Could liquid silicone rubber become a more accessible technology?
Injection moulding liquid silicone rubber (LSR) has, historically, been the domain of specialist moulders. In spite of growing consumer demand, LSR is still seen by many as a difficult material to work with.
Now, a new partnership between German consultancy Das Kunststoff-Zentrum (The Plastics Center – also known as SKZ), Toolcraft (a machine tool manufacturer based in Georgensgmünd near Nürnberg, which also offers contract injection moulding services), and Munich-based injection moulding machine manufacturer KraussMaffei aims to improve the accessibility of LSR moulding.
SKZ is known for its capabilities in traditional thermoplastic processing. Going forward, however, cross-linking plastics such as LSR will play a more prominent role for SKZ. Professor Martin Bastian (Head of the Institute) and Georg Schwalme (Head of Injection Moulding) recently selected KraussMaffei as their technology partner for silicone processing.
KraussMaffei reports that the team at Toolcraft had made separate enquiries about processing LSR around the same time – and so the IMM manufacturer took the opportunity to connect all three groups.
It’s not KraussMaffei’s first mission to enlighten processors on the possibilities that come with mastering the technique. Last year, the group held a virtual event, dedicated to liquid silicone rubber processing. In one talk, experts acknowledged the challenges associated with fluctuating viscosities, which can lead to inconsistencies in part quality.
Using a reusable coffee cup lid, the KraussMaffei team, together with the mould maker ACH Solution, demonstrated the feasibility of moulding two different versions of the lid in one mould, and in one shot. KraussMaffei said its APC plus (adaptive process control) function is designed to deal with fluctuating material viscosities, with adaptive colour metering being one such solution.
LSR is especially popular in the medical sector. Another talk at last year’s digital event focussed on the current trends in this market – and indeed, the first product to be created under the KraussMaffei-Toolcraft-SKZ collaboration will be a medical application with a part weight of 0.5 grams.
What’s the aim?
Under the collaboration between the three firms, SKZ and Toolcraft plan to build up the expertise necessary for successfully processing LSR, which will allow Toolcraft to offer it as a contract service, and SKZ to offer expert advice and vocational training in the field.
KraussMaffei is providing all-electric injection moulding machines (PX 50 at SKZ and PX 121 for Toolcraft) as well as the technical expertise and consulting for all matters involving the challenge of processing liquid and solid silicones.
In the coming months, SKZ and Toolcraft will work on designing, creating and optimizing a new LSR mold. The low viscosity of the material and the fact that the temperature control is the reverse of that used for thermoplastics are just some of the challenges the two firms will need to overcome.
Two years of learning lie ahead
Highlighting the complexity of the process, Toolcraft is working on an assumed timeframe of two years to gain “comprehensive mastery” over the process and the mou ld-making. By this point, SKZ believes it will also be well positioned to offer consultancy in LSR.
KraussMaffei says it will continue to support the project throughout this period, and provide an update upon its conclusion.