Arthur Turner, managing director, Rainford Precision
Abrasive waterjet cutting has been around for four decades, but fine abrasive waterjet (FAW) cutting—which employs smaller diameter, abrasive sapphire garnet orifices and nozzles—is now being offered for industrial use and not just research.
A key development in the world of micromachining has been the improvement of machine positioning accuracies, allowing target points with a tolerance of ±2.5 µm to be achieved. This improvement in positioning as well as the ability to achieve smaller cut widths, down to 0.2 mm, opens up new possibilities for designers and manufacturers.
Initially, machining issues experienced through the use of mechanical machining, milling and drilling were solved by the introduction of laser machining and electrical discharge machining (EDM). However, new materials that are being developed have given rise to issues with burning or heat-affected surfaces. Laser machining and EDM are therefore not suitable for every application.
The FAW cutting process uses cold water and a small amount of abrasive material, so does not create heat like other machining processes. This makes it especially suitable for aerospace and medical applications where laser machining and sink/wire EDM technologies have problems.
Together, Finepart Sweden—a Swedish manufacturer of micro abrasive waterjet cutting machines—and its UK representative Rainford Precision Machines are working towards the realisation of new capabilities for FAW cutting.
Finepart Sweden has introduced new features on its Finecut WMC (waterjet machining centre) 500 II (Figure 1) for tackling current micromachining issues, such as a two-axis tilt and swivel cutting head (Figure 2) and two-axis workpiece holder. Users are therefore no longer limited to producing only 2D workpieces.
Figure 1: The Finecut WMC (waterjet machining centre) 500 II.
Figure 2: The new two-axis tilt and swivel cutting head on the Finecut WMC 500 II.
Also incorporated on the Finecut WMC 500 II are linear drive motors and glass measuring scales for control of the X, Y axes, which allows for a rapid feed rate of 40 m/min and minimal positioning time. This is a significant differentiator when comparing the Finecut WMC 500 II with traditional waterjet cutting machines.
The use of non-conductive materials such as ceramics and glass for manufacturing at micro scale in the electronic and space science industries can be problematic with laser machining and EDM technologies. FAW cutting enables these materials to be machined more easily. Furthermore, it allows for the realisation of thin walls, as shown in Figure 3 of a glass star with 0.55 mm thick and 10 mm high walls.
Figure 3: A glass star with 0.55 mm thick walls by 10 mm high produced on the Finecut WMC 500 II.
A 230-grit garnet can be used to achieve finer surface finishes with Ra 0.8 µm. Naturally, surface finish is attributable to material thickness, material machineability and cutting speed, therefore all of these factors need to be taken into account when considering FAW cutting for component production.
The cutting process is performed at 4,000 bar in pressure, although this does not mean that the material must have a minimal thickness to be suitable for FAW. Sample, 0.18 mm thick, stainless steel components have been machined without distortion or burrs at feed rates of 400 mm/min (Figure 4). If the material is softer and able to flex, solutions can be found by using sacrificial plates either on the top or bottom or in both positions.
Figure 4: A sample, 0.18 mm thick, stainless steel component produced on the Finecut WMC 500 II.
Rainford Precision will present the Finecut WMC 500 II on stand H19-300 at MACH 2018, which is to be held at the NEC (National Exhibition Centre) in Birmingham, UK, on April 9–13.
Rainford Precision Machines
Finepart Sweden
Biog:
Arthur Turner has been involved in micro machining for over 20 years, providing solutions to manufacturing problems in industry and academia. His area of expertise is mechanical cutting techniques and strategies for producing components to tight tolerances and high surface finishes. He is the managing director of Rainford Precision Machines, which supplies ultra-precision machines and material specific cutting tools as small as 8 µm diameter specifically to companies that require micro components or features.