Surface World May 2019 Surface World May 2019 | Page 70
PRODUCTS & PROCESSES
driving comfort, noise minimisation, weight,
durability, power transmission, accuracy of fit,
frictional resistance, stability, turning circle and
corrosion resistance are all optimised so that
the drive shaft efficiently fulfils all these
requirements to the greatest possible degree
Only when the shaft has proved its perfect
performance in subsequent laboratory and
practical tests does it go into serial production.
Always scalable to demand
Whether it is a longitudinal, side or cardan
drive shaft – the process always begins with a
customised concept. On the basis of detailed
customer specifications regarding shaft centre
distance, material, form and type of connection,
torque, weight and performance, Neapco’s
experts develop a design which they agree on
with the customer’s engineering team.
One of the Düren-based company’s basic
principles is always to make the front shafts
the same in order to avoid differences in
vibration. In order to follow up on the pure
idea by presenting their customer with an
initial result as soon as possible, Neapco
combines mechanical and virtual procedures
in the development stage. Quick decision
processes enable the specialists to prepare
prototypes very rapidly and put them into
serial production. For example, in its
prototype shop, Neapco may mill
components like bell or tulip housings
from solid blanks for test assemblies or for
pre-tests, or perhaps occasionally weld
together shafts just to get a first impression.
Even jobs like rotary swaging can be
performed at short notice thanks to access to
the in-house production line. It is because
of this enormous flexibility and job-based
scalability that Neapco, a relatively medium-
sized company in German terms, can
successfully hold its own against strong
competitors. In multi-stage tests, the
prototypes are then subjected to up to 2,500
test cycles which are conducted according
to the detailed specifications of the customer.
But the shafts are not only put through
their paces in Neapco’s own test facility.
In addition, when close to serial production,
their efficiency, functionality and durability
are checked in real-world operation on the
test ground and in road tests.
Surface coating
at the drop of a hat
Anywhere from 50 to 200 prototypes are
constructed for each shaft before it is ready
to go into serial production, which at
Neapco may involve the manufacturing
of just a small batch or in large quantities
depending on the particular intended use.
On average, the company delivers up to
5,000 individual assemblies per year –
complete systems consisting of drive shafts
with joints and collars. Manufacturers of
premium brands in particular expect the
shafts to have corrosion-resistant coating,
even in the prototype stage. But the
special coating is also expected to give
the components the high-value look of the
later serial products.
This is an elaborate and always extremely
time-sensitive job, for which Neapco identified
the surface engineering company Pallas as an
eminently suitable partner. For many years
now, the automotive supplier has been relying
on the comprehensive procedural competence
of the surface treatment experts at Pallas with
regard to its tool-making needs. Whether
these needs are for the coating of worn-out
bearings with hard metal, or hard chromium
plating as protection against wear or
corrosion for shafts, or non-stick coating for
filling machines – thanks to the wide range of
equipment, working materials and procedures
at its disposal, Pallas is always ready with the
optimal solution for every task and is able to
do the job practically at the drop of a hat.
Depending on the specific procedure and
working material, coating thicknesses from
just 20 microns up to several millimetres can
be achieved. Due to the lack of restrictions
on base materials and a virtually unlimited
choice of coating materials, thermal coating
has a very versatile range of application.
By combining several thermal spraying
methods, in many cases Pallas actually
improves the efficiency of the surface
treatment even further. Cost-intensive
components, time-sensitive functions or
required enhancements of the properties
of the components often make having such
thermal coatings done by Pallas the only
viable option. And these years of proven
experience in the creation of customised
thermal coatings are what made Pallas the
perfect choice to also handle the surface coating
of the drive shaft prototypes for Neapco.
The first challenge related to the low-
distortion application of the electrostatic
powder coating. To preserve the dimensional
accuracy of the hardened shaft, Pallas first
had to find a powder that melts at a low
temperature. Normally, powders are used
that melt at temperatures of 180°C and
higher. But, in the coating of the drive shafts,
under no circumstances was a temperature
of 160°C to be exceeded in order to stay
below their annealing temperature.
As a qualified expert for coating materials,
Pallas helped the automotive supplier with
the selection of a suitable plastic powder.
A second challenge relates routinely to the
extremely laborious manual masking before
the coating process. Many a surface coater
has already thrown in the towel due to
the sheer number of inaccessible places
and special masking requirements. Each
component needs masking with a variety
of special masking tapes – a very time-
consuming task.
In the case of shafts for electrically powered
cars, the specific challenge is that, instead
of the usual radial masking, covering of
the upper surface has to be ensured.
Thanks to its great experience and the range
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MAY 2019
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