Page 20 - MMI-Oct2022- upload

Source: Modern Machine Shop Source: Modern Machine Shop Source: Modern Machine Shop

Fig 5: Another capability needed for laser Fig 6: Final machining of production parts is an Fig 7: The area above and below the turning line
powder bed fusion: milling to resurface additional machining capability needed for metal around the OD of the part shows the precision
build plates. additive manufacturing. This photo and the two of metal additive manufacturing. The turned
preceding ones all were taken at RMS, a medical section is obviously a truer circle, but the as-
device manufacturer established in CNC machi- printed form is not far off. Because of this
ning that nevertheless decided to allocate speci- precision, machining for additive manufacturing
bined with polymer composite al machining capacity to additive manufacturing. entails light cuts. Part of the expertise of
producing this microturbine housing involved
in place of metal for the shaft forecasting just how much extra stock to add
of the tool, together delivered to the printed part for machining.
a weight savings of 40 to 50% away as one of the final steps of
compared to what a conven- that cycle.
LPBF is tional tool at this size would The photo illustrates a signifi- bed fusion by means of a wire
arguably
the most have required, Kennametal cant point: Design for additive EDM machine developed for this
wide- says. Reducing tool weight is manufacturing is to a consid- application; resurfacing of build
ly used valuable even in cases where erable extent design for ma- plates for re-use via face milling
and best the tool changer is not a poten- chining. Production metal parts of these plates on a vertical ma-
established tial limiting factor. Less mass made additively can have or- chining center; and the setup for
process means less energy used to ac- ganic, intricate forms that per- finish machining a 3D printed
for making celerate the tool up to full rota- haps could not be realized in any components on a small machin-
metal tional speed during machining, other process, but those parts al- ing center doing finer work. The
produc- and, therefore, less cost. most always will need machin- point: A fully developed produc-
tion parts ing to get to their final toleranc- tion metal 3D printing operation
additively, 2. Design for AM Involves es. An effective additive process requires machining infrastruc-
and ma-
chining is Design for Machining needs to anticipate how the ture in various forms.
used in at Fig 3 shows another part devel- part will be held in the machine
least three oped by DMG MORI. The com- tool that will complete the part 4. Machining for AM Focuses
different, pany makes both metalcutting — so to an extent, machining is on Light, High-Value Cuts
distinctive machine tools and metal ad- part of additive manufacturing, As additive manufacturing
ways in ditive manufacturing systems and machining knowledge is advances to take on more and
support (both laser powder bed fusion part of what is necessary to de- more of part production, it will
of this and directed energy deposi- sign and engineer the additive change the kinds of machining
process. tion), placing its team members build effectively. that is performed and the role
in good positions to explore that machining plays. Com-
tactics for using additive and 3. Laser Powder Bed Fusion pared to other types of near-
machining in harmony. On this Entails a Sequence of net-shape parts, additive parts
3D-printed medical implant, a Machining Steps need little machining, but the
cylindrical post is added to the Machining for metal additive machining needed is particu-
form that is 3D printed. This manufacturing goes beyond larly critical.
adds material and adds addi- just finishing the 3D-printed The part in Fig 7 illustrates this.
tive build time, but the payoff is part. LPBF is arguably the most The 3D-printed microturbine
much easier machining to com- widely used and best estab- housing needs OD finish ma-
plete the part. The part would lished process for making met- chining, but it is necessary to
otherwise be difficult to hold al production parts additively, look closely to see the differ-
and locate, but the post pro- and machining is used in at ence in precision between the
vides a feature that the chuck of least three different, distinctive original 3D-printed form and
a turn-mill machine can readily ways in support of this process. the machined section above
hold for a rapid machining cycle Fig 4, 5, and 6 illustrate this. Seen it. That is, the additive form is
within this machine tool type. here is part separation from the not precisely round the way
The cylinder is then machined build plate used in laser powder the CNC turned area is, but it is

20 | November-December 2022 Modern Manufacturing India