Market: Steel mill - slab extractors
Product: AG626 & SPA3

A company who designs and manufactures steel mill equipment was approached by one of our representatives with the AG626 multi-turn absolute encoder as a possible alternative to the current feedback devices they were using. The principle application at this company are slab extractors used to move extremely high temperature steel slabs in and out of furnaces. Each extractor moves in two axes; the first axis is an up/down movement using twin hydraulic cylinders; the second axis is a trolley car and the corresponding track for horizontal movement in and out of the furnace. In the case of the hydraulic cylinders, multi-turn absolute encoders are needed to precisely monitor the height of each cylinder so the control can keep them moving in unison. The encoders on this axis are driven by a sprocket and chain which is gravity tensioned. The second axis requires multi-turn absolute encoders to indicate the position of the trolley car on its track.

The feedback system they had used until now was a resolver system. This system included a resolver and a resolver integration package. The complete resolver package was costing them over $3000.00. We quoted our standard AG626 and SSI Conversion kit for less than half that price.

The AG626 with the SSI conversion kit was chosen to replace the resolver for a variety of reasons but primarily because of its price advantage. Other reasons include the AG626's exceptional resistance to the extreme environmental conditions found in these steel mills. Most optical encoders are thought by the steel mill industry to be less rugged than the resolver but the AG626's rugged magnetic design eliminated this argument by providing them a feedback device with extremely high resistance to shock, vibration and environmental contamination. It also has extra shielding to negate the affects of EMI/RFI noise. Finally the AG626 has the wide temperature ranges necessary to operate in this environment: -40 to +100 degrees C and provided them with increased resolution: 4096 steps/360 X 4096 turns.

The customer also was concerned about the resolver's requirement for a transmission cable with special impedance's etc. The AG626 only requires a common cable with an overall shield eliminating this potential problem and the additional cost associated with it.

The customer planned to use a Delta Tau PMAC controller card which was to be housed in control panel with a VME backplane. Since the PMAC does not have an SSI input card the SSI conversion kit was necessarily included in our package. The SSI conversion kit made the SSI protocol transparent to them, provided a parallel output which could be fed into a PMAC piggyback 32 point I/O card and gave them a pre-engineered and easily implemented solution.