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the component. He was also impressed by the performance
of the tool, in particular, its short processing time.
The UNIFY combines precision and efficiency and has proven
to be a new, strong partner for series production in the
medium module range.
New coatings follow the increased
performance requirements
LMT Fette has long ago realized the need for in-house
development of coatings tailored to specific applications to
significantly increase the efficiency of gear cutting. And it
stepped up to the plate. During development, the focus was
also on the need for increased hot hardness, not least to
enable customers to benefit from excellent cutting data at an
ever higher performance level. Following intensive research
on their in-house coating machines the first development
phase resulted in the presentation of the nano-structured
multilayer coating Nanosphere 2.0.
Subsequently, the second development phase was launched
with the aim of developing a coating that was tailored to the
high performance of the SpeedCore and solid carbide gear
hobs. The HT layer (High Temperature) was created. Based on
an AlCrN composition, just as it was used for Nanosphere 2.0,
experts developed an even finer, nanocrystalline structure
with improved coating adhesion. This resulted in an even
further increase of the wear resistance.
Cutting materials and coatings could therefore be driven to
maximum performance in recent years. For gear cutting,
cutting speeds of up to 600 m/min are now possible (image
3). When layers were first developed around 30 years ago,
this was only around 150 m/min. The development of cutting
materials from HSS to PM-HSS went hand in hand with a
constant increase in high temperature strength and very fine
grain carbide. The new high-performance cutting material
SpeedCore has also markedly reduced the difference in
performance between PM-HSS and carbide.
Silently into the future
There is currently a strong focus on electromobility in the
automotive industry. One of the pioneers in this field is an
American company and one of its suppliers uses gear systems
by LMT Fette to manufacture gear wheels. And there is a
strong focus on one subject - noise levels.
with two speed gearboxes in the beginning which would
have been beneficial for acceleration from 100-200 km/h.
However, due to problems with the service life of the
gearboxes which were robust enough, they decided to go for
a single speed gearbox.
In this case, the electric motor is located between the two
wheels in a very compact manner and combines the electric
motor, the gearbox and the inverter which converts direct
current to alternating current in one single unit.
The dimensions of the gears are similar to those in the
gearboxes of conventional cars. However, to meet the
increased requirements with regard to low noise levels,
extremely high precision is required. The manufacturer
has therefore chosen the tool system gear hob plus
ChamferCut(image 4).
In cooperation with gear cutting machine manufacturer
Liebherr in Kempten, LMT Fette has perfected the ChamferCut
milling system - it enables the chamfering of gears straight
after hob cutting. The ChamferCut can either be fastened on
a mandrel together with the gear hob or it can be used as an
individual tool on a separate milling spindle. In either case,
the result is a high-precision, constant chamfer on the gears.
Of course, the known performance characteristics for
gearboxes such as a long life and optimum dynamic behavior
still apply. However, in contrast to a combustion engine the
electric motor is virtually silent. The gearbox, therefore,
needs to match that. For the manufactured gearbox of the electric car this high
chamfer quality plays an important part in achieving low
noise levels. And the cutting costs per gear could be markedly
reduced as a second gear cutting step is eliminated which
would be required with alternative methods such as press
deburring.
The above mentioned automotive company experimented www.lmt-tools.com
36 | january-february 2019 |
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