Kondia mill stepper motor, DRO Advice needed

Here is the situation as short/detailed as i can make it:

I have a Kondia CNC powermill (Bridgeport Clone). It *had* Summit/Dana bandit cnc, that has been removed due to condition/parts availability/outdated platform.

At this point, I need powerfeeds for X,Y,KNEE,QUILL. I need a DRO also.

Here comes my findings *so far*:

I see that for the price of dedicated axis power feed boxes, I could easily buy a less expensive open stepper motor drive packages. I could use a pulse generator to control these individually ( cheap on ebay, I'm very electrical and won't have an issue there). Pretty sure that would work to drive and lock an axis. I am also aware you get what you pay for....

With that, i am noticing i am coming close to "re-cnc-ing" the mill in the above.

I also would like to retrofit a DRO on all 4 axis. I see a nice set up on ebay with scales $600ish. Has what i want, i can deal with the glass scales.

I *ALSO* see there is such thing as closed loop stepper motors with position feedback. (See questions)

My usage of the mill:
Non official business for now.
Small parts, singles, few offs (may increase slightly, but never a production environment ).
Occational Modification of some really heavy parts (engine blocks, heads). Some repetitive.

Repair of wide range of parts.

My thoughts/questions/things i have thought of so far:

Motor size, what would sufficiently move each these axis, in both a "manual" and CNC setting? I would like enough resolution/torque for a slow speed flycutter situation, for example, in x and y. 600 oz. With 2:1 ratio for slow speed control resolution(i am aware stepper motors make more torque at low rpm). ?

1000 oz for knee? Maybe 4:1? Larger oz?

300 oz for quill? 1:1 ? It is a worm drive and not a floating quill as it is was a cnc model. This requires me to use a tap head for power tapping to help match feed speed power tapping manually. Would like good speed resolution here. Would a 2:1 drive be a better choice here?

If i use this as CNC some, I am NOT LOOKING for fast Rapids, or even youtube worthy operation would be looking to that for basic repetitive operations or possibly multiple pieces with rounds/other, that are time consuming manually.

Can a closed loop motor be used to present coordinates on a laptop en lieu of an DRO? In other words, do the motors feedback position while i am moving it manually, and would that reasonably be viewable in say mach3 or the like? If i could SKIP buying a DRO, I can spend more on the CNC aspects.

For a lower performance (i mean this in terms of speed) CNC, and using the steppers for power feed, would a package simular to this link,
Work in such a situation? I am aware it is not the gecko drive set up, and there is more to buy, and some sellers do better providing everything for a bit more(the accessories add up).

I am capable of making/have access to equipment for parts, for this, elsewhere if needed, and not scared of electrical (I'm a maintenance tech at a production plant).fabing this up will not be an issue.

Sorry for the ultralong post, trying to fit all the details in to start with.

A lot of questions, and thanks in advance. If there are any key words or phrases that could be provided for particular info, i can go read, and would appreciate it.

Why not look for used Bridgeport servos on Ebay?
Or, buy a used CNC Bport from a machinery dealer?

I don't think steppers are going to have nearly enough torque for a mill. They are used mostly in applications with zero cutting forces (3D printers, hobby level lasers). Even if they kinda work, they won't take much of a beating before they're toast. Unless someone recently came out with a really powerful, accurate stepper you'll be better off with a retrofit kit or used assorted servos.

I wouldn't be the first to put steppers on a Bridgeport. I have serservos sitting here. One in pieces. They are huge. And were direct drive. They stick out over a foot each direction. I'd rather put a shorter belt drive motor underneath, gain the real-estate back. Also would rather not have the y axis motor sticking me in the family jewels every ten seconds. Then the expense of drives for them.

Go to the Linux CNC web site (If it still exists, IDK)

Everything you ask and more is there......

Steppers are FINE! Much simpler to set up than servos. (NO TUNING PID loops to contend with. Just match the motor to the load!)

That old Bandit box will do amazing things!

You'll get better answers over the the CNC zone forum. Few here will have experience with homebrewed stepper "conversions". CNC zone is more hobby machine oriented than this forum.

Vancbiker said:

You'll get better answers over the the CNC zone forum. Few here will have experience with homebrewed stepper "conversions". CNC zone is more hobby machine oriented than this forum.

Click to expand...

I was less than impressed with the quality of contribution on the "zone" site. But that was 20+ years ago......

CalG said:

I was less than impressed with the quality of contribution on the "zone" site. But that was 20+ years ago......

Click to expand...

Last I went there it was still pretty hobby machine heavy, but that's the realm of steppers and Mach whatever. Almost nobody here deals with machines running steppers and PC based controls.

CalG said:

Go to the Linux CNC web site (If it still exists, IDK)

Everything you ask and more is there......

Steppers are FINE! Much simpler to set up than servos. (NO TUNING PID loops to contend with. Just match the motor to the load!)

That old Bandit box will do amazing things!

Click to expand...

Linuxcnc site is still quite alive. Both servos and steppers. SEM MT-xx servo motors are adequate for your mill. Having been there ... done that I would not bother to motorize the W axis. Belt driven ratios of 2:1 work out about right for X, Y and Z. You will get better control out of encoders on the ball screws than glass scales. Not enough counts on the glass scales; they are difficult to tune. However if you want good absolute position then one can use encoders on the servo motor or ball screw with a linear (glass) scale for final position. Check out the linuxcnc wiki. Use scales that are 5X the accuracy you want to hold.
Linuxcnc does have configurations that use position encoding with steppers. Not ideal but can be made to work. When a servo lags commanded position you can correct. When a stepper lags you are already in trouble and is is difficult to correct. Can be done you just have to run the steppers well within their limits. I use Servo Dynamics brushed drives (1525BR) on both my BP sized mill and my Mazak V5.
Hope this helps. The journey can be quite interesting.