For proof of concept modeling, prototyping and even up to pre-production prototypes, rapid prototyping or 3D printing is a technology I have learned to love and appreciate. My recent investigations into this technology have been nothing short of surprising. For many years, I have the idea that plastics were really the only materials they could use this methodology. I had heard bits and pieces about rapid prototyping using metal, but did not look into it until recently. Metals were one thing, but to my great surprise, even materials such as glass and ceramics are being used for rapid prototyping. This last one was a great surprise, as ceramics and glass have very high melting temperatures, sometimes in excess of 2500° C.
3D Printing Exposure & Experience
My first exposure to rapid prototyping or 3D printing demonstrated manufacturing parts that had the appearance of the object of interest, but the surface finish was very poor. I had to use my imagination a bit to imagine an assembly made from these parts, as they did not fit together very well, would break easily, and were the most part not functional-merely display models.
When I started having my own parts built by 3D printing, the technology had improved considerably. My first batch of parts were functional, but the surface finish left a bit to be desired, as they had a rough, layered-like appearance. My recollection is that this method was known as fusion deposition modeling, or FDM. A few months down the road, I used a different technology, something known as Poly Jet. This technology improves the part’s appearance by an order of magnitude, as well as making them far more structurally sound. Fusion deposition modeling (FDM), when used in thin sections, results in a fairly weak part which may break along the long axis of the layers.
3D Rubber Prototype Example
Another project had me dealing with soft, rubber -like material, similar to what may be found in the sole of a running shoe. Much to my surprise, material such as this can be readily adapted to rapid prototyping technology. The same project may require short-run molding to be generated, and, no great surprise here the same CAD files that are used for making the 3D printed parts can then be used to make the molds. This is one heck of a cost-saving measure.
Metal Prototyping
Rapid prototyping – metal part technology (there are several) that I found most interesting is known as direct metal laser centering, or DMLS for short. Virtually any metal that is capable of being powdered can be used to make parts using this technology. Suppliers claim that the material is “full density”- meaning that there are no voids in the parts generated using this method, as there can be using FDM-type methods in plastics – structural strength should prove sufficient for making functional prototypes. It remains to be seen if these parts can be successfully heat treated. My initial feeling on this is that I cannot see a reason why they should not be capable of this.
At any rate, all of these great new tools can save lots of time and money faster construction of prototype parts which makes design changes extremely easy and inexpensive with little or no limits on materials used.
Norman T. Neher, P.E.
Analytical Engineering Services, Inc.
Elko New Market, MN
www.aesmn.org