Correct Boards for SCM Record 1 Retrofit

Hello! I am wanting to retrofit a 1993 3 axis SCM Record 1 CNC router with LinuxCNC to replace the existing NUM 720B control.

The three axes are driven by ac servo motors which have Yaskawa CACR SR_BE1 series servo amplifiers which take analogue input and give encoder feedback (6 wires line driver or 3 wires open collector ). The spindle is run by a variable frequency inverter (speed control is analogue).

There are about 44 inputs and 36 outputs going to and from the old NUM 17.20 PLC. I doubt it would be practical to try to interface LinuxCNC with it? The inputs are 24 volt, but the outputs are mostly 120 volt ac so I suppose I would need to get some relays if I am going to replace the plc with an electronic board. The machine has a 7 position rotary automatic tool changer and a 5 spindle drilling block. I am wondering what the appropriate driver boards for this retrofit would be. Thanks, Eric Froese

I work with an older SCM Routomat with a NUM 1040 control that I have been contemplating retrofitting for a few years now. (It has been one minor controller malfunction away from a brain transplant for a while now.)

I would tackle this with a Mesa 7i77($199) and something to plug it into (5i25,6i25,or7i92 for $89) and how ever many Smart Serial cards it takes to get enough IO. The 7i77 card alone would cover 32 inputs, 16 outputs, the servos/encoders and the spindle. You'd still need 12 more inputs and 20 outs. There are a couple of ways you can get there. You could buy one 7i64 ($198) with 24 in and 24 out. or you could buy a 7i74 ($69)+two 7i84($79 each) for a total of an additional 64 in and 32 outs ($227).

I think you can (I would certainly try to) reuse the old NUM relay boards. (I think they use 24v outputs.)

Scratch that last option, I just remembered if yours like mine you might need a step generator for the tool changer, it would be cheaper to replace one of the 7i84 cards and the 7i74 with a 7i76 ($119) giving you the same number of digital io plus 6 step generators and another analog spindle control.

Total cost would be close to $500. Pretty cheap when you compare with the cost of retrofitting a commercial controller.
7i92($89)+7i77($199)+7i76($119)+7i84($89)=$496 for 6 analog out, 6 encoders, 6 stepgens, 96 inputs and 48 ouputs.
or
7i92($89)+7i77($199)+7i64($198)=$486 for 5 analog out, 5 encoders, and 56 inputs and 40 outputs

Thanks for the reply and the idea of using the old relay boards! I’ll have to look into that. My tool changer is turned by a stepper motor, but it appears to be set up to be controlled by inputs and outputs on the PLC... I think I’ll get a 7i76 to be safe tho.