Material conditioning as a guarantee of quality

TARTLER metering and mixing systems prove their worth in silicone casting processes

The range of processes used for the industrial manufacture of silicone and silicone rubber parts for medical and orthopedic technology extends from injection molding and direct casting to pressure casting and layer-by-layer casting. Across these various technologies, the optimal preparation of the materials—typically liquid A/B components—proves to be a decisive factor for product quality and process efficiency. Finely tuned to the requirements of this preliminary production stage, the German equipment manufacturer TARTLER offers innovative system solutions for mixing, dispensing, and conveying that can be scaled to meet specific customer needs.

Across various methods, the production of silicone products is generally defined by four process stages: dosing and mixing the materials (usually supplied in liquid form); pouring or injecting the prepared mixture into a pre-made mold; and curing (vulcanizing) and demolding the molded part. The choice of technology depends on specific requirements. While liquid injection molding (LSR) is used for high-volume production, direct casting typically yields components with simple geometries; pressure casting produces particularly dense, solid molded parts; and layer-by-layer casting is used for large objects. In medical and orthopedic technology, silicone and silicone rubber components excel wherever elastic, dimensionally accurate, and thermally resilient parts or products are required. Examples include prostheses and liners, anesthesia masks, pacifiers, shoe insoles with massage elements, and training models for medical professionals (such as palpation models for breast cancer diagnosis or dental models featuring simulated mucous membranes). A critical factor determining final product quality across almost all manufacturing processes for these items is the continuous, high-precision preparation of material components prior to molding. This involves specific siloxanes (Component A) alongside fillers, additives, or color pastes (Component B), which are dosed, mixed, and fed into the next stage of processing using specially designed machinery. TARTLER’s silicone processing systems—comprising the Tardosil, Nodopur, and Nodopox series—are specifically engineered for this quality-critical preparatory stage. Thanks in particular to their modular design and the high-precision process control they enable, these “Made in Germany” dosing and mixing systems are now found in many silicone production facilities. Depending on the characteristics of the materials used, they can also be equipped with TARTLER’s intelligent follower plates and highly effective degassing technology. This offers significant added value for the operator, as it allows the systems to be optimally integrated into industry- or customer-specific processes and facilitates the achievement of high quality standards.

Three factors are important

To accurately select the ideal TARTLER system, three primary parameters must be considered: material viscosity, homogeneity, and processing temperature. For instance, the Nodopox metering and mixing system is best suited for materials that are highly viscous, homogeneous, and non-self-leveling at room temperature. The Nodopox system can be configured as a single- or multi-component unit and features an integrated Siemens control system to manage mixing ratios. TARTLER programmers configure the PLC modules to meet specific customer requirements and tailor them to the particular application. Pot life and shot size—as well as the mixing ratio in systems with volumetric flow control—can be adjusted via the control system’s touchscreen. If materials are supplied in cylindrical containers, their delivery can be optimized using follower plate technology. Furthermore, TARTLER offers various patented vacuum options and buffer containers that can be automatically filled from refill stations. All these features ensure an uninterrupted supply of material.

If a silicone processing application primarily involves the use of low- to medium-viscosity, self-leveling materials, the Nodopur series metering and mixing system from TARTLER is the ideal choice. While the standard configuration is a single-component (1K) station, it can be upgraded to handle up to eight components. Operation is managed via a Siemens touch panel, and the system’s internal PLC is programmed to meet specific customer requirements by TARTLER GROUP experts. If the system is equipped with volumetric flow control, the mixing ratio can be adjusted within very short cycle times. In Nodopur models lacking this control feature, the drives receive their target speed values from the PLC following system calibration. To enhance product quality and reduce scrap, material components can be transferred and degassed under vacuum.

Solution for high- and low-viscosity materials

TARTLER’s Tardosil series systems come into play whenever both high- and low-viscosity components need to be processed during silicone production. They can be scaled to meet specific customer requirements and integrated into various process environments—for instance, by adjusting container sizes, flow rates, cycle times, the level of automation, and more.
Incidentally, for silicone processing applications involving dispensing into the closed molds of an injection molding system—such as in LSR technology—TARTLER offers the option of equipping all its systems with pressure-controlled volumetric flow dispensing. This is highly beneficial, as the components must be delivered continuously and with repeatable precision at the exact mixing ratio required. Even handling extreme mixing ratios proves unproblematic, as all TARTLER systems utilize the company’s proprietary dynamic, rotating, disposable plastic mixers.