1987 Bridgeport Production Center Interact 412 to Mach3 Conversion

[JHChoppers]

One of the cool things that I like about this system that is not advertised on the MachMotion site, is the electronic gear box parameters.  The servos have 2500 lines on the encoders that generate 10,000 pulses per revolution that would normally make for a very slow system.  However, the electronic gear box setting allow you select the resolution on the axis you want (ie: 0.0002 in/step), this allows for both accuracy and speed when connected Mach3.  It’s a programmable step multiplier with a scale from 0.005 to 200.

A second plus is the software CD from the manufacture.  This application allows you to dynamically monitor various parameters like Load, RPM, Current, etc in real-time.  You can also program and tweak all the parameters and setting on the user interface and save them off as a backup.  This makes setting up X and Z axis easy too.

Here are a couple of the software screens from the CD included with the servo driver:

[Sam]

Looks like your gonna have a great machine when you git'er all done, Joel.

[manmeran]

One of the cool things that I like about this system that is not advertised on the MachMotion site, is the electronic gear box parameters.  The servos have 2500 lines on the encoders that generate 10,000 pulses per revolution that would normally make for a very slow system.  However, the electronic gear box setting allow you select the resolution on the axis you want

you have a 2500 line encoder that is 10,000 pulses per revolution
so if connectd direct with for example 5mm ball screw then you would need 10,000/5 =2000 steps per unit
at 3000rpm that would be 2000 x 3000 =6,000,000 pulse per min
divide by 60 and you get 100.000KHz pulserate required.
then i think you need SS for 100Khz.

now electronic gear ,i think we can use for when i dont want use SS.
for example , mach send 1000 pulse and gear box convert to 3000 pulse.
If I make mistakes,pls correct.

Amir

[JHChoppers]

Step multipliers are common with high resolution encoders.  The ones that I have used before are typically programmable from 2x 4x 8x and 10x.  What is nice about the TSTA20C, is that you can select and ratio from 0.005x to 200x. 

On our VMC, we have 5 turns per inch ball screw and a 2:1 drive pulley for a total of 10:1 (10 turns on the servo will move the table 1 inch)  The encoder has 2500 lines with 10,000 pulses per revolution.  So with a target Mach3 Step/inch of 0.000125 (or 8000 Steps/Inch) I would need a 12.5x step multiplier.  My target max RPM is 2500 or 250 IPM (limited by the stock thrust bearing rating), therefore we can set the Mach3 kernel speed to 35Mhz.

Attached is a spread sheet that we used for the calculations.  There are 2 examples, the one described above and one with 0.0001 steps/inch target.  The Numerator and Denominator values is what the driver needs for the electronic gear box setting.  Based on that ratio, the Mach3 kernel speed required to generate the pulses for a target IPM is also calculated.

Screen shots of the kernel speed and motor tuning are in the spread sheet too.

Hope this helps,
JH

[JHChoppers]

Been thinking a lot about how the spindle orientation will work.  The stock machine has a Spindle Encoder and Spindle Home Sensor connected off the spindle with a small pulley as shown in the picture below:

After doing some test attempting to stop to spindle and decelerate to the same spot each time, I have learned that this almost works.  I can get it to stop close to the same spot, but not good enough for a reliable tool change.  Its only off by a couple of degrees, enough to consider a different plan.  

The new plan:  replace the stock encoder mechanism with a small dc servo while keeping the mount and 1:1 pulley.  Add a home position notch and senor to the pulley.  Keeping the server motor disable while the spindle is on, the switch on the servo when the spindle if off, find home on the pulley and index to tool change orientation position.  

Concerns:  Q: the servo will turn into generator when the spindle is on and back drive the servo driver.  A: use a relay to disconnect the servo motor from the driver outputs and connect only during a tool change, make sure the servo driver is in reset when the outputs are connected and disconnected.

Some additional pictures below of the servo mount under construction:

[cnc-it]

Hi have you still got the Fanuc spindle drive? It should do the spindle orientation and work with the encoder as that is what it is set up to do. Not sure if you could get this to work with Mach though?
I have the same Fanuc drive on my Bridgeport..1984 vintage and still works great...orientation is spot on never misses a beat!

John

[JHChoppers]

John,

Its long gone.....  3 phase is not an option for me.  This machine will run on 220VAC 30Amps Single Phase when we are done with it.

Thanks,
JH

[cnc-it]

Sorry JH forgot you are running single phase..keep up the good work!

John

[JHChoppers]

No problem, not like everyone in world should remember the current status of this project LOL

JH

[capsteve]

JH,
  man its great to see someone else performing bridgeport surgery. ive got a 1989 interract 142, but i started with the camsoft plan........
bought the pro version and ran with the illusion that i could make this thing work like a swiss watch.....i've been on that project for almost a year.
i put servo dynamics servos with encoders, replaced the limits switches and added home switch capability, added an mpg with touch screen. the works....
but, that software may be very capable but it is very not user friendly and very..very clanky....(technical term...) when i use the mpg there is a delay of a sec or two before movement
and i cant seem to make smooth movements under load..not to mention the screen, interface, and parameters are handled through an archaic dos like operating system.
   i decided to dump the camsoft and run mach3, i really want to learn how the tool changer is handled for programming. i love the mach i use in my other small machine its worked flawlessly from day one......i just didnt think it had the capability to run the larger machine with a toolchanger...

steve