Design and Analysis of Hydraulic Press: Working Principle, Components, and Comparison of Conventional and Modified Press

This study focuses on the design and analysis of a hydraulic press using Simulink. It covers the working principle and components of hydraulic press, including double acting cylinder and pressure relief valve. The study also includes a comparison of the characteristic features of conventional and modified hydraulic press, analyzing parameters such as piston position, velocity, flow rate, and fluid power wasted through relief valve. Proposed modifications to optimize the press are also discussed.

Contents
List of Figures.............................................................................................................................................2
Chapter 1.....................................................................................................................................................3
Introduction.............................................................................................................................................3
Chapter 2.....................................................................................................................................................4
Literature review.....................................................................................................................................4
Chapter 3.....................................................................................................................................................6
Working principle of Hydraulic press......................................................................................................6
Principles of hydraulics.......................................................................................................................6
Hydraulic System................................................................................................................................6
Working of Hydraulic Press................................................................................................................6
Components of Hydraulic Press:.........................................................................................................6
Hydraulic Fluid................................................................................................................................6
Double acting cylinder.....................................................................................................................6
Pressure relief valve:........................................................................................................................7
Chapter 4.....................................................................................................................................................8
Development of case study......................................................................................................................8
Chapter 5.....................................................................................................................................................9
Analysis and comparison of characteristic features of presses.................................................................9
Conventional Press..............................................................................................................................9
Modified Proposed Press...................................................................................................................16
Chapter 6...................................................................................................................................................22
Comparison of results and graph plotting in excel.................................................................................22
Chapter 7...................................................................................................................................................24
Health and safety practices....................................................................................................................24
Safety check of pipes.........................................................................................................................24
Thin pipe analysis..............................................................................................................................24
Other safety feature of proposed design.............................................................................................24
Chapter 6...................................................................................................................................................26
Result and Discussions..........................................................................................................................26
References...............................................................................................................................................27

List of Figures
Figure 1 Double acting Hydraulic cylinder.....................................................................................6
Figure 2 Pressure relief valve..........................................................................................................7
Figure 3 Hydraulic circuit of Hydraulic press.................................................................................8
Figure 4 Input to 4-way valve through actuator..............................................................................9
Figure 5 Rod velocity in conventional press.................................................................................10
Figure 6 Rod position in Convention press...................................................................................11
Figure 7 Flow delivered by pump in conventional press...............................................................12
Figure 8 Flow through relief valve in conventional press.............................................................13
Figure 9 Hydraulic circuit of Proposed Hydraulic Press...............................................................14
Figure 10 Rod velocity in Proposed Press.....................................................................................15
Figure 11 Rod Position in Proposed Press.....................................................................................16
Figure 12 Flow delivered by pump in proposed press...................................................................17
Figure 13 Flow going through relief valve in proposed design. Amount of fluid wasted through
relief valve is almost 2.5 times less...............................................................................................18

Chapter 1
Introduction
The hydraulic press was invented by John Brahmah as one of the first pieces of machinery that
used hydraulics as its prme mover. It consisted of a plunger pump attached inside to a large
cylinder and a ram. This press found wide use in England because it provided means of applying
large forces in industries.
Today, hydraulic power is used to operate tools and mechineries of varying sizes. In a garage, a
mechanics uses hydraulic jack to raise the end of an automobile, dentists and barbers use
hydraulic power to lift their chairs to a convenient working height. Hydraulic doorstops keep
heavy doors from slamming and hydraulic brakes have been standard equipment for
automobiles. Automobiles are equipped with automatic transmissions and power steerings, both
of which are applications of hydraulic power. Construction workers depend upon hydraulic
power for the operation of various components of their equipment, for example, the blade of a
bulldozer is operated by hydraulic power.
Hydraulic systems in engineering applications are composed of pumps, motors, pipes, pistons,
valves, filters, and accumulators that use nearly incompressible fluids. Such systems are found in
machine tools, earth-moving equipment, power transmissions and aircraft control surface
servomechanisms. Almost all hydraulic systems are equipped with a pressure regulator to
maintain the working pressure at a predetermined level.
Hydraulic press finds uses in mass production involving the cold working of metals, usually in
the form of thin sheet or strip. Press working is one of the extensively employed methods of
fabricating parts of intricate shapes with thin walls. Press working processes apply large forces
for a short time interval which results in cutting or shaping the sheet metal. Since, press working
does not involve heating of the parts, close tolerances and high surface finish can be obtained on
the part. The unit cost of labor for operating the press is fairly low since presses can produce
components at fast rates.

