[astro02]

I have a 1973 series II nc that runs but needs a brain transplant!!! Te machine is in good condition. I would like to keep the stepper motors on it and it has a fourth axis rotary table. I need to know the specs of the steppers so that I can decide what the best approch will be for the retrofit. I would also like to get in contact with any one that has completed such a task for advice. I have all the manuals for the machine but the info on the steppers is not in the books.

Any help would be greatly appreciated!!!

[Karl_T]

That series II has REALLY large steppers. I used a 12amp 48 volt unit on a series 1(same steppers, I think). It was from Ahha, http://www.ahha.com/techdat2.htm I see its priced at $2000 for two axis, you'll need four. This unit would work well, but it might pay to shop around a bit longer.

There was a series of articles in "Home Shop Machinist" on refitting a bridgeport series 1 to CNC with Mach 3 control. A great read.

[astro02]

Thank you for responding. I have looked at AHHA. It would fit my machine well. The reason I am wanting technical data for the stepper motors on my machine is so that I can evaluate the options of some thing like Geco or others. I am still very interested in AHHA and would concider this system but dont know much about others am would like direction from others that have gone down this path already.

Please advise

[craig96us]

I have a series 2 retrofit that was formerly a Boss 6 machine. I am running Gecko G202 stepper drives on ~82VDC with no current limiting resistors (7A). The G202's receive marching orders from a Picosystems Universal stepper Controller board, and EMC CNC controller software. During testing, the steppers began stalling at around 180IPM. I am running at 120IPM with no step loss problems. I believe the the picosystems board is the key component that makes running reliably at 120IPM a possibility. This is due to the super clean step pulse trains that this board produces. I have been running the machine about 4 months in this configuration with no problems. I cannot recommend running the G202's over 80VDC, but I am getting away with it... So far!

Good luck!

/Craig.

[astro02]

Thanks for the info!
Do you have any parts list and documentation like wireing diagrams ect. that could help me get started

[Dfennell]

Hi, I've got Bridgeport Series II NC with a 4j head that I converted to CNC a few years ago. I used the stock steppers (they are really, really powerful), gecko 210 drives and a 65v 20 amp home built power supply using a toroid transformer. Ran Mach II. Ran like a dream. I got the wiring diagram for the steppers over at the yahoo!groups bridgeport site http://groups.yahoo.com/group/bridgeport_mill/ or the CAD_CAM_DRO site http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/ (can't remember which). Do a post over at the CAD_CAM_DRO group and I can just about guarantee you'll have the diag in your hands by tomorrow morning.

[Dfennell]

.

[Dfennell]

Oops... here it is... I forgot that I wa the one that did the drawing a few years back. This is the wiring diag for the sigma motors. Man, I'm gettin old.

The drawing is for bipolar parallel, and the resistors are depictions across the coils, it's internal and you don't need to add resistors to the circuit. This setup on a G210 moves fast and has incredible torque.

[Dfennell]

Also, give the gecko and Mach III route serious consideration... it is a fantastic setup for very little outlay of cash. Buy a nice PC to dedicte to the mill; I used a Dell 2.2ghz that I bought brand new for $349 straight from Dell that was a screamer. It's a very nice setup.

[craig96us]

Hi Astro02--

I didn't draw any schematics for my installation, but basically here is what you need to do:
1. Remove all of the old Boss electronics parts from the control and power cabinets that are not related to spindle control.
2. You will need to find a wiring diagram for your steppers. Mine are Superior motors, but some of these machines had Sigma motors - They are wired differetly. You will want to wire the motors "bipolar parallel" to the Gecko drives. Use the G202, or G212 drives as they were designed to be used with larger motors.
3. Build a DC power supply to feed the Geckos. I built mine from the 230/115VAC isolation transformer I salvaged from the original Boss 6, a bridge rectifier, and a couple of capacitors I salvaged from the original Boss 6.
4. Wiring your breakout board to PC, and Gecko's will vary depending on which breakout you decide to use. Wire according to the documentation that comes with the breakout board.
5. Next, wire the limit switches, and verify that each limit switch will trigger an appropriate response in your CNC software before you apply any power to the stepper drives.

