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Good evening.  I am not sure if this is the right area to ask this question, but here goes.  I am converting a Novaturn lathe that has a Sprint 1200 (400) DC motor controller and I am using a Mesa 7i76U to handle the connections.  I have the steppers moving properly, the e stop and limits working properly but am very apprehensive about connecting to the Sprint 1200 because I dont want to damage anything.  Anyway, after days of reading, testing, and more reading I am finally reaching out for help.  Does anyone know the correct wiring to connect the 7i76 (TB4) spindle connectors to the appropriate Sprint connectors?  I need to be able to turn the motor on, adjust speed, etc.  The motor does not reverse.  The contacts on the Sprint are (1) +10, (2) MIN, (3) I/P, 4 COM, (5) RUN, (6) TACH, (7) COM.  Any guidance would be appreciated.

Hi everyone,
I'm hoping that someone can help me get my head wrapped around this, and point me in the right direction.  I've spent over a dozen hours reading through threads on this forum and elsewhere - yet, I can't figure out how to proceed.

My machine is a Bridgeport Series I CNC (Boss 6) mill - and it's sitting in my shop in original condition.  I'm new to CNC (having only dabbled with my Ender 3 3D printer).  However, a close friend of mine who's helping me has a couple of HAAS mills and is a guru with Autodesk Fusion.

I've investigated numerous options for updating this machine.  The more I study this, the more confused I've become!  The simplest answer for a person like me seems to be to install an Acorn board.  I'd rather not.  I don't want to get vendor-locked (more than I have to).  The thought of a company going under and leaving me in the position of having to gut the machine and start over is not appealing.  I don't want to pay a subscription.  I like the openness and configurability of LinuxCNC, and I'm a big fan and daily user of Linux (Red Hat Academy instructor).

My goals:
* Get the old Bridgeport back to making chips again.
* Have the ability to both use this machine as a CNC, and as a glorified manual machine (using LinuxCNC as a DRO).
* Not spend thousands of Dollars on this project (if possible!).

My thoughts:
* Mount a 12" touchsceen monitor in the original control panel housing for interacting with LinuxCNC.
* Hang a pendant on the side of the original control panel housing.
* Pick up a Huanyang VFD for the spindle drive (these seem to be well-supported and well regarded?).
* Replace the ancient original Bridgeport steppers with modern closed-loop NEMA 34's (1100-1200 oz in).

My questions:
* What should I run LinuxCNC on?  I've got a spare RPi 4 sitting in my drawer.  I've got a couple of Supermicro Intel Atom-based ITX server motherboards lying around.  What's the most intelligent way to go?
* It seems that a parallel port interface is the "old-school" way of doing things.  Now, it seems that most prefer an Ethernet interface.  Is there a disadvantage of going one way or another?
* Since I have to replace the steppers anyway, is it foolish to go with a "traditional" setup rather than Ethercat?  It seems like Ethercat will be considerably more expensive (like twice the price or more) - but is it worth the price?
* Everyone seems to agree that Mesa boards are the "gold standard."  How do Pico Systems' boards compare?  Jon Elson lives like 20 miles from my house.  Does anyone have experience with his customer service?  Is it foolish to consider anything other than a Mesa?
* If I go with a Mesa setup, which direction should I go?  If I use the RPi, I could go with the 7C80 or 7C81 - I could also run an Ethernet setup.  If I use the server motherboard, I could go with a parallel port setup or an Ethernet setup.  Is there an advantage of going one way or another, here?
* If I go with a given Mesa board, what else will I need to buy?  It seems that some of the Mesa cards (like the 7C80 and the 7I95T) will hook directly to the stepper drives, while others require a separate daughter card (BoB)?
* What hardware (if any) would I need in order to use the encoders on the steppers as a DRO?  Will any of my hardware selection above affect my ability to have this feature?
* Will a cheap Amazon/Aliexpress stepper motor/drive/power supply set work, or will I need to buy the stepper drives separately?  If I need a particular stepper drive, should I go with a Gecko or something else?
* If I run a touchscreen and a pendant, is there any reason why I will need a keyboard hooked up to this machine (once it is configured)?

Sorry for all of the (possibly stupid) questions.  The DIY CNC and especially the LinuxCNC ecosystem is far more vast than I imagined.  I really did attempt to "do my homework" before asking.  There just seems to be a lot of somewhat conflicting information (possibly, due to changing technologies and best practices over the years?).

Thanks for any advice that you can provide to me!

I am looking for guidance on how to setup the C axis as a second spindle.  This is for a rose engine lathe (otbok.info/index.php?n=Main.RoseEngineLathe) where we need to use:

1. the Spindle to rotate the piece, and
2. the C axis to rotate the rosettes used to impart the design

We turn these quite slowly, certainly less than 10 RPM, and at times speeds approaching 3 or 4 minutes per revolution.  Thusly we are using stepper motors for both axes.

The end goal is to drive the spindle and the C axis simultaneously, but specifying a relationship percentage for their rotational speeds.  For example,  Is there some documentation I can read which describes 

1. How to setup LinuxCNC to treat the C-axis as a secondary spindle, and
2. The G-code I would use.

Apologies if this is already been asked and answered:  I searched the forum and could not find it.

Personally I would close the feed back loop with linear encoders, this will give actual feed back position, with a mesa FPGA this is a very well worn track with plenty of info available. Same for the spindle and encoder that also employs an index.
Sorry I'm too broke to have experience with Ethercat so really can't make a comment that maybe of use.
What kind of lathe are you working with ?
I'm kind of lucky with my Frankenstein Myford ML7\Super 7 in that I have plenty of room for the stepper motors, the only issue was the X axis, but I was able to use 10mm ballscrew and unlike most other lathes the nut is fixed to the carriage casting rather than running under the cross slide.

And for my techno babble mate, lathes conventionally use a XZ setup, Z being the carriage and X being the cross slide.
Also very few lathes, I can't think any that the average Joe would have access to lathes that use linear rails, mostly dove tails for cross slide and top slide and either plain rectangular ways for the bed,eg Myford, rectangular single prism, think 7x14 mini lathe or dual prism for the more industrial type. These are just the ones I can of off the top of my head.

Sorry to the OP for getting a bit off track.

Luckly I installed a disk brake on my lathe's spindle during the retrofit (brake is operated with pressurized air). This works pretty well for holding the spindle during cutting in a specific angle.

Not a problem, hope it was helpful.

Regarding spindle orient... I'd hoped to use orient for my lathe as a 'poor-man's c-axis' once I realized that caxis.comp wasn't doing what I wanted.

I quickly realized that is orient by itself won't hold a position.  You either need a spindle brake, or you need a servo drive that is in position mode (internally).  Servo drives in velocity-mode don't necessarily hold a position rigidly, but LCNC is perfectly capable of treating a position-mode servo drive as a spindle.

LCNC can orient a plain old VFD to a pretty exact position, but that does no good if you're trying to use live tools once the spindle is in the appropriate position.

I think you're on the right track for your first steps.  Get the spindle working as well as you can, then add the orient function.  Orient is simple in concept, but tuning and nailing the position can be tricky and time-consuming.  Especially if you have a heavy spindle/chuck.

Something else to consider... your spindle encoder need not be super-high resolution for spindle/orient functions, but for eventual c-axis work the higher the resolution the better.  And that can become a rabbit-hole when trying to balance high encoder speeds with high resolution... while remaining budget friendly.