Synching motor drives help please

I have a production line that contains 3 separate pieces of equipment, let’s call them A, B, and C. Parts are transferred from A to B and then from B to C. Each is driven by its own separate motor controlled by their own Siemens VFD motor drive. A and B are synched speed and position using a 3rd device called a Synchron Controller made by a German company Mall+Herlan model Gleichlaufregler GLR 2.1. This works good for speed and position for A to B where B is the master and A is the slave. Its takes an analog speed input from B drive, outputs an analog speed to A drive, uses 2 input pulses one each from A and one from B, 1 pulse equals 1 cycle. Drive B is set up to run at a constant speed while drive for A uses the analog output from the synchron controller to adjust the speed. It uses the inputs to position them in time.
I need to do this for B to C. Currently, B and C are not synched up but I need to synch them for better production and to reduce scrap. Has anyone ever heard of the Synchron Controller mentioned above, I don’t have any info nor can I find anything on the internet about it? Does anyone know of something I can use that does the same thing? Having a hard time finding anything that does not use encoders.
The line runs 84 pieces per minute so it’s not that fast. Is there a better easy way to do this? The entire line is controlled by a Siemens S7-400 plc but it does not have analog output module. Just think adding a 3rd controller between B and C would be least expensive and easiest.
Any help or advice on the subject would be greatly appreciated.
Thanks, MRT19

Is this unit on an M+H machine?

Oh, & how tight does the synchronisation have to be?

Machine B is a Sprimag but the other 2 were locally built some time ago. The line is pretty much a "home built" production line. I have a descent size "window" on the transfer from B to C. I am trying to hit a vacuum slot on a wheel so the timing could be off a little and still be okay. The timing from A to B works fine so I am thinking it should be okay for the other.

Is there no analogue output on the Siemens drive that you could programme for the 3rd machine to follow?
Which drive model is it?

I need C to be the master, I can not change its speed due to the process. So C is the master to slave B, and then B would be the master to slave A.

A - Siemens MicroMaster 440 using analog input
B - Siemens MicroMaster Vector using analog output
C - Siemens MicroMaster Vector with all analogs open

So the MM Vector on B could take a direct analogue input from the analogue OP from C?
Then the analogue OP from B would go to the analogue input on A?
C>B>A
M>(S/M)>S
C analogue op > B analogue ip / B analogue op > A analogue ip

I would guess that you should be able to scale them OK, my Siemens laptop with all the docs & SW on is not to hand, sorry!

You'd have to check the scalings, burdens, etc. but I've seen something similar done with other kit, as long as the lags etc. can be allowed for?

I see where this method may get the speed to match but what about the positioning. Have you ever heard of the Synchron Controller?

Thanks for the replies.

I don't know your plc, but here is my thoughts.

can you put an encoder on c and do the math to convert it into a speed? then feed that speed value into drive b which is the master for a?

regards,
james

Since your looking for inexpensive and stand alone
Look into the old Fenner Contrex M track
Google that
I think they are still available
You need a position controller on this system

I don't quite see how you can match position without some sort of position feedback device, encoder, resolver etc.
I've not come across the device you mention, but, I did the normal search & came up with M+H as a machine builder, so it may be a badged unit.
You must then have an encoder or other position feedback device of some sort on machine B which is read & fed into the synchronisation controller which then compares this with the encoder, or other position feedback device on machine A, compares the two, then uses its analogue output to vary the slave velocity so the positions match?
This is the only way I can see that you can feed the position of machine B back to machine A, & match them, the only synchronisation controllers I know of have all needed a position input from the master & slave machines for comparison in the controller, which then generates the deviation signal to control the slave drive.

Both A and B send a pulse to the controller, 1 pulse per cycle. The controller must use these pulses to adjust the speed of the slave A to get the pulses at close in time as possible.

JRW, thanks, I will look into the Fenner Contrex M track.

OK, so you have a rudimentary position feedback, then you could do the same with machine C, find or add a once per rev switch, proximity or something and use this to feed a synchronisation unit.
You could also look at http://www.motrona.com/, not used their products, but they do seem to have the function you need in a small package & they have distributors in North America

I would use a high resolution encoder on C and gear B AND A to C. The master should always have a high resolution encoder. Using analog for velocity reference is lame if position need to be synchronized. Gearing should be done using positions. To do it any other way is less than optimal unless there are times when A and B can move independently.
Gearing A to B and B to C is poor technique. I can explain why but take my word for it.

just use the signal from master B that is going to A as input for slave C oke needs scaling etc, and a max setting of B (now the same i think)