To determine optimum stack height, simply compute the tool path for several different material thickness’. For example, if you are cutting 1/8″ aluminum, simply compute the path at 1/8″, ¼”, 3/8″, ½”, 5/8″ and so forth, and determine which stack size cuts fastest. You will lose some precision the higher you stack, but you will gain cutting speed up to a point. Depending on material and part geometry, the optimal stack height ranges from about ¼” to ½” (6 to 13 mm).
Parts made from stacked titanium sheets
If your part has a lot of corners, then stacking the material will be less advantageous compared to a part that has few corners. This is because the waterjet needs to slow down for corners, and when you increase the stack thickness, it has to slow down extra for the corners.
There is also some extra time needed in setup when stacking materials, to make the parts will not float away or the plates shift when cutting. The extra time and effort needed for fixturing stacked materials can cut into the productivity gains. Stacking is mostly useful when working with extremely thin materials such as 0.040″ (1 mm) sheet or when doing large production runs with thin material.
“Un-stacking” thick parts
If you need a part cut that is 2″ (5 cm) thick, it will be much faster to cut four ½” (1.2 cm) thick parts, then weld them together. This can save you a lot of money, if your design considerations let you do it.
Stacking dissimilar materials
It is possible to cut materials that are of different composition that are glued to each other. For example, a cover plate made from plastic that has a foam backing on it. Glue the foam to the plastic first, then cut them both together as a unit. This can save production time, and insure the parts line up perfectly. You may need to experiment to determine the best speed for the new “material.”