Addressing the material handling challenges of composites manufacturing

The high strength and performance characteristics of composites have been the driving force behind the increasing use of these materials within the aerospace and automotive sectors. Both of these sectors are renowned for developing and influencing advanced manufacturing techniques and processes, which then migrate out into other manufacturing sectors.

The disruptive changes currently taking place within the automotive and transportation industry overall is further increasing the demand for lightweight components. In addition, other sectors such as renewables, where harnessing wind energy is a key part of our future energy security, is another area where the use of composites for advanced structures will continue to expand the uptake of these materials.

Manufacturing processes require specific handling solutions The different manufacturing stages and processes used in composites production bring with them their own unique challenges. In the Resin Transfer Moulding (RTM) manufacturing process, the required shapes are cut from the dry FRP textiles on CNC cutting tables. These sensitive workpieces then have to be picked from the cutter and transferred to a table or loaded to a magazine temporarily before further processing and “laying-up.” 

During this operation different layers are placed on top of each other in a defined order to create a specific layer structure. These operations require careful handling of the individual workpieces, and within the aerospace sector for example, it is not possible to use needle grippers for fear of damaging the integrity of the fibres. Instead, specialist high flow vacuum grippers are used.

These gripper systems, which have a suction rate of up to 650 litres of air per minute, only produce a vacuum of 100mb therefore making it possible to handle these delicate pieces successfully without deforming the product.

Within the automotive sector however, the handling of the individual cut workpieces using needle gripper systems is permitted, and many of the individual composite components produced for high performance cars and motorsport are handled using this technology.

Needle grippers penetrate the workpiece with up to 24 needles. The needles on both sides of the grippers move in opposite directions generating the necessary tension to hold the textile securely. Prepreg materials present an altogether different set of handling challenges. Before the prepreg materials can be processed, which is usually done through hot pressing, the adhesive material is cut to the appropriate size on a cutting table. 

With the protective film on the material removed manually, the pre-cut prepreg pieces are then stacked on top of each other in a specific order, with the various layers forming a kit. The kit is then placed within the moulding press, where the material is pressed and cured. 

The challenge in handling prepreg materials is ensuring that the cut piece does not remain stuck to the gripper during the handling process and allowing it to be released precisely. Furthermore, care needs to be taken to ensure that the gripper does not become too heavily contaminated.

In this application Schmalz suction plates provide an even vacuum distribution, and their flat design also prevents the workpiece from being drawn into the gripper, protecting the semi-finished products from permanent deformation.

Processing Sheet Moulding Compound (SMC) requires a completely different approach to overcome the material handling challenges. Cut from a roll into the desired size and shape, the long fibres of this material are embedded into a duroplastic matrix and are randomly oriented.

The grippers used to handle and place these workpieces are generally special needle grippers with the high penetration force required to pick up the stack of individual layers and position it in the moulding press.

At the final stage of composite component production, the cured and often still hot components must be gripped securely during their removal from the mould tool, but crucially without leaving marks on the workpiece surface.

Suction cups manufactured from HT1 are ideal for this process. These suction cups are both heat-resistant and free of substances that contain silicone or could impair any subsequent painting processes. 

If FRP components are to be coated at a later stage, this avoids potential surface imperfections. Just as composite materials have found their way into a multitude of different applications, the gripper and handling technologies required to process these materials have also evolved to provide the optimum solution which meets the unique criteria for each stage of the process.