An “Aerospace Mylar” is an un-dimensional engineering drawing on a stable base polyester material called Mylar. Aerospace mylar drawings have a highly accurate tolerance of +/-.005” and are typically very large format (up to 48” X 180”). During the manufacturing process, the part that is imaged on the Mylar is cut in metal, then place on the Mylar to check for accuracy. Because of the requirements for very tight, accurate tolerances in the building of aircraft, accuracy is highly important. The slightest deviation can cause malfunctioning parts in the finished aircraft.
Over time, as Mylar drawings age, they can yellow, shrink and warp, causing distortions in the allowable tolerances. Adding to this problem is the fact that the distortion can vary over the length and width of the drawing. This means that at one end of the drawing the distortion may be very small, while at the other end it can be much larger, based on the varying conditions under which the drawing was stored. When this happens, tolerances become disproportional, and cannot be easily corrected during the manufacturing process.
For this reason, many aerospace companies convert their Mylars to electronic CAD files. Electronic CAD files do not deteriorate over time and greatly reduce the cost of engineering changes because they eliminate the need to completely redraw the Mylar for modifications or corrections. In addition, CAD files can be easily duplicated stored in database files for easy retrieval and can be electronically transferred over geographic distances when workloads need to be shared among off-site engineering groups.
Most aircraft in operation today were created from manual mylar drawings and need to be converted to CAD files in order to improve logistical support over the life of the aircraft. To maintain manufacturing integrity, the results of any such conversion must be an exact representation of the original drawing, which means that during the conversion process, the file has to be corrected for any deterioration in the mylar which has affected tolerances and accuracy.
CATIA is the Preferred 3D CAD tool for the Aerospace Industry and DOD
CATIA (Computer Aided Three-dimensional Interactive Application) is a multi-platform CAD/CAM/CAE commercial developed by the French company Dassault Systemes. In 1984, the Boeing Company chose CATIA as its main 3D CAD tool, becoming its largest customer. In 1990, General Dynamics choose CATIA for designing US Navy submarines.
CATIA supports multiple stages of product development, from conceptualization through design, manufacturing, and engineering, while it also facilitates collaborative engineering across disciplines, including surfacing & shape design, mechanical engineering, equipment and systems engineering. CATIA enables the creation of 3D parts and it provides tools to complete product definition, including functional tolerances, as well as kinematics definition. This multi-functionality of CATIA is what makes it the number one 3D CAD tool for aerospace.
Mylar to CATIA 3D Process
What does it take to succeed in the conversion of thousands of un-dimensioned Mylar drawings to CATIA 3D? Experts recommend the following six steps:
- Technical Review of Mylar Drawings
- Pre-Scan Clean-up of Mylar Drawings
- Scanning Mylars with Large Format Technical Scanner
- Enhance Scanned Image
- Check for Quality Control of Scanned Image
- Convert to 3D
In today’s military and business environment, success depends upon the quality and accessibility of information and the speed in which the information can be disseminated. The accuracy of the final CATIA 3D file is of paramount importance. it is essential that the measurements be as accurate as, if not better than the original Mylar drawing when it was new.
This type of accuracy requires an expert in the conversion of Mylar aerospace drawings to CATIA 3D. Download our white paper for more information.