A gentle giant - Wepuko Pahnke

O+P REPORT
A gentle giant
55 MN open-die forging press boasts new hydraulic drive
Since 1985, Wehlar-based Edelstahlwerke This machine superseded a 40 MN press ope-
Budenis AG has been very successfully ope- rating at the Same location, which was no lon-
Wetz'ar-based rating the 55 MN open-die forging press sup- ger able to satisfy the increasingly exacting
werke has been Operating a 55 MN
open-die forging - -. press since 1985.
A't more than 10 m high, almost 7 m
wide and 5 m deep, it is
considered the
machine of its tvDe in
plied by Pahnke Englneeringin Düsseldorf. requlrements.
operates 24 hours a
day, 7 days a weekit is
probably also the most
productive. As part of
a renovation initiative,
the entire low-pres-
Sure System was re-

Buderus employs this machine predomi-
nantly to produce plastic profile steels and
power machine components. "The former has
cenainly made us market leader in Europe
and probably also in the world. For our power
machine construction components, we enjoy
a Number 2 position", explains Dipl.-lng. Ralf
Rech (BEng), Technical Manager for the For-
ged Products Division at Buderus Edelstahl.
"We produce approx. 8000 Ions per month in
the forge."
The intention in 1985 was to achieve an out-
pul of 4000 tons per month through using the
new 55 MN press in favour of the old 40 MN
press. This target was exceeded for the fint ti-
me after just six months. "Through a process
of seamless optimization, even the steel
blocks are now slightly larger, we have sur-
passed new record targets time and time
again, raising capacity to what is today 8000
tons", explains Ralf Rech. "This probably ma-
kes it the most productive press of its size in
Germany. lt also works in double shifts around
the clock and is only at rest over Christmas,
New Year, Easter, Whiiun and on May 1 - the
periods known as coal and steel holidays".
This is how, within 9 years, they've managed
to double productionl
Modified sinusoidal drive (PMS)
The hydraulic drive of the 55 MN open-die for-
ging press is based on the system developed
by Pahnke. referred to as the modified sinusoi-
da1 drive (PMS). "The basic principle of this
drive for a press is not our invention", sap Di-
PI.-lng. Michael Pahnke (BEng), Managing Di-
rector of Wepuko Hydraulics - 'a simple versi-
on of this System was employed on a C-co-
lumn press as far back as the 30s."
Figure 1 shows this press. The press cylin-
der is connected directly to the pump piunger
of a single cylinder crank pump. This involved
the sinusoidal piston movement being trans-
ferred directly to the press plunger through
the water column between the two pistons.
The masses are thus continuously accelera-
ted and decelerated. Any pressure peaks and
dips that would cause sudden switching or
cavitation are avoided, even at high stroke ra-
tes.
The real breakthrough for this drive system
then came after the development through to
Standard production of the rapid-reverse. ra-
dial reciprocating pump by Wepuko (Figure 2).
The basic principle of this recently patented
drive is illustrated by (Figure 3). The "modified
sinusoidal drive" (PMS) uses pumps with ad-
justable flow rates and reversible flow direc-
tions, so that the working speed and the wor-
king direction can be altered without control
valves. "It is therefore descrlbed as a valve-
less drive", says Michael Pahnke, "although
of Course a series of largely passive vahres is
required to perfonn protection, feed and auxi-
liary functions."
Renwating the press
On what meäsures-are the success figures
quoted above actually based? Replacement of
the original press by the new 55 MN press
was only possible by accepting soße conditi-
ons which limited plant Operation. Ralf Rech:
O+P REPORT
1 : Pre-war press accommodating the
2: Variable Wepuko radial piston pump
3: Pahnke-rnodified sinusoidal drive (PMS)
with accumulator return
'The new 55 MN press had to be modified to
suit the existing foundations of the previous
40 MN system.''
Therefore, the hydraulic drive was restric-
ted to the space occupied by the old water-
accumulator control. This meant that the rec-
tangular oil tank had to have a very narrow
design to fit into the space available. This re-
sulted in severely restricted access for ins-

O+P REPORT
achieve Progress or should we go for a broa-
der Solution to eliminate all the weak points at
the Same time?
It was decided that the main tank renovati-
on work shouid involve replacing and optimi-
zing the entire low pressure system of the hy-
draulic unit following a concept elaborated in
cwperation between Wepuko and Buderus
experts.
4: View of the tank and pump room
The new concept
Firstly, a new pump room had to be constructed
for the low-pressure unit to provide the
space for an adequately dimensioned larger
main tank (Figure 4). This completely new design
of low-pressure unit enables
Water Resources Law requirements to be satisfied
through high-positioned circular tanks
for the main and leak-oil reservoir, which are
accessible from all sides.
Operating reliabiiity to be improved through 4
screw pumps actinq as feed pumps with dopections
and repair Similar irsues arose with
the leak oil tank, which were soon to prove
detrimental. Uliimately. the small tank and the
correspondingly weak pre-filling unit dictated
that the press could only be operated with 9 of
the 12 main pumps actually provided.
With these Hmitatiom, performance limiü
had been reached by the end of the 90s.
"We discussed our options", explains Ralf
Rech todays "What is the best solution"?
Should we confine renovation to the tank Only?
This will only invohre finance but will not
wmtream 'lters (fui-flow fi~teringL
the press to be operated safely with all 12
main pumps ; this promotes homogenizing Of
key Plans (quality improvement)t energy
Savings arid an increase in 'Ystem productivitYn
the energy consumption of the system during
idllnq to be reduced to 30 to 40 % throuqh an
5: Working room of ihe 55 MN opendie forging press