large bevel gears - arnesen marketing company · 2010-09-01 · olper straße 10–12 · 51491...
TRANSCRIPT
The Technical Magazineof the Gearing Partners Klingelnberg and Liebherr
No. 19/2010
Shaping
Large Bevel Gears
Efficient Gear Cutting in High-Strength Materials
Breakthrough to a New Dimension
2sigma RepoRt 19/2010
sigma REPoRT No. 19
Publisher
Sigma Pool
Klingelnberg GmbH Peterstraße 45 · 42499 Hückeswagen Germany
Liebherr-Verzahntechnik GmbH Kaufbeurer Straße 141 · 87437 Kempten Germany
Editorial Staff
Andreas Montag Phone +49 2192 81-370 [email protected]
Editorial Contributions
Dr.-Ing. Christoph Bunsen, Dipl.-Ing. Rudolf Houben, Dipl.-Ing. Stefan Jehle, Dr.-Ing. Andreas Mehr, Dipl.-Ing. Günter Mikoleizig, Dipl.-Ing. Michael Potts, Dr.-Ing. Wilfried Schäfer, Joachim Schuon
Editing and Design
C&G: Strategische Kommunikation GmbH, Olper Straße 10–12 · 51491 Overath Germany www.c-g-gmbh.de
Text: Tobias Hartmann Graphics: Viola Dreyling
Photos
C&G:, Klingelnberg, Liebherr
IMPRINT
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Cost Effective Shaping
Blue Competence®
Breakthrough to a New Dimension
Ready for Large Tasks
Customer Portrait SCHOTTEL-Group
Automatically More Productive
3sigma RepoRt 19/2010
Extending our LeadershipGaining a strong position through Blue Competence®
Dear Readers,
Energy efficiency and conserving resources are important
issues of our time, which have received special attention from
the world’s media in recent years. They are not exactly new
topics, and German industry in particular has been addressing
them successfully for some time. Even if we do not always
manage to attract media attention for our many improve-
ments, large or small, which we achieve, it is in the nature
of our engineers to continue accomplishing more from less.
I would even say that it is one of the core competencies of
German engineering. In the Sigma Pool, both Liebherr and
Klingelnberg have initiated the development of dry cutting of
gears and together with our customers we have successfully
introduced and implemented this process in today’s state of
the art large batch gear production. For example, most bevel
gears today are “dry-cut”, using no oil as lubricant, with
better surface quality and are machined in only 1/3 of the
time. I believe that we very rarely find a better example for
improving productivity and quality and at the same time save
valuable resources. Consequently it is not necessary for there
to be a contradiction between environmental protection and
competitiveness.
The German machine tool sector has already done a great
deal to assume a leading role in respect to energy efficiency.
For example, machines from Liebherr and Klingelnberg are
equipped with maintenance-free direct drives, converting
the energy from braking back into electrical power instead
of wasting it as heat. Additionally, systems are used to switch
off power on idle devices. All this means that our machines
are already energy efficient, despite their high power ratings,
and they are bringing the current trend towards resource
protection to the shop floor right now.
Liebherr and Klingelnberg are by far not the only companies
who have adapted their machines to become more energy effi-
cient. Many other German machine tool builders have already
worked intensively on this issue. Their efforts are apparent in
the Blue Competence® campaign run by the German Machine
Jan Klingelnberg CEO Klingelnberg Group, Board Member of the VDW
Tool Builders’ Association e. V. (VDW). You will find more about
Blue Competence® on Page 9. We – the companies partici-
pating in this campaign – wish to underline the fact that
German machine tool makers are already providing machines
to the global manufacturing environment that combine pro-
ductivity, quality and reliability with a real contribution to
energy efficiency and sustainability. Already today, our ability
to do this significantly sets us apart from our global compe-
tition and gives the user of our equipment a leading edge in
Blue Competence®.
Our commitment to environmental protection and support for
the Blue Competence® campaign is not just a moral obliga-
tion. We believe that accepting the challenge and using our
technological know-how to further improve energy efficiency
and resource protection in our machines will extend our
market leadership and make us better and more successful
companies in the future.
We are conscious of our responsibility for protecting the
environment and making efficient use of energy. Taking part
in Blue Competence® gives us the opportunity not only to do
something beneficial, but to talk about it as well!
I wish you interesting reading.
Yours
Jan Klingelnberg
4sigma RepoRt 19/2010
efficient use of energy in manufacturing – a vital competitive factor. German machine tool manufacturers traditionally rely on energy-saving solutions which reduce resource costs. the outward expression of this philosophy is found in the Blue Competence® framework.
Identifying Potentials – Using Resources Efficiently
5sigma RepoRt 19/2010
“Blue Competence®”
Reduced idling power
Today’s machines are often optimized for the working process
and less attention is paid to the idling process. In order to en-
sure the machine’s temperature stability outside the working
process, idling energy is often not used productively.
High-efficiency ancillary units
In hydraulic systems, for example, 8 Watt valves can be used
instead of the normal 30 Watt valves. It is also possible to use
electric motors with a higher efficiency rating, reducing the
energy employed. Some customers are already using these
ancillary units. Higher investment costs are quickly paid off in
lower energy costs.
Intelligent standby modes
Measurements from the automotive sector show that the
electricity requirement for manufacturing plant in the stand-
by mode, for example during a works assembly meeting, still
amounts to roughly 60 % of the energy used in normal pro-
duction.
Just as in the case of the idling process, there is a conflict
of goals with ideal temperature control of the machine. The
length of time which a break in production will take and the
point at which the machine must again have reached the ideal
process parameters are factors which always need to be taken
into account here.
Condition monitoring
Continuous condition monitoring discovers unused poten-
tials or “power hogs“ in the energy demand of the machine.
Air consumption in production (unscheduled escapes of com-
pressed air) can, for example, have a negative effect on the
energy balance.
Minimization of operating supplies
The energy and resource balance of a machine tool can also
be optimized by minimizing the use of operating supplies. In-
stead of re-lubrication at intervals it is possible to use lifetime
lubrication for bearings. Over-dimensioned cooling systems,
quality problems with filtering and oil carried off with chips
from the process likewise lead to unnecessary use of operat-
ing supplies.➔
The manufacturing companies increasingly factor energy effi-
ciency into their processes. Rising energy prices influence the
cost-effectiveness of production – the focal point is their core
element, the machine tool. This is the starting point for cur-
rent efforts to identify and release the efficiency potentials
which – despite all previous optimization – are still slumber-
ing in the system.
The electric motors in the machine tool are the chief devour-
ers of electrical current. They power the main spindles, pro-
vide hydraulic pressure and move cooling lubricant and chips
through the system. In reality, however, the situation is much
more complex: there are potentials for optimization at the
most diverse points.
If one looks holistically at the energy requirements of a machine
or at its energy saving potential, the following main areas of
relevance appear:
process optimization•
need-based drive power•
reduced idling power•
high-efficiency ancillary units•
intelligent standby modes•
condition monitoring•
minimization of operating supplies •
Process optimization
The task is to optimize machine tools in such a way that their
consumption of resources is minimized. Because idling power
constitutes a large proportion of total energy consumption,
it is advantageous to machine workpieces as rapidly as possi-
ble, so that if there is a shortage of parts the – most efficient
possible – standby mode is activated. Liebherr provides the
plant user with measuring and visualization tools to optimize
sequences in this respect.
Need-based drive power
Many of today’s machine tools are overpowered. This is due
partly to the demand for flexibility – the machines should be
designed for larger future applications – and partly to a kind
of “arms race” aimed at having the highest drive power in the
market. The power actually used for the application is often sig-
nificantly less than the potential provided by the machine.
6sigma RepoRt 19/2010
“Blue Competence®”
Example from practice: hydraulic shaping machines
Liebherr hydraulic shaping machines illustrate the potential
improvements in energy efficiency which can be released by
systematic changes in design and process technology.
Hydraulic shaping machines are employed in the manufac-
turing of large module gears, which for geometrical reasons
cannot be produced using rotating tools – for example inter-
nal gears. If especially large forces are needed to manufacture
these gears, the machines work on hydraulic rather than
mechanical principles (see Fig. 1).