With this configuration, you will use the original Bridgeport spindle controls provided that you read the factory schematics, and didn't remove any original spindle control electronics.

When I built mine, I made an aluminum plate with the G202 drives mounted on it that I fastened to the large heatsink on the back door of the control cabinet near the bottom. This put the G202 drives just above where the original stepper wires come into the cabinet. I was able to use the original stepper wiring, but I had move some wires around on each of the steppers.

I am running EMC on a 400Mhz intel Celeron box, which works great with my Picosystems USC. If you use a basic breakout board like the Campbell, or PMDX borads, you will need to have a faster PC. The Picosystems USC board has an onboard microprocessor which generates the step pulses instead of the PC... At this point, the Picosystems USC will only work with EMC software. The MACH 3/4 software won't drive the USC board at this time. If you decide to go with the MACH 3/4 software, you might want to consider using the Gecko G100, which will provide you with microprocessor controlled step pulses.

Hope this helps!

/Craig.

[astro02]

Do you have or know whare to get the electrical specifications of the stepper motors on a BP series II Nc?
How did you know how to build the power supply?
Is there only 1 power supply that feeds Geco drives to all 3 or 4 axis on your mill?
If only 1 power supply feeds all the drives how did you size it?
Why are there 3 transformers on my machine now I think they output 56VDC and dont know the amps?
Can I / should I use one or all of these power supplies for the retrofit?

sorry about all the questions but i need to know

Thanks

[craig96us]

Hi Astro02--

Answers:

>Do you have or know whare to get the electrical specifications of the stepper motors on a BP series II Nc?

I found a reference plate on one of my steppers. I have attached a photo. you could also try contacting Cardinal Engineering for specific stepper information. I got my stepper wiring diagram from their website.

>How did you know how to build the power supply?

In a previous life I was an electronics tech on US Navy Submarines. Although I have forgotten a lot of the electronics theory, I remembered enough to get me in the ballpark with the power supply. I have also been lurking on CAD_CAM_EDM_DRO yahoo mailing list for several years, and have a Shoptask CNC I put together back in 1999.
Briefly, the factory stepper power supply provides 56VDC at up to 8.2A. 56VDC*8.2A=459.2Watts. I know that the Gecko G202 drives will handle 80VDC at 7A, or 80*7=560W... Hmmm... Gecko's will handle the factory power level without any trouble, and based on how the steppers performed on the Boss 6 control, I figured I would be able to feed them ~500W without having any overheating trouble. This set my power supply target. My original intention was to build a 75VDC power supply to stay well within the Gecko's power limits. I simply guessed that the isolation transformer would be large enough to supply the power I needed. The bridge rectifier and capacitors were scavenged from the original Boss components I pulled to do the retrofit.

>Is there only 1 power supply that feeds Geco drives to all 3 or 4 axis on your mill?

I used a single power supply to feed all three Gecko's. It is advantageous to use a single power supply for all three axis because a deceleration surge from one of the axis can be absorbed by the remaining axis which decreases amount of power a single Gecko would have to absorb in the case of an emergency stop, or fast deceleration. Mariss of geckodrives reccomended running a single power supply. Fuse the power supply on the AC side of the transformer per Mariss' recommendation.

>If only 1 power supply feeds all the drives how did you size it?

Shoot for a transformer in the 1200-1400VA range if you are buying a new transformer. I don't remember the formula for calculating VA, but your power supply will need to be able to support 70% or so of the maximum power draw of all of your steppers combined. I figured in the worst case, my transformer would be undersized, and would get hot in operation. It remains cool to the touch, so it will probalby survive forever...

Why are there 3 transformers on my machine now I think they output 56VDC and dont know the amps?