Chapter 2
Literature review
1. Neville Saches: Author focused on the causes of failure and gives the brief introductions
about the ductile fracture, fatigue failure and stress concentration. Paper also discussed
load responsible for failure i.e., internal pressure, bending, torsion or a combination
(Sachas, 2009).
2. P.E. Uys, K. Jarmai, J. Farkas: Cost effective design of a multipurpose hoisting device
that can be easily mounted on regular farm vehicle was attempted. The optimization is
constrained by local and global buckling and fatigue conditionsand is solved by means of
the leap-frog algorithm (Uys, et al., 2003).
3. Sinha and Murarka: Authors represented a 3-D complex structure and found that an exact
analytical method of stress and deformation analysis is time-consuming. A simplified
plane stress FEM model for a hydraulic press structure was identified for its analysis.
Certain significant guidelines have been obtained for the design of press frames which
resulted in savings in computational time, core memory requirement and cost of analysis
(Sinha & Murarka, 1988).
4. Muni Prabaharan and V.Amarnath: Topology optimization is applied on various
components of scrap baling. Topology optimization results in a better product design
along with being cost effective (Prabaharan & Amarnath, 2011).
5. LeRoy Fitzwater, Richard Khalil, Ethan Hunter: Topology optimization method outlined
herein convinces to re-think the way aircraft structure is designed. Topology optimization
requires further development to achieve effective use and to aid in producing quality
designs (Fitzwater, et al., 2008).
6. S.M.Bapat and Dessai Yusufali: Authors have investigated on a 30 ton hydraulic forming
press machine. Analysis of the frame structure in terms of its material, geometry and
stressed induced was performed. Hydraulic press continuously deals with the stress that
may be compressive or tensile because press machine always works under impact load
condition. Different components of the machine are subjected to different types of
loading condition and are analyzed by using ANSYS. Weight optimization of press frame
and upper head reduces thickness of the frame structure and material (Bapat.S.M. &
Desai.Y.M, 2009).
7. B.Parthiban: Author conducted study on C-type hydraulic press structure and cylinder. It
is studied that the structural design of the frame depended on the pressing force which
determined for the required rigidity, the dimensions of dies influencing the size of the
tool area, work area accessibility that determined by the shape of the press frame. The
frame and cylinder are modeled by using modeling CATIA (Parthiban, et al., 2014).
8. Pedro G. Coelhoaet: Authors conducted a study on structural analysis and optimization of
hydraulic press brakes. Based on the model of the bending process in press brakes
defined by Timoshenko theory of beams, workpiece bending errors have been derived by
considering the influence of dimensions, shape and initial deformation of the structural
components . Shape optimization and dimensional optimization is performed to achieve
uniform bending angles over entire length and optimal initial deformation decreasing the
bending error (Coelhoa, et al., 2005).

9. H.N.Chauhan and M.P.Bambhania: Authors shows that, FE Analysis has been applied on
a frame of 63 ton power press machine.. It is said that Instead of sharp corner of the c -
frame, fillet is provided to reduce failure in the structure. Amount of fillet depends on
load condition experienced by frame and it is analyzed by using FEM Tool. It is
concluded that simulation software is the powerful tool for prediction of plate required
for a given load. This analysis given the result of reduction in thickness of plate of frame
structure, material saving and as well as cost benefits (H.N.Chauhan & M.P.Bambhania,
2013).

