Friday, March 22, 2013

What is 3D Printing and How Does it Work?

The phrase 3D Printing has popped up in the media everywhere from Jay Leno's garage to the cover of multiple tech magazines. Many people are curious to learn more, but given the adolescent stage of the technology there isn't much information to be found. Here I try to address that lack of information.
Q: What is 3D Printing?
A: The process of making a three-dimensional object from a digital model.
I've broken everything down into three main sections. In the first section I outline and explain the most popular types of 3D printing. The second section addresses the characteristics of 3D printed objects. Finally, the last part discusses current desktop 3D printer software.

Types of 3D Printing

Just like there isn't one way to print on paper (ie. laser vs inkjet), there are multiple ways of 3D printing an object. The types of 3D printing most popularly used in the industry are Fused Deposition Modeling, Selective Laser Sintering and Stereolithography.

Fused Deposition Modeling (FDM) is the most popular type of 3D printing on the market. If we pull apart the name...
  • Fused: to join or blend to form a single entity
  • Deposition: to put or set down in a specific place
  • Modeling: the activity of making a three-dimensional representation of a thing
... it becomes much less intimidating. FDM is a fancy way of saying it attaches layers of plastic on top of one another in order to make a thing. I typically refer to this type of printing as a "glorified hot glue gun" because it works the exact same way: The extruder pulls in plastic filament (or string) and pushes it through a very hot piece of metal which then 'extrudes' (or spits) it out in a specific pattern.

The other two industry popular types are called Sterolithography (SLA) and Selective Laser Sintering (SLS), and both refer to a process where a laser or other focused light source is pointed into a bath of liquid plastic or resin that when hit with the light source will harden. The machine will draw layer by layer precise images in the liquid which will harden as it goes. When it is finished, you are left with a solid model. The biggest hurdles for SLS and SLA to overcome are the objects they produce are still very brittle, in addition to the high cost of this resin and technology relative to FDM machines.

Characteristics of 3D Printed Objects

A photograph can have high-resolution or low-resolution, where high-res is a lot of pixels very densely packed together so our eyes see one smooth picture, and low-res has fewer pixels and therefore the picture looks more blocky and less smooth.

High-Resolution Photo
Low-Resolution Photo

In 3D printing there are also high-resolution objects and low-resolution objects. A high-res object is one that has very very thin layers (some can be thinner then a slice of paper) so that you end up with a very smooth object where it's tough to see each individual layer. Whereas a low-res object has fewer and thicker layers, where you end up with a rougher object where you can very visibly see each layer.

High-Resolution - Beethoven Bust 
Low-Resolution - "Wells" The Robot

High-resolution objects take longer to produce than low resolution. This is because for every one layer of a low resolution object there could be 5x as many layers in a high resolution object. Each one of those layers is extra time spent printing but can make a substancial difference in visual quality.

3D Printable Materials

As FDM machines are the most popular on the market, the materials those machines use are also the most popular right now. The material, called filament, is packaged much like spools of thread but are much larger and have plastic instead of cotton "string".

Spools of PLA Filament
Acrylonitrile Butadiene Styrene (ABS), is one of the most popular plastics. It is traditionally used to make all sorts of plastic home goods and is the material of choice for 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. ABS plastic slightly shrinks when it hardens which can cause an object to curl off of the build platform. To combat this machines incorporate a heated build platform; the equivalent of making your object on a hotplate.

The other most popular polymer is Polylactic Acid (PLA), a bio-degradable plastic made from corn. PLA is very strong and rigid; ABS is softer and more flexible. It's a popular choice for filament because as the plastic hardens it stays very true to its original size and does not require a heated build plate.

Experiments are being done with bleeding-edge materials like nylon, wood fiber, and polycarbonates by hobbyists in an effort to expand the library of materials for 3D printers.

SLS and SLA machines do not use plastic filament. Instead, they use a liquid resin (in this case an un-hardened plastic) that, when hit with the light source, hardens into a solid.

Although still in it's adolescence, 3D printing is quickly maturing and with it will come untold wonders.

Modeling Software - If you want to take a foray into 3D Printing, modeling is your first step. Historically, 3D modeling has been a challenging thing to do. The software has often been unwieldy and infuriating to navigate. Here is a list of programs that are helping to change that.

123D Design -
Part of a suite of modeling software by Autodesk aimed at beginners to 3d modeling. The whole suite is provided for free and has companion iPhone apps that allow you to make 3D models of real things with your phone's camera. 

Sketchup -

A Google-supported product, SketchUp is also popular, free and well documented.

Autodesk Inventors Fusion -

Of the four programs, this is the most dense and has the highest barrier to entry. Definitely more in the advanced category, this is free software that gives more precise control of the modeling once you get the hang of the interface.

Thursday, March 21, 2013

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.