hp tooling 2020 #1

materials & tools
Creating stator bores in a single operation
Powerful tools for electric motor production
The position of the automotive
industry is clear. Over the
next ten years practically every
car maker will be building electric
cars by the million - with
clean electric motors and as
plug- in hybrids. However, the
question remains: are the right
tools available for the large-scale
production of electric motors?
At EMO 2019, CERATIZIT
demon strated an extremely effective
tool programme that provides
the perfect technical and
commercial solution for every
ma chining task encountered in
the production of electric motors.
The two newly developed
fine boring tools for the highperformance
high volume production
of electric motor housings
are simply outstanding.
Present situation
The machining demands represented
by the housing of a car’s electric
motor are no different from those of
an internal combustion engine, apart
from the stator bore of the thin-walled
electric motor housing. Depending on
the size and type of the motor, the
stator bore will vary between approximately
Ø 200 mm and 300 mm, extend
to a depth of more than 300 mm
and must satisfy extremely tight accuracy
requirements; for example, tolerances
conforming to IT6 and roundness
criteria as low as 2/100 mm.
These are huge challenges for a finishing
tool designed to produce the
complete bore in a single operation
in high volume production. However,
they have to be met if electric motors
are to be produced in a timely and
economic manner in quantities in excess
of 100,000.
Solid steel tools are ill-equipped for
these tasks, as they are far too heavy
for most machine spindles. The solution
is to be found in lightweight
bodies that reduce the tool weight to
somewhere below 20 kg, which today’s
standard CNC machining centres are
able to accommodate. Available in
multi-step designs for complete machining
applications, they feature
several cutting edges per step and in
some cases guide rails as well. Despite
their light weight, fine boring tools
like these must possess a high degree
of rigidity to successfully transmit the
power to the cutting edges and hence
achieve the required tolerance results
Additively manufactured
high-end solution
With its new fine boring tool, which
is additively manufactured throughout,
CERATIZIT has developed a special
tool for stator bores that satisfies
all the stipulated requirements and
leaves nothing to be desired in terms
of machining speed and precision.
The totally new design makes it rigid
enough to satisfy IT6 tolerance requirements
and the corresponding
roundness criteria.
Despite its large diameter (in excess
of 200 mm) and considerable length,
the developers have managed to keep
the weight of the fine boring tool below
17 kg and designed it to accommodate
the tilting moment of machining
centres. That such a lightweight
tool can be manufactured at
all is down to the experience in 3D
printing gained over the years by
CERATIZIT. The delicate, optimally
braced structure of the base body can
only be produced by an additive manufacturing
(AM) process. Experienced
AM designers, who are not only aware
of the potential offered by generative
manufacturing but are also familiar
with the requirements of 3D printing,
have used FEM calculations to investigate
the effective forces and optimise
Produce stator bores at unbelievable
levels of efficiency; with the new
special tool from CERATIZIT
that will soon be possible
the topology of the structure. The result
is a fine boring tool whose design
can be scaled almost at will to meet a
customer’s needs. With four cutting
edges per step and up to five steps per
tool, even challenging boring tasks
can be completed at high feed rates in
a single operation.
Effective plug & play solution
The PCD cutting edges are soldered
into cartridges that are also additively
manufactured. This eliminates any
heat input into the base body and
prevents the associated deformation.
Once the loaded cartridges have been
fitted into the designated fixtures in
the base body, CERATIZIT grinds the
tool to precisely the required size -
10 no. 1, 2020, March