Looking at Waterjets

Waterjet systems have come into their own for a variety of material cutting applications, whether it is for carpet and headliners or for door panels and instrument panels.

Waterjet systems have come into their own for a variety of material cutting applications, whether it is for carpet and headliners or for door panels and instrument panels. High pressure water—shooting out of a small diameter nozzle (e.g., from 0.007 to 0.018 in. diameter) at 55,000 psi—provides precise, narrow-kerf cuts. Key issues for cutting, like most all production processes, are low cycle time and flexibility. This is being addressed in an increasing number of applications through the use of standard industrial robots, which also help contribute to economy. Sven Lennartsson, president of ABB-IR Waterjet Systems (Wixom, MI), says that thanks to the consistent quality provided at high throughput rates, a waterjet system can have a cost advantage over manual operations "even in low-wage areas." Although the company offers both open systems, with a waterjet gun-wielding robot placed out in the open adjacent to a worktable, and closed systems, with the robot residing in a box, Lennartsson and his colleagues think that there will be greater utilization of enclosed systems in the U.S., a design that has become popular in Europe.

This is the Cutting-Box2 system, which is a comparatively compact unit (105 in. side to side; 147 in. front to back [including the table]; 114 in. top to bottom) for cutting parts including door panels and instrument panels. The integrated design of this unit permits easy setup, as the robot, index table, sound enclosure, and internal floor are all mounted on a common frame. The system ships as a single unit. According to Timothy Donovan, Automotive account manager, ABB I-R Waterjet Systems, "In the U.S., waterjet systems can get a bad name because of the noise and the mess." A design intent of systems like this is to keep the noise level low—below 80 decibels—and to contain the water being used. The use of enclosed systems is more typical in European manufacturing operations than in the U.S. In the U.S., a common approach, according to Sven Lennartsson, president of ABB I-R, is to have an open system with the fixtures being used to help dampen the noise. He admits that whereas the enclosed systems have a higher initial cost, the fixtures used in the open systems can add up to a higher long-term cost when initial build and maintenance costs are calculated.

Here's a bigger Cutting Box model. Note how on either side of the work table there are two different types of parts. As there is a robot inside the box doing the water cutting, it is simply matter of employing a different program for each of the parts. According to Sven Lennartsson, "During the past five to six years there has been a drastic improvement in the speed and performance of robots. They are able to provide more accurate lines and arcs." He attributes much of this improved capability to faster and better microprocessors and enhanced control algorithms. ABB-IR is, of course, a joint venture between ABB, which is well known for its robotic technologies, and Ingersoll-Rand, which has long been a leader in waterjet technology.

Inside an enclosure, this six-axis ABB IRB 2400L robot has the ability to reach different parts fixtured on the worktable. Note the structural steel weldment that permits the inverted orientation of the robot. Earlier versions of enclosed systems utilized five-axis gantry systems instead of robots. However, because robotic equipment has become more widespread for a variety of industrial applications, robots are more economical than the gantries. They are, in effect, off-the-shelf products. Lennartsson says that the robots help provide superior quality than can be achieved by other means, which typically include manual cutting or the utilization of punch tools. Compared with manual approaches, the benefit is one of consistent quality. And the robots are quick, too. As compared with the tooling, waterjet streams don't dull as metal tools do, so they don't require resharpening.

This open cell approach is more common in the U.S. than it is in Europe. One of the key reasons for the use of the open approach is that it allows integration into existing production lines more readily. Typical examples of in-line installation are for cutting holes in things for options, such as in headliners and floor carpets. Also, the open system allows more production flexibility in terms of load/unload operations as compared with the closed systems. However, given increased concerns with the plant environment and with safety, the people at ABB-IR anticipate closed systems catching on in the U.S.