Precise cutting kept well in-hand

By Deron Roberts, Jet Edge 

Having built a name for itself by building rugged, durable machines, our company, Jet Edge, a global designer and manufacturer of ultra-high-pressure water-jet systems for precision cutting, surface preparation and coating removal, realized it had to make an important component change.

We needed to replace the handheld control pendants we deploy with our products. These operator interfaces were failing prematurely because they couldn’t stand up to the water-jet environment, and our St. Michael, Minn.-based company wasn’t about to risk damage to our hard-earned reputation. Compounding these concerns, the manufacturer of the handheld control pendants wouldn’t honor the warranty, forcing Jet Edge to replace the devices at our own expense.

These devices are especially critical, because they provide a remote operator interface to the AquaVision Di motion controller, allowing the waterjet systems’ operators to control the machines anywhere inside the work envelope.

With costs mounting, our company launched a review process to find a new pendant. We would be successful.

Cutting a Fine Line
Waterjet cutting is exactly what it sounds like—it uses a powerful jet of water to cut cleanly and precisely through material in a single pass, without shredding or crushing it. In the formation of the jet stream, water is pressurized up to 60,000 psi (4,100 bar) by a hydraulically-powered intensifier pump. The pressurized water passes through an attenuator (accumulator) that stabilizes the jet stream by providing constant flow and pressure.

The waterjet cutting action results from ultra-high-pressure (UHP) water being forced through a pre-mounted sapphire orifice as small as 0.003 in (0.076 mm). The pressurized water exits the orifice at extremely high velocities (in excess of 2,900 ft/sec) as a coherent stream to produce a clean cut with a kerf—the width of the groove made by the cutting tool—also as narrow as 0.003 in., maximizing material usage (See Figure 1 below). The compact, lightweight cutting head is designed for on/off applications with frequencies of 50 cycles/min.

	FIGURE 1: PERFECT YOUR SLICE
	The water jet stream is pressurized up to 60,000 psi and is forced through a pre-mounted sapphire orifice to produce a clean cut as narrow as 0.003 in.

Our PC-based AquaVision Di motion controller on a Windows XP platform enables extremely accurate cuts with a high degree of repeatability over a wide range of materials and shapes. “The controller includes a customized Visual Basic-based human-machine interface (HMI) that guides the user through the various processes from job setup to production,” says Bert Olson, Jet Edge’s electrical engineer.

Single parts, part arrays, mirroring, scaling, rotation, and plate alignment all are managed through the controller, which is fully networkable. That means part programs can be generated offline and easily transferred to the system’s hard drive for production.”

The interactive process trajectory automatically varies feed rate and acceleration based on known characteristics of the specific job recipe, such as material type, thickness, water and abrasive flow, and nozzle size, which are stored in an on-board database. This achieves required precision, while eliminating guesswork.

“Dynamic tool offset, or cutter compensation, is employed real time,” says Olson “This eliminates the need to reload a part program to the controller if the nozzle/orifice grows due to erosion and produces out-of-tolerance parts. Optional real-time pump control allows remote starting and stopping of the pump, dual-pressure set points for hard-to-pierce materials, and unlimited data logging of every needed process parameter.”

Operators use the handheld interface to control feed-rate override, test the jets, return to path, and block retrace. They can do dry runs to see the path without running the jets. With the pendant, they control the ultra-high pressure intensifier pump, which powers the waterjet, controlling the pump’s pressure, turning it on and off, and changing the water pressure from low to high and vice versa.

The pendants are especially useful for plate alignment on the waterjet and for starting the cut. Without the handheld interface, the operator would have to go back and forth to the controller to jog the head to the right position (See Figure 2 below). It’s also useful for adjusting the sub Zs (independent Z-axis per cutting head) because the remote pendant allows the operator to get close to the material.

FIGURE 2: JOG IN PLACE

Without the handheld interface, the operator would have to go back and forth to the controller to jog the cutting head to the right position and to adjust the independent axes.