Fully Additive: Towards 3D Printed Mechatronic Systems – part 1

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Tank filling sensor, image provided by Martin Hedges

3D Printing of structural components in polymers, metals and ceramics is becoming well established industry driven by the unique freedom of design benefits that are unattainable with other traditional manufacturing techniques.

By Martin Hedges, Neotech

Rapidly maturing processing technologies are also allowing 3D Printing to increasingly compete on an economic basis and the first low volume manufacturing applications are emerging. Adding electronics functionality to 3D Printed parts to produce complete mechatronic systems is the next logical step in this evolution.

Integrated Electronics

The demand for increased integration of electronics into structural components is driven by many factors across a wide range of industries. With the advent of the Internet of Things (IoT), an increasing number of products are equipped with sensors, actuators, antennas and/or displays functionality, enabling them to communicate with other ‘smart’ devices and to interact with the real word.

In the automotive industry the need to reduce cost, weight and add intelligence to vehicles drives demand for more integrated mechatronic systems. To obtain this high level of functional integration, technologies like 3D Moulded Interconnect Devices (MID) have been applied. Compared to traditional electronic systems that are based on planar PCBs, MIDs offer numerous benefits, (see figure 1).

In particular arranging electronics directly on structural parts offers new opportunities for the design. In most cases, MIDs consist of thermoplastic substrates that are produced by injection moulding. As a result of the high costs of the mould tools, the use of this technology is only economically reasonable when large quantities of the same part can be produced. Furthermore the structuring processes used to create electronics circuits require wet chemical processing that is environmentally damaging and costly.

 

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Figure 1 – Benefits of 3D Electronics

 

To overcome these issues, Neotech AMT GmbH has been pioneering 3D Printed Electronics (3D PE). In 3D PE, functional inks with defined electrical characteristics are printed using a range of non-contact print technologies. To enable the production of circuits with a high degree of geometrical complexity, printers with 5 axis range of motion and material appropriate pre- and/or post processing techniques are used.

Volume production

Technology development of 3D Printed Electronics has been rapid with the first mass production running since mid-2015. Liteon Mobile Mechanical SBG use Neotech’s patented 45X printer to print 3D circuits on moulded PC/ABS cell phone frames. To achieve the necessary high production volume (millions of parts per year), printing is conducted on 4 parts simultaneously.

“By combining 3DPE technology with ‘classical’ 3D Printing techniques such as Fused Deposition Modelling (FDM) a viable process route for lower volume manufacturing can be established.”

These 3D PE systems can also be used for low volume production as well as prototyping, since there are no part-specific masks or tools required. Figure 3 shows a sensor prototype consisting of injection moulded PA tank with a printed circuit layout and capacitive sensors. SMDs are added to finalise the filling sensor function.

By combining 3DPE technology with ‘classical’ 3D Printing techniques such as Fused Deposition Modelling (FDM) a viable process route for lower volume manufacturing can be established. 3D Printers exist that can dispense conductive ink or filament between the layers of structural material. However, these printers possess only three axes of motion freedom.

Each structural layer is created by moving the deposition tool in the X-Y plane, before moving the tool or the construction table by one layer height in Z-direction. Strictly speaking, these techniques are only operating in a 2.5 dimensional space, generating parts consisting of stacks of 2D printed slices. When using FDM, this approach has some disadvantages:

  • The slicing of the part geometry in the CAD model leads to stair step patterns on any required round surfaces.
  • If electrical circuits can be added they can only be printed within the X-Y plane, whereby it is impossible to add circuits on external surfaces.
  • Electronic components can only be placed in X-Y planes and not on inclined body surfaces.
  • The produced parts exhibit anisotropic mechanical behaviour – individual layers are connected only moderately.
  • To build overhanging geometries, the creation of support structures is necessary to prevent the part from collapsing, which increases material use and process time.

The second and final part of this article will appear here in week 29.

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