Chapter 3
Working principle of Hydraulic press
Principles of hydraulics: Hydraulics is the science of transmitting force and/or motion through
the medium of a confined liquid and is based on Pascal’s law. In a hydraulic device, power is
transmitted by pushing on a confined liquid. The transfer of energy takes place because a
quantity of liquid is subject to pressure.
Hydraulic System: A hydraulic system confines a liquid in such a way that it uses the Pascal’s
law to transmit power and do work. The oil reservoir serves as a storehouse and filters, strainers,
and magnetic plugs removes harmful impurities that clog passages and damage parts. Heat
exchanges are used to keep the oil temperature within safe limits and prevent deterioration of the
oil.
Working of Hydraulic Press: Since the hydraulic press works on the basis of Pascal's Law, its
working is similar to the one of the hydraulic system. A hydraulic press consists of cylinders,
pistons, pressure relief valves, hydraulic pipes etc. The system comprises of two cylinders; the
fluid is poured in the cylinder having a small diameter. The piston in this cylinder is pushed to
compresses the fluid in it and flows through a pipe into the larger cylinder. The pressure is
exerted on the larger cylinder and the piston in cylinder. The force applied on the fluids by the
smaller cylinder results in a larger force in the larger cylinder. Hydraulic presses are used in
industries where a large pressure is required for compressing metals into sheets.
Components of Hydraulic Press:
Hydraulic Fluid The hydraulic fluid has four primary purposes: (1) To transmit power, (2) To
lubricate moving parts, (3) To seal clearance between parts, and (4) To cool or dissipate heat
Double acting cylinder: Double acting cylinders have two opposing effective areas which are of
the same or different sizes. They are fitted with 2 pipe ports which are isolated from each other.
By feeding fluid via ports “A” or “B” (Figure 1), the piston may transfer pulling and pushing
forces in both stoke directions. This type of cylinder may be found in nearly all types of
application.
Figure 1 Double acting Hydraulic cylinder (Bickers, 2016)

Pressure relief valve: Pressure relief (Figure 2) valves are used in hydraulic system to limit the
system pressure to a specific set level. If this set level is reached, the pressure relief valve is
activated and feeds the excess flow from the system back to the tank. This valve is always
arranged as a bypass valve. The pressure relief valve is also known as a safety valve.
Figure 2 Pressure relief valve (Filters, 2018)

Chapter 4
Development of case study
This study is aimed to design a hydraulic press in Simulink using hydraulic blocks and analyze
various systems characteristics like piston position, piston velocity, flow rate delivered by pump
and fluid power wasted through relief valve when the press is bottomed out.
It is assumed that press simulated here develops a maximum pressure of 95e5 Pa inside
cylinders. The fluid is delivered through a fixed displacement pump with nominal pressure of
100e5 Pa and relief valve is set at 95e5 +/- 5e5 Pa. Power source for pump is a constant angular
velocity motor running at 188 rpm. A 4-way valve is used to connect cylinders with the pump.
The motion of 4-way valve is controlled through a servo-valve actuator whose input is shown in
Figure 5. The valve is gradually opened till 2 secs and is held at full open for a total of 3 secs and
is then gradually returned to partial opening in reverse direction to enable piston to reach the
initial position.
The whole system is simulated for a total of 10 secs and various parameters are analyzed as
shown in proceeding sections.
Based on the waste fluid that flows through relief valve as shown in Figure 9, it is concluded that
fluid power is wasted when the press is required to hold the bottomed-out configuration for an
extended period of time. To optimize the press and reduce the wastage of fluid power, following
modifications are proposed:
1. Replacement of fixed displacement pump with a variable displacement, pressure
compensated pump.
2. Installation of closed feedback and control system to drive the servo-actuator.
It is assumed that efficiency of motor driving the pump is not of concern. The volumetric
efficiency of pump is 0.92 and overall efficiency is 0.8. The internal diameter of pipes is 0.02m
and each segment of pipe is 3m in length with internal roughness height of 1.5e-5m. The
resistance to fluid flow offered by flow rate sensors is negligible. Connection of piston rod with
translational sensor is ideal. The mass that piston rod acts against in both cases is same and equal
to 100kg with translational spring constant of 15000N/m and damping constant of 2N/(m/s). The
gain of servo-actuator is also kept at 50 in both cases.
The following chapter gives a comparison of various characteristics obtained from analysis of
conventional and modified hydraulic press.

