My first day on the job I met Duncan Murdock. It was 1989, and I sat in on a paper slitting meeting. I sat and listened and learned. Duncan was a senior tech (not a regional manager as he is today), and was clearly on top of the technology and the application. Although he was young, he explained to the engineers and designers exactly how to design the slitter’s cross beam, the redundant cutting heads (to ensure 24/7 operation) the catcher tank. He understood how the paper would flow at extremely high speed, across the top of the catcher, and how the catcher top would create the right airflow to keep the paper down and flat without billowing.
A waterjet stream acts like a beam when cutting, much like plasma cutting and laser cutting. These types of non-rigid cutting tools have to address the beam flexing and changing within the target material to minimize part cutting errors.
What is taper?
Taper in waterjet cutting is when the entrance width of cut is different than the exit width of cut.
What is stream lag?
Stream lag causes corner damage when the exit point lags behind the entrance point, shown in the bottom of the part below.
Plasma cut parts often exhibit an upside-down V-shaped taper where the width of cut is wider at the bottom. Laser and waterjet exhibit a normal V-shaped taper (more narrow width of cut at the bottom). Plasma, laser and waterjet can all yield stream lag errors when cutting a part.
Today waterjet is one of the fastest growing machine tool processes in the world and has over 30,000 systems installed. But how did it begin? I’ve seen many different claims over the years as to the start of waterjet. There is only one thread – one sequence of events – that I subscribe to, and that is the specific sequence that leads to the commercialization of waterjet for the cutting of soft materials in the 70’s.
Let’s start with the basics.
Waterjets are cool. They cut cool – they look cool – and the more you understand how they work and what they can cut the more you appreciate the technology. After 30 years of waterjetting I still marvel at water and sand cutting through super hard materials. It’s just water and abrasive, for goodness sake. How cool is that?!