points of the spray. As a result, the bone integrates
with the implant that much more quickly.
Machining Changes
DiSanto has two Arcam additive manufacturing machines. They
run so quietly and unobtrusively that the company currently has
them in a space that used to be an offce.
The company has about 55 CNC machines in-house. With
the advance of additive manufacturing, the role of CNC
machining will change, the company says. Some machined
parts will be produced additively instead. However, because
of the machining needs of additive parts, and because of
the need for complementary machined components, machining activity is likely to increase.
The savings in CNC machining are also signifcant,
Dunn says. While it's true that an EBM surgical
implant almost always needs machining, that
machining is slight because the part is near-netshape—much nearer to net shape than casting or
forging. As a result, all of the machining passes on
an additive part are inherently fnishing cuts. The
costs related to roughing—including time, material
and tooling—no longer have to be paid.
In addition, this fnish machining tends to consist of relatively simple cuts. A part such as a hip
stem has historically been produced through complex fve-axis machining, but Dunn says he expects
DiSanto to rely on fve-axis machining much less
in the future. Geometrically complex features can
be produced more easily through EBM, he says,
and additive manufacturing can also be used to
give the part extra features that make the remaining
machining easy. The hip stem might be generated
with a boss for a vise to hold during milling, for
example, with this sacrifcial feature cut away when
machining is done.
Yet in spite of these savings, the machining
activity at DiSanto is likely to grow with additive
manufacturing, he says. The reason is not just because additive parts need to be machined, but also
because they create the need for other machined
parts. An aspect of DiSanto's machining activity
that might be surprising to an outsider is the extent
to which the shop machines plastic. Implants such
as hip stems and knees are metal, but implants
often come with plastic components that are part of
the implant's operation. Knee implants, for example, come with plastic liners that essentially serve
as cartilage. Through various workholding and
toolpath techniques, DiSanto has become profcient at quickly producing these non-metal parts.
As additive manufacturing expands the number
and variety of metal implants DiSanto produces,
Dunn expects his company to have even more opportunity to apply its expertise at machining these
related plastic components.
AdditiveManufacturingInsight.com February 2014 — 7