Friday, March 1, 2013

Thoughts on ABS as a Filament

Additive manufacturing has been a popular topic lately. It was mentioned in President Obama's State of the Union address as an economic opportunity and appeared in Big Bang Theory in one of their schemes. I wanted to share some of my thoughts on desktop manufacturing and its trajectory.

The majority of '3D printer' manufacturers consider the capability to use ABS filament with their machines the gold standard.  They declare it to be 'experimental' and 'cutting edge' compared to other materials, but in fact the opposite is true. Allow me to explain.

First, a little history on of this type of manufacturing-- invented in 1989 by S. Scott Crump as a means of rapid prototyping, Fused Deposition Modeling (FDM) is the technical term for describing a process that attaches tiny layers of plastic on top of one another in order to make a thing. I sometimes describe this type of machine as a "glorified hot glue gun" because it works the exact same way: The extruder pulls in plastic filament (or string) and spits it out through a very hot piece of metal in a specific pattern.

The first plastic filament that Crump used was Acrylonitrile Butadiene Styrene (ABS), a popular plastic that is used to make all sorts of plastic home goods and the ever popular LEGO. It's high performance in impact resistance and durability make it a versatile plastic. ABS is petroleum based and gives off a toxic fume when heated, this is not an issue with proper ventilation to the machine. Part of the appeal of using ABS for injection molding is the plastic slightly shrinks when it hardens making it easy to pop out of the mold. However, this is exactly what makes it so difficult to use with FDM technology.

Here, shrinkage causes the object to curl off of the build platform leaving you with a warped object. A couple of things have been invented to combat this, the most effective of which is the heated build platform or build chamber. Which is either the equivalent of making your object on a hotplate or inside of box that you ran your hair dryer in. Both methods have been developed and refined since Crump's first experiments.

It's most frequently compared competitor is Polylactic Acid (PLA), a bio-degradable plastic made from corn. It is extruded at slightly lower temperatures than ABS but the biggest difference is it can be used at room temperature with little to no warp. PLA is very strong and rigid; ABS is softer and more flexible. When making complex moving objects in PLA you need to have very accurate tolerances as its strength makes it less forgiving.

ABS is a great material, from which more high resolution objects are being made everyday. This isn't experimentation though, this is refinement -- real experimentation is not in trying to do more with ABS, whose limitations are familiar to us, but in exploring new materials.

If we are truly trying to reach the next level of innovation whether it be in our ability to lower the cost of machines, make them more reliable, or expand their capabilities, all of it is hinged on our progress in material science -- On machines without a heated build element we can already use PLA, nylon, and wood based filament. With nylon its possible to make things ultra flexible, thin, strong and durable. The wood filament is cutting edge and makes it possible to cut, sand, or stain the object like regular wood. All are used at room temperature. These are just three materials that expand the capabilities of FDM technology and some of the most exciting innovations since Crump started.

If we remove the materials needed for a heated build element we have already lowered the price of the machine. With exploration of new materials, like the three I've mentioned, we can increase the reliability by focusing on materials that don't warp and have fewer sensitivities. With each new material, the properties of each expand the capabilities of the machine and it's application.  If we focus on finding cheap, renewable, and diverse materials we will be well on our way to the next generation of machines;

ABS was adopted for it's familiarity and has been successful for developing FDM technology. But the future of additive technology is about accessibility, affordability and capability, all of which the limitations of ABS fail to provide for. Machines that make useful objects reliably with very few sensitivities will win in desktop manufacturing. It's time we make way for the next generation.