Waterjet - Forming, Joining, Fasteners
With waterjet, you can design parts using the same geometry as shearing, punching, plasma cutting, etc., but that often leaves money and opportunity on the table. Waterjet makes square and rectangular holes as easily as round holes, and filleted outside corners as easily as square. If you're designing with the expectation of waterjet cutting your parts, taking advantage of waterjet can save considerable effort in subsequent fabrication and finishing.
Waterjet is a natural for all sort of woodworking-inspired joinery. Mortise-tenon connections can be loose, with bolted or snap-together assembly, can serve as a starting point for plug welds, or merely serve to locate parts for fillet welds. (In the waterjet world, this is more commonly referred to as tab-slot design.)
Welding setups benefit from self-aligning tab-slot "T" joints and from self-aligning finger joints for outside corners. Tabs can be cut to locate plug welds in the neutral plane. Corner finger joints can be cut to extend to half the mating corner thickness, in effect turning an outside corner weld into a miniature inside corner fillet weld, for great economy in welding, distortion control and finishing.
Finger joints can, alternately, extend flush or past the mating edge, for filler-less TIG welds easily finished square for art and other aesthetic applications.
Fabrication further benefits from Poka-Yoke, i.e. asymmetric joint design where parts mate only the one correct way.
The joinery examples below show a range of design options.
Please read For Makers for useful design information regarding tolerances and clearances.
Click the left image for a live example showing a spring-loaded tab-slot assembly in 12ga mild steel. The smaller part has four tabs. The larger part is sprung apart until the tabs snap in place. The tab ends are then plug welded.
These structural connectors were cut in 1/2" A36 steel, with tabs to locate pieces, then fillet welded.
These kerf plates and beam hangers were cut in 3/8" A36 steel, using similar joinery, then fully welded and finished with the joint details no longer visible.
This part in 3/8" steel was waterjet cut, including the tap pilot holes. The holes were chamfered both sides, then power-tapped, using our Bridgeport.
Raw waterjet holes are generally adequate as tap pilot holes down to M4 or #8-32. Below that, the taper is large relative to thread depth; it's better to cut undersize and drill out.
Waterjet holes are in general adequate for PEMs (self-clinching press-in fasteners).
This is a brake-formed welded fabrication of 12ga steel, with PEM nuts.
These boxes are waterjet cut in .09" 5052 aluminum, brake formed, then assembled using 3/16" high strength aluminum blind rivets. These are later powder coated.
Random orbit sanding is expedient finishing for this part. The edges are deburred but still sharp. They're smoother after powder coat.
Waterjet is in general adequate for POP rivets.
Designer Jonah Griffith's 180" countertop is cut in sections in 8 ga stainless steel, joined with waterjet-cut locking dovetail joints with a few-thousandths fit. The sections are secured from below via weld studs. This was an experiment that worked out well.
This dovetail joint in 1/2" steel is primarily for show. It was cut tight and hand-filed to fit; then given a blackened-and-waxed architectural finish.
This was an expedient prototype. The blade with notches was cut from a single-edge razor blade. The frame was cut with mating frobs, peened in their centers to fix the blade in place.