Sheet Metal Industries, October 1999, Published in England
In today’s climate, being “green” is something that we all have to think about. EasiJet offers a solution for metalworking companies -- a system that recycles waterjet sludge.
The Waterjet Abrasive Recycling Dispenser (WARD), developed over the past 2 1/2 years, is now able to remove the sludge from the waterjet tank and recycle it. Waterjet operators have been able to recycle 50% or more of the abrasive for reuse, according to US distributor, EasiJet.
US companies that were discarding used abrasive can now recycle it, saving thousands of dollars per month. These savings can be applied to the company's profits, be used to purchase new equipment or be passed on to the customer in the form of lower prices for cut parts. EasiJet is now bringing the product to the UK and is actively seeking a distribution centre.
The WARD employs a series of patented nozzles, all switched on automatically, to suction the sludge to the unit, where it is washed and passed through several screens. The smaller, unrecyclable garnet and fines from the cut material fall through the primary screen. The larger, reusable abrasive particles are then passed into the dryer, through a secondary screen and into a hopper for reuse. Sometimes this abrasive cuts faster than new abrasive, due to a lower percentage of contaminates and new jagged edges on some particles. During the washings, water from the waterjet tank is used, with only 1.9 - 3.8 litres of fresh water per minute needed for the final rinse. All water is returned to the tank. The recycled abrasive is able to be reused immediately or mixed with new abrasive, depending upon the cutting need.
A waterjet company with a 75kW pump can use 1.36kg of abrasive per minute. If the company purchases garnet for US$0.35 per pound, they would be spending US$63 per hour on abrasive alone, costing US$630 for every ten hours of operating time. With a WARD 24 and cutting softer materials, this same company might recover 70% of the abrasive, saving over US$9,000 per month. With these kinds of monthly savings, abrasive recycling is the key to open a treasure chest of business opportunities!
Thousands of minuscule, red, glassy, mineral particles, surrounded by gallons of highly pressurized water, explode from an opening no larger than a human hair at thousands of miles per hour. In their forward propulsion, the gemlike particles erode the material, leaving some of them smaller than at the beginning of their journey. These tiny grains shave off particles of the material being eroded, leaving a swath of eroded space in their wake. The shaved-off particles fall together with the garnet, into a large, water tank. The erosion process is violent, but anyone observing this phenomenon would be able to approach the erosion point with no more harm than a fine mist on their protective eyewear. This accelerated erosion procedure is controlled by a technologically advanced machine with tremendous memory and calculation abilities. Those familiar with abrasive waterjet cutting surely recognised its description.
Waterjets can cut almost every material on earth. For more than a decade, waterjets have cut through materials as diverse as foam, acrylics, stone, marble, phoenalics, aluminum, steel, inconel and titanium. Waterjets are operated by a computer called a controller, utilising specialised software for waterjet cutting. The head of the waterjet, containing the orifice and nozzle, is mounted on a gantry for mobility in up to six axes. During abrasive waterjet cutting, anywhere between 272.2g and 2kg per minute of abrasive (typically garnet) is used, depending upon the size of the pump and the speed of the cut. Water pressure can be over 4,000 bar.
The advantages of abrasive waterjet cutting are numerous. Waterjet cutting leaves no heat affected zone, no large start holes, no heat distortion and no serious danger for the operator. Some materials cannot be cut at all with heat, as this would affect the material in an adverse way. With abrasive waterjet cutting, parts can be cut along a common line between nested parts, thus saving on expensive material. The slower the cutting speed, the finer quality finish on both sides of the kerf. The controller can even be programmed to slow down for corners, in order to ensure a quality cut.
The consumables in heat cutting are the gases, which are burned up and cannot be recovered or recycled. This used to be the case with the abrasive in waterjet cutting, with companies spending thousands of dollars per month to use, remove and dispose of the garnet. Due to this high cost of garnet lost to landfills, abrasive waterjet cutting often lost potential jobs to oxyfuel, plasma or laser cutting.
In addition to the obvious savings of abrasive associated with the WARD, there are additional savings in tank cleaning and sludge removal costs. At present, waterjet companies must stop cutting long enough to empty the waterjet tank of the sludge, causing a considerable downtime with the waterjet. This downtime of course costs the company money. The removal of the sludge is another expense incurred by the waterjet business, which is reduced by the WARD. Some leaking from dumpsters where sludge is awaiting disposal can cause other problems.
A number following the acronym, WARD, denotes the size of the screen in inches. Therefore, a WARD 24 utilises a 24 inch/60.96 cm screen during the washing and separating process. The WARD 24 is the first commercially available recycling system for operators, regardless of the type of waterjet in operation.