The piston principle of a hydraulic shaping machine functions
as follows: a shaping tool is linked to a piston rod. This piston
rod is hydraulically operated from both sides – it is either it-
self the piston or it is operated by a cylinder-piston system.
Hydraulic pressure is now used to move the tool down (usu-
ally shaping motion) and up (reverse stroke – the process may
also partly include “drawing”).
The oil pressure and oil mass, or more precisely the oil mass
flow, are now fixed as a function of the geometry and tech-
nology parameters and controlled via a servo-valve. The
geometry parameters include the position and length of the
gear being machined, the technology parameters include
among other variables the cutting speed and chip thick-
ness.
During the shaping process, the following requirements
arise, starting at the top dead center: the piston must be-
gin its movement with maximum acceleration so that it has
reached the technologically desirable cutting speed before
entering the workpiece. It must then provide the chip remov-
ing force at a speed as constant as possible. The piston rod is
decelerated in as short a time as possible, so that it does not
collide with the geometry of the workpiece when it leaves
the gear. Once the cut is finished, the tool exits, and comes
to a standstill within a few millimetres. It is now retuned as
quickly as possible to the starting point (reverse stroke). This
stroke must take place as rapidly as possible – it has a sig-
nificant influence on the total machining time. The software
and metrology control the individual process steps and mon-
itor them in a closed loop.
In order to guard against all eventualities, the hydraulic
sub-assembly produces at least the pressure and mass flow
required to operate the above process steps reliably, and is
Fig. 1: Internal gear on a hydraulic shaping machine
7sigma RepoRt 19/2010
“Blue Competence®”
Load Sensing“If a continuously displaceable directional valve is to achieve a through-flow independent of load pressure and hence capable of providing sensitive speed control for the load, the pressure dif-ferential across the directional valve must be kept constant. Inno-vative systems of this kind, which apart from providing sensitive control also reduce losses, are characterized as “load-sensing”. Load-sensing systems are fitted either with a fixed displacement pump and a pressure compensator or, to save more energy, with a combined pressure/through-flow control system”.
(from Gerhard Bauer: Ölhydraulik. Grundlagen, Bauelemente, Anwendungen, 9th edition 2009)
dimensioned accordingly. The servo-valve blows the product
of generated pressure and mass flow which is not needed by
the process back into the tank.
Specific measures to optimize efficiency
There was an important starting point here: might the assem-
bly be oversized, not with regard to the maximum power itself,
but with respect to the ratio of constantly available maximum
power to the power required in the process?
Together with the Institute for Fluid Power Drives and Con-
trols of the RWTH Aachen (IFAS), the Liebherr development
team performed measurements and tests. While a machine
was being commissioned for a customer, a technically demand-
ing shaping process was observed and the pressures and mass
flows were measured at various locations (e.g. servo-valve
inflow and outflow). Relatively poor process efficiency became
apparent: the power maintained was substantially greater than
actually required. A principle well known in hydraulics, but not
yet exploited in the hydraulic shaping machine, provided a rem-
edy in the form of load-sensing (see info box).
The change in design was based on calculations by IFAS.
Simulation software determined the energy requirement for
the individual steps in various shaping processes with varying
external loads. These measurements were also used to verify
simulation of the corresponding operating point. ➔
8sigma RepoRt 19/2010
“Blue Competence®”
The energy flow diagrams (Fig. 2) indicate the enormous po-
tential for savings by this process. In the concrete example,
the energy input is reduced by 28 % for the same effective
useful power.
In order to profit from theses improvements, the new machine
must be fitted with a variable displacement pump and
additional measuring devices.
To this is added the appropriate software to ensure that the
process takes place reliably and in the usual quality under all
conditions. Now that the new system with load-sensing has
been proved in practice, it can be retro-fitted to existing
machines, replacing the former hydraulic system.
The example of hydraulic shaping machines shows that it is
worth looking even at mature systems – there is always some-
thing to improve. ■
Joachim Schuon
Head of Control Development and Electrical DesignLiebherr-Verzahntechnik GmbH Kempten
Dr.-Ing. Christoph Bunsen
Head of Design and Development Liebherr-Verzahntechnik GmbH Kempten
M
otor
pro
cess
80
% e
ffici
ency
Pu
mp
70%
effi
cien
cy
Shap
ing
hydr
aulic
s Pump input power14,450 W
Electric motor power loss3,612 W
Pump power loss4,414 W
Hydraulic power10,036 W
Storage 472 W
Effective power2,088 W
Flow controller1,000 W
Cylinder friction (forward and reverse stroke)449 W
Valve losses 6,344 W Losses in safety valve and yoke 104 W
Power loss· RSV in tank line 186 W· Tank line 180 W
Power loss· RSV in inflow 123 W· Feed lines 82 W· High-pressure filter 37 W
Pu
mp
70%
effi
cien
cy
Shap
ing
hydr
aulic
s
Pump input power10,387 W
Electric motor power loss2,597 W
Pump power loss3,116 W
Hydraulic power7,271 W
Effective power2,083 W
Flow controller548 W
Cylinder friction (forward and reverse stroke)450 W
Valve losses 3,141 WLosses in safety valve and yoke 211 W
Power loss· RSV in tank line 255 W· Tank line 307 W
Power loss· RSV in inflow 0 W· Feed lines 239 W· High-pressure filter 108 W
M
otor
pro
cess
80
% e
ffici
ency
Proc
ess F
orce
15
kN
BEFo
RE10
0 %72
%
AFTE
R
Fig. 2: Energy flows of a shaping machine with hydraulic main drive (example of an energy flow diagram for 26 mm plunge depth)
Proc
ess F
orce
15
kN
9sigma RepoRt 19/2010
“Blue Competence®”
Energy-efficient solutions are something German machine
tool manufacturers have been providing for a long time. With
their campaign on Blue Competence® – Taking the initiative
on energy and environment – they are also actively putting
this across to the outside world.
Numerous different measures improve the use of resources
in machine tools. In recent years, for example, more energy-
efficient components have been fitted to machines, together
with closed systems for recycling surplus energy. Added to
this are demand-related energy use and process planning
aimed at global system optimizetion.
These improvements mark out German suppliers in contrast
with their international competitors. They have a clear market
advantage in relation to Asian suppliers, for example, who
are only now beginning to utilise feedback-capable drive and
inverter technology in their machines.
One aim of the Blue Competence® campaign will be to make
the technology benefits of German machine tools clear to
customers, and systematically stimulate demand.
But Blue Competence® is not just market driven. Efficient use
of resources is something legislators are equally concerned
with. As part of an EuP directive, the European Commission
plans to lay down what is needed for an energy-saving
machine tool. At the beginning of this year, it commissioned
preparatory studies looking into mandatory requirements in
this sphere. For its part, industry has already been working
with the EU commission for some time on a voluntary self-
regulation concept, including realistic steps to improve prod-
uct efficiency.
As part of this voluntary commitment, the approach fol-
lowed by the German Machine Tool Builders’ Association e.V.
(VDW) has been to systematise technical and organisational
measures and assess their efficiency potentials. In this pro-
cess, the VDW is providing the chair and secretariat for a new
ISO working group which will lay down internationally agreed
standards for efficiency measures and ways of rating them.
Blue Competence® represents a pledge by German machine
tool builders that their products will meet the highest
requirements in terms of energy efficiency and will comply
with applicable standards. ■
Taking the initiative on energy and environment
A guest contribution by:
Dr.-Ing. Wilfried SchäferCEO of the German Machine Tool Builders’ Association e.V. (VDW)
10sigma RepoRt 19/2010
Ready for Large Tasks
11sigma RepoRt 19/2010
Large Measuring Centers
In manufacturing, precise measurements are the cornerstone
for complying with very tight tolerances and ensuring the
efficiency of the entire operation. Large measuring centers
have to be fast and easy to operate in order to determine the
current quality of the workpiece and decide on any necessary
corrections in the process chain.
