3D Printing comes of age


This blog is about chemical and energy developments of interest to me and, I trust, also to readers following these posts. Since I have wondered for some time about how 3D printing works, I decided to investigate and this is the result. (Full disclosure: this post is largely taken from an article about the same subject I recently wrote for the Scarsdale Inquirer, my hometown newspaper.)

The most important thing to know is that 3D Printing is an “additive” technology used to produce a very large variety of objects that are currently made in a traditional manner from many different materials. Thus, objects now made from metals like steel, brass, or aluminum or from wood or marble start as a block and are cut, machined or chiseled to form the desired shape .This is termed  a “subtractive” technology, where material not wanted is removed to create the desired object. Other items may be made using a mold, but the mold itself is made using “subtractive” technology. The 3D printer (which really isn’t a “printer” at all)  is a machine controlled by specialized software that is coded to lay down successive, additive microscopically thin layers of rapidly solidified or solid material that represent “slices” of the object that is being produced in an “additive” manner.  The software is created with a computer-aided design package or with a 3D scanner. The material used to feed the printer is called the “filament”.

Imagine making a tapered vase with base using a 3D printer. Thinking in two  dimensions, you would see (if you could look into the machine) that the first material laid down by instantly solidifying polymer is a small circle (the base) that rapidly rises to a quarter inch or so in height as successive hypothetical horizontal “slices” are added to form the base of the vase. Then, even smaller hollow rows of circles start to build, expanding as the object rises a number of inches to form the tapered vase. This, of course happens with great speed. Voilà, a vase made by 3D printing!

Such a vase could have easily been made with a mold, but as shapes become more complex, molds become more difficult to design and 3D printing overcomes this problem.  Change the example to a pitcher with handle. The software will faithfully copy the two-dimensional image and build up the handle as part of the pitcher as it directs the “printer” to add the successive layers of the handle part now part of the “slice”. That is how 3D printing can be used to make complex objects.  3D printing can produce an extremely complicated metal part that is almost impossible to make with subtractive technology, which would usually include some welding.

A great variety of 3D printing processes have been and are being developed, using a large variety of materials.  Stereolithography is a laser-based process that works with photopolymers, laser-sintering and laser melting works with powdered materials, (including metals), fused deposition modeling uses extrusion of thermoplastic materials and material jetting is a technology somewhat similar to the way ink jet printers work. That technology allows simultaneous deposition of a range of different materials. An important point is that for most of these technologies, materials, and applications some post-processing steps are required, including curing, sanding, polishing, and painting. Plastic resins such as ABS, polylactic acid and nylon are currently the most common materials used.  But they also include titanium and cobalt chrome alloys, aluminum, metal and ceramic powders, etc.

An important advantage of 3D printing versus subtractive manufacturing processes  is that in the additive process no material is wasted, while in the subtractiv process up to 90 percent of the original block of material may be wasted.

3D printing is an “enabling technology that drives innovation while being a tool-less process that reduces costs and lead times”. More and more applications are being developed for various industries. Examples include hip and knee implants, hearing aids, orthotic insoles for shoes, surgical guides for specific operations and jewellery(e.g. glass fiber-filled nylon), food and the fashion industry(mannequins, face models, shoes, hats, bags). The aerospace industry has been an early user of the technology with GE  (turbine parts), Airbus, Rolls Royce and Boeing  high profile users to make first-of-a-kind parts. Car companies are also early adopters of 3D printing technologies. A drivable prototype of an electric car has been 3D printed(!). Another excellent application is making spare parts for cars, appliances, and other consumer items that are old and out of stock.

Mass customization and competition will make the cost of 3D printers, filaments and software come down fairly rapidly. At a reasonable cost, it will be a fun thing to have around the house.

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2 Responses to 3D Printing comes of age

  1. David Oxley says:

    Hi Peter, Good article. You could add that there are several different technologies viing for this technological space. Powder sintering and liquid acrylic curing coming to mind. Used for several years in the Plastics industry to make prototypes to show customers and to check that the part can be assembled. One problem we had was the strength of the part was not as high as that from solid moulded plastics and there are voids in the sintered part. These can be filled with liquid resin and then cured to give an acceptable finish. There is a good exhibition at the London Science Museum, showing examples of metal parts for dentistry and biodegradable bone transplants. At present the powder used for additive moulding is much more expensive than the pellets used for injection moulding, and I guess the filament version is costly too. The process is very slow, given that you build up the object thin layer by layer. Yes an exciting addition to processing technology, but designers need to consider the properties of the finished object. Regards
    David Oxley

  2. Peter Spitz says:

    Thanks for your knowledgeable comment, David. Best to you and Ann!


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