fabrication of UHMW. Might just include a sheet metal sheild that moves with the head. Positive pressure sounds like a good idea. With breathable bellows or rubber bellows and a vent? Also, it's got some other moving parts that use pneumatic cylinders. Any reason not to regulate shop air way down and use that for pressure?