Material mix in 3D printing

Article of 30 September 2016  

Material mix in 3D printing | Image: Stratasys

Dental fillings, cycle helmets or prototypes of components – the range of things that can be produced with 3D printers is getting wider all the time. These parts are usually made from just one material.

In order to open up more application areas for ‘printed’ products, 3D printers are being developed in the meantime that combine different compounds in multi-material components. In the DIMAP* research project, a process is being researched with which robot joints can be designed and printed using different materials. Festo is involved in this project as a user.

Printed layer by layer

Instead of milling a workpiece out of a solid block, when it comes to 3D printing, components are constructed layer by layer. A 3D drawing, created with a CAD programme, acts as a basis for this. The software used by the system breaks this model down virtually into many individual levels, which it then constructs step by step. During the so-called PolyJet process, which is used in the DIMAP project, the materials are applied as liquid droplets, similar to a inkjet printer. An ultraviolet lamp then cures the liquid layer. This process is repeated until the part is finished. Besides different materials, various colours can also be printed.

Material mix in 3D printing | Image: Stratasys
Image: Stratasys

Producing a robot joint in a single printing process

The aim in the DIMAP research project is to investigate to what extent ceramic, conductive, lightweight and robust materials are suitable for printing a robot's arm with integrated joints. For the first time, the necessary bearings, the lightweight kinematic structures, the pneumatic actuators and the conductive tracks used for this are expected to be printed using the PolyJet method. In this respect, the materials must be correctly matched with each other, which is why fundamental material research is necessary by the project partners.

The objective is to achieve the highest possible degree of functional integration – that means having the least possible individual printed parts in order to keep down the time and cost involved in assembling them. If the main parts of the robot's arm are printed as multi-material components, connecting component such as screws can largely be dispensed with.

Research into material properties

There are still a lot of open questions about the materials, which have to be answered by carrying out research. For example, there are currently only a few materials that are suitable at all for the PolyJet method. They must be liquid in order to flow through the nozzles, they need to harden quickly and withstand different stresses depending on the area of application. In robot arms, for example, they must constantly endure friction and stretching, which has not yet been possible so far. As the exact material properties are still largely unknown, this is an important research area for the further development of 3D printing. Until now, products from the PolyJet printing method have mainly been used as design prototypes.

A Video made by the manufacturer of the 3D printer, Stratasys, explains how the method works.

Material mix in 3D printing | Image: Stratasys
Image: Stratasys

*The project name DIMAP stands for "Novel nanoparticle enhanced Digital Materials for 3D Printing and their applications shown for the robotic and electronic industry”