The objective of this project was to not only obtain a better understanding of how to manufacture with waterjet machining, but also to understand the inherent advantages and disadvantages of its use. Waterjet machining is a subtractive method of manufacturing, removing material where necessary to fabricate a complete part. Cutting with water jet machining is done by blasting ultra-high pressure water mixed with an abrasive garnet onto a plate of material intended for the final part. The mixture induces an accelerated and concentrated erosion of the material, allowing for a complete cut to be created at the area of application. The fabrication process is computer controlled, allowing the waterjet to fabricate intricate and unnaturally curved parts. In order to demonstrate the functionality of waterjet machining, a dragon-shaped bottle opener and an elaborate Zelda Triforce crest were water jet cut.
Zelda Triforce Crest
The initial DXF file drawing
The water jet cut Zelda Triforce
The Dragon Bottle Opener
The original DXF file drawing
The water jet cut dragon bottle openers
The bottle opener in action!
Through the use of a water jet the following parts were made: six dragon shaped keychain bottle openers and a Legend of Zelda Triforce. Having followed the dimensional constraints and requirements of the interior rounds being no smaller than .04 inches in diameter and hole sizes being no smaller than .06 inches in diameter, these parts came out exceptionally with smooth faces and no edge deformation, as seen in the pictures of the finished parts on the cover page; they matched the 3D CAD very closely. In addition, the bottle opener operates flawlessly and repeatedly, as demonstrated in Figure 7, and thereby achieved our initial goal to create a functional part. Both parts did however have coarse side edges where the pieces were cut out. This can be attributed to the abrasive nature of the waterjet abrasive.
Potential problems include the following: rounded inside corners instead of rounded outside corners, stream lag, and tapering.Knowing that the water jet cutter could not create sharp internal corners, we designed the inside corners to be rounded. Designing these features allowed us to create parts that matched our design while avoiding problems due to the limitations of the waterjet machine.
The cuts did not run into any issues with stream lag or tapering. This is likely because a part thickness of 0.25 inches was thin enough for the waterjet to cut through without losing significant water pressure. Stream lag normally occurs when the entering point cuts more quickly than the exit point and tapering occurs when the material decreases the stream power within the cut.
Another potential problem that was a cause of concern were the thin features in the Legend of Zelda Triforce design. It was a concern that if the thin features that bridged the triangles to the wings and the legs to the main body were too thin, then they could risk being snapped. Fortunately, the problem was avoided by giving the part a comfortable margin of thickness and rounding out the internal corners.
