Page 28 - MetalForming November 2017

Waterjet
Waterjet
Cutting:
Cutting:
Focus on
Focus on
Stream Velocity
Stream Velocity
With ever-higher pressures available for waterjet cutting, fabricators can leverage the power to produce more precise cuts and save on abrasives.
Here’s a tip:
Pump pressure is
the key consideration determining how efficiently a machine can cut.
Operating at pressures reaching beyond 90,000 psi—90 times greater than pressure in a fire- hose—waterjet-cutting machines can produce supersonic streams the width of a human hair to precisely cut all manner of soft materials. Add abrasive garnet, and cutting power increases by as much as 1000 times to cut virtually any material in any thickness.
But a waterjet-cutting machine is more than just water and abrasive. Responsibility for turning these com- ponents into a true shapecutting sys- tem falls to the machine, including the X, Y and Z table axes, cutting-head wrist axes, and material support catcher; the control system, including the program- ming software, operator interface, drive motors, and position and velocity feed- back components; and the pressure apparatus, which includes the pump, cutting head and plumbing.
In the early-1980s, typical high pres- sures in waterjet-cutting machines hov- ered around 36,000. Every decade since, pressure has increased, moving to 55,000 psi by the end of the 1980s and 60,000 psi in the mid-1990s. In 2004, Flow International introduced the HyperJet pump, rated at 94,000 psi, and the pressure ceiling had been raised again.
With abrasive waterjet cutting, the abrasive particles within the waterjet stream erode the material and make the separation cut, with water as the abrasive accelerator. Higher pressure increases
26 MetalForming/November 2017
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