Development of an NC equipment level controller in a hierarchical shop floor control system

Abstract

The methodology of developing an NC equipment controller in a Computer Integrated Manufacturing (CIM) System, which is based on a philosophy of hierarchical shop floor control, is presented in this research. The underlying architecture consists of three levels of control: shop level control, workstation level control and equipment level control. The focus of the research is on developing functionality and structure of an equipment controller. The equipment level controller (ELC) performs three basic functions: planning, scheduling and execution. The ELC first modifies machining parameters of tasks assigned by its superior workstation controller for local cutting conditions, then incorporates separated tasks so as to generate the tool path between two adjacent tasks; then it selects the required tasks from alternate tasks and decides on a sequence for each part; then it converts CLDATA file into machine-specific NC codes. The equipment controller then searches for an operation sequence of tasks for multiple parts by which the equipment can efficiently process these tasks. Finally, the equipment controller executes all the tasks based on a control logic that dictates the sequential control of task execution. This equipment level controller can provide operational flexibility and improve the machine level performance, and the establishment of it acts as a first step toward a highly automated, integrated manufacturing system.