Die-casting and Precision Machining

Figures 1 and 2 show a gear used in the lead screw drive train of a screw cutting lathe that was
made in about 10 minutes with an abrasive waterjet. This custom gear was needed to achieve a
1/2-in. pitch for a spring winding application. It ran as smoothly and quietly as the other gears in the

train. machining Components,Note in Figure 2 that the keyway and close-fitting bore also were made with the abrasive
waterjet.
Figure 3 is a planetary gear system in which the round holes
in the planets are used to carry workpieces in a lapping
machine. The total time to make the entire system in 1/8-in.
steel was less than 40 minutes.machining Components
Figure 4 is an internal gear driven by a spur gear for an
application in a winch. In this case, the key is built into the
spur gear rather than using a keyway. Note that the ratchet
and pawl also are abrasive waterjet machine-made parts.
Even odd-shaped gears can be made by an abrasive
waterjet, which also can form racks and mating gear sectors
in a manner that easily facilitates a linear motion by pulling a
lever.
Sprockets and Chains
Ordinarily you would not make your own chain, but what if
you wanted to lift 300 tons? You then would be forced to make your own. Links in the chain in
shown in Figure 5 were made with an abrasive waterjet and assembled into a chain that can lift a
300-ton object.machining Components
It would be more common to make a sprocket and
buy the chain. Sprocket geometry can be found in
Machinery's Handbook, and it is quite easy to
follow the specifications, machining Components,draw the desired sprocket,
and produce it with an abrasive waterjet.
Cams
With the advent of low-cost servo drives and
control systems, cams are used less than they
were in earlier times, but they still provide a lowcost
means of making particular motion profiles.
Cams also can be used as wedging mechanisms
for locking movable elements in place.
Cams can be made very quickly on an abrasive
waterjet. The major portion of the work is
determining the desired cam shape. Once the
shape is known, making the cam is as simple as
loading the CAD file into the machine and pressing
go[START?].machining Components
Figure 6 shows a cam ready to be cut according to the function:
R = 2 + Sin(Theta)
machining Components,A hole with a keyway has been added so the cam can provide a reciprocating motion.
Springs and Flexures
Two types of springs can be made on an abrasive waterjet. One type flexes normal to the plane of
the X-Y table, and the other flexes parallel to it. Figure 7 shows a spiral spring typically made from
a thin sheet of heat-treated spring stock. The spring is held on its outer diameter, and the moving
member is attached to the central hole. machining Components,The spring is very rigid in the radial direction, but quite
flexible in the axial direction. If two such springs are placed a short distance apart, one above the
other, they provide a quite good flexural bearing for limited motion.