Having as their goal the development of a concept for the automated drilling and fastening of different aircraft type panels in a single assembly cell, engineers at Brötje Automation GmbH came up with a modular and flexible solution called the MPAC (multi-panel assembly cell). The research was done with a partner team, Spirit AeroSystems, with three units being approved for production use.
In view of the customer’s requirement to create a modular cell applicable to different panel sizes, a new positioning unit was designed. The 10-axis MPAC positioner provides a significant work envelope unlimited in X direction and with a 180° A-axis providing the versatility needed to drill and to fasten the specified production panels, as well as yet to be defined for future work packages.
The positioner consists of the outer and the inner system. These two systems are independent of each other and run on their own X-rails systems. The outer system is composed of a D-gantry design carrying the Y axis, the vertical mast for Z-direction travel, and the rotary A and B axes with the upper riveting head.
The inner system also includes the linear axes for X, Y, and Z motion and the rotary A and B axes for positioning of the lower ram assembly. The upper and lower head components are automatically positioned perpendicular to the outer mold line of the workpiece. The inner and outer positioners function in a master slave mode to a common tool center point.
All movements needed for fastening access are derived from the positioner. This static workpiece concept eliminates earlier requirements for large towers and rotating work frames common to other known riveting machine configurations. The movements out of the positioner are faster and result in a considerable floor-to-floor time reduction.
The workpiece is just located on simple small stands, which are mounted at floor level on cup and cone locators. Panels of varying lengths and contours can be loaded in a row with a low level work line. Both fixed and flexible tools are accommodated within this design.
The location for the panel position is variable in that specific positions need to be predesignated. This concept for holding the panels is unlimited in the X-direction and, therefore, easily expandable for future applications.
The loading and unloading can be done via automated guided vehicle (AGV) or overhead crane. The possibility for using an AGV brings the advantage of eliminating waiting time for facility overhead cranes to arrive. In addition, the loading/unloading process of the panels can be performed concurrently with the automated fastening operations. This is possible as other work positions within the X-axis envelope are accessible at any time by the material-handling system. Also, other needed preparation on the panels can be performed in position while automated fastening in other X positions is under way.
Downtime related to panel movement is virtually eliminated, which contributes significantly to reducing the floor-to-floor time.
For installing the machines in the customer’s facility, simple steel plates at floor level are all that is needed; no pits and other expensive foundation preparations are required. All components of the MPAC are installed at floor level. This results in a low work line.
All components needed to be accessed during fastening operations by the operator or maintenance personnel are reachable from floor level. This eliminates complicated access platforms and also increases the time that the MPAC is available for production.
This article is based on SAE technical paper 2009-01-3091 by Thorsten Dillhöfer of Brötje Automation GmbH and Bill Bankston of Spirit AeroSystems.