SAE Update - September 2021 - 13

FOCUS: ADVANCED
MANUFACTURING
Like many manufactured products, multiple
processes and inspections are required to
make Metal Additive Manufactured (MAM)
parts. Not only are these different
operations necessary for the part to have
the desired geometry and properties, but
the order in which the different operations
are performed are equally important.
Having the correct order of operations in
MAM are important to:
* Ensure that the part can meet
requirements (geometry and
properties).
* Leave the part in the ideal condition for
subsequent operations.
* Minimize the cycle time and economic
loss if the part is discrepant.
This order of operations needs to be
considered during the design and analysis
of the part, as it can influence both of
these. Using a typical process flow with
Laser Powder Bed Fusion (L-PBF) and
Directed Energy Deposition (DED) as
examples, things that a product team
needs to consider are:
1. Build file and/or part serialization -
Optional step that happens during
build file setup to create serialized
parts for traceability. These can be
unique to the part or the build file.
While this is easy to do with MAM, it is
sometimes debated if creating unique
identifiers disqualifies the process as
fixed.
2. Intermediate Stress Relief -
UPDATE
Generally applicable to DED,
intermediate stress relief operations
may be necessary when parts are
large, complex, or made from alloys
that generate high residual stresses
(e.g., Ti-6Al-4V); or a combination of
the three. One reason is to prevent
the part from cracking due to the
residual stresses. Another is to avoid
distortion that can result in
misalignment of the tool path and the
location of the previous layer, which
would result in a pronounced stitch
line or lack of fusion. Cylindrical parts
like the one shown on page 14 will be
less susceptible than parts with flat
sections or small radii.
3. Part Cooldown - The energy put into
the part to fuse the feedstock
together generates heat in the part
and in the chamber or powder bed if
applicable. It has to be cooled down
before the parts can be handled.
4. Remove from Machine and DePowder
- Necessary first step after
build is completed.
5. Stress Relief - This is often required
prior to removing the part(s) from the
build plate (L-PBF) or clamping
fixture (DED). The primary reason is
to prevent residual stresses from
causing the parts to move during
removal, which can result in
undercutting or overcutting or
inconsistency in the part geometry
for subsequent operations.
September 2021
13
SAE Update - September 2021

Table of Contents for the Digital Edition of SAE Update - September 2021
