Additive’s idiosyncrasies — producing functional parts
The figure (6 and 7 in the picture gallery) gives an example of how extensive these support structures might be. The component relates to a project by a Penn State undergraduate student, Vincent Maranan, who applied additive manufacturing to produce a wheel’s upright (connecting the hub and brake calipers to the suspension arms) for a competition involving student-designed race cars. On this part, the supports that were needed to preserve the bow-like features, the triangular peak and the large central bore together accounted for 50 percent of the build time for this part.
How are supports such as these removed when the build is complete? Additive manufacturing of metal parts still lacks an automated way to perform this step. Thus (perhaps strangely), one of the most advanced metalworking technologies is often followed by one of the most primitive. The supports on end-use production parts that are made through additive manufacturing are often removed with hand tools including a hammer and chisel.
Did the part in the previous example have to be built so that it stuck up into the air like a shark fin? Maybe not. It could have been laid down on its side. Less support material would have been needed in this arrangement, and with less vertical height to cover, the build time would have been much less. But in this orientation, certain features of the parts might not have formed as accurately. Growing the part at something near a 45-degree angle might have offered an effective compromise. In additive manufacturing, searching for the right orientation of the part is an important aspect of finding the most efficient and effective process.
Simpson says this is part of the reason why the CAD model by itself no longer conveys enough information to define the part. CIMP-3D saw a demonstration of this in a recent experiment in which it sent the same CAD model to three different providers of additive manufacturing services. Penn State graduate student Andrew Coward, who is involved in gas turbine research, designed a complex test part with features relevant to turbine components. All three additive suppliers were asked to produce the test part on their DMLS machines. Unknown to one another, all three independently chose to orient the part in different ways, and all three produced different results. Coward actually got back four parts, because one of the three suppliers tried it two different ways. Each of the resulting four parts was true to the CAD model in some details and violated it in others, and each part’s set of true features and faulty ones was different from all of the others.