The inner life of gear trains for wind turbines is especially
quality-sensitive. These include cylindrical gears, cylindrical
Where large powers and high torque are required, large gears are the answer: in marine drives, cement and coal mills, wind turbines and hydroelectric power plant. to provide a sustainable guarantee of high standards with respect to running properties, efficiency and low noise emissions, test facilities must assure quality and design in the manufacturing process. Klingelnberg has completely redeveloped its range of large industrial measuring centers and adapted them for current market needs.
gear shafts, rings with internal gearings and planetary gears.
Safe, reliable operation – even in heavy weather conditions
– is absolutely essential, as the only way to safeguard a long
and economic operating lifetime.
The increasing size of parts is leading to ever greater chal-
lenges for production quality. Customers or classification
societies need complete documentation, and this can be
assured only by regular measurement and testing. The high ➔
12sigma RepoRt 19/2010
Large Measuring Centers
The rotary table and the linear axis measuring attachment are
supported on a load-bearing machine bed. Combined with a
suitable foundation, this provides a geometrically reliable base
for the measuring machine. The machine design enables inspec-
tion of various diameters and distances on the the same work-
piece in one set-up. The gear measuring centers are optionally
available with a straight horizontal measuring axis, including
a 3D stylus system or a downward angled measuring arm.
The horizontal axis is useful in versatile applications for disc-
shaped workpieces and shafts and for gear-cutting tools. The
angled variant is particularly suited for testing gears in planetary
systems used in the wind power sector. Here the task of mea-
surement is to test internal gears with large gear widths and
to perform high-precision dimension, dimensional (MFL)
measurements in workpiece bores. The angled measuring arm
can move the 3D stylus head inside the bore close to the mea-
suring point, ensuring high measuring accuracy.
Special features are used to facilitate loading prior to a mea-
surement. Shaft-type workpieces can optionally be clamped
with a column and tailstock for a fixing range up to 2,500 mm,
so that they can be fixed between centres. Disc-shaped work-
pieces are placed on the rotary table of the measuring machine.
Depending on the size of the workpieces, extra fixtures are
available for this purpose. To make an accurate measurement,
Legend: highlysuitable ••• planned () verysuitable •• notplanned o suitable •
Measurements
P 150–P 350 P 150 W–P 350 W
Cylindrical gear outside teeth ••• ••
Cylindrical gear inside teeth •• •••
Cylindrical gear shafts ••• ••
Bevel gear wheel •• (•••)
Bevel gear pinion shaft ••• (••)
Worm gears ••• (••)
Gear worms ••• (••)
Gear-cutting tools •• o
MFL-shafts ••• ••
MFL-bores • •••
Roughness cylindrical gear ••• (••)
Roughness bevel gear ••• (••)
Grinding burn cylindrical gear (••) (••)
Gear Measuring Centers
Workpiece diameter Workpiece weight
mm kg
P 150 1,800 8,000
P 150 W 1,500 8,000
P 250 2,800 15,000
P 250 W 2,500 15,000
P 350 3,800 20,000
P 350 W 3,500 20,000
requirements for process reliability and the associated quality
documentation call for robust metrology near to the produc-
tion line. Manufacturers of large gears consequently need high-
precision measuring devices which can be operated as easily
as possible.
The new range of models in the P series meet this need.
Klingelnberg now offers continuous measuring technology in
the applications sector up to 3,800 mm. This satisfies maxi-
mum quality requirements and the standards of the classifica-
tion societies. The new machine versions combine demanding
geometry measuring tasks with high-precision gear measure-
ment.
Main goal: shorter floor-to-floor measuring times
Measuring centers for large gears are suitable for measuring
workpieces with an outside diameter up to 3,800 mm and a
weight up to 20,000 kg. The machines have a rotary table and
three linear measuring axes for acquiring measuring data. The
new rotary table provides high running accuracy (radial and
axial runout < 0.5 µm) – important prerequisites for accurate
measurement of size, shape and position deviations during
a single work cycle. A high-precision angle measuring sys-
tem is integrated in the rotary table axis for rotational posi-
tion acquisition. 3D stylus systems with digital data encoders
are used for optimum measured data logging on the tooth
flanks. The traversing paths of the linear axis allow inspection
of up to 800 mm in the horizontal plane and vertical distances
up to 2,000 mm. The rotary table and the linear measuring
axes are powered directly by AC motors for greater guiding
accuracy.
13sigma RepoRt 19/2010
Large Measuring Centers
the position of the workpiece axis is
determined in relation to the rotary table
axis. On the P series machines, this can
be done by scanning the reference sur-
face. All measuring movements are then
performed within the workpiece coordi-
nate system.
The control compensates deviations
in a range up to 10 mm. This feature
greatly simplifies loading of the mea-
suring machine, as the operator no
longer has the time consuming task of
aligning the heavy workpieces with the
rotary table axis. Centering elements
together with a mm scale are quite suf-
ficient. As an alternative, the measur-
ing machines can be aligned mechani-
cally via an air bearing integrated in the
rotary table. This can be used to align
even heavy workpieces exactly.
Using the control software, the oper-
ator can quickly create a measuring
program to define the measurement
sequence. He enters the test param-
eters together with the standards or
directives for analysis. The desired and
actual form can then be compared
reliably using the analysis software. This
is important, as large gears with high
profile and tooth trace loads need es-
pecially large modifications. Measuring
times are shortened by programming
fixed measurement sequences, and the
centre performs the prescribed steps
iteratively.
There are various ways of documenting
the results (Fig. 1): apart from print-outs
there is the option of further on-line
processing. The bevel gear closed
loop concept networks the inspection
machine with the other production
units via a database, so that logged
data can be transferred directly to the
gear machining process and the tool
settings.
Versatile adaptability
In addition to the standard equipment, users can opt for additional features
to customize a measuring center. This enables them to respond specifically to
a measuring situation.
Depending on the application, the extra features will substantially reduce
measuring time and provide more flexibility. Special locating and centering ele-
ments aid positioning of disc-shaped workpieces, allowing external or inter-
nal centering. A plastic coating prevents the workpiece from being damaged
during crane loading. The resulting centering accuracy in the millimetre range
is sufficient to start the measuring run immediately. ➔
Fig. 1: Inspection chart: Involute and Lead
14sigma RepoRt 19/2010
Additional mounting tables with different diameters (Fig. 2)
are available for large ring-shaped workpieces. These are
designed to be changed with a short set-up time and effort.
The fixtures used on the rotary table also fit the mounting
tables.
Centers are preferred for fixing shaft-type workpieces. Tail-
stocks in different types are available. Detachable columns
with a tailstock are used for small workpieces or gear-cutting
tools. Fixed columns with tailstock are available for testing ex-
tremely long and large shafts, enabling measurements on up
to 2,500 mm fixing lengths. The column can be moved using
a wireless remote control to adjust the arm for the necessary
fixing length or to adapt it for the loading position.
An optional automatic stylus changer speeds up the process if
a number of different measurements are made in succesion.
The stylus is then changed automatically during the measur-
ing sequence. Precision is maintained due to the high center-
ing accuracy of the stylus holder plate. If the stylus still needs
to be calibrated for certain measurements, this is done outside
the center of the machine. The operator sees the necessary
instructions for a manual stylus change on the screen.
The P series machines also have an optional
feature for measuring surface roughness on the
tooth flanks. The procedure is simple to adapt and func-
tions on the skid plate principle. The parameters it provides
a single run, together with other measurements, are the
centre line average (Ra), the average peak-to-valley height
(Rz) and the maximum peak-to-valley height (Rt). The spe-
cial stylus system is changed either manually or automatically.
Appropriate roughness sensing systems are available for the
respective module sizes.
Precise results can be obtained only if the workpiece tempera-
ture at the time of measurement is taken into account. A differ-
ence of a few degrees Celsius from the reference temperature
(20 °C) will cause results to deviate by two-figure microme-
tre amounts when determining test parameters for profile
tooth traces and for the base tangent length. To avoid such in-
accuracies, the new P machines provide an optional work-
piece temperature sensor. This has to be placed manually on
the workpiece prior to the measuring run. The temperature
measurement takes only a few seconds. All subsequent mea-
surements are then related to the reference temperature.
