3D Printing

Rabbit Proto & An Overview Of 3D Printed Circuit Projects

The concept of 3D printing circuit boards at home is one that excites many in the maker movement. That concept has seen a number of developments over the last year that has brought the dream closer to home. The latest is Rabbit Proto, a print head add-on thatplugs into your 3D printer, enabling it to print complex conductive traces. The project joins a number of efforts ranging from RepRappers to Microsoft. The project source code, documentation, and example designs are open source, and available now.

Since the first RepRapped circuit early in 2009 the promise of home 3D printed circuits has continued to entice development projects within the open source community. Within industrial 3D printing — or additive manufacturing — set, Optomec, Xerox and others have produced innovative patented methodologies to successfully 3D print conductive materials in a fully functional manner. Jennifer Lewis, a Harvard Materials Scientistrecently come up with a type of Lithium Ion “Ink” that allows her to 3D print battery cells. Just this month IBM has produced a device which some have referred to as being a 3D printer, although it is more a microscopic subtractive process, that has applicable uses for chip production. This is an evolving field, and one in which progress is being made on a number of fronts.

The crux of the key benefit of the Rabbit Proto is that it allows the user to easily print circuits inside of the plastic design itself with no interruption to the 3D printing process. The user is also empowered to print circuits onto three dimensional surfaces, and can deposit relatively complexconductive patterns in the process.

Rabbit Proto is compatible with all RepRap printers having a dual-extrusion board. The team hasinstalled Rabbit Proto onto a Rostock Max and a Mendel Prusa V2 with success. The device can reportedly also be modified to adapt to other kinds of 3D printers. The Rabbit Proto prints ‘Anything that can fit inside a 10cc syringe’ but the onus is on its potential for conductive inks. The team is currently using the ‘electric paint’ produced by Bare Conductive, a design and technology studio based in East London, UK. The paint is water-based, highly viscous and shear sensitive, it has a density of 1.16 g/ml and a surface resistivity of 55 Ω/Sq at 50 microns.

The Rabbit Proto is available in three forms; you can buy it on its own for it to be fitted onto your current printer for $350, with an attached filament extruder head for $450, or go all out and buy a fully assembled 3D printer complete with Rabbit Proto for $2,499. Rabbit Proto invite 3D printer manufacturers to contact them regarding potential of compatibility.

There has been an increasing range of projects regarding 3D printing and the printing of electronics, a summation of which is provided here for your information:

The Argentum, a rapid prototyping machine designed for the sole purpose of generating printed circuit boards ‘at the click of a button.’ usingSilver Nitrate Solution with TBA additives and Ascorbic Acid Solution with TBA additives. The purchasable printer was originally known as the EX1 and received successful crowdfunding on Kickstarter last year.

Microsoft researchers used a RepRap 3D printer with a third print head modded to spray CuPro-Cote copper paint and Electrodag 915 silver paint. The copper paint is water-based, lower cost, lower conductivity and designed for large area applications, such as EMF shielding. The silver ink is solvent based, higher conductivity, and designed for small area applications, such as scanning electron microscope sample preparation. The team used a number of approaches and the paper makes for a must-read. They concluded that the research ‘demonstrated the ability to combine 3D printed mechanical structures and three dimensional conductive traces.’

Reprappers have tried paste-dispensing silver-filled liquid polyimide and sintering/melting lowtemperature metal alloy powder on cardboard /FR4.

Carbomorph: A composite of Carbon Black: an amorphous form of carbon, produced from the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar and a small amount from vegetable oil, and polymorph: a commercial formulation of polycaprolactone (PCL). PCL is a biodegradable polyester with a low melting point of around 60°C and a glass transition temperature of about −60°C.

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