Chapter 5
Analysis and comparison of characteristic features of presses
First we give the circuit diagram followed by block diagram, actuating signal to servo, piston
velocity, piston position, flow delivered by pump and flow wasted through relief valve in
conventional press followed by same features of proposed modified press.
As can be seen from the diagrams. The rod velocity is much more stable due to a feedback and
control system which makes the rod position follow the actuation signal more closely. The fluid
flow required from the pump is also reduced and wastage through relief valve is almost 2.5 times
less. This results in saving in fluid power which means less energy expenditure in the motor and
less part wear down.
Conventional Press
Figure 3 Conventional Press Circuit

Figure 4 Hydraulic circuit of Hydraulic press

Figure 5 Input to 4-way valve through actuator

Figure 6 Rod velocity in conventional press

Figure 7 Rod position in Convention press

Figure 8 Flow delivered by pump in conventional press

Figure 9 Flow through relief valve in conventional press

Modified Proposed Press
Figure 10 Proposed Press circuit

Figure 11 Hydraulic circuit of Proposed Hydraulic Press

Figure 12 Rod velocity in Proposed Press

Figure 13 Rod Position in Proposed Press

Figure 14 Flow delivered by pump in proposed press

Figure 15 Flow going through relief valve in proposed design

Chapter 6
Comparison of results and graph plotting in excel
Data from Simulink is first extracted to workspace by ‘to workspace’ block. The imported data from
conventional and proposed press design is combined with time step from simulation. This data is then
extracted in form a nx3 array in excel file. The subsequent plot of various characteristics thus obtained are
presented in following figures.
0 0.45 0.9 1.35 1.8 2.252.7 3.15 3.6 4.05 4.54.95 5.4 5.85 6.3 6.75 7.27.65 8.1 8.55 9 9.459.9
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
Piston Velocity
Conventional Press Proposed Press
0 0.45 0.9 1.35 1.8 2.252.7 3.15 3.6 4.05 4.54.95 5.4 5.85 6.3 6.75 7.27.65 8.1 8.55 9 9.459.9
-0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
Piston Position
Conventional Press Proposed Press

0 0.450.91.351.82.252.73.153.64.054.54.955.45.856.36.757.27.658.18.55 9 9.459.9
0
0.0001
0.0002
0.0003
0.0004
0.0005
0.0006
0.0007
Flow Rate from Pump
Conventional Press Proposed Press
0 0.450.91.351.82.252.73.153.64.054.54.955.45.856.36.757.27.658.18.55 9 9.459.9
0
5E-11
1E-10
1.5E-10
2E-10
2.5E-10
Waste Flow Rate
Conventional Press Proposed Press

Chapter 7
Health and safety practices
Safety check of pipes
According to the ASME Process Piping Code (B31.3) (ASME, n.d.)
p= 2∗t∗S∗E
D−2∗t∗Y
where
p = internal pressure
t = wall thickness
S = material's tensile strength
D = outer diameter
Y = wall thickness coefficient (B31.3-2002, Table 304.1.1) (ASME, n.d.)
E = material and pipe construction quality factor (B31.3-2002, Table A-1A) (ASME, n.d.)
Maximum internal pressure = 107 Pa
Material tensile strength = 475 MPa
Outer diameter (m) = 0.02+t
Y =0.4 (Temp assumed to be less than 900F)
E=0.8
Therefore, the minimum thickness of pipe is calculated to be t=0.3 mm
Here, t < D
6 , hence the assumption of Y is valid.
Thin pipe analysis
Calculating hoