Hardware advice

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!

Step 1: Get it operational.
Step 2: Make it long-lasting (LM guides work withput grease for a little while, but will eventually wear down and break if not properly lubricated; a system without a dust-collection solution will work fine in the short-term, but will eventuall get all gunky).
Step 3: Make improvements as you see fit.

Don't get ahead of yourself.
Use whatever you have at hand for now, then buy improments if needed.
If you don't have something (i.e. a VFD), buying a good one might be a good idea because that way it will last forever.

Perhaps the Raspberry Pi can be connected to the stepper drivers directly (via the GPIO header).

Why would you replace the steppers?

The old ones might work just fine.

Brushless motors should last almost forever (like 1000 years or so).

There is no reason a brushless motor should break or degrade.


Before you do anything, you should really give that poor old machine a good cleaning and then grease/oil moving parts and spray WD-40 over stationary exposed metal pieces to prevent rust.

Remember that most induction motors need to be relubricated every 10 years of normal service.

Thanks for your response!

This machine has an auto oiler on it - so that will be one of the first things I mess with to ensure it's working correctly. I've seen some people state that the oiler nozzles on these machines can become clogged with gunk from sitting for so long.

Yep, the first order of business will be to remove the two big control cabinets from it, and vacuum all of the "man glitter" off if it, and give it a bath and a lube!

I'm looking at replacing the steppers for several reasons. Based upon the information I've found about these machines on various forums:
* The steppers are an old design. They apparently ran at a higher voltage than most modern steppers. This requires special drives (like a DM1182). For less than the cost of a suitable "high voltage" drive, I can buy modern steppers with matching drives and power supplies:
www.omc-stepperonline.com/ys-series-3-ax...ower-supply-3-clys90
* Given the age of the steppers, many people are stating that they are likely weak - due to the age of their magnets and the type of magnets they used.
* From what I understand, these steppers are not closed-loop.
* Again, according to others, these steppers are "notchy" and "jumpy". They aren't as smooth as modern steppers, and don't have the accuracy/resolution (though, they are probably plenty accurate for my needs).

I'm sure that some "Double-E" out there could figure out how to connect a RPi's GPIO to the existing stepper drives. However, that's well beyond my level of expertise. The existing drives are cards that are plugged into a sort of backplane. They have Bridgeport's name on the boards, so I assume that they are proprietary. There's a document floating around, which explains how to reuse the existing stepper drives and steppers with Mach 3:
manuals.chudov.com/Bridgeport/Series-I/H...Boss_6_to_Mach_3.pdf

This looks like something I could absolutely do (substituting LinuxCNC for Mach 3). I could pick up one of Byte 2 Bot's parallel port hats, and run a BoB to drive the original Bridgeport electronics. However, it also seems like a lot of work to go through - just to rely on ancient, obsolete drives, steppers, and power supplies. In the end, I have an "oddball" system that is difficult to support. These original drives were also known to run pretty hot.

IIRC, the voltage of the motor is lagely irrelevent because the driver regulates current, not voltage.

Perhaps an overpowered 220V microstepping would work?

Might not be the right product:
www.aliexpress.com/item/1005007883772858.html

What voltage do (did?) the original (preexisting) stepper motors use?

I would avoid stepperonline, they seems a bit shady.
Like dishonest shady (their business is built on selling knockoff leadhone stuff, shat can you expect?).

However, it's up to you.

Gecko Drives are widely-regarded as a good option.
Though you can probably only afford them in USA due to tarrifs.

Thanks for the response!

The original drives are Bridgeport cards plugged into a backplane and mounted to a three foot heatsink. These apparently take "quadrature" inputs - not "step and direction?"

I'm not sure who made the original motors. I've been unable to find any markings/tags on them (maybe I need to unscrew the back plate, and look inside?). From what I've read, Bridgeport used a couple of different brands of steppers on these - either "Sigma" or "Superior." Apparently, they are "high voltage" steppers, and require a "high voltage" drive to run.

Do you presently have a power supply for the stepper drivers?

What is it?

Is it regulated or linear?

What voltage is it?

Does it work?

Much of what I know about the factory steppers came from postings made by "Boss5" over on the CNCZone forum:
www.cnczone.com/forums/bridgeport-hardin...ills/210116-cnc.html

Thanks for the advice about SteppersOnline. Where do people typically buy their China-brand steppers and drives? Is there a better source I should investigate?

I've certainly looked into Gecko for the drives. However, to my knowledge, they don't build drives that are a proper match for my steppers.