The use of composite materials in 3D printing is the subject of ongoing research. Specifically, in this case, with voxeljet’s 3D printing technology platform, whereby 3D printing has been used to make a water soluble form to produce a complex composite motorcycle rocker arm.
Composites are the new frontier of manufacturing materials. They are also the old frontier, as humanity has been using them since the beginning of civilization, starting with mixing mud and straw to make bricks. The idea is that two or more materials with significant physical or chemical properties are combined to produce a material with characteristics that are different from the individual components.
Composite materials include cements, fibre reinforced polymers, metal composites and ceramic/metal matrices (such as the one used by GE for its GE9x jet engine that we reported on last week). In voxeljet’s case study, the composite laminate structure is built on a form generated by 3D printing. Although it is not a one-step process, it makes it possible to produce a complex body within a few days, thus making it ideal for prototypes and small series runs.
The 3D printed form is porous and first needs to be closed for safe processing, during the lamination process. This is done by using Zirkofluid 6672, a slurry based on alcohol as a dispersion agent, made by Hüttenes-Albertus. The parts are then dried in a convection oven.
In the successive step, a coating is applied to fully close the pores. voxeljet used the water-based Acquaseal, by Swiss-based Aeroconsult. The part is then dried again in a convection oven at 60° – 80° C for 20 minutes. Once the prepared form is ready, a polyester material is used and reinforced with glass fiber tissue.
The mixture of the two materials is brushed onto the 3D printed form until the desired wall thickness is achieved. The 3D printed form – which at this point is fully enclosed into the composite layer – is removed by drilling holes at locations where metal inserts will be applied during subsequent work steps. The internal form is subsequently dissolved by dipping the entire rocker arm in warm water, possibly using a syringe to produce the required convection in the longer channels.
While we wait for new (and simplified) ways to 3D print directly using a greater variety of composite materials, this type of hybrid process encompassing 3D printing provides an interesting transition solution.
