Development Assistance for Lightweight Applications
Standard Mold Units for Forming and Backmolding of Organosheets
In order to support prospective customers in a way that is fast, easy and inexpensive when it comes to developing thermoplastic lightweight components out of organosheets, a team of specialists in lightweight construction specially developed an extremely flexible standard mold unit. Merely the forming cavity has to be built to produce prototypes or pre-production parts.
Lightweight construction with organosheets remains a major issue when talking about very lightweight and strong components. Many potential users are yet reluctant to approach the topic, mainly those from industries other than automotive. The engineering company GK Concept GmbH in Dresden, Germany, attributes this to the times for development being too short in many cases, along with low budgets. In some cases, they see insecurity for lack of specific knowledge as another reason. As a result, possible development projects are frequently not being tackled at all.
Starting from this point, the idea was developed to design a suitable standard mold unit. The project team comprised experts from Georg Kaufmann Formenbau AG in Busslingen, Switzerland, GK Concept, as well as HRSflow, hot runner specialist from San Polo di Piave in Italy.
Standard Mold Unit with Hydraulic Needle Valve System
A standard mold unit was eventually designed and built, which can be equipped with either a 1- or a 4-cavity hot runner with hydraulic needle valve system. Both mold halves have ejectors to handle the most diverse geometries. The reason for this is the fact that the components reinforced with organosheets are often structural components. Depending on the respective concept, they may feature reinforcing ribs on the side of the nozzle or opposite. With the standard mold 700 x 700 x 1200 mm large, component geometries with external dimensions up to 400 x 400 mm are realistic.
Temperature control for the hot runner system is very precise, enabling application of engineering polymers within a narrow processing window. Antiwear protection for nozzle head and needle is designed for glass fiber-reinforced plastics with up to 30% glass fiber content. Consequently, even polyamide 66 with a 30% glass fiber reinforcement (PA66 GF30) can be processed at temperatures between approx. 280 and 310°C. This combination of mold and hot runner is also applicable for the production of lightweight components with a matrix of polypropylene (PP) or PP GF30.
Low Wear with Glass-Filled Materials
Needle points in the hot runner nozzles are conical. This minimizes wear when processing highly abrasive, glass-filled materials, while at the same time improving gate qualities. The applied hot runner nozzles by HRSflow are suitable for average shot weights up to 1000 g, in their 4-cavity version, while the 1-cavity variant was designed for 200 to 500 g shot weights.
On the manifold side, the hot runner system is insulated in a way that allows only small amounts of heat to reach the mold. Additionally, both mold halves are equipped with two insulating plates each, so as to thermally disconnect the cavity inserts from the standard mold unit’s supporting frame.
Standard Mold with Variotherm Process Technology
What is more, the standard mold is designed to enable variotherm temperature control, thus making it possible to combine this process to organosheet processing, too. Variotherm temperature control is especially interesting if, e.g., producing structural parts with thin reinforcing ribs by using long flow paths. The process is also suitable to safeguard good image qualities, when producing parts with very delicate surface structures.
Using a standard mold to manufacture thermoplastic lightweight components with organosheets reduces the time required for development up to the first prototype parts. Starting a new project, only the mold cavities have to be specially produced and the respective ejector plate adjusted. In particular, if manufacturing left and right-hand versions of components, this saving is due to provide an even greater return.