Automated coil handling and in-process inventory system

The coil handling and inventory system at the Rockport Works of AK Steel was conceived and designed concurrently with the buildings and process facilities for the new plant. Simulation was used to define movements and the size of coil locations. A central computer system communicates between level 1, 2 and 3 systems.

Automated coil handling and in-process inventory system

Included in the early design stages of the Rockport Works were several goals for the in-process coil handling system known as CHIPS (coil handling in-process system):

·  Know the location of every coil at all times.

·  Direct the movement of coils to, from and between processes.

·  Automate as much of this movement as possible.

·  Adjust to changing requirements for coil routing and storage.

This system is required to service cold finishing operations that include coil receiving, carbon and stainless pickling, stainless annealing and pickling, cold rolling, bell annealing, temper rolling, galvanizing/galvannealing, warehousing and shipping.

Design methods

When approaching a project of such magnitude, numerous elements must be analyzed. Coil tail orientation requirements for each process entry and exit conveyor were considered to minimize the rotation of coils with a crane.

This study extended to the coil orientation on each automatic guided vehicle (AGV) coil stand and transfer car, and included each process routing combination of source and destination.

Static math models were built to evaluate crane speeds and acceleration/deceleration rates in terms of move cycle time. Several scenarios were studied for varying coil field sizes and the locations of process conveyors.

Combinations of required crane and AGV moves from area to area with varying frequencies were simulated. Frequency of moves was based on coil sizes, process production rates and all possible combinations of concurrent process operations.

Two dynamic computer simulations were built; one was created using SLAM (simulation language for alternative modeling software from Pritsker Corp.) and the other was built with Arena (simulation software from Systems Modeling Corp.). These models included details for each process, crane, AGV, transfer car, truck, rail car and inventory field. Time study data were used for manual cranes, and static model data were used for the automatic cranes and AGVs. Many scenarios were run, varying the combinations of processes in operation. The effects of each process consuming and producing coils at their maximum frequency were determined, including all processes simultaneously operating at their respective maximum speeds.

These simulation data were used for determining:

·  Required number of coil locations in each building.

·  Required crane speeds and acceleration rates to meet the throughput requirements.

·  Required number of AGVs and AGV coil saddle stands at each station (Fig. 1).

·  Optimum locations for process entry and exit conveyors with respect to crane utilization and coil flow.

Output from the simulations was used in determining the best method of moving coils during the various stages of construction of the Rockport Works. Five evolutions of coil movements were identified as the various processes were completed.

For each coil movement, the required automation step; were defined. These details included the data transferred between systems, decisions required by CHIPS and the automatic guided vehicle system (AGVS) and device safety interlocks necessary to ensure that equipment does no: move while a crane is picking up or setting down coils. All coil movements were examined with normal and multiple exception conditions.

CHIPS was designed to be a central system capable of communicating with all other systems. It performs the following functions: coordinates delivery and pickup of coils to and from process lines; updates in-process coil inventory to the level 3 business system; and coordinates coil receiving and shipping with the level 3 system. CHIPS also feeds commands to the automatic cranes and the AGV system, processes operator input and sends jobs to manual crane operators. The system also manages safer. interlocks through PLCs and remote I/O.

Suppliers

VAI Automation, Inc. (formerly Digital Interface Systems or DIS) was chosen to supply the CHIPS system. VAI also supplied the level 1 PLC systems for the automatic cranes Control Engineering Co. (CEO and Elwell Parker Ltd (EPL) were chosen to supply the automated guided vehicles and the AGV system. Alliance Machine supplied the automatic cranes, which included Electromotive Systems drives and Geotronics laser-positioning systems.

Each supplier was required to assemble the system as much as possible and perform a systems integration test prior to shipping the equipment to the plant site for installation. This testing scheme contributed to the early start-up of each process in the Rockport facility.