The factory Boss stepper power supply provides 56VDC at a maximum of 8.2A. The three phase transformer can be thought of as three separate transformers that share the same core. The lowest AC voltage that I could tap off of mine was 62.2VAC. Rectified, 62.2*1.414=87.9508VDC! Far too much voltage to feed a G202... The original stepper power supply uses bucking coils to reduce the AC voltage that is fed to the rectifiers. I was not comfortable trying to use the three phase transformers along with the bucking transformers for my retrofit power supply. I don't understand how they work together well enough.

>Can I / should I use one or all of these power supplies for the retrofit?

I have not hear of anyone using the three phase transformer for the retrofit stepper power supply. I read a couple of posts from folks who said they were going to try and remove a few wraps from the transformer to reduce it's output, but I never saw any posts claimins any success.

sorry about all the questions but i need to know

No problem! I kind of flew by the seat of my pants with my retrofit. Teh best advice I can give is to join the Yahoo CAD_CAM_EDM_DRO mailing list, and search the archives for "Bridgeport", and "power supply". There is a lot of knowledge on that list! Hopefully I have given you a place to start from.

Good Luck!

/Craig.

[craig96us]

Hmmm... Looks like my attachment didn't make it... Try two...

[jb2590]

Craig, do you have any problems with missed steps when cutting steel and other hard materials ? i would like to do an upgrade and would like to keep the original steppers. are there encoders on these steppers to make sure it actually moved? if i can be sure i wount miss steps ill just keep the old motors instead of going to servos. im comfortable with *nix software but i have never checked out emc, if the pico systems board will be better on the step controls and making sure i dont lose any steps than i have no problem running it. most of my computers are already running linux and freebsd anyway. so its no biggie as long as it is precise and maintains tollerances. let me know what you think . thanks, John

[craig96us]

Sorry I didn't catch this message earlier!
The only issue I have had with missed steps was due to backlash compensation problems with EMC. With backlash compensation set to .000" I have never had any lost steps. I cut mostly aluminum, so I can't say for sure what your performance will be cutting steel. My "seat of the pants" feeling is that you won't have any problems with lost steps in steel with EMC/Picosystems/G202's. Clearly the original steppers won't achieve the same rapid speeds that a good servo system will, but if you are willing to live with ~100-120IPM rapids, you will be money ahead putting together a system like I have. I have fiddled with adding encoders to my setup, but have not put together the couplers/brackets yet. I did find that I had to decrease the acceleration and max feedrate when I did some testing with a 500 line encoder on Z. I was getting followng errors before decreasing accel and max speed. The steppers have performed so well without the encoders that I never mounted them.

If you can avoid backlash compensation with this setup you will be ahead of the game - even if you decide to go the servo route.

Hope this helps!

/Craig.

[jb2590]

Craig thanks for the info. this will probibly be how i will go. i guess i need to download emc and check it out, and see what its all about.

John

[craig96us]

If you are considering the picosystems USC card, you should contact Jon Elson via his webiste pico-systems.com regarding the version of EMC that you will run. I am using an older version of EMC that has been updated with patches from Jon. I understand that Jon is working on updated drivers that work with the new version EMC2. I don't know if EMC2 is really ready for prime time yet, but Jon can help you decide if EMC2 is in your future. Good luck with your retrofit!

/Craig.

[wddanie]

Craig, what kind of accuracy do you get on your retrofitted BP S2? Do you have a MPG pendant you use with EMC? Why did you choose EMC over Mach?

I am planning a retrofit on a Shiz AN-S and like the idea of closed loop control, which I think can be achieved with the Pico Universal Step controller if I feed it encoder signals. Does that sound right or am I missing something?

Thanks,

Doug

[wddanie]

Dfennell, what kind of accuracy do you get from your reftroffited BP S2?

Thanks,

Doug

[craig96us]

Most parts have been within +/- .001", +/- .002" at the worst.

I have a bit of backlash in my ballscrews that I believe is the source of the inaccuracy. I would like to take the ballscrews apart and try running larger balls, but have too many other priorities!

It is really easy to get caught up in the "little issues" and spend a whole lot of time and money to obtain just a little more accuracy. I expect the machine will hold this accuracy for a long long time as a hobby machine! If I end up needing more accuracy, I can always address the ballscrews then!

/Craig.