An aerospace manufacturer that builds and machines composite wing skins had developed a complex set of operator procedures to minimize the potential for machining errors. The materials and labor invested in each wing skin prior to machining totaled more than $200,000 and any mistakes could be very costly.
The procedures required the operators to manually transfer programs from network directories to multiple devices. The program names were based on the specific type of wing skin being processed and as such, were cryptic. The procedures also required the operators to coordinate interaction between a flexible fixturing structure, probing and validation routines on a CNC control, and Windows based programs for adapting NC programs to “fit” each wing skin in its unique fixtured position.
The challenge was to develop a system that would automatically lead the operators through these procedures. And to automate all the file transfer, data gathering, data analysis and program manipulation steps.
CNC Engineering, Inc. developed a system that consisted of a PC -based Cell Control and two software modules. One module, running on the cell control, is used to lead the operator through the processes and to handle all the data functions. The other module is used to provide the manufacturing engineers with a convenient way for writing, dry-testing, and modifying the scripts needed to define the processes.
The “script” is based on a series of steps with each step having multiple tasks. Tasks are divided into 4 major categories. One or more of the following behind-the-scenes computer objects supports each category:
- CNC objects for loading NC programs and gathering and responding to macro variable information.
- Fixture objects for loading and executing appropriate fixturing programs
- Data transfer and program execution objects for performing pre-defined data and program tasks
- Operator objects to provide operators with specific instructions and seeking operator verification or data input as necessary.
Tasks and steps are organized into a script by the engineering department for each specific wing skin process. The operators then only need to retrieve the proper script for the part being machined and follow the explicit instructions.
The potential for human errors was greatly reduced. Scripts could be defined “dry run” and reviewed by the engineering department. Paper based procedure manuals were eliminated. Operators no longer needed to perform error-prone activities such as selecting programs from network drives. An audit trail of activities is produced as operators are led through each step and task.