Article Title
Article Title

All-In-One Printing

by Josh Zeisel

In many industries, weight is a key measured metric for a successful product. Aircraft, race cars, and buildings all aim to make structures as light weight as they can. A car's true performance is measured not by how big the engine is, but by its power to weight ratio. The higher the ratio, the faster the car can accelerate and the less fuel it needs to keep its top speed. Engineers continually strive to take as much material out of a car frame as they can, but they are limited by machining tools and techniques. Yet, even with a high tech 5-axis machine, there is still material left that is basically useless to the structural integrity of the part. Imagine if an engineer no longer had to design a part all while keeping in mind how to machine the part. This is where 3-D printing comes in.

Three dimensional printing is just as it sounds. It works exactly like our desktop printers, taking information from our computers and transferring it onto the paper. While 2-D printers take information from a Word document or websites and transfer them to paper, 3-D printers take their information from Computer Aided Design (CAD) software and makes a 3-D part. Like 2-D printing, 3-D printing places a layer of liquid material that dries before another layer of material is added.

Most CAD software can already transfer the digital information to a machine that makes the physical product. Computer Numerical Control (CNC) machines have multiple axes and cutting tools to machine (or “make") the designed part out of a metal block or forging. But there are extra steps that need to be taken when using CNC machines. Most times, an extra tool has to be made so the block of metal that is being machined sits in proper location and orientation. The order of cutting processes also needs to be pre-programmed. For instance, a hole will be drilled after all of the cutting processes are done so the machines can change cutting tools without human assistance. It is simply more efficient to make as many cuts as possible with one tool before switching to a different one.

Currently, 3-D printing is used mostly for prototyping. Plastics are commonly used as they are cheap and easily melted, which goes in lock-step with the purpose of prototyping, to decide fit and form rather than actual testing. These techniques have been done with plastics over and over again. It's great and all, since you can make interlocking bearings...but who wants interlocking bearings? There is only one way to describe them, and that's "useless." So we can make useless things and items that can't be tested or used for high stress, high fatigue systems. All I can say is it's a good thing we have lasers.

There are two techniques that can form metal 3-D printed products and they both use lasers. They are called Electron Beam Direct Manufacturing (EBDM) and Electron Beam Freeform Fabrication (EBF3). They are basically the same process, but developed by different people. Both EBDM and EBF3 use electron beams, or lasers, to melt metal wire so that it can be printed layer by layer onto a substrate to build the final printed product. Lasers are used because they can easily get the metal wire hot enough to its melting temperature while using a small amount of energy to do so. These direct manufacturing techniques are based on the well-known technique of welding. Welding melts metal wire so that two pieces can be fused together at a joint. Welds are very strong, meaning these 3-D melted parts are very strong as well. Any metal that can be welded can be used in these printing processes: aluminum, steel, titanium.

Another key aspect of these techniques is that they can be done in full vacuums, or outer-space. The hard part about sending structures up into space is that they have to survive the launch, which comes with incredibly high vibrations and g-loads. Structures are designed to withstand these loads, but once they make it into space there are almost zero loads they have to withstand. This causes the objects to be overdesigned for the environment they live in for 99% of their life because they have to withstand the loads associated with the 1%. NASA is planning on using EBF3 direct manufacturing to build parts in space that do not need to survive launch loads. They will be able to build larger structures that weigh less and will finally make to travel in gigantic starships like those in Star Trek a reality.

But with what materials? Currently, titanium has the best strength to weight ratio meaning it is very strong for how much it weights. For comparison, titanium has a strength to weight ratio of 1.06 million while aluminum has a strength to weight ratio of only 0.34 million. Titanium also has better fatigue qualities, able to withstand vibrations and repeating forces better than aluminum. The problem with titanium, however, is that it is very expensive to produce. It is so expensive that every shaving that comes off a machine titanium part is accounted for and recycled. With the accuracy of 3-D printing, there will be no titanium waste, making the cost of titanium manufacturing decrease.

Believe it or not, aluminum was once very expensive too. This was because the process of making aluminum was not yet well known. Once an efficient process was developed to produce aluminum, its price dropped. Things like aluminum foil and aluminum cans became readily used and available to the public. With these types of manufacturing techniques, titanium will also eventually become readily available to the public. You may even be able to start buying titanium foil rather than aluminum foil.

The conductivity of titanium is lower than that of aluminum, so covering your tuna casseroles with titanium foil will keep it warmer longer, which will keep your food out of the stove for longer. Your electricity or gas bill will be lower and you can spend that money you saved on your new iPhone 7 with a unibody design that is 3-D printed out of titanium rather than machined out of aluminum.

Photo courtesy of Creative Tools

Josh Zeisel is a professional mechanical engineer and graduate of Boston University. His favorite meal is a chicken parm sub and an orange soda. On clear sunny days you might look up and find him flying something. Strike up a conversation with Josh at josh.zeisel[at]theinclusive.net