[Dave.Kellogg]

Hi All,

I'm thinking about how to break down the CNC conversion of my RF-45 into managable stages. I'd like to keep the machine as usable as possible between stages, to help convert itself. I also envision that some of the later stages requie more $$$, so I'd like to pace the expendatures for motors, PC, etc.

One thought is to convert the axes (perhaps one at a time) from acme to ballscrew. Then at a later stage I'll add the servo motors and computer control.

I'm very aware that a plain exchange from acme to ballscrew will cause huge problems with back-driving.

But this is my thought (and question): What if I arranged a spring-applied brake/clutch on the ballscrew that would be automatically released when the handwheel is turned? If the handwheel is not being turned either CW or CCW, then the brake is applied. Turning the handwheel in either direction would release the brake, but only while the handwheel is torqued.

I'm still mulling over just how the mechanism would work. A shallow 'V' ramp is one thought. (Suggestions are welcome!)

But I'm also interested in opinions as to the overall feasibility of the approach.

The objective of breaking the build up with an intermediate temporary mechanism is attractive, particularly for those of us without a spare mill. Once the full CNC control is available, I'd remove the handwheels and clutches.

Any thoughts?

[underthetire]

We run ballscrews on ALL our bridgeports without any kind of brake. As long as the gibbs are adjusted correctly, no problems. Sometimes on larger cuts, we do lock an axis with the gib locks.

[hoss2006]

just put a little tension on the gib lock if you feel any back driving, most likely during climb cutting.
Also, unless you put a left hand ballscrew on the y axis (usually), you'll have to get used to cranking it opposite of normal.
My preference would be to cnc with the stock screws first, then go to ballscrews as I have in my phase 1 and phase 2 conversion for the g0704.
Hoss

[SCzEngrgGroup]

It would make a whole lot more sense to do what many here have done: Put the motors on FIRST, using the stock leadscrews, and have a CNC machine you can use to make parts. Then replace the leadscrews with ballscrews later. There's no way, short of electric/hydraulic/air brakes, that an automatic brake like you describe won't allow the axis to move some distance before the brake engages. Plus, you'll spend a lot of time building such a mechanism, and getting it to work reliably, only the throw it all away once you finish the conversion.

On all of my machines, I first built very simple, crude motor mounting brackets, and got the machine running as CNC machines in a day or two. Then I used that new CNC capability to make "nice" parts to do the final conversion. The initial conversion can usually be done with little more than a hacksaw, hand drill, and perhaps a very small number of very simple, manually milled parts. Do just X and Y first, and you've got 90% of the functionality of a 3-axis machine with very little effort or cost.

Regards,
Ray L.

[TiagoSantos]

I agree - it's much easier to just bolt on the motors to the stock leadscrews initially! If you adjust the brass nuts you'll probably have under 0.010" backlash. You'll still hate it, but it WILL be usable for a while. I made the motor mounts for my RF-40 pretty much like Ray mentions - hacksaw, hand drill (and a file to enlarge the holes that weren't quite drilled in the right place! haha..) and some very basic milling on the RF-40 itself.

Once that was done, I had a rough but functioning CNC mill that helped me machine the ballnuts and bearing mounts when I bought the ballscrews a few months later.

I've been doing it in as little baby steps as I think it could ever be done, small improvements at a time while trying to make sure I always have a machine to keep working with. But I do appreciate your thought of spreading the expenses over a larger amount of time, and the motors and controller are probably the biggest single expense most of us make on our conversions. On the other hand, if you get that one done and over with, you're much more likely to be willing to make the smaller subsequent purchases - rather than spending a couple grand bit by bit, and in a few months/years, when you're tired and frustrated, having to stomach the thought of splurging a big chunk on the electronics!

[Mad Welder]

Hi there Dave:wave: I'm another one who left the ballscrew change till later and used the stock leadscrews with temporary motor mounts and I use my build now to build better parts for itself. as my build is a build in progress...like yourself I've only one mill......now mine is only a baby brother to your RF45 but have a glance at other build threads and you may get ideas of what some of us are doing

[Dave.Kellogg]

I knew I'd get some good feedback -- So I'm glad I asked!!

Looking at the project the way you guys suggest makes a lot of sense. Basically, it is just reversing the electrical and mechanical parts of the project, and I'm OK with that.

Thanks for the responses!
Dave Kellogg

[asuratman]

Hello,
What about lathe, anybody run ballscrew on manual lathe?