“The Increasing Efficiency of Waterjets”
By: Richard Ward
Advanced Machinery Hotline, Jan. 2001
Also published in print:
Advanced Machinery Hotline, March / April 2001
The introduction of the Waterjet Abrasive Recycling Dispenser (WARD) is the latest innovation to make a substantial change to the operating cost and productivity of running an abrasive waterjet cutting system. In fact, the savings generated through recycling abrasive are so great, that for a larger user of abrasive, they could comfortably exceed the payments on a capital investment of over $350,000!
In the Manufacturing Community, the need to constantly seek to reduce operating costs while increasing productivity is endless. Equally demanding are the end users’ demands to supply more of the same product, with improved quality, yet at a lower price.
It is the working of these demands against each other that incubate the need for innovation, creativity and fresh, new thought. Without the need to strive for higher goals, the likelihood of providing better quality products to end-users would diminish.
Waterjet cutting, a relative newcomer to the machining industry, has faced several challenges since its introduction. The initial issues were the need to provide higher pressures up to 60,000 psi in a consistent and viable manner. This led to the development of specialized high pressure seals with an average life in excess of 250 hours.
The next hurdle was to provide a nozzle that could focus the mixture of water and abrasive, usually garnet, traveling at 2200 mph into a sharp, coherent stream. Key to the design was the need for the nozzle to last more than a few minutes, which was typical with the initial nozzles used. With the accomplishment of long life nozzles, the waterjet industry began its real entry into the market place and faced the next challenge of developing more efficient waterjets.
These long life nozzles enabled waterjet operators to predict the life and wear pattern of the nozzle, allowing parts of greater accuracy to be cut. This in turn quickly brought about the demand for higher accuracy gantries to match the accuracy achievable with the nozzles.
Intelligent software that could predict automatically the cutting characteristics of the stream in the countless materials that can be cut with waterjet was next, allowing waterjet cutting to continue its double digit annual growth. Recycling Abrasive
The ability to reuse up to 90% of abrasive, the major cost item in operating a waterjet, is quickly being felt throughout the industry with the introduction of the Waterjet Abrasive Recycling Dispenser (WARD). Operators are facing the pleasant options of either reducing their prices or increasing profits or a combination of both.
From waterjet's inception, operators were always led to believe it would not be viable, or possible to recycle the garnet. In the last year, this has clearly been proven wrong, with almost all major waterjet manufacturers now offering the WARD as an option. Recycling abrasive offers savings that cannot be ignored. The largest buyers of the systems are existing waterjet operators who, in a matter of minutes, can calculate the savings achievable through recycling, and the pay back period. Some operators are finding that it is easily achievable to have a pay back period of 3 - 6 months.
Another myth being quickly dispelled is the quality of cut with recycled abrasive. In fact, depending on which abrasive is used, results clearly show recycled abrasive can cut faster than new abrasive, with an increase in all aspects associated with waterjet cutting. It is believed this is achieved as the alluvial, rounded garnet crystals tend to have portions of the crystal knocked off them as they are accelerated down the nozzle. The then leaves a sharp exposed edge that is more aggressive in the cutting process. The result, faster cutting times with better quality.
The WARD is designed to ensure the quality of abrasive dried for reuse is consistent through automatically disposing of the smaller, undersize abrasive. Waterjet operators are amazed to find that within 3 minutes of removing the abrasive from the base of the waterjet tank, dry, ready to use abrasive is available at approximately 120 - 200 lbs per hour. The WARD only dries the good reusable abrasive.
Closing the pricing gap between laser and plasma
The overall savings in recycling could be up to 40% off the total operating cost of running a waterjet system. If these savings are then passed on to the end user, the effect will be vastly different cutting costs, narrowing the gap between laser, plasma and waterjet cutting. At present there are many 'too close to call' opportunities that are lost to alternative cutting processes. Waterjet abrasive recycling will change this. It is not possible to recycle the gases used for heating, limiting the ability to reduce cutting costs significantly with laser and plasma cutting as has been done in waterjet cutting with the WARD.
The WARD is an innovation set to change the face of waterjet cutting forever, and is already the beneficiary of the 2000 MANNY award, a prestigious award for engineering and manufacturing excellence.
Once again, innovation and development, pressed by the ruthless demand for change has created an environment where those rising to the challenge to recycle valuable abrasive, have succeeded. It is only time until the next challenge surfaces.
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