RV AC Unit Housing Project

A friend's RV, showing signs of age, presented a challenge with its air conditioning unit controls. Over two decades, the original housing had become brittle and deteriorated significantly, with approximately 30% of the pieces missing. While the remaining fragments were painstakingly reassembled and glued, an attempt to fabricate a replacement housing proved necessary. 

Upon receiving the fragmented housing, my initial task was to reconstruct its original form. Based on the existing markings and draft angle, I concluded that it was injection molded from ABS plastic, a common material in automotive applications. This particular housing dated to the early to mid-1990s. As illustrated below, the housing was severely damaged, with substantial portions missing. Online searches yielded no results; the part was not only obsolete, but photographic references of the original were also unavailable. My next step was to apply developer spray, as the black, reflective surface was unsuitable for 3D scanning (particularly problematic for chrome and transparent components). Prior to application, I confirmed the developer spray's solvent was compatible with ABS plastic, avoiding potential damage from acetone-based solvents. Reversing a broken part is challenging enough; scanning a melted, flammable mess would be considerably more difficult. 

The subsequent step involved 3D scanning, which was performed from three distinct positions and subsequently stitched together. This unified point cloud was then converted into a semi-watertight mesh. For this process, I used an Einstar scanner, leveraging its VCSEL scanning technology (comparable to a much lower resolution version of iPhone facial recognition). The resulting model was initially imported into Fusion 360 for datum alignment before final export to Geomagic Design X for feature extraction. The intermediate step in Fusion 360 was necessary due to the difficulty in establishing parallel and derived datums from the housing sides, given the existing draft angles and overall geometry, which were crucial for accurate component location. 

A precise 3D model was developed using SolidWorks 2023 and exported as a .STEP file for compatibility with Bambu Studio. The prototype was fabricated using Polymaker orange PLA Pro filament. This distinct color was selected to ensure high visibility of any markings made on the housing during subsequent design revisions. 

Following the printing process and support removal, a fit and function test was conducted to validate the proper meshing of all internal mechanical components. After incorporating necessary design revisions to address the initial failure points, a final prototype was printed, assembled, and delivered.