The angled measuring arm of the W version is fitted with a
monitoring camera. The ultra-compact camera can be fixed
flexibly on the measuring arm according to the intended mea-
surement and the required viewing angle. Its primary task is
to let the operator view the position of the stylus on the
Fig. 2: Mounting table with support and centering element
15sigma RepoRt 19/2010
Dipl.-Ing. Günter Mikoleizig
Head of Design and Development for Gear Testing MachinesKlingelnberg GmbH
monitor of the control unit when measuring inside gear teeth,
and make any necessary corrections.
Feedback from the industry is the basis for developing new
gear testing machines and measuring concepts. The main
focus is on key market requirements for faster processes with
simultaneously high quality standards. The modular design
enables us to customize measuring devices for individual
demand in the industry. ■
Gear measuring center P 150 W Accurate and fast measurements of workpieces upt to 1,500 mm diameter and a weight of up to 8,000 kilograms
Large Measuring Centers
Measuring arm with monitoring camera
16sigma RepoRt 19/2010
one-off and small batch production revolves around one central question: how can I automate production with small batch sizes and a big part range cost-effectively?
Automatically More Productive
17sigma RepoRt 19/2010
Pallet Handling System
This leads to further questions: What level of automation do I need to man-
ufacture small batches and a wide range of variant geometries most cost-
effectively? How can I decouple people’s jobs and work times from machine
requirements? Companies with pallet handling systems for manufactur-
ing centers achieve efficient one-off production through increased machine
utilization and extended unmanned operation, coordinated using flexible
control software.
Manufacturing batch sizes of 1 means companies face one central problem
again and again: a low level of automation hampers optimum use of machine
capacity, resulting in comparatively long machining and set-up times and high
unit costs.
Cutting unit costs by 20 %
Raising the level of automation in one-off production cuts wage costs and
boosts machine efficiency. Liebherr’s PHS handling systems tap unused
potentials and cut unit costs by more than 20 %. For workpieces with around
two hours of machining time, costs can be cut by as much as a third. This is
achieved by optimizing machine workloads, reducing manning requirements
and slimming down total investment.
Fixtures are set up in parallel time to primary machining, using separate sta-
tions (Fig. 1) which are available in different variants: for moving, tilting and
turning. Meanwhile the operator can make use of machining running time
for other tasks, meaning that set-up costs are not included in the machine
hourly rate. Flexible fixtures with all-
purpose clamping systems help to keep
down the number of pallets required
(Fig. 2). Multiple reclampings lengthen
machine running times and increase
work inventories in a system. ➔
Fig. 1: Performing set-ups alongside primary machining time takes the pressure off the machine hourly rate
Fig 2: Flexible fixtures with all-purpose clamping systems are the key to a smaller pallet park.
Reduce unit costs by more than 20 %
optimum use of machine capacity•
lower total investment costs•
trouble-free runs with tailor-made software control•
2 machines with pallet changer
1 machine with pallet changer and PHS
unit costs
unit costs
batch batch
18sigma RepoRt 19/2010
Pallet Handling System
Pallet handling systems also cut labor needs by extending un-
manned running times – you can get a third shift and extra
production at weekends.
Lower total investment costs
Wasted productivity due to sub-optimum use of machine
capacity creates a higher ma-
chine requirement – you can
reduce this by improving ca-
pacity utilization to as much
as 90 %. For example, in-
stead of two machines with
a pallet changer, achieving
a capacity utilization of just
75 %, you can use just one
machine with a pallet chang-
er and a PHS pallet handling system – giving you approx-
imately the same number of units. If you need more at a
later stage, you can retrofit the system with extra machining
centers. Extra investment costs are paid off in a comparatively
short time through higher productivity, depending on your in-
dividual plant situation.
optional fixture and materials management
Efficient coordination of resources used for a certain kind of
work or production is a central problem in machine plan-
ning. All too often, unnecessary stops hold up the production
flow. So how can one design and control the use of fixtures
and material so as to save time and costs? System-integrated
fixture and materials management can underpin your
manufacturing environment. Unfinished and finished parts
are stored in the system on europallets, together with the
change over fixture parts. Where necessary these are placed
ready for the operator next to the set-up station. You cut
logistics effort and space requirements significantly.
Consulting identifies individual improvement potentials
In the planning phase, you work jointly with Liebherr to de-
velop a solution which suits your needs. After analyzing cur-
rent status, you choose the system modules you need for your
application. Then, prior to commissioning, Liebherr trains your
personnel in system areas like NC programming and tools,
preparing them for their new tasks.
You need optimization in small series production, too
Due to growing product individualization, small series pro-
duction is playing an increasingly important role by com-
parison with mass production. You have to realize a wider
parts spectrum and various different work processes just as
you do in one-off production – though for a larger number
of units. The task for your company is still to reduce non-
productive times and expand
unmanned or low-manned
operation. Depending on your
needs, the pallet handling
system can also support small-
series production – providing
an extra robot is available to
load the machine. You can
realize this either in an un-
manned operation or along-
side one-off manufacturing, using another machine if one is
available. You get the same significant increases in productiv-
ity as in one-off production.
Workshop operations are still possible
For manual maintenance and testing work, operators can
still access the machining center via the patented front open-
ing (Fig. 3) and use the machines in workshop operations.
This accessibility likewise means that you can load the ma-
chine manually or load heavy parts using an indoor crane – a
significant advantage for automated systems.
“…We know about all the things users
are going to need…”(Stefan Jehle / Liebherr-Verzahntechnik GmbH)
Fig. 3: Simple access via patented front opening
19sigma RepoRt 19/2010
Pallet Handling System
Dipl.-Ing. Stefan Jehle
Product Manager Liebherr-Verzahntechnik GmbH
version sizepallet with workpiece
workpiece diameter
kg mm
PHS 750 PHS 750-L 500 1,000
PHS 750-M 750
PHS 750-H 1,200
PHS 1500 PHS 1500-L 1,500 1,150/1,800
PHS 1500-M 2,000
PHS 1500-H 2,500
PHS 3500 PHS 3500-L 3,500 1,900/2,500
PHS 3500-M 5,000
PHS 3500-H 6,500
Software prevents down times due to missing parts
Cell control is by the modular Soflex PCS system
(Fig. 4), specially developed for controlling manu-
facturing processes. The software keeps process-
es transparent and optimizes your use of capacity
– an important contribution to lean production.
Down times due to missing parts or missing NC
programs are significantly reduced. The ability to
manufacture in line with demand, right down to
lot size one production, benefits companies with
varying production schedules. Tied-up capital is
freed for other tasks by reducing inventories. The
software controls workpiece transport, manages
interim storage, tools and fixtures and provides
NC machining data. It is flexible so that you can
adapt it for individual plant needs: if desired, it
can coordinate additional areas of production not
linked to the pallet handling system, and visual-
ize them clearly on the central control panel. The software
communicates with all common controls and higher-level ERP
systems. “Our background in our own gear manufacturing is
a huge advantage when it comes to design of pallet handling
systems: we know about all the things users are going to
need”, Stefan Jehle, product manager at Liebherr Gear Tech-
nology, points out referring to the company’s knowledge of
the sector. If there are problems during unmanned operation,
the system texts the operator on his mobile phone, so that he
can carry out remote diagnosis or maintenance on line.
Modular building blocks
Liebherr’s PHS pallet handling system comes in three versions,
for workpiece diameters between 1,000 and 2,500 mm and
weights from 500 to 6,500 kg. These different sizes and the
storage system with its modular design mean you can find in-
dividual solutions and add elements as you go along, to give
yourself a tailor-made pallet handling system (Fig. 5). ■
Fig. 4: SOFLEX-PCS-Software visualizes processes clearly and optimizes your use of capacity
Fig. 5
20sigma RepoRt 19/2010
Cost Effective Shaping Efficient Gear Cutting in High-Strength Materials
Gear shaping in high-strength materials is still a largely unresearched area. Liebherr presents state-of-the-art insights emerging from fundamental studies of the topic.
