Ball Screws in Bridgeport mill?

Roger, this is great and I looked at EMC2 closely, installed it etc. In the end I decided to keep the Bridgeport as a manual mill. The downside is just too great. That's as pertains to me personally. I admire people who convert manual machines to CNC, but in my very personal case, I think that the downside is greater than the upside.

There is a downside if you can no longer use it manually. My Bridgeport CNC mill has handles so I can flip a switch to turn the motors off and run it as a manual mill. I don't know the details of your ballscrew ends, but I was thinking of you installing a timing belt pulley and the handles for running manual control. That way, switch the motors off and you have a manual mill, switch the motors on and you have a CNC mill. In manual mode, motors off, the friction of the motors would help hold position so the table wouldn't backdrive so easily.

I'm guessing that the loss of manual mill control is what you are considering the downside. Other than that the downside is the cost of the motors, drives, interface, and a space for the computer to control the CNC part. Motors and drives can be found on eBay or old machines with bad controls. Anyway, you don't have to give up your manual machine to add CNC capabilities.

RogerN

If you look up Anilam on eBay and look at the knee mills, you can see they use handwheels that the handle folds in.

Also a small picture here.

RogerN

You CAN use ballscrews in a manual mill, although you need to lock and unlock the axes all the time, as the ballscrews offer no resistance to back driving.

Most likely, what these are for was other outfits bought manual mills and retrofitted them for CNC use. Centroid, Bandit, etc. did that. The BOSS CNC frames were only made available to maybe a few other machine builders on a limited basis.

The ballscrews have no backlash, and don't develop the pattern of wear in the center that happens with the steel screws on bronze Acme nuts, leading to inaccuracy.

Jon

My own main concern is that while doing the conversion, I will somehow break something and make the mill unusable, due to my inexperience. That's the downside that I have in mind. If I had more money, and more space, I would get myself a ProtoTrak or some such or even try a manual conversion on a spare mill. As it stands now, I cannot afford to be left without my mill.

Also, with the DRO, I can do the things I usually need to do. Right now, CNC is interesting, but not very necessary. So why risk losing what I have and need, for something that I do not really need.

Ok, I was wondering what this downside was. The only time you would loose manual use of your mill would be when installing the ballscrews. I've had similar concerns about changing my machine controls. My lathe control never worked since I owned it so I didn't have anything to loose in doing an EMC2 conversion. For the mill, I plan to use the same connectors as the existing control. That way if I have difficulty getting things going, I can just plug back into the original control and run until I get the bugs worked out.

I don't know your goals of your metalworking but I remember your milling from coordinates. I thought it would be nice to have the motors move to the coordinates for you. It's something to keep in mind in case you have more of a need for it someday.

RogerN

If you have servos or steppers and a control, , you can easily use Jog to move the slide around, if you have ball screws when doing one off cutting.

Its not rocket science

Gunner

"They couldn't hit an elephant at this dist..." Maj. Gen. John Sedgewick, killed by a sniper in 1864 at the battle of Spotsylvania

Iggy, I found this example of a model engine flywheel that was machined on a hobby CNC mill.

RogerN

I agree. On the other hand, it would be a lot easier to do on a manual machine -- an evening's project -- if the spokes were straight.