Injection molding machinery producer Engel Austria GmbH is well-acquainted with companies active in liquid silicone rubber processing in and around Wels, Austria, as it is headquartered in nearby Schwertberg.
Like the LSR molders and toolmakers in the region, Engel stressed the importance of training apprentices as a measure to compensate for a severe shortage of qualified and experienced staff.
Leopold Praher, Engel's sales manager for elastomer, liquid injecting molding and thermosetting plastics processing machinery, said his company has 50 apprentices.
LSR processors in the area have plenty of apprentices of their own: Rico Group has 25, Elmet Elastomere Produktions- und Dienstleistungs GmbH has 30, and Starlim Sterner Group has 60. Plus, Praher said, Elmet also is renowned in Upper Austria for training staff for other companies, too.
Praher, who has been on the Engel staff for 30 years, talked about companies such as Rico, Elmet and Starlim, which all got their start in LSR toolmaking before adding molding, while retaining mold making as a core competence, too.
"I think they will sometime want only to mold, as there is more money in molding than in tool making with all its more complex problems," Praher said.
Starlim's mold shop, which is exclusively fitted with Engel molding machines, was described by Praher as an air-conditioned facility with cleanliness not far off clean room standards. Aside from having more space in production by placing mixing and dosing units in the cellar underneath the injection molding machines, Praher said it also means more stable processing temperature.
By including camera inspection and control, Praher said Starlim has perfected it all, not forgetting use of computer tomography, primarily in development and prototyping.
"Many companies are trying to get to this level," Praher said.
UV cure slow to catch on
UV curing LSR is an area in which Praher was "fully involved" with LSR supplier Momentive, but Engel has not pursued it further, despite energy saving through curing at 40° C instead of conventional curing at 170-180°C.
Praher said UV curing would have been provided a "huge advantage" in multicomponent molding LSR by enabling use of lower-heat-resistance thermoplastics, but it has been difficult to find applications for the process.
"There is no self-adhering LSR for this area. The material would be expensive, and the large LSR producer's interest is more in larger volumes," Praher said.
Wacker-Chemie has a UV-curing grade, "which we tried in a two-component soap tray, but that was shown on the Wacker booth at a K show already some six years ago."
In LSR optical lens molding, Praher said there are Engel machines at Optoflux GmbH in Nuremberg, Germany, an optical components producer that was, until purchase by financial investors in June 2014, part of optical products and spectacles producer Eschenbach.
Optoflux has molded LSR lenses for LED matrix headlamps included on the Mercedes E-Class car. Praher revealed to LSR World that Engel will show this type of lens at NPE2018, produced on a mold from ACH Solutions.
Praher added: "You certainly need a precise machine to produce them."
Praher said automotive lighting specialist Hella cooperates in LED matrix headlamps with Automotive Lighting Group and that Engel has a lot of contact with Wieselburg, Austrian-based lighting producer ZKW Group GmbH.
On Industry 4.0 and associated manufacturing execution systems (MES), Praher said Engel is a pioneer on account of acquiring Technische Informationssyteme GmbH (TIG) last year.
There is apparently no conflict in TIG acting in the market with processors using other injection molding machines, "but it may be a question of whether others accept it," he said.
Irrespective of the role played by MES, Praher says Engel's iQ Weight Control plays an important role in LSR molding, more than in thermoplastics molding. This is as LSR is a compressible material like oil or water, so that iQ Weigh Control can monitor associated variations and eliminate them during molding by adjusting injection with use of reference curves.
Similarly, with iTemp working together with Engel's Flomo temperature controllers, it can be assured cold runners and nozzles have constant temperature that ensures a continuously stable process. When it comes to iQ Clamp Control, Praher says it can be used to reduce clamping force slightly when a LSR part has already become significantly vulcanized. The result is less wear on tools and lower energy consumption. Fully automated molding of flash-free parts is the ideal for now and the future, Praher said. He admitted there are some articles that cannot be made free of flash and are overflooded, but then the flash should be automatically removed
Engel has at least two machines available for trials. While visiting the production and technical departments, Praher pointed to the much lower footprint of a machine with piston instead of screw feed, which is an option to consider for materials that do not depend on shear action of a screw. But Engel supplies 90 percent of LSR molding machines equipped with screw feed, Praher said.
Clean room challenge
Engel has investigated how to prevent contamination during molding of thermoplastics in one case and LSR in the other under clean room conditions, and results have been summarized in a report by application technology specialist Helene Schöngruber and the medical business unit Vice President Christoph Lhota.
Using a clean room module at Engel from Max Petek Reinraumtechnik of Radolfzell, Germany, it was first found that relatively high mold temperature when curing LSR means there is a challenge in both particulate and silane mist contamination of molded parts. The significant amount of heat works against conventional top to bottom laminar airflow measures. So clean airflow from bottom-to-top was introduced, along with sucking out of the air at the top of the clean room module, the sucking ensuring full silane mist removal.
Engel Austria and Max Petek have industrially implemented this unconventional approach, which they say could become standard in high-temperature injection molding.