SLC's and Encoders

Retrofitting a Cincinnati press with new SLC controls. Customer wants the rotary cam limit switch replaced with and encoder. The more I check around, the more questions I get. The encoder needs to be absolute and talk to the SLC. Right now I am leaning toward a DynaPar TTL absolute encoder connected to a 1746-IG16.
Good idea, bad idea?

sounds ok. i was using some abs encoders that had parallel outputs for 24V and then you can use standard 1746-IB16 or 1746-IB32 cards.

Don't use a TTL encoder unless it is within 15 feet of the SLC. I have used the AMCI Duracoder DC 25 with 24v DC very successfully with an SLC 1746 ITB16.They come as absolute binery or gray code. I reccomend using gray code. I have posted a gray code to binery converter for the SLC on this site somewhere.

http://www.plctalk.net/qanda/showthread.php?t=11739&highlight=code

you don't have to limit yourself to encoders with parallel output.
you can get absolute encoders with network interface like for devicenet etc.

Keep in mind that absolute encoders are good for ONE TURN. A multi-turn encoder will cost very big buck$, and require a LOT of I/O unless you go with the devicenet, or serial connection.

I agree with John on this one. I've used and had very good luck with AMCI resolvers on stamping presses with their resolver/SLC card that they make.

I have a couple of CB&W presses using an Allen Bradley Encoder interfaced to a 1746-IG16 (TTL) card in the 5/03 rack.

It has approx. 30' of cable and works fine. Using it basiclly as a 0-359 degree reading and keying off of that.

ps: AB Encoder (845D-SJDZ14ADCK4)

Use a standard Pulse Encoder (1024 PPR => 2.84 Pulses per Degree => .351 Degree per Pulse) and a highspeed counter.

Also include a Zero-Reset sensor (or limit switch).

Everytime the Zero-Reset is tripped reset the current pulse count, in the highspeed counter, to zero.

Make your moves and position decisions based on pulse count.

atgrof,

I have just realised what sort of machine you are talking about here, WARNING - modifying the controls of a press brake/clutch is not for the faint-hearted or the inexperienced.

You cannot replace the RCLS on a press/brake with an encoder for control purposes, you can add an encoder to give the PLC position information but the control still needs to be on cam switches. If you are going to use an SLC for the direct control you need two, working as a redundant fail-safe pair. AB do special solutions for press controls. Look under "Metalforming" in the AB literature libruary. They only show a mocrologix version now but they did do an SLC press control system. Here is another AB solution attached.

I don't know what the regulations are like in the US but I would get the power press manufacturer in to help with this job.

AMCI make a dual resolver that you can use for the redundancy purposes to two different PLC's. A-B also has a group that does just stamping press controls. They used to be known as the PACS group, but I'm not sure what their name is now. I'm pretty sure they work out of Cleveland, OH. The SLC was the first PACS clutch/brake kit developed and later on added the MicroLogix kit. I believe they support the AMCI dual resolvers/plc cards they manufacture.