Original Date: 10/20/1997
Revision Date: 01/18/2007
Best Practice : Automated Tool Manufacturing Computer System
Traditionally, most tools are designed by conventional, manual methods that use 3-D computer aided design (CAD) systems. These methods usually require the designer to spend substantial time in defining a tool’s surface. Considering alternatives, the Northrop Grumman Corporation, Military Aircraft Systems Division began using automated tool design methods on one of its U.S. Air Force programs. These automated methods demonstrated enough potential that the company continued to fund their development after the program ended. The result was the Automated Tool Manufacturing Computer System (ATMCS). This automated, part geometry-based, tool design system is now used in the new F/A-18 E/F program as well as other Northrop Grumman projects, has provided significant improvements to the Division’s operations, and is currently being licensed for commercial sale and use.
ATMCS is an automated CAD tool which uses CAD drawings of parts, created in CATIA or Unigraphics, as a basis for generating tool designs. The designer specifies the type of tooling being built (e.g., resin transfer molding; master model; ply locator template; trim and drill; integral stiffened; billet; eggcrate) and the tool material (e.g., steel, carbon, composite). The tool designs are dependent on the designer’s knowledge, experience, and application of design rules. The actual part drawing is then specified and viewed. The designer defines the characteristics (e.g., part surfaces, boundaries) and can edit the default tolerances provided by the system. ATMCS uses all of this data as well as Corporate and program-specific, knowledge-based design rules to generate tool drawings. The completed CAD drawing can be output to CATIA or Unigraphics formats. Additional features not included in the default process (e.g., material thermal expansion, spring back calculations and analysis) can be run manually within ATMCS by the designer. ATMCS operates on Silicon Graphics, Hewlett Packard, and IBM Risc platforms, and produces drawings which are interchangeable among the three platforms.
The tool design drawing, generated by ATMCS, can also be used by other CAD/CAM systems to do a variety of tasks (e.g., numerical control cutting; composite ply location and nesting; material requesting; and cost estimating). As a result, overall cost estimates are improved because linear inches of material cut and rates thereof are used in calculations in addition to material costs. ATMCS’s rapid design generation allows for easier updates with changing part configurations and enhances the Integrated Product Teams’ discourse and process. Northrop Grumman’s main subcontractors also use this automated CAD tool. ATMCS saves considerable time and money in tool design, as well as unanticipated and surprisingly high savings in tool fabrication, actual part fabrication, and assembly.
Quantification of ATMCS’s benefits is readily available, based on the comparison of the original F/A-18 C/D program to the new E/F program. Northrop Grumman achieved a 97% time savings in tool design by using ATMCS to generate composite eggcrate tool structure designs for E/F versus the conventional CAD method for C/D. Composite tools are also preferred for composite materials to minimize thermal mismatch. Northrop Grumman achieved a 60% time savings in tool design by using ATMCS to generate steel billet tool designs instead of the conventional CAD method. This savings yielded a cost variance of 60% of the funds allocated for this effort which were returned to the U.S. Navy.
Northrop Grumman has also documented extensive savings in the rest of the fabrication process. Tool fabrication time decreased substantially using ATMCS. A typical, composite header board tool which originally took one week to fabricate now requires only six hours an 85% time savings. The improved tooling accuracy has led to easier part fabrication and assembly processes. After building 1,300 C/D airplanes, it still takes four days to do the final assembly. During the first and all subsequent final assemblies of the E/F airplanes, the process takes only four hours an 87% reduction in time.
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