Page 13 - 3D Metal Printing Summer 2016

After completing the CAD design
and saving the work in STL format, the
file went to Xilloc, a Dutch company
enlisted to produce the guitar. Using
an EOS M 400 machine, Xilloc printed
the guitar body using AlSi10Mg alu-
minum. The powder-bed fusion sys-
tem spreads layers of metal powder
and employs a laser to draw slices of the CAD model onto lay- ers of the powder. Wherever the laser strikes the powder, the material fuses and bonds to the previous layer, with the rest of the material remaining in powder form. The process repeats, layer upon layer, until the entire part is complete.
After removing the loose powder, the remaining part is attached to the machine’s build plate. This makes metal pow- der-bed fusion systems vastly different from polymer-based powder-bed fusion systems. With polymer systems, the unmelt- ed powder supports any overhanging part features. After print- ing, the powder is removed and the part is sand-blasted to clean the surface. With metal AM, support material (Fig.
3) anchors the overhanging features
(those exceeding around 45 deg.
from vertical, depending on
the material being used).
Rather than supporting
the overhanging fea-
tures, the support
structures serve to
remove heat from the
part, secure it in
place, and prevent
distortion from heat-
related stress in the part.
Fig. 2
Insights in Metal Printing 3D
unless they are teardrop-shaped). Also, the angles of the rose petals, wherever possible, were designed to
be greater than 45 deg. in order to minimize the need for support mate- rial. From a usability perspective, all barbed-wire spikes were designed to point inward to minimize the risk of injuring the musician. To minimize weight, a wooden core was used inside the main body of the guitar.
Time to Print
Effectively, the entire
part is welded to the build
plate and support material is used where required. The first step after
Fig. 3
printing, then, is to remove the part form the base plate, often accomplished using wire-EDM or with a bandsaw. (Often, parts undergo thermal stress relief prior to removing them from the build plate, to help prevent distortion and warping.)
Delicate, Challenging Support-Structure Removal
After removing the part(s) from the build plate, the support structures must be removed. This is where most of the post- processing time is spent. For the guitar, support-structure removal took more than four days using a combination of methods and tools, including long-nose pliers, mallets and
chisels, screwdrivers, tweezers and dental picks. The supports between the rose petals, in
particular, proved difficult to remove due to limited access. And, the top surface of the
guitar required milling to remove the coating
of support material. (Xilloc printed two guitar bodies, and removing the sup- port structures from
the second body took just 1.5 days).
The arduous task of improving the surface finish came next. Straight off of the AM
system (Fig. 4a), the surface finish could
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SUMMER 2016 • 3D METAL PRINTING | 11