Original Date: 05/08/1995
Revision Date: 01/18/2007
Best Practice : Rotational Molding Process
McDonnell Douglas Aerospace (MDA)-St. Louis has adopted and adapted a manufacturing process that has been extensively used in the toy and automobile industry for years. Using this process, known as rotational molding, on Environmental Control System and crew station aircraft ducts, initial tooling costs were lowered, and the process eliminated the need to fabricate a tool each time a part was built.
Traditionally, the ducts were fabricated out of Kevlar. While the Kevlar design offered certain advantages such as strength, it had inherent disadvantages. For example, typical cycle times of 30 days and 21 different manufacturing steps were to be expected. The process was labor intensive, material was expensive, and tooling was difficult to manufacture and had very limited life. Additionally, this process dictated that the ducts be tooled to the inner mold line which increased variability at installation.
In 1993, MDA installed the rotational molding equipment at its facility. Implementation of this technique and material required some engineering changes and concurrence in order to change the base material. MDA recognized that this is an emerging technology in the aerospace industry, with room for refinements and capability enhancement. Today, ducts are tooled to the outer mold line which reduces variability at installation, and five day part cycle times are the norm. In addition, process steps have been reduced from 21 to seven.
Total cost for project implementation was approximately $334K, but MDA-St. Louis has projected a five-year project savings of $802K based on the redesign and reprocessing of only 17 different ducts. The projected savings, based on the quantity of 17 ducts, is in excess of $30M over the life of one type of aircraft. The candidate part count is up from 17 to the current count of 90 ducts. Several additional part candidates are being considered for a redesign effort. This technology also lends itself to other part categories and should provide additional dollar savings.
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