Plastic’s fantastic for additive manufacturing process

Barely a week (sometimes barely a day) seems to go by without news of a new additive manufacturing machine, process or material reaching <i>Eureka</i>'s inbox. Naturally, this is sometimes the cause of a certain amount of cynicism about the claims made in these announcements, particularly when it becomes apparent that the machine or process in question is actually a work in progress.

However, one machine that does seem genuinely to have moved things forward and is far from a work in progress is the Arburg Freeformer, which was given its world premiere at the K 2013 Show in Düsseldorf. This success continued at the Euromold Show, where the Freeformer also impressed trade visitors from the mould construction, design and product development sectors. Unlike conventional additive manufacturing techniques, with Arburg Plastic Freeforming (AKF) standard granulates are melted as they are in the injection moulding process. The process makes use of 3D CAD files, that are read in directly by the Freeformer. After start-up, everything else takes place automatically. A nozzle closure with piezo technology builds up the desired component layer by layer from miniscule plastic droplets without using support structures. During this process, the item under construction is moved by a component carrier with three or five axes. The discharge unit with nozzle remains stationary, while the component carrier moves. As one of the world's leading manufacturers of injection moulding machines, Arburg enjoys a well-established reputation as a reliable partner in the plastics processing industry. "The Freeformer and the Arburg Plastic Freeforming (AKF) technology have expanded our product portfolio and mark our entry into additive manufacturing, which will benefit the entire industry," says Arburg's Herbert Kraibühler. The potential of the Freeformer and of Arburg Plastics Freeforming (AKF) was demonstrated at the recent Euromold Show, with two exhibits which produced different one- and two-component parts from standard material. The demonstration was supplemented by the exhibition of wide-ranging components produced using the new technology. "Our exhibits were extremely well received by the public. Visitors were impressed with the look and feel of the surface quality of the components, most of them assessing it as exceeding expectations," says Dr Oliver Kessling, Arburg's department manager for plastic freeforming. Because the Arburg Plastic Freeforming (AKF) process uses standard granulates, rather than special resins, powders, strips or other pre-fabricated materials, this means that a wide selection of materials and colours are available. The material costs are accordingly low. These low costs and the fact that the user is not restricted to expensive proprietary materials whose supply is controlled by the machine manufacturer is potentially the most game-changing aspect of the Freeformer. Material preparation in the Freeformer is very similar to that for injection moulding. The machine is filled with plastic granulate and a heated plasticising cylinder ensures an optimally prepared plastic melt. The parts are produced from tiny droplets of plastic, which are produced by the fixed discharge unit featuring a nozzle and a patented piezoelectric nozzle closure. This enables fast opening and closing movements to produce the plastic droplets under pressure. With the movement of the three- or five-axis component carrier the desired part is being built-up layer-by-layer from droplets. With the optional five-axis execution a wide range of undercuts without support structures can be realised. This means that even complex 3D geometries can be produced waste-free with minimal material consumption, achieving highly cost-effective results. However, the Freeformer can do even more. The version with two discharge units can also be used to process two components. In this manner, movable hard-soft combinations, for example, or parts with a special appearance or texture can be produced, in which both components are firmly joined and the parts can be used functionally. Arburg has consistently followed the same approach with the Freeformer as with its injection moulding machines, developing complex technology in-house and making it simple to use. The parameters required for the construction of the parts are automatically generated by the Freeformer control system with a gesture-controlled multi-touchscreen. This receives the 3D CAD data for the components to be manufactured in the form of .STL files, processes it automatically through slicing, after which production can start. No special programming, processing knowledge or extensive training is required. One aspect that proved extremely popular among developers and design offices in particular were the plug-and-play features of the Freeformer. The parts are produced completely free from dust and emissions. The machine is therefore suitable for virtually any application environment, whether in production, the office, the design department or a clean medical technology environment. No extraction or filtering equipment is required. The Freeformers are mobile and universally usable, thanks to their compact dimensions and immediate production readiness. The machines are simply connected to the power supply and production can begin straight away. In addition to questions relating to technical features and availability, questions have also been asked in relation to the production of parts and the plans for other Freeformer sizes. Herbert Kraibühler answers these by placing the Freeformer in the context of the company's overarching philosophy of production efficiency: "The Freeformer is the ideal addition to our range for the cost-effective production of plastic parts. The central question for our customers in the future will be: 'How many parts do you plan to produce, how quickly and in what quality?' Injection moulding will always be the right solution for the production of high-volume runs in top quality. One of the benefits of the Freeformer is that it operates without a mould on the basis of 3D CAD files. It is possible to change products in just a few minutes, producing one-off parts or small-volume batches as required." Another key breakthrough here is the ability to process more than one material at a time through the use of multiple 'discharge units', giving rise to parts that integrate hard and soft polymer elements or multiple colours.