21sigma RepoRt 19/2010
Moreover, there is a lack of fundamental scientifically-based
knowledge needed to design gear shaping processes for mate-
rials of this nature without previous testing, and to realize them
immediately in production. Users and machine tool and tool
manufacturers consequently face very high risks when they
decide to use a manufacturing process of this type.
objectives and procedure
The objective of Liebherr-Verzahntechnik GmbH is to be able
to design a reliable and efficient gear shaping process for
high-strength materials with a tensile strength Rm of 1,100
to 1,400 N/mm² by varying technology parameters and tool
technology, while achieving economic tool lives.
The wear mechanisms in gear shaping of conventional gear
materials (Rm < 1,100 N/mm²) are known, involving, for ex-
ample, crater wear and cutting edge rounding or shifting.
It is not known what types of wear and what wear mecha-
nisms occur during the shaping of high-strength materials.
It is, however, necessary to know this in order to design and
optimize tool technology. The
first step is, therefore, to ac-
quire and characterize the
wear mechanisms on the tool
as a function of the materi-
al and its strength and of the
technology parameters.
It is also important to create
a basis or reference for previ-
ous knowledge from research
or from industrial practice. This
makes it easier to transfer all
the empirical technology and
tool parameter know-how
[6] for a known material, for
example 42CeMo4, to higher-
strength materials. Liebherr has
conducted initial fundamental
studies in close collaboration
with industrial partners. The
resulting insights have already
been integrated into current
production. This report pres-
ents a small selection of uni-
versally applicable results. Our
technology experts will gladly
assist you with further ques-
tions. ➔
Shaping
Starting point and motivation
Alongside the development of new alternative drives, the
trend towards more efficient conventional gears continues
undiminished. One central feature is lightweight and com-
pact gearbox construction, frequently resulting in hard-to-
access machining points like shouldered shafts, inside gears
or outside gears next to collars, where for design reasons
there is only limited scope for tool withdrawal. Gears of this
nature remain the special province of generating gear shap-
ing. Apart from the types of gear already noted (Fig. 1),
another field of applications for generating gear shaping
is the machining of inside gears, where tool withdrawal is
not restricted by a kind of floor. In this area, shaping com-
petes directly with the usually productive broaching process.
The choice between gear shaping and broaching for inside
machining is made on economic grounds and with an eye to
the required workpiece quality.
Machining gears in high-strength and hardened materials
Obtaining the high load capacities which power gear trains
have to achieve increasingly depends on the use of high-
strength or even hardened materials. Research studies into
the machining of hardened steels [2] and the use of broach-
ing [3] and shaping [4, 5] in gearmaking have led to the fol-
lowing conclusions: Machining hardened steels is possible in
principle, but not cost-effective. Process reliability continues to
be very low, so that the use of gear shaping as a hard finishing
process has never become established in industry.
More widespread is the shaping of materials with a tensile
strength Rm of 900 to 1,100 N/mm². The current trend is
towards high-alloyed and high-strength materials with a tensile
strength between 1,100 and 1,400 N/mm². Machining these
materials economically and with high precision is currently one
of the main challenges for gear shaping.
This trend conflicts both with long years of experience by
machine tool, tool and gear manufacturers and with inten-
sive research activity in the field of generating gear shaping –
even today we have no trustworthy principles and know-how
for technology and tool design or knowledge of wear mech-
anisms which could enable us to predict:
achievable gear and surface qualities, •
process stability and•
tool lives.• Fig. 1: Gear making cases which are the special province of gear shaping [1]
22sigma RepoRt 19/2010
Shaping
Results of wear investigations on shaping cutters
Fig. 2 compares the wear on ASP2052 cutters with a TiN coating (top) and
with a (Ti,Al)N coating (center) used to machine an EN-GJS-900-8 with a ten-
sile strength of 900 N/mm² (generally referred to as ADI900). The cutting edge
of one (Ti,Al)N-coated cutter (bottom) was also intentionally rounded. The
design of the cutting data and the geometry of the cutting wedge were iden-
tical on all three cutters. They were tested at constant cutting parameters. All
three cutters were used up to a width of wear land VB of 0.15 mm and the
resulting tool lives were documented (Figures 3 and 4).
As is apparent in Fig. 2, the design of the cutting edge and the choice of coat-
ing both influence the wear behaviour. All three tools exhibit abrasive wear,
but the cutting edge wear resistance is significantly better on the (Ti,Al)N
variant with the rounded cutting edge (bottom). This contributes to a clear
increase in the tool life attained at the same width of wear land.
Influence of tool technology on the tool life
It is already known for other machining processes like turning and milling that
a systematic rounding of the cutting edges will substantially lengthen tool
lives. Tests to date have demonstrated that this also applies to gear shaping.
Fig. 3 shows the tool life diagram for an ASP2052 tool with (Ti,Al)N and a
defined cutting edge rounding used to machine various test materials.
The tensile strength of a 42CrMo4 was varied between Rm = 900 N/mm² and
Rm = 1,000 N/mm². Increasing the tensile strength by 100 N/mm² causes the
WorkpieceModule 3 mm
Pressure angle 20°
Gear width 40 mm
Reference profile DIN861 2
Coating (Ti,AI)N
Cutting edge rounded
Cutting parametersCutting speed 25 m/min
Generating feed 0.3mm/DH
Infeed per cut 2.25 mm
No. of cuts simulated 3
Infeed depth 6.75 mm
Tip chip thickness 0.14 mm
Mean chip thickness 0.09 mm
Fig. 2: Wear behaviour on different shaping cutters
Fig. 3: Tool life diagram – machinability of different materials (ASP 2052 tool material with (Ti,Al)N and cutting edge rounding)
Nu
mb
er o
f cu
ts
Cutting speed (m/min.)
0 10 20 30 40 50 60 70 80 90 100 110 120
350
325
300
275
250
225
200
175
150
125
100
75
50
25
0
42CrMo4V 42CrMo4V2 EN-GJS-900-8 C10
C10
23sigma RepoRt 19/2010
Shaping
Dr.-Ing. Andreas Mehr
Applications technology for grinding and shapingLiebherr-Verzahntechnik GmbH
tool life at a cutting speed vc of 25 m/min to fall considerably.
In a comparison of tool lives, the EN-GJS-900-8 material with
a tensile strength of 900 N/mm² lies between the 42CrMo4
with 900 and that with 1,000 N/mm². This means that the
EN-GJS-900-8 with the same tensile strength of 900 N/mm² is
harder to machine than the 42CrMo4. Fig. 4 below summa-
rizes the achieved tool lives in metres per cutter tooth for the
type of tool concerned under the same test conditions.
outlook and further steps
Together with an industrial partner and Kempten university
of applied sciences, Liebherr has submitted a research ap-
plication on the generating gear shaping of high-strength
materials, in order to acquire further fundamental know-
how. The next tests will focus on the question of how chip
thickness affects the wear behaviour of the cutters and their
tool lives. In addition, machining tests will be performed on
further material variants with tensile strengths exceeding
1,200 N/mm² – all with the central objective of increasing the
future efficiency of generating gear shaping in high-strength
materials. ■
WorkpieceModule 3 mm
Pressure angle 20°
Gear width 40 mm
Reference profile DIN861 2
Cutting parametersCutting speed 25 m/min
Generating feed 0.3mm/DH
Infeed per cut 2.25 mm
No. of cuts simulated 3
Infeed depth 6.75 mm
Tip chip thickness 0.14 mm
Mean chip thickness 0.09 mm
Literature
[1] Verzahntechnik Lorenz GmbH & Co: Verzahnwerkzeuge – Ein Handbuch für Konstruk-tion und Betrieb, 3rd edition, Karlsruhe: G. Braun GmbH, 1977[2] Ackerschott, G.: Grundlagen der Zerspanung einsatzgehärteter Stähle mit geometrisch bestimmter Schneide. RWTH Aachen, doctoral thesis, 1989[3] Klinger, M.: Räumen gehärteter Werkstoffe. RWTH Aachen, doctoral thesis, 1993
Fig. 4: Comparative tool life as a function of tool type
Too
l lif
e (m
/to
oth
)
Tool type
TiN (Ti,AI)N (Ti,AI)N rounded
[4] Peiffer, K.: Wälzstoßen einsatzgehärteter Zylinderräder. RWTH Aachen, doctoral thesis, 1991[5] Vüllers, M.: Hartfeinbearbeitung von Verzahnungen mit beschichteten Hartmetallwerkzeu-gen. RWTH Aachen, doctoral thesis, 1998[6] Doerfel, O.: Optimierung der Zerspantechnik beim Fertigungsverfahren Wälzstoßen. University of Karlsruhe (TH), doctoral thesis, 1998
24sigma RepoRt 19/2010
Rubrik
Large bevel gears can only be used to the optimum if all the steps in their production are interlinked from the very beginning: starting from design through manufacturing and on to assembly inside the gear housing. Klingelnberg’s new large bevel gear manufacturing unit is the core element in the large bevel gear process chain. It is the basis for producing high-quality bevel gear sets, with short delivery times and planning reliability for customers.
