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Using water and its suppliers installed sys­tems to cut floor carpeting and other interior linings. Today, water-jet systems have practically replaced punching and mechani­cal methods for this work. This is because the punching tools needed for complex shapes are highly complicated, making them very expensive. Worst of all, they are completely inflexible and have to be rebuilt every time changes are made to the shapes of the work pieces. For those who haven’t come across it before, the concept of using a jet of water to cut materials is mind-boggling. But with extreme water pressures and abrasives added, water-jet cutting is feasible for a wide range of materials. W ATER-JET CUTTING was first used in 1975, when it was introduced to produce wooden puzzles. It replaced a method in which saws were used to cut out the individual pieces. Besides working with a higher precision, the new method also produced less dust. For many years water-jet technology was used only for mar­ginal applications, for example to cut deep-frozen products and ice-cream. As the versatility of the method was recognised, so-called water-jet job-shops were TOP OF PAGE: Robots used for waterjet cutting have coiled high-pres­sure pipes to provide elastic compensation for changes in angle & twisting of the robot’s wrists. 4  Silicon Chip set up. The technology employed in these shops was almost exclusively two-dimensional, with abrasive being added to the water whenever harder materials had to be cut. Water-jet cutting is most often used to replace traditional punching of materials and not sawing or other cutting methods such as laser or plasma cutting. The main advantage of water-jet cutting is that, unlike punching, it does not require a special tool for each work piece. The first systems for producing parts with three-dimension­al shapes were developed in 1985. Computer-controlled water-jet robots were used first by suppliers to the automotive industry, who employed them to cut roof linings for cars. In the following years, the automotive industry Abrasive water-jets Water-jet technology can be used to cut virtually every material, even steel and aluminium. For example, Crane Fruehauf Ltd. of Norfolk, UK, uses large abrasive water-jet cutting tables to produce the cylindrical containers for road tankers. Due to the high energy of the abrasive water jet, thicker aluminium and steel plates can be cut than with laser or plasma cutters. Unlike laser or plasma cutters, water-jet cutting causes minimal heating. With laser and plasma cutting, the heat devel­oped affects the cut edges, which require further work before the parts can be welded. Also, water-jet cutting is generally insensitive to distur­bances such as vibration caused by other metal-forming processes. With water-jet cutting, Crane Frue­ hauf is able to cut a large variety of different materials. As a rule, the system is used to cut 3mm thick stainless steel and structural steel at a rate of 600mm per minute. More commonly, water-jet technology is used to cut plastics and composites, especially fibre composites, laminated struc­tures, and glass-fibre reinforced and wood-fibre-based com- robots for r-jet cutting Waterjet cutting is used in the manufacture of numerous interior parts of motor vehicles. The result is very clean cut material and no need to make custom punches or jigs. posites. Oscillating cutting methods or conventional machining cannot be used for these materials because they don’t give a clean cut. Much of the interior trim of modern passenger cars can be produced using water-jet cutting, for example the roof, door and boot linings, rear shelves, carpets, instrument panels and bump­ ers. German car maker BMW uses the method for cutting out its instrument panels. This relatively new technology is largely the result of development work carried out by ABB I-R Robotised Waterjet, a joint venture set up by Asea Brown Boveri and Ingersoll-Rand. ABB I-R is the market leader in water-jet cutting equipment for three-dimensional applications and to date the company has in­stalled more than 250 systems worldwide. Water-jets cut with high precision. The main characteris­tics and benefits are summarised below: •  Suitable for cutting composite, textile or fibreglass reinforced materials. •  Minimal heat produced. •  No dust, odours or smoke produced in the workplace. •  Surfaces of the cuts are of a high quality. •  Cutting forces are low. •  Only simple work piece fixtures are needed. •  The tool is always sharp as there is no wear. •   Tool radius can be less than 0.15mm, allowing sharp-edged contours to be cut. Very high water pressures This 3-D water-jet cutting system at Crane Frue­hauf Ltd in the UK is used to cut 3mm thick stainless steel and structural steel at a rate of 600mm/minute. Installed in the cutting box is an electrically driven pump that drives June 1997  5 A water-jet cutting tool consists of: (1) a high pressure pipe; (2) a nozzle made of diamond, sapphire or very hard metals; and (3) a screwed cap. Hard metal nozzles are used when abrasives are added to the water. In this water-jet process, two ABB robots and an automatic shell-lifter are used to cut car head linings in one operation. The finished head lining is then ready for installation in a car. a high-pressure unit. A conventional hydraulic system with a power input of 20-40kW provides the driving force for one or more double-acting pressure boosters which produce the required pressure in the water jet. The working pressure lies between 3,000 and 4,000 bar (equivalent to 43,000 to 58,000 psi), depending on the application. The nozzles are made of sapphire, diamond or very hard metals, with an internal diameter of 0.1-0.5mm, to create a very thin jet. Hard-metal nozzles are needed when abrasives are added to the water. The maximum distance between the nozzle and the surface of the material being cut is about 50mm. After it has cut through the work piece, the jet turns into a spray and imme­diately loses its cutting ability. The particles removed during cutting are washed out with the water and are collected by filters before it drains to the sewer. The amount of water used is quite small – an average of 1.5 litres/minute per nozzle. High noise levels CAD animation allows systems envisaged by a customer to be shown in three dimensions, allowing techni­cal evaluations and the fixing of cycle times. 6  Silicon Chip The process is extremely noisy. For a system pressure of 3500 bar and nozzle diameter of 0.5mm, the velocity of the water-jet is about 800 metres/ second which is about three times the speed of sound. The resulting noise level is somewhere between 110dB(A) and 120dB(A). Because of the risk of physical injury and the high noise levels, the only feasible way to operate water-jet Modified robots ABB robots used for water-jet cutting are modified for wet working conditions. They have specially designed high-pressure piping, including a modification to solve problems caused by the rotation of the robots’ wrists. This involves the pipes being wound in a coil around the axes to provide elastic compensation for changes in angle and twisting of the wrists. As well, the robots are suspended from a gantry. This gives more working space than with floor-mounted robots and ensures that the robots remain relatively dry, since they do not stand in water. CAD animation To speed up the design, construction and installation of customised, robot-based systems, ABB I-R has developed CAD anima­tion of water-jet cutting projects. It enables proposed systems to be shown in detail on a computer screen. The design of the installation, cutting tools and robots are all simulated to allow a detailed evaluation of the overall system. Preliminary studies, such as technical analyses and the determination of collision risk, can be carried out at an early stage. In addition, cycle times can be fixed and the operating times of the individual robots can be harmonised. CAD animation allows the robots to be programmed in paral­lel with the actual construction of the system. CAD animation also enables the robot programs of systems already installed to be easily rewritten for new or modSC ified products. SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏  3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏  Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________  Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Acknowledgement: this article has been adapted from the original which appeared in the January 1997 issue of ABB Review, published by Asea Brown Boveri Ltd. Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ cutting equip­ment is via robot or numeric control. Water-jet cutting tools in 2D-installations are guided by AC-driven linear units. ABB industrial robots are used in 3D cutting installations to allow optimum control of the water jet. For example, a six-axis robot can manipulate the nozzle in any required direction while ensuring the right cutting angle. The nozzle is moved along either linear or spherically curved paths at high speed and with very good repeatability. June 1997  7