3D printing | technology
functional prototypes, Arad estimates it has reduced its time to market by five weeks and prototype production costs by 80%. UK-based Digitally Engineered Solutions (DES) is
and moulding conditions used). Sella acknowledges there are areas where further
work is required. He points out that, currently, tradi- tional CNC can hold tighter tolerances on moulds than 3D printed examples. In some cases an accuracy of 0.1-0.2 mm is enough but for many industries and parts a higher level of precision is needed. In addition, the surface finish of 3D printed cavities can be an issue. This is more a problem with visible parts rather than technical parts that the end customer does not see. And there is a need to improve the thermo-mechanical properties of 3D printed moulds to increase the number of parts that can be produced per mould cavity and the overall quality of the injected parts. That said, the technology is capable of delivering
serviceable parts. Water metering specialist Arad Group, for example, is using PolyJet technology in its prototyping. Demanding requirements govern the design, testing and production of the watertight components that protect its electronic hardware and the ultrasonic welding process used to seal the parts together can only be tested effectively on real compo- nents in the final material. Typically, these parts have been produced using an aluminium test mould or even the final steel mould. These metal moulds cost any- where from US$5,000 to US$20,000 and can take from four weeks to three months to produce. If the welding trial reveals a need for design improvements, the mould making process starts again and the cost multiplies. Arad now creates injection moulds for these parts using its Stratasys PolyJet 3D printer. The moulds are 3D printed using Digital ABS material in four parts: the core, cavity and two inserts to create the negative draft required for the step joint. The total printing time is just ten hours and the male and female parts are ready for mounting on the injection moulding machine immedi- ately. Arad typically uses two different polymer materi- als for testing - Grilamid TR90 (amorphous polyamide) and ABS 757. Once the parts are injection moulded, they are welded together with the electronic components inside. By using 3D printed injection moulds to produce
www.injectionworld.com
now offering digital tooling for the production of low volume plastic injection moulded parts. The company says digital tooling produces custom injection moulds for low volume production of parts in the correct polymer and colour, significantly quicker and cheaper than current alternative options. Costs can be up to 80% cheaper when using digital tooling instead of conven- tional steel or aluminium, and months can be saved in the product design process, the company says. DES says digitally printed moulds are not high
volume production tools. However, during the design and testing phase, they offer a clear advantage over conventional injection moulding and 3D printing. Product designers and manufacturers can use the moulds to produce realistic parts to perform thorough functional testing without worrying about conventional cost-prohib- itive tooling. Flaws based on the final production process, geometry or choice of plastic can be discovered early, when they are easiest to fix. This can reduce costly, time-consuming mould corrections, increase product innovation and speed product development.
Verifying designs Prototype and low volume production parts manufac- turer ProtoLabs says that 3D printing is being used mainly for design verification prior to final tooling. “As the 3D printing processes improve, there could be opportunity for 3D printed parts to replace low volume moulded parts, particularly for complicated geom- etries,” says a company spokesperson. “Largely though, 3D printing is complementary to injection moulding. 3D printing will continue to improve in materials and processing speed. This will create opportunities for 3D printed parts to be utilised in mould-making for complicated geometries, or process optimisation like conformal cooling.”
Left: A DMLS mould insert with conformal cooling circuits and final injection
moulded part manufactured by Innomia and Magna. Cycle time was reduced by 17%
May 2016 | INJECTION WORLD 17
Left: A bank of SLA machines from 3D Systems installed at the ProtoLabs European facility in the UK
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