Breakthrough to a New Dimension
25sigma RepoRt 19/2010
Large Bevel Gear Cutting
The high power capacity of large bevel gears is in demand
above all in marine drive technology, in cement and coal dust
mills and in cone crushers. The groundwork for the appli-
cations-oriented design of a bevel gear based on custom-
er’s specifications takes place in the Klingelnberg KIMoS soft-
ware package (Klingelnberg Integrated Manufacturing of
Spiral Bevel Gears), supplemented by the calculational com-
petence of Klingelnberg’s in-house experts. Table 1 overviews
the input variables and results for a basic design. The macro-
geometry is fixed, allowing for the required power transmis-
sion and transmission ratio, combined with the constraints
imposed by the application, such as operational load peaks,
efficiency and noise behaviour. The proof of strength calcula-
tion determines safety factors for root and flank damage us-
ing the methods laid down in the standard, and compares
results with the specified values.
It is increasingly important to take the environment in which
the gear will operate into account back at the design stage.
Manufacturing and assembly tolerances, load-induced deflec-
tions and thermal influences all cause changes in the relative
spatial position of the pinion and wheel during operation. ➔
Input variables for the basic design are:
torque and speed of rotation•
application•
required safety factors for tooth root • and tooth flank
Results of the basic design are:
macro-geometry • (number of teeth, dimensions, …)
load capacity parameters according to DIN/ISO • and other standards
Table 1: Basic design
26sigma RepoRt 19/2010
Large Bevel Gear Cutting
This is associated with changes in the
contact pattern position and in the back-
lash. The displacement parameters which
appear can be quantified on the basis
of a holistic static and dynamic analysis.
As part of microgeometry optimization,
systematic flank modifications are made
to compensate these displacements and
obtain an optimum load contact pat-
tern. The flank geometry calculated with
KIMoS is used for a tooth contact analy-
sis to visualize the unloaded and loaded
contact pattern positions (Fig. 1), taking
the operating environment into account.
In this way, it is possible to guarantee
a high degree of planning security at a
very early stage of the product develop-
ment process.
From the melt to the blank
Production of the blank is the first step
in the actual manufacturing process.
The material used for large bevel gears
is almost exclusively 18CrNiMo7-6 case
hardening steel. This is characterized by
high attainable case hardening depth
combined with high core hardness. In-
house regulations on purchasing and
delivery with enhanced requirements
in terms of chemical analysis, grain
size, purity and hardenability are used
to supplement DIN EN 10084, entail-
ing melt selection. During hot working
to a rolled or forged blank, it is neces-
sary to guarantee a minimum strain of
4, combined with optimum grain struc-
ture. The blanks are then soft annealed,
tempered and rough turned on all sides.
Documentation of material properties
Large bevel gear process chain
Fig. 1: Tooth contact analysis in KIMoS: load-free, loaded contact patterns and ease-off (top to bottom)
Drive (Optimization of Concave Pinion Flank)
Contact pattern for Mt = 51725 Nm V=0.00mm, H=0.00mm, J=0.00mm
(Gear flank, Drive) 10mm
Max. pressure 1288 MPa
0 MPa 130 Mpa 1300 Mpa
Tip
Root
Toe
Heel
Tester contact pattern for Mt = 1902 Nm V=0.00mm, H=0.00mm, J=0.00mm
(Gear flank, Drive) 10mm
Tip
Root
Toe
Heel
KIMoS*
designdimensioning
27sigma RepoRt 19/2010
Large Bevel Gear Cutting
Fig. 2: The C 300 gear cutting machine performs the soft gear cutting and subsequent hard gear cutting process
C 300 gear cutting machine
neutral data machine•
cyclo-palloid process using • a monobloc cutter head => twin spindle
dry cutting•
pre-setting and • take-down station
Fig. 3: Cutting tool
SPIRON-U
and required test results, e.g. ultrasonic and magnetic crack
testing, takes place in the form of an approval test certificate
according to EN 10204.
In the main, manufacturing of large bevel gears is accompa-
nied and checked by the classification societies. One main
requirement is clear identification of the feedstock through-
out the process sequence. Particularly during mechanical pro-
cessing for the purpose of producing turned pieces, it is nec-
essary for the sample number and class stamp to be preserved
on the workpiece. This can be ensured by introducing a suit-
able stamping groove early on, in the rolling or forging blank.
Otherwise the workpiece will need to be restamped by an
approving officer during processing.
Efficient gear cutting on large bevel gears
Soft gear cutting takes place on the newly-developed C 300
bevel gear cutting machine (Fig. 2). This CNC-controlled neu-
tral data machine operates on the proven continuous cyclo-
palloid method using a monobloc cutter head. For this pur-
pose, the machine has twin spindles, allowing the pinion to
be machined in a single fixture. The pre-setting station con-
sists of a rotary table fitted with a measuring arm. This is
used to determine the runout deviation of the workpiece
placed on the faceplate. The operator receives the informa-
tion needed to correct the workpiece alignment via a display.
The finished workpiece is placed on the take-down station so
that the workpiece which has been set up simultaneously ➔
blank production green part machining tool setting
28sigma RepoRt 19/2010
Fig. 4:Closed-Loop
DimensionierungDesign
KIMoS
Large Bevel Gear Cutting
with main process time can in its turn be fed into the machin-
ing position. This guarantees minimized workpiece chang-
ing times.
The SPIRON-U system (Fig. 3, Page 27) is a completely new
tool concept developed for the C 300. It has enabled the dry
cutting process with coated cemented carbide tools, already
established and proven in series production, to be transferred
to the soft machining of large bevel gears. Together with the
elimination of cooling lubricants, it allows to dispense with
cost-intensive tool conditioning through the use of inserts with
four usable cutting edges. The universal tool system is con-
ceived on a modular basis. It consists of cutter head bodies
with nominal radii of 350, 450, 550 and 650 mm. These are
not restricted to one spiral direction, and can be employed
for both soft and hard gear cutting. The universal blades are
classed by their nominal modules (14–46 mm), each covering
a specific normal module range. A nominal module comprises
four blades: inner and outer blades for the left and right spirals
respectively. The high productivity of the SPIRON-U system is
based on consistent realization of a number of starts z0 = 7 by
dispensing with taper and middle tap – former systems work
with three or five blade groups. The proven concept of skiving
with CBN blades was adapted for the larger number of starts
on the cutter head in hard finishing.
Closed Loop
The new generation of CNC-controlled gear cutting machines
has introduced the closed-loop concept to the world of large
dimensioningdesign
KIMoS
heat treatmentmeasurement and any adjustment if necessary
soft gear cutting
29sigma RepoRt 19/2010
Large Bevel Gear Cutting
bevel gear manufacturing. It ensures that the property profile
of the finished gear always corresponds to the concept with-
in close tolerances. The heart of the closed-loop concept is a
central production database, where the data records devel-
oped with KIMoS are provided for production. All stations,
beginning with the CS 300 tool-setting unit and going on to
the C 300 gear cutting machine and the P 300 gear measur-
ing center, are networked via this central database, and can
work interdependently (Fig. 4)
The CS 300 tool-setting unit reads in the KIMoS data
records from the central database. The cutter head body is
first equipped manually. It possesses radial slots into which
the blades can be fitted smoothly. Apart from measuring
radial and axial runout, the unit also positions the blades
radially in an automated cycle, fixing them from the rear with
the required torque by means of the integrated screwing
unit. The achievable radial runout tolerance is ± 5 µm, and is
finally documented in a test certificate.
