[JerryBurks]

Just a question of curiosity:

I built my machine using high grade Kuroda GG1515 ground ball screws, pre-loaded for zero backlash. They do an excellent job and I try to keep them in good shape with proper lubrication and dust shields.

As it happens I place parts to cut typically on the same spot of the table, mainly out of convenience. Now I am wondering if I should rather clamp them on different spots to distribute the wear on the screws and linear bearings better. Or are the screws and ballnuts anyway so durable that it does not matter and they will survive me, given that I use the machine in average an hour per day? Most of the work the machine does is short stroke 3D and V-Carve. I could not find much information about durability and wear on the ball screw manufacturer's web sites.

Any opinion? Thanks!

Edit: Sorry, that question belonged in the higher level section, not the project log.

[RomanLini]

Hi Jerry I'm not a Mech Engineer just a designer but as far as I know ground screws are case hardened and will probably have better life than most of the linear bearings people buy especially those chromed steel round rails (China style).

However even on top quality machines that have seen lots of use you can see wear marks on screws and rails etc, so it's worth keeping in mind that the part of the machine you are using is getting more wear than the part you are not using.

You might try asking in the metalworking machine section of the forum there are more ME types there and their machines make higher forces, so wear is more prevalent and they can probably give more info.

[louieatienza]

I believe Nook has a life expectancy calculator on their website. THK also has a downloadable document with the formulae. But IIRC a member here did the research a while back and for a rolled ballscrew it can be in the millions of feet. I would guess a precision ground ballscrew, made to tighter tolerances, should last longer. Also keep in mind that your machine is nowhere near the weight that ballscrews are capable of handling; far exceeding the load rating of your linear bearings!

The best place to ask would be the mechanical engineering, linear and rotary motion forum; there are a couple guys that are experts there.

[ger21]

I've been using big, heavy, and fast routers for the last 15 years.
One for 10 years, moving about 1000 lbs at 500-600ipm at very high acceleration for about 40hours/week, with no noticable wear.

The one at my current job is bigger, heavier, and twice as fast. It's 5 years old, but I don't expect to see any wear on this one either.

They do both have automatic lubrication systems, but there's really very little friction involved. They move so freely that the 1000+ lb head will start moving if you lean against it with the power off, with the screws being backdriven.

[JerryBurks]

Thanks for the feedback. It looks like I should not really be worried and place the work pieces anywhere I want. I just don't have any practical experience with ballscrews and thought it would not hurt to ask. :wave: