High-temperature, high-pressure, blazingly fast and versatile - Wickert composite press in lightweight construction research
For various aerospace research projects involving thermoplastic and hybrid high-temperature fiber composites, the scientists at the Institut Neue Materialien Bayreuth needed a multifunctional press. Their wish was fulfilled by the mechanical engineering company Wickert, which customized a unique system for them. With the help of the press, the researchers also want to develop digital process chains and technologies for the production of aerospace structural components in the future.
Hot processing temperatures, a very fast component transfer and extremely short closing times, as well as a high, rapidly building press force, are the most important features of the "egg-laying lizard". This is what Dr.-Ing. Thomas Neumeyer calls the Wickert WKP 6000 S composite press with a pressing force of 600 t and a piston stroke and installation height of 1,500 mm each.
Neumeyer knows what he is talking about, because as head of the Plastics Division at Neue Materialien Bayreuth GmbH (NMB), he drove the acquisition of the press. He was supported in this by Juri Kolodi, his scientific assistant.
Other requirements for the system were: It had to operate with high precision, be easy to operate and be able to record process data as widely as possible. Due to the limited space available at the site, a compact design was also required.
After a Europe-wide invitation to tender, the choice fell on the offer of the composites specialist Wickert Maschinenbau from Landau in the Palatinate. The system has been in operation at the North Bavarian research institute since the beginning of 2020.
There were a few hurdles to overcome before installation. For one thing, the designated hall has only narrow gates, and for another, various other machines were already standing there. The press had to be moved into place on the narrow paths between them. Wickert found a smart design solution to the challenge and then brought the press into the building lying down. The peripheral equipment was also installed in a space-saving manner on a platform accessed via a retractable ladder.
An all-round press for foamed, fiber-reinforced and hybrid components
"With the press, we can produce customized molded parts from foamed materials and fiber-reinforced thermoplastics, as well as hybrid components with metal," explains Neumeyer. In addition to the processing temperatures of up to 450 ºC, the high press force of 6,000 kN is needed to form metal sheets. "Thus, we can combine the two NMB focal points, metals and plastics, into hybrid materials at the press."
Hybrid components are of interest to researchers because they allow material properties of materials to be combined. For example, in the case of a plastic seat shell, the NMB employees also press the metal fasteners in a single work step. This makes it possible to combine the resilient fiber composite part with functional elements with little effort.
Flexible and future-proof
The aim of the scientists at the institute is to develop individually adapted materials, robust manufacturing processes and predictable component properties for specific industrial applications in each case. "We deal with the entire value chain," says division head Neumeyer, "with material selection and molded part design as well as with the manufacturing concept and prototype production. For this, we use industrial-scale equipment such as the Wickert press." Since the requirements for the press are constantly changing along with the projects, the researchers need the most flexible and future-proof equipment possible.
For this reason, Wickert designed the press so that it is prepared ex works for expansions with additional peripheral components. The coupling of a PU injection system in the meantime was thus possible without further ado. All interfaces are also already prepared for the injection molding unit that is still planned.
Juri Kolodi, a research assistant in the plastics department, points out further possible applications: "In our experiments to produce components from particle foam without steam, the press serves as a mold carrier. And thanks to the large clamping surfaces, we can easily press nonwovens for full-scale automotive exterior parts."
Transfer and press force buildup in 4.2 seconds
Thermoplastic composites will also play an increasingly important role in the aerospace industry in the future. For the processing of organic sheets based on the high-performance thermoplastics required for these applications, the semi-finished products must be tempered to 450 ºC and then pressed under pressure in the shortest possible time and without cooling. In their raw state, the gels of multilayer, staggered composite fibers are still pliable; only when formed under temperature and pressure do they assume a stable shape.
This challenge was solved by means of automated high-speed linear handling. For this purpose, an infrared preheating station for the components is mounted behind the press. From there, the preheated organic sheets are transferred by a shuttle system to the front of the lower die, which is also around 250 ºC hot. This closes immediately. At the same time, the press force of up to 6,000 kN is built up.
To ensure that the preheated laminates do not cool down, the press is designed for extremely precise and fast closing movements at speeds of up to 300 mm/s. The result is that the entire transfer takes only a few seconds. The result: the entire transfer takes just 4.2 seconds - including die closing and the buildup of the press force.
Heating and cooling in many ways
Thin raw materials, up to about 30 µm thick, such as foils, tiles and organic sheets, which lose heat quickly, are tempered in the infrared oven so that they can be transported quickly into the mold.
For other semi-finished products such as 30 mm thick tiles, on the other hand, it is important that the heat is dissipated as quickly as possible. For this reason, the 1,250 mm x 1,250 mm clamping surfaces of the press can be heated electrically up to 450 ºC and can be cooled with water. Here, the Wickert press scores with a very homogeneous temperature distribution with accuracies of up to ± 0.3 K on the hot platen surface.
Various devices are available for dynamic die temperature control. With water as the heat transfer medium, they achieve temperatures of up to 200 ºC, with oil up to 300 ºC. Using an inductive temperature control unit from RocTool, it is even possible to heat molds quickly to 500 ºC and also cool them again quickly. Wickert has integrated this temperature control of the tools supplied by the same manufacturer into the press control system, from where it can be controlled centrally.
"The different tempering systems help us to produce fiber-reinforced components from standard to high-temperature plastics with a high surface quality in a short time," explains Juri Kolodi.
For precise pressing at all times - even with off-center loads on the clamping platens - the WKP 6000 S also features active control of the plane parallelism of the upper and lower molds. This limits deviations to a maximum of 0.025 mm/m.
Process data is becoming increasingly important
Since numerous parameters have to be evaluated in all projects, not least, extensive process data acquisition is part of the press concept that Wickert designed for the research facility. "Already in our current work with structural components in the high-temperature range, traceability is very important. The importance of comprehensive data acquisition and intelligent evaluation will also increase in the future across linked process chains," emphasizes Thomas Neumeyer.
Joint project from 2022
From 2022, he wants to work with his team on the trend topic of digital manufacturing and monitoring for the aviation industry. To this end, he envisioned a continuation of the cooperation with the press manufacturer, which he describes as very pleasant, flexible and solution-oriented: "We want to work with Wickert on the development of the control technology required for this and jointly develop solutions."
About Neue Materialien Bayreuth GmbH:
Neue Materialien Bayreuth GmbH is an independent non-university research institution that develops novel material variants and the associated energy-efficient processing methods in the thematic field of lightweight construction for plastics, metals as well as composites. Sustainable solutions are created to optimize existing materials and production processes for specific applications. State-of-the-art plant technology enables research and development on an industrial scale as well as the production of prototypes.