All machine setting data required for soft and hard machin-
ing are defined in the KIMoS data record. The section of the
data record necessary in each case is read in by the C 300
bevel gear cutting machine from the central production data-
base. As compared to gear cutting machines of the mechani-
cal generation, this has the following advantages:
Eliminating the laborious manual setting of individual • machine axes from paper setting data means that tool-up times are minimized. At the same time, the machine operator in terms of set-up activities is disburdened.
The individually driven machine axes provide enhanced • degrees of freedom and hence greater flexibility for achieving suitable flank shape modifications.
The P 300 gear measuring center is also integrated in the closed-
loop concept. The nominal data for the pitch and topogra-
phy measurements are read in from the production database.
The actual data of the measurement are also saved in the ➔
CS 300 tool setting unit
testing radial and axial runout•
radial blade positioning•
integrated screwing unit•
P 300 gear measuring center
measurement of pitch and topography•
computer-aided four axis continuous path control•
aligning aids•
tool settingpremachining for hard gear cutting
measurement and any adjustment if necessary
30sigma RepoRt 19/2010
pinion or wheel final machining testing
KIMoS
hard gear cutting C 300
Large Bevel Gear Cutting
Fig. 5: P 300 test certificate
corresponding data record (Fig. 5). If required, these can
be subjected to a nominal/actual comparison using the
KOMET software. After selecting suitable parameters the
resulting correction data can be transferred via the database
to the gear cutting machine.
In practice, a separate data record is made for each customer
job, to carry out the machining and measuring process
correctly and avoid mix-up. This also assures full documenta-
tion of all relevant process steps.
Heat treatment and hard finishing
Heat treatment in the form of case hardening is absolutely
essential to ensure that the material can meet the demands
and stresses imposed on gear components. This is the only
way to create the graded properties profile: a hard and wear-
resistant surface combined with a tough core. Heat treat-
ment is a core competence for bevel gear manufacturing. The
capacities of the in-house hardening shop were therefore
expanded alongside construction of the new large bevel gear
production facility, and adapted to match the spectrum of
manufactured products.
Heat treatment necessarily entails hardening distortions,
whose minimization is a constant priority. The process chain
was therefore extended to include measurement of distor-
tions on the components. This step directly follows mechan-
ical processing, in the scope of which the reference surfaces
for gear cutting on the pinion and wheel bodies are
machined. On the basis of measured results, data records
required for hardskiving are adjusted individually. The object
is to achieve minimum flank removal, in order to assure a
maximum remaining case hardening depth on the workpiece,
allowing for the required flank modifications. Short process
times are also ensured.
The wheels are first hard machined and measured. After ad-
justment, the same is done to the pinion. This is followed
by final mechanical processing of the wheel body or pinion
shafts and finishing of the bearing seats. Final inspection ends
the process chain.
Documented quality – ready to use
Certification as required is provided to document that the
customer’s specifications and the requirements of the classifi-
cation societies have been fulfilled:
inspection certificate for the material•
contact pattern photographs•
test certificates•
heat treatment certificate (relating to the case • hardening depth achieved)
documentation of mechanical properties•
Each gear set is subjected to a final contact pattern test after
hard gear cutting, in which contact patterns determined un-
der a small test load have to match the prescribed values
31sigma RepoRt 19/2010
final inspection
Large Bevel Gear Cutting
Dipl.-Ing. Rudolf Houben
Head of Calculation and Design Bevel Gear DivisionKlingelnberg GmbH
Klingelnberg’s New Large Bevel Gear Cutting Line
The new manufacturing location in Hückeswagen
Adding two C 300 machines to the • production area: manufacturing bevel gears up to 3,000 mm diameter
Klingelnberg’s definition of large bevel • gears: diameter 1,100 to 3,000 mm; module 16.5 to 50
simultaneous expansion of existing • capacities in the heat treatment plant
heat treatment of bevel gears up to • 3,000 mm diameter according to the requirements of all classification societies
measuring and test machines up to • 3,000 mm also available
Guidelines for the new production facility
reduce delivery times•
close the process chain•
increase productivity•
optimize set-up times•
reduce idle times in the • process chain
reduce quality costs•
*KIMoS accompanies the entire process chain, provides data for the individual machining steps and makes appropriate updates.
from the KIMoS tooth contact analysis. Provided assumptions made during
dimensioning in relation to displacement values during operation are main-
tained, the contact pattern tests made under load at the customer’s works
should also correspond with the simulated load contact patterns. In certain
cases, a practical certification allows the customer to operate a bevel gear set
of given geometry at a higher power.
Closing the loop
Numerous steps of machining, calculation and documentation lie between
the initial design and the finished and assembled gear set. Two criteria are
crucial along this path:
At the end of the path, the central quality requirements for a bevel • gear have been fulfilled: sustainable load capacity, minimal losses and low noise emissions.
The manufacturing process has been fully documented and is lean – • ensuring the shortest possible process times.
By combining high performance calculation tools with a process- and applica-
tion-optimized machine park, Klingelnberg provides the entire manufacturing
spectrum for large bevel gears from a single source. ■
On the High Seas
Storm-force winds, high waves and extreme temperatures – to reach their goal at sea, offshore supply vessels have to stay maneuverable, even under the hardest conditions. this is an environment that tests men and materials to the limit. the SCHotteL-Group manufactures marine propulsion systems for ships like these, and the bevel gears used in these drives have to meet special demands in terms of operating lifetimes and safety.
32sigma RepoRt 19/2010
33sigma RepoRt 19/2010
SCHoTTEL-Group
34sigma RepoRt 19/2010
SCHoTTEL-Group
Combi Drive (SCD) In the Combi-Drive, the electric motor is integrated vertically in the supporting tube for the rudderpropeller. This arrangement of the electric motor makes the concept comparable to a rudderpropeller with vertical power input (L-system). As neither an upper gear unit nor a cardan shaft is required, the unit remains extremely compact, and from the point of view of the shipyard it is very simple to install in the ship, saving a great deal of space.
Wind force 9. The captain of the supply ship Bourbon Mistral
maneuvers to dock safely with an offshore platform. Powered
by two SCHOTTEL Combi-Drive (SCD) rudderpropellers, the
ship delivers up to 2,700 t of supplies to its destination.
Ships and platforms in the offshore sector are not just ex-
posed to very high stresses. The reliability requirements are
also immense. Any damage would entail downtimes, result-
ing in enormous costs. Shipbuilders and suppliers bear a high
responsibility for the safety of people, the environment and
investments.
As a supplier for the shipping industry and manufacturer of
marine propulsion units, the SCHOTTEL-Group produces a
central component in the complex overall system of the ship.
The 360°-rotatable SCD 2020 propeller units each have a
diameter of 2,650 mm and transmit a power of 2,700 kW –
enough to guide the 4,720 t deadweight plus payload of the
roughly 90 m long Bourbon Mistral precisely to its objective.
Future-oriented technology
A diesel-electric drive, for which the SCD is designed, propels
the supply ship efficiently through the seas. This type of drive
combines mechanical and electrical elements. Intelligent and
efficient power management ensures high efficiency in diesel-
electric ships. This future-oriented technology is increasingly
popular in the marine sector – particularly because of its high
energy efficiency.
Unlike a conventional diesel solution, a diesel-electric con-
cept no longer needs intermediate shafts to transmit power
from the engine. All that is required is cabling to feed current
to the electric motor. This space-saving concept creates
additional loading space in the stern. The flush-mounted
asynchronous electric motor is integrated vertically in the in-
hull supporting tube for the rudderpropeller. The mechanical
gear unit is located in the underwater pod. Power is trans-
mitted from the vertical to the horizontal via a spiral bevel
gear set.
