hp tooling 2020 #1

processes
Additive manufacturing:
Opportunities for cutting tool manufacturers
written by: Thomas Götz, Andreas Gebhardt and Dr. Marco Schneider,
authors from the Fraunhofer Institute for Manufacturing Engineering and Automation IPA
Currently, small and medium sized enterprises
(SMEs) within the German cutting tool industry
encounter a wide range of challenges. Customer
requirements in terms of productivity, quality
consistency and tool life are constantly rising.
In addition, the sector is undergoing a profound
change driven by digitization and a fundamental
transformation of the automotive industry due to
powertrain hybridization and electrification. From
a market perspective, the industry is increasingly
exposed to competition with low-cost cutting
tools mainly from Asian countries.
Hence, for German cutting tool manufacturers and particularly
SMEs reduction of manufacturing costs as well
as access to new technologies and manufacturing processes
are keys for maintaining their technological leadership
position on the world market in the medium to long
term. The issue of suitable technologies and innovative solutions
for the future production of cutting tools was addressed
within the framework of the “Innovationsforum
Zerspanwerkzeuge” at last year’s International Exhibition
for Metal Working (AMB). The forum was organized by the
Fraunhofer Institute for Manufacturing Engineering and Automation
IPA in Stuttgart funded by the Federal Ministry of
Education and Research (BMBF).
The manufacturing chain of the
cutting tool industry
Today, cutting tools are predominantly made of composite
materials, preferably hard metals based on tungsten carbide.
Here, powder metallurgy is today’s state of the art
process via high temperature pressing and sintering [1,2,3] .
The sequence of operations typically involved in a powder
metallurgy process is depicted schematically in figure 1.
The process utilizes metal powder that is mixed with a
binder into a feedstock [4] which is then compacted into
green parts through a molding and pressing process and
sintered to bond the particles together [5] . This manufacturing
process allows for the production of simple geometries
as well as near net shape geometries such as indexable inserts
[2] . For more complex geometries as is the case with
milling tools for example, further machining operations
need to be applied with geometrically undefined cutting
edges by means of high hardness abrasive grinding [1,2,6] .
This process is time and cost consuming and limits the design
freedom of the inner and outer cutting tool structures
significantly [1,2] . While macro-geometric features like chip
flute geometry are limited by both the shape and kinetics
of the grinding tool, the integration of internal tool structures
such as internal coolant channels is impossible or
requires considerable efforts [2] .
During the last decade, suitable Additive Manufacturing
technologies (AM) have emerged, however, that provide
the opportunity to manufacture individual components
with a high degree of design freedom. These technologies
like Selective Laser Sintering (SLS) are based on
powder bed fusion and use a laser to selectively solidify
the powder. Figure 2 shows the manufacturing process. SLS
gains the geometric information out of a 3D CAD model
that is sliced into layers of a certain layer thickness [7] . The
parts are then produced in a cyclic process. In a first step,
powder is applied in layers to a retractable platform inside
a building chamber. Subsequently, cross sections of the
component to be manufactured are scanned and locally
fused by the energy input of a laser beam and solidified.
In the last step of the cycle, the building platform is lowered
by one layer thickness before a roll applies new powder
on top of the previous layer. The sequence of powder
figure 1
Steps of the powder metallurgy process [Fraunhofer IPA]
36 no. 1, 2020, March