AdditiveManufacturingInsight.com September 2014 — 11
In general, DMLS works by melting very fne
layers of metal powders from the bottom up until
the build is complete, creating a single homog-
enous part made of steel. To start, a thin layer of
pure tool steel powder material is applied to the
building platform. A powerful laser beam then
fuses the powder at exactly the points defned by
the computer-generated component design data.
The platform is then lowered and another layer
of powder is applied. Once again the material is
fused so as to bond with the layer below at the
predefned points.
When it comes to insert repair, however, DMLS
has a different approach. "You don't repair the in-
serts by welding together two broken or damaged
parts," explains Daniel Kundig, owner and manag-
ing director of Ecoparts (ecoparts.ch). "Instead,
you completely rebuild the damaged area of the
insert. This ensures a homogeneous microstruc-
ture in the parts, without having visible weld lines
on the repaired insert." After the DMLS process,
inserts can be post-processed (for example, via
milling or polishing), as required. The insert's func-
tionality is saved and reestablished.
DMLS melts material back onto the damaged
area, and metals used in DMLS offer very good
mechanical properties, Mr. Rozkosny says. For
example, MS11.2709 maraging steel offers a
Damaged area cut-off.
Repaired area after
surface fnishing.
hardness ranging to 54 HRc. (Heat treatment can
be used to adjust the hardness between 34 and
54 HRc.) In addition, different tool steels can be
combined, limited only by the size of the sintered
surface and weldability of the materials. DMLS also
runs in an airtight chamber under an inert nitrogen
atmosphere, ensuring a very good metal structure.
Finally, it offers short lead times and suitable quality,
Mr. Rozkosny says.
Innomia and Ecoparts do see a few limitations
to using DMLS, however: (1) current chamber size
(250 x 250 x 325 mm) limits the size of parts that
can be repaired; (2) surface fnish is rough (about
10 Ra), requiring conventional fnishing processes;
(3) the layer-by-layer process demands a fat sur-
face; and (4) only one material (1.2709) currently is
approved for tooling. However, the high accuracy
and surface quality after fnishing that DMLS offers
make it an ideal platform for tooling applications,
including tool repair. Also, inserts repaired using
DMLS are proving to prolong tool life.
Images
courtesy
of
Innomia.