applications feature | 3D printing
Local Motors’ Strati 3D
printed vehicle was produced using Sabic LNP Thermo- comp materials
his visit to Techmer PM in January this year. The electric-powered car was also displayed at the NPE exhibition in March.
Freeform future Arburg is best known for its injection moulding machines, but it is also making a high-profile entry into the AM market with its Freeformer machine that uses regular pellets like the BAAM process, but which delivers the melt in tiny drops rather than as a continu- ous extrusion. Freeforming is conceptually similar to ink-jetting with photopolymers (a system offered by Stratasys), a key difference being that the drops are in melt form rather than a UV-curable liquid. As with injection moulding, the granulate is first
melted in a plasticising cylinder. A stationary discharge unit with a special nozzle then applies tiny plastic droplets layer by layer onto the part carrier using high-frequency piezo technology at a specified duty cycle of 60 to 200 hertz. The construction chamber of the Freeformer offers space for parts with maximum dimensions of 190 x 135 x 250 mm. With Freeforming, surface quality of the part is largely
Techmer ES supplied carbon fibre reinforced compounds for the 3D printed body and chassis of this AC Cobra replica
determined by the size of the droplets, which in turn is determined by the size of the nozzle. Different nozzle sizes are available: 0.15, 0.2 and 0.25 mm, producing pellets between 0.2 and 0.3 mm in diameter. Part density can also be modified, not only by the material, but also by filling strategy and processing parameters, Arburg says. Mechanical properties are determined by the material and also by such processing parameters as chamber temperature. Arburg says mechanical properties of parts produced by the Freeformer can be close to those made by injection moulding. The nozzle size also influences the processing parameters. The smaller the nozzle, the tinier the droplets and the finer the surface texture, but the slower the process. In principle, any unfilled plastics material can be used, Arburg says. Standard and customer-specific
grades are available. Material availability is good, and there are specific dyed materials. At present, materials that work on the Freeformer are ABS, TPE, polycarbon- ate and amorphous polyamide (PA12). Grades based on PA6 and polypropylene are under development. Limitations are put on material possibilities by the chamber temperature (no more than 130°C) and melt temperature (no more than 350°C). “The Arburg Freeformer experts are creating and optimising the processing parameters for standard materials,” says a company representative. “This includes the detailed creation of material profiles, the optimisation of part geometries, as well as, where neces- sary, adaptation of the machine technology. The result of this development work is already available for ABS, PA12, PC, TPU and a special support material, with further materials, e.g. high-temperature plastics, to follow. The use of reinforced materials is not being considered useful for Freeforming, because the glass fibres wouldn’t fit through the nozzle. A big advantage, however, is the possibility to produce functional two-component-parts.” As with some other 3D printing processes, Free-
forming can make use of “lost” support materials to create special designs, such as parts with integral chambers or overhangs. In a typical case, a water soluble material based on polyvinylpyrolidon (developed by BASF) can be used. Freeformers can be equipped with a second discharge unit to deposit the support material. This also enables the production of two-com- ponent (e.g. hard-soft) parts. Depending on the additives (including colours)
incorporated into a material, the parameters for the Freeforming process have to be slightly changed. “In the material qualification process, our team optimises each and every parameter – similar to injection moulding – so that finally, the customer just has to press the start button and the Freeformer knows what to do,” says Arburg. “The Freeformer works with commercial masterbatches. However, some pigments such as titanium dioxide are more abrasive than others. The more abrasive the pigment is, the more frequently the nozzle has to be changed.”
54 COMPOUNDING WORLD | May 2015
www.compoundingworld.com
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