Michael Potts is the technology team leader for SCHOTTEL in
Wismar on the Baltic coast. He points out the significance of
reliable gears. “The most important components in rudder-
propellers are the angular gears, which transmit power via
bevel gear sets. Spiral bevel gears are used, because of the
very high torques that have to be transmitted. Klingelnberg
cyclo-palloid gears are characterized by constant whole depth
of teeth and an epicycloid tooth lengthwise profile. The high
contact ratio on this type of gear, combined with their good
noise behaviour, create optimum conditions for our appli-
cation”.
High precision gears
The gear sets used in the SCD drives are manufactured using
the HPG process. In this gear cutting operation, after rough-
ing and case hardening, the pinions and wheels are finished
using CBN tools developed specially by Klingelnberg. This
results in gear sets with high surface quality and precision.
Manufacturing complies with load capacity and classification
society standards. The HPG gears
used by SCHOTTEL for
offshore applications
achieve quality grade
4 or better
RubrikSCHoTTEL-Group
(according to DIN
3965). The
optimum mate-
rial for this kind
of application is
18CrNiMo7-6
steel, which
Klingelnberg
employs as a
standard in bevel gear
production.
Drive manufacturers
take special care to
ensure that the drive
housings are very
stiffly designed. The
bevel gear sets have to be
safeguarded against the excessive loads
and associated displacements which can
occur under extreme conditions.
Ready for extreme conditions
The Bourbon Mistral has successfully
completed its mission. Thanks to the
perfect mesh of the captain's craftmanship,
his skilled crew and reliable technology.
This combination equips the ship for even
the toughest conditions. ➔
35sigma RepoRt 19/2010
Klingelnberg bevel gear in assembly
36sigma RepoRt 19/2010
SCHoTTEL-Group
Cooperation between the SCHoTTEL-Group and Klingelnberg is not confined to offshore applications. Bevel gears from Hückeswagen are also used in so-lutions for the company’s other target markets. In this interview with Sigma Report, Michael Potts, the SCHoTTEL team leader at its location in Wismar, talk-ed about working with Klingelnberg, about SCHoTTEL products and about their field of applications.
Sigma Report: Mr Potts, can you give us an overview of the
range of products which SCHOTTEL offers. What solutions do
you provide in the marine propulsion sector? What are their
main features?
Michael Potts: Our original core product is the SCHOTTEL
rudderpropeller, SRP for short. Then grouped round the SRP
we have other products
we’ve brought on to the
market throughout decades
of company development: the Twin Propeller, Transverse
Thrusters, the Pump-Jet, the Controllable-Pitch Propeller and
the SCHOTTEL Combi-Drive.
Sigma Report: Aside from the offshore segment, what other
applications are your propulsion units operating in?
Michael Potts: Our units are used in tugs, ferries, river craft,
cruise liners, yachts, specialized tankers and military craft.
Sigma Report: How do you go about designing and devel-
oping the bevel gear sets? Can you give us an idea how you
work with Klingelnberg?
Michael Potts: As suppliers for shipyards, we initially receive
a series of design specifications for the drives, including the
Michael Potts runs through the SCHOTTEL group’s products and their fields of application. The core product is the rudderpropeller
37sigma RepoRt 19/2010
SCHoTTEL-Group
Dipl.-Ing. Michael Potts
Group Manager Technology WismarSCHOTTEL GmbH
Twin-PropellerA continuous propeller shaft, on which the bevel gear is mounted, powers two propellers rotating in the same direction. One advantage is that a smaller diameter is required. This technology is used especially in classic ferries.
Transverse ThrustersThis type of unit is mounted in the bow sections of ships and ensures that they can be maneuverd precisely up to the quay. In terms of bevel gears, the structure is the same as that of the rudder- propeller.
Controllable-Pitch PropellersThese propulsion units are especially suitable for container ships, where high maneuver- ability is of only secondary importance. The controllable pitch propellers have a long propeller shaft with hub. They transmit powers up to 30 MW, and unlike rudder- propellers cannot be rotated and are not 360° steerable.
Pump-JetShallow draught vessels benefit from this type of drive, for example the M boats used by the German Defence Force. Water is sucked in and the flow accelerated before being ejected as a jet at the stern, creating the thrust. The pump-jet is also 360° steerable.
bevel gears. What power is required? What kind of engines
are already there? What is the situation we have to install the
drives in, and how much space is available? What’s also im-
portant is where the ship will be used and its applications
profile. Is it an ice-going offshore supply ship, for example, or
a harbour tug in the Mediterranean? These ship parameters
effect into dimensioning of the bevel gear unit.
For the design itself we define data like the mean normal
module, the number of teeth, the contact stresses, the displace-
ment and the installation space. These data are the basis for
making the drawings and they are transferred to Klingelnberg’s
developers specified as macro- and micro-geometries.
Based on the gear sets which Klingelnberg makes accord-
ing to these data, which the classification societies evaluate
on the spot, SCHOTTEL carries out a load test. Based on the
contact pattern of the prototype, we can then go ahead with
production.
Sigma Report: What role does the feedback you get from
the Klingelnberg development department play?
Michael Potts: We naturally make our specifications as ex-
act as possible, but obviously we also rely on the competence
of our partners – after all, they are the experts where bevel
gears are concerned. In the many years we’ve been working
together we’ve developed a good working relationship, and
built up confidence on both sides.
Sigma Report: Mr Potts, thank you very much for talking
to us. ■
38sigma RepoRt 19/2010
SCHoTTEL-Group
SCHoTTEL-Group
The German SCHOTTEL group is one of the world’s leading
manufacturers of high quality marine propulsion systems. It
develops and produces all-round steerable drive and maneu-
vering systems and complete propulsion systems with powers
up to 30 MW for vessels of all types and sizes.
For more than fifty years, shipbuilders and shipowners have
placed their faith in SCHOTTEL propulsion units. The company
supplies both standard drives and tailor-made solutions.
Since it was founded in 1921, the company’s main focus has
been on introducing technical innovations to the market,
making it an important player in the world of shipbuild-
ing. Its propulsion systems power ships of all types and sizes
reliably and cost-effectively. In addition to supplying propul-
sion and manoeuvring systems, SCHOTTEL staff are on call to
assist clients with intensive advice and service. Local presence,
expert on-site know-how and comprehensive service are
fundamental principles of the company philosophy.
Propulsion systems are manufactured at three locations, Spay
on the Rhine and Wismar in Germany as well as Suzhou in
China, using the latest machines and planttechnology.
SCHoTTEL milestones
1921 Josef Becker (1897–1973) founds his craft enterprise in an old barn
1934 Purchase of the present company site and naming as the SCHOTTEL yard
1958 Founding of the first foreign subsidiary in the Netherlands
1986 Delivery of the largest rudderpropeller, with a power of 6,000 kW
1999 Takeover of WPM Wismar Propeller- und Maschinenbau GmbH and creation of a subsidiary, SCHOTTEL-Antriebstechnik GmbH, located in Wismar
2005 Josef Becker posthumously receives the Elmer A. Sperry Award for his invention of the rudderpropeller, making a substantial contribution to improving worldwide transportation
2008 Expansion of production capacity in the factories at Spay, Wismar and Suzhou
2010 Founding of the SCHOTTEL Academy and the Josef Becker research center
Michael Potts explains how the rudderpropeller (SRP) works. This patented all-round steerable marine drive is based on two angular gears, which transmit the torque from two horizontal drive shafts in the hull via a vertical layshaft to the horizontal drive shaft of the propeller; a principle also known as the Z-drive.
39sigma RepoRt 19/2010
Klingelnberg GmbHPeterstraße 45
D-42499 HückeswagenFon +49 2192 81-0
Fax +49 2192 [email protected]
Klingelnberg AGTurbinenstraße 17CH-8023 Zürich
Fon +41 44 2787979Fax +41 44 2731556
Liebherr-Verzahntechnik GmbHKaufbeurer Straße 141
D-87437 KemptenFon +49 831 786-0
Fax +49 831 [email protected]
www.liebherr.com
www.sigma-pool.com