the design of a 165 mn open die forging press - Wepuko Pahnke

Authors: Michael Pahnke; Wepuko Hydraulik GmbH, Metzingen, Germany
phone +49-7123-1805-30; e-mail: pahnke@wepuko.de
Wang ChunMing + Liu DaHua, CITIC Heavy Machine Corporation, LuoYang, China
THE DESIGN OF A 165 MN OPEN DIE FORGING PRESS
An open die forging press with a maximum
forging force of 165 MN (16500 t) for bar and
shape forging and an upset force of up to 185
MN for concentric forging is going to be the
most powerful press of this type in the world.
The press construction will follow the typical
design by Pahnke Engineering, which is well
known around the world.
It is of course always a challenge to design
and build the largest machine of one type.
Special care must be taken about the selection
of the materials, their structure and design
principle. It must be considered how the parts
can be produced with the necessary quality on
the available manufacturing equipment and
how the parts can be handled and assembled.
Naturally, also the design work as such,
including careful calculations with most up-todate
methods, was a challenge.
In close cooperation between the designers
and the manufacturing experts, we are building
a machine which is not only unique in its
capacity, but also different from the
conventional design. The manufacturing of all
components is now in progress. The assembly
of mechanics and the hydraulic system has
started, so we will be able to report on the
commissioning and the production on this
outstanding machine during the next IFM.
1. The background for this extra large
forging press
Let us take a brief look at the customer first:
Citic Heavy Machine Corporation (HMC) in
Luoyang, China is a long time manufacturer of
very heavy equipment for mainly the Cement
and Mining industry. They had steel making
capacity of up to 400 t liquid steel and several
open die forging presses up to 84 MN (8400t).
About three years ago they received the
approval from the central government to
increase their capacities. The steel plant
should be upgraded to a capacity of up 900 t
pouring of liquid steel to produce ingots and
shape castings of over 600 t weight. To forge
the largest ingots a new open die press with a
capacity of 165 MN for cogging and 185 MN
for upsetting was planned. The upgraded steel
and casting plants are already in operation and
were used for the production of the press
frame castings.
Fig 1 Typical product of Citic HMC
2. The selection of the basic criteria
for the design of the press
The starting point for the selecting of the
technical parameters for the press mechanics,
the hydraulic drive system and the sizing of the
manipulator is, of course, the products. Very
large ingots with a weight of up to 500 t (after
the head is removed) are difficult and slow to
handle and stay in the forging press a very
long time during the forging process.
Fig 2 5000 kN Pop-up Turn Table

Therefore the press design and the design of
the handling equipment needed to take the
weights and the huge heat energy into
consideration. The pop-up turn table for
example, which is capable of lifting the 500 t
ingot looks quite different from the “normal”
design.
Fig 3 Loading/Unloading in a two column press
For the press design careful considerations
were done to check the possibilities and the
advantages of the known design principles.
Finally the choice was made for the two
column version with pre-stressed frame.
Fig 4 Crane access to a two column press
It offers many advantages, mainly the better
access for loading and unloading, the
possibility to come closer to the press centre
with chains and with the handling equipment,
and the less obstructed view field of the
operator.
Fig 5 Operator’s view on a two column press
A very big advantage for this frame layout is
the possibility to flatten and finish much larger
rings.
Fig 6 Space for ring forging in a two column press
A very valuable side effect with respect to the
heat influence is that the columns are a little bit
further away in this design. This is more
significant than one might think when you keep
in mind that the bulk o
f the energy transfer from the forging into the
frame happens through radiation and this
energy flow reduces with the square of the
distance. Further the hollow column, which is
open on the back side, generates a cooling air
flow in the inside through a natural chimney
effect.
The most common arguments against this
design are that firstly the two column frame is
not as stable as a traditional four column frame
and that secondly all large presses have four
column frames.
The first argument is simply wrong as the basic
physical comparison of the area inertia against
bending proves, as shown here by the criteria
of eccentric load capacity. It is a well known
fact and used since ancient times in buildings
and bridges that a rectangular cross section
offers more stability against bending than a
round or square section. Naturally, the
engineer must use this effect in the proper
way, otherwise the press frame may indeed
end up too flexible.
Fig 7 Eccentric load capacity of a two column press
The second argument is of course only a
demonstration of lack of self confidence or lack
of engineering knowledge. As long as the
components for a certain design can be
produces with existing of newly built
equipment, there is no natural limit for any type
of design.

Fig 8 80 -100 MN two column open die press
Why should a press frame design that has
been proven to be good on smaller presses
hundreds of times by numerous different press
manufactures not be good for the largest
press. Besides, the next smaller examples for
presses with this design are not that far away
with the press with 100 MN maximum force at
Japan Casting and forging and with 110 MN
force at Creusot Forge. They are both in
production since more than 30 years now, one
even with an oil-hydraulic drive system.
Fig 9 90 – 110 MN two column open die forging press
3. The selection of the hydraulic drive
system
Larger presses are mostly being powered by
water accumulator systems. This is again
mainly because of tradition and to a large part
because most of these presses or their
predecessors in the same plant have been
built at a time before large oil hydraulic pumps
and valves were available. Nowadays it makes
no sense at all to supply a new water-hydraulic
system. It is much more expensive to build and
it requires much more down time for
maintenance and repair, including
unscheduled stops. This makes such a system
totally uneconomical especially as it consumes
more power too. Also environmental aspects
may quickly turn into the opposite if you look at
the details.
So the decision for an oil-hydraulic drive was
made early, but more needed to be looked at.
A drive system on any press operates a large
amount of the total time in an idle situation.
Whenever the product must be loaded or
unloaded, whenever it must be repositioned or
tuned and whenever a die must be changed or
adjusted, the drive system is not under load.
Even the coffee brakes or the shift changing of
the operation crew adds to these idle times,
because it makes usually no sense to shut the
system down and re-start it during such
pauses. The larger the press, the more is the
percentage of these idle phases. On big
presses like this the idle times of the drive are
typically much more than half of the total
running time. This leads to a close look of the
energy efficiency of the drive, especially when
it is not working under load.
This is where the today well known “Pahnke
Modified Sinusoidal Direct” drive (PMSD) has
its big advantage. This system, which was
developed by Pahnke Engineering under
Hans-J. Pahnke in the 1970 th , is based on the
servo controlled variable volume radial piston
pump, designed also by Hans Pahnke and
manufactured since 1960 by Wepuko.
Fig. 10 Principle of PMSD drive

