1946 Bridgeport M Head Retro WriteUp

[DennisCNC]

Here is my almost finished CNC retro. The machine is a M head BP. It is three phase and old. The ways and lead screws are in ok shape, at least good enought for the things I make.

Computer:
P3 800Mhz with 128MB RAM, 10gig HD, AGP Video Card.
Runing Mach3 at 35Khz

CNC Controller Box:
3 Centent 10uS Drives on big heat sink at 5amps
Transformer 220V to 47V
Capacitor 41,000 uF
Diode bridge
Circuit braker
Fuse for each drive
Screw terminal bar
CNC4PC breack out board
5V supply from game port
Line filter
Fan

Motors:
Zebotronics 720oz, 200 step
Drive 2:1 #25 chain



The motor mounts are flexible a little to keep the chian tight. The X motor has a adjustment screw in the middle of the plate. I know this is not the best way to drive a machine but I had the sprokets sitting around useless. I can not measure any backlash in the chains. The screws have a little backlash the X has .004 and Y .007 the table movement .0009.
The motors will move the table up to 60IPM and will cut 1/2 aluminum plate with a 3/8 end mill to 45IPM.
The limit switches need to get connected and a E-Stop button. Also a pointing device for the monitor is needed, I'll try to get a light pen for that.
I still need to make covers for the chains and handles. You can see I made one in the picture. I don't have the Z done yet as this is the more involved axis. But working on a few ideas.
I am very happy at how it is perfoming!
I hope this thread will encourage and/or help some one with a BP retro. It is worth every penny and minute spent!!

[jdelaney44]

Great example of what one can do without going nuts on the $$$. This might be the first one I've seen done with chain. Most folks argue against chain. But, you appear to have it working.

Your initial data is promising. Thanks for the post.

[DennisCNC]

Maybe chains are not good for machines runing ~200IPM but they work great on my machine. When the table is traversing I tried stoping it, with all the force I could push I was unable. So I figure it has about ~275 lbs of force or more. And this is with old lead screws. I need to find a long enought ballscrew for the X as I have a Y screw already. Then the table force will be over ~325 my guess.

[wallyblackburn]

It sounds like you still have the original (non-ballscrew) leadscrews installed - true? If so, how is that working and/or hindering performance?

wrb

[DennisCNC]

Yes, I still have the old leadscrews. I think the biggest problem is friction if I try to accel to fast, but i have it at 1.2 units/sec and thats fast enought for my projects. I will be cutting a 1 inch 34 tooth gear with a 1/32 endmill out of aluminum soon then I will really see how the backlash in the screws shows up. That will be about 16 passes to get .33 inch.

[Ken_Shea]

Dennis,
The need to cut .330 deep may present a problem using a 1/32 end mill, the depth of cut on these is usually only about .060-.090 or so, even if you could get the DOC it would likely not be suitable for cutting aluminum because of flex.

Ken

[DennisCNC]

^^ Your right, I think I will cut two and glue them together.

[DennisCNC]

This mill has a new home now

[rustamd]

Yep

[rustamd]

Here it is right after it was moved, not connected yet..