3D Printing Takes Off

It is now possible to print many objects through 3D printing technology.

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Rapid prototyping and additive manufacturing (AM) techniques traditionally served aerospace and medical industries that had a need to make complex parts quicker, using less raw materials, and at lower cost. The demonstrated success and usefulness of parts printed with 3D printing techniques has convinced printer manufacturers, material suppliers, investors, and researchers that it is worthwhile to make 3D printers more user-friendly, cost-effective, and convenient. As a result, interest in 3D printing has skyrocketed and spread to many other industries.

Businesses can print parts on their own commercial production printers or send designs to rapid prototype or 3D printing service providers to print on their printers. Home users can print their own or others' designs on home printers. Here's a look at the most important 3D printing technologies and where they're heading.

Stereolithography

SLA (stereolithography), the first AM technology developed in the early 1980s, uses a UV laser to harden a liquid photo-curable polymer. Each pass of the laser over a tank filled with resin solidifies a thin surface layer into plastic in the shape of a cross-section of the part. As a platform lowers, successive layers are built. The completed structure emerges from the liquid bath and receives a clean to remove excess resin and a UV light cure to eliminate the sticky surface. Technicians typically remove support structures by hand, and sand, bead-blast, paint, or dye the final parts for customers.

This Airbus A380 part was created using 3D printing technology.

Over the last two decades, SLA processes have evolved to include many more materials, including composites and other performance plastics that offer temperature stability, strength, durability, and rigidity, making this process common and useful for many industries.

Fusion-Based Techniques Layer Molten Materials

Fusion techniques build parts from thin solid wires or ribbons of extruded materials. Print nozzles heat the feedstock to a molten or almost melted state and deliver the liquefied materials to a build a location where they harden upon cooling. Parts are built with multiple passes of either a moving stage or moving nozzle. Many different materials, metallic alloys, microstructures, and geometries are possible.

Fusion printer manufacturers now offer product lines capable of creating parts of various sizes, from production systems with large print envelopes to more compact desktop printers. Manufacturers have made it simple to replace printheads and feedstock spools and cartridges, and some, such as Stratasys, offer recycling programs so customers can return modeling and support material canisters, cartridges, and spools for reuse.

UV Curing Jetted Liquid Resins

Another AM technique produces 3D parts with multiple materials at once by jetting layers of liquid resin and immediately curing each layer with UV light. The Objet PolyJet printheads can print more than a dozen materials in different colors in a single piece in one print job, and currently prints more than 60 photo-curable materials producing parts with a wide range of durability, flexibility, complexity, and transparency.

Powder-Based Sintering Processes

3D printers based on sintering technologies start with a bed of powder. A roller spreads a thin layer of heated material, and a laser melts or sinters it into a solid form in the desired cross sectional shape. The platform lowers, rollers apply another thin layer of powder, and the laser melts or sinters again. When the part is complete and the powder cools, technicians blow or brush additional powder away, and bead blast the surface.

Researcher working on Organovo’s NovaGen which created the first “printed” human vein.

Placing Cells

Other processes like Organovo's NovaGen, creates tissues such as veins and muscles from cells placed in a print cartridge and layered onto conduits of hydro-gel supports in the desired shape. Removing the gel leaves the tissue structure to remain.

More Materials - More Applications

Today, parts are printed with almost any material: plastics, waxes, paraffins, glass, metals, ceramics, concrete, dental stone, composites, sand, paper, hydrogels, and even chocolate or other food. Many materials used in 3D printing have high enough strength or other properties, such as moisture resistance or the ability to withstand high temperatures, to not only function as prototypes, but as durable, production-grade parts suitable for end-use.

Dental labs use 3D printing to create custom surgery guides for oral surgery, molds for crowns or custom implants, bridges, and caps, and, according to Joris Peel's article in i.materialize, most in-the-ear hearing aids in use in 2011 are from 3D printers.

It is now possible to print performing parts, everything from shoes to jewelry, bicycles to furniture, building materials to bone scaffolds, safety glasses and replacement jaws. Even though 3D printing may save weeks or months producing prototype parts compared to other technologies such as metal forming, printing items one or several at a time is currently slow, so these technologies won't replace large scale manufacturing in the next several years.

Support structures are necessary in many designs, so they are printed along with the part and removed after printing. Some printer manufacturers have sped the support removal process by printing them with materials that dissolve in liquid solutions so technicians don't have to remove them by hand. Heat, ultrasonics, and circulation make the process more efficient, and water-based solutions may make the process more environmentally friendly.

Some materials used for printing themselves may be recyclable, such as HDPE. But, the many additives, stabilizers, finishes, and binders used in some AM techniques can irreversibly change the composition so the final product itself is not. Some printer manufacturers are developing printing processes that create fully recyclable parts, and printing many bio-based plastics is possible, such as some forms of nylon and polyethylene, or the inexpensive Polylactic acid (PLA) polymers made from the sugars and starches in biomass or other renewable non-food plant sources.

Debbie Sniderman is CEO of VI Ventures LLC, a technical consulting company.

It is now possible to print performing parts, everything from shoes to jewelry, bicycles to furniture, building materials to bone scaffolds, safety glasses, and replacement jaws.

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