With this pump, today named RX-type, the
press movement can be powered and at the
same time controlled directly by the pumps
acting onto the main and return cylinders
without directional valves in-between.
Fig 11 Radial piston pump RX
This arrangement produces a very smooth
shock-free and therefore reliable press
movement with minimal wear on all mechanical
and hydraulic components.
The biggest advantage of this system however
is the high energy efficiency, which can be
optimized also for the periods of idle running to
a degree where this drive consumes up to 30%
less electrical power than that of most valve
control systems. The direct motion control by
pumps and the maximizing of energy saving
can today only be realized with this type of
radial piston pump.
4. The realisation of this system
The design of the hydraulic drive was not a
major challenge. The fact that this press is
driven by 20 of the largest RX-pumps instead
of the 12 so far used as a maximum number in
three other press drives only required
increasing of the components or their number
and of course a lot more space in the pump
room and the piping channels.
The design of the press frame was much more
of a challenge. Besides careful considerations
of the materials and their properties for large
pieces, detailed calculations were done by
three independently working engineers.
Naturally, finite element analysis was done
more than once to optimize also the critical
stress concentrations. Further to this, FEM was
also used to investigate the potential of the
frame to start swinging under working
condition. Special design details minimized the
danger of resonance and the mathematical
analysis showed that the smallest resonance
frequency would be just over 5 Hz. As it is
simply impossible to generate anywhere near
300 strokes per minute on such a large press
there is ample safety against unstable
swinging of the press frame.
Fig 12 FEM structure of 185 MN press
The other major concern was the size of the
individual frame parts. Any designer should
prefer to use as few pieces as possible to
avoid connections with their additional wear
and potential for failure and additional
requirement for maintenance and repair. A
normal frame for a two column press consists
of four pieces: the base plate on the bottom
the cross head on the top and two columns.
However, for presses with a force above 100
MN one soon reaches weights of these pieces
exceeding 200 t of finished weight. The
available number of manufacturers with
equipment to produce such heavy castings,
heat treat, and machine them quickly reduces
to the number of fingers which we have on our
hands. So quite often, the design must be
modified to split the main parts of the frame
into two or more pieces. By the way using
welded main parts instead of castings does not
help. Typically the problems for manufacturing
such large steel structures increase when
trying to change to weldings.
Citic HMC wanted to manufacture the press in
their own shop. So the design proposals were
discussed intensively between our engineers
and their experts from the various production
departments. Since this customer invested into
higher steel casting capacity, as well as into
accompanying heat treating and machining
facilities. The frame design was finally fixed to
a five piece model where only the base plate
was split into two pieces. Top cross head,
columns as well as the moving beam all are

made in one piece. The heaviest piece weighs
about 430 t after machining, requiring well over
600 t liquid steel for the rough casting. The
total press mechanics will weigh over 4000 t.
Fig 13 TFP 165 press
32 tie rods pull the frame parts together over a
length of 22 meters pre-stressed to such high
level, that the frame is like one piece for
probably its entire life. This concept of using
numerous slim tie rods rather than only one
per column is well proven. A few years ago the
tie rods on the 110 MN press had been
checked and after nearly 30 years of operation
the maximum deviation in the pre-stress found
on all of the tie rods was below 10% and
therefore negligible.
Fig 14 165 MN Top cross head
The press frame will be protected against
accidental overload by an electronic stress
measuring system similar to what we regularly
use on large closed die presses.
The hydraulic drive of this press occupies a
pump room extending 25m by 50 m. The
installed electric motor power is 11500 kW with
a peak power consumption of 14 MW.
The forging system will be completed by an
integrated railbound forging manipulator with
2500 kN carrying capacity and 7500 kNm load
moment. This machine from DDS will also be
the strongest of its kind.
5. Preliminary Results and Forecast
Early 2006 the order for this system was
placed with us. Today the press and system
are completely designed and delivered (Fig
15) and the assembly has started. The main
challenge of producing the large castings was
successfully mastered by CITIC HMC. The
decision for the design criteria has so far
shown to be right. The production of these XXL
pieces was possible and without problems.
The components of this large hydraulic drive
have been put onto their positions in the pump
room and piping is being installed.
Commissioning will start soon. If the progress
of work continues as smoothly as it has so far,
the production on the world’s largest open die
forging press will commence less than two
years after placing the first order for the
equipment. Thus most likely we will be able to
report about production on the exceptional
machine on the next IFM.
Fig 15 Layout of 185 MN forging press plant