INNOVATION | LIQUID SILICONE RUBBER
Above: Sigmasoft simulation of injection
moulding the LSR/PC phone holder
Wittmann Battenfeld, with dosing system and mould design by Elmet. Sigma Engineering demonstrated the use of its Sigmasoft Virtual Molding simulation package for the part’s produc- tion on its K2019 stand. At the AMI conference Payam Semsarilar, engineering support specialist at Sigma, discussed how Sigmasoft enabled widening of the process window for the phone holder’s moulding. The two components are produced in the same mould, so the temperature distribution inside both the PC and LSR cavities is key to producing a good part and also keeping the process efficient. After an initial calculation of the two single components was done to gain insights in the filling, packing and curing behaviour of both components, a full Virtual Molding analysis was carried out to analyse how the mould behaved during production. A virtual
design of experiments was then conducted which showed that the PC component’s temperature had a bigger influence on the curing degree than the mould’s temperature inside the LSR cavity. This discovery led to changes being made that widened the process window and increased the curing rate. The experience of injection moulders process- ing LSR in a two-component application was also a subject of discussion at the AMI conference. Markus Landl, Head of International Business Development at LSR moulding specialist Rico Group, led the audience through decision-making criteria for using LSR in multi-shot applications. Processors tend to decide to use multi-shot technology for one of three reasons, he said. For some, it is simply the idea that the technology is “nice to have” as they would like to be perceived as a state-of-the-art company. This does not factor in the technology’s potential for product augmenta- tion. This is the second reason: the benefits of using multi-shot for product innovation, part and function integration, and to enhance a product’s performance and ease-of-use. The third reason is when multi-shot is a “must-have”, as the customer has made it mandatory for reasons such as cost reduction due to function and assembly benefits. A more systematic approach to multi-shot decision making was presented by Landl. The processor should determine the strategic deci- sions, such as whether it has the right capability to start production, and whether the market environ-
Sole shows LSR’s 3D printing abilities
Dow’s Silastic 3D 3335 LSR material for 3D printing is being used in an innovative project to manufacture shoes customised to individuals. Footwear brand ECCO’s Quant-U project involves taking an individual’s biomechanical data to 3D print LSR midsoles customised to the wearer’s foot shape and natural movements — all taking place in-store in less than one hour.
Silastic 3D 3335 LSR was formulated by Dow for additive manufacturing and it has low viscosity to aid printing and rheology for high resolution and accuracy. In ECCO’s customised shoe midsoles, the elasticity and recovery of the material optimises energy return, cushioning and foot stability. Dow created Silastic 3D 3335 to be
20 INJECTION WORLD | April 2020
as fully functional as any other LSR, said Michael Backer, Research Specialist at Dow Performance Silicones, at AMI’s LSR Innovations conference in March. Also presenting at the conference was German RepRap, which has developed liquid
additive manufacturing technology that is used for printing the ECCO LSR midsole.
Dow has carried out tests on Silastic 3D 3335, which Backer said show that the material achieves mechanical properties closely matching those of injection moulded LSR, making it suitable for functional prototypes. He showed two demon- strators (both designed by German RepRap) 3D printed in Silastic 3D 3335: the Wave, a structure of two parallel walls only 0.1mm apart; and the Diamond, a hollow structure.
Left: Dow’s Silastic 3D 3335 LSR material is used for 3D printing individually customised midsoles in ECCO’s Quant-U project
www.injectionworld.com
IMAGE: SIGMA ENGINEERING
IMAGE: DOW
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