Waterjet/Laser cutters in-house?

[Cory]

Originally Posted by asid61

What makes a waterjet a better option than some kind of CNC router? For the metals that FRC uses, wouldn't a router of equivalent price do the job just as well?
Just thinking about the lower operating costs and maintenance and the very-close speed of the cut, what makes a waterjet better than a CNC router in general? For the speed thing I'm just going off Youtube videos showing waterjets working and CNC routers working, so I'm not sure if I have a good grasp of the capabilities of a waterjet.

In a very broad sense, with some points not being of concern in FRC:

• Workholding is much simpler with a waterjet. There is no lifting force and very little lateral force.
• No risk of work hardening stainless or other alloys
• Programming is trivial in comparison. No need to decide on depth of cut, width of cut, feeds and speeds, or to ensure the sheet is held down locally to avoid deflection while cutting. You select the contours, tell it which side to cut, the material type, thickness, and desired cut quality, and it does the rest. There's some editing, but it's a much less involved process.
• Smaller internal features can be machined
• Much thicker parts can be effectively cut (definitely not a FRC consideration)

Speed may or may not favor a router. If you have a good enough router that can cut full depth, it probably wins. Piercing start points for cuts is extremely slow on water jets. If you had a boatload of pockets in a part, a router may well cut it faster due to so many pierces. Feed once pierced is somewhere in the 40-90 IPM range for optimal cut quality on 1/4" Al for a water jet, depending on PSI and pump HP. We run full depth contours on 1/4" plate on our very rigid CNC mill at ~30 IPM with a 1/4" cutter and 55 IPM with a 1/2" cutter (both are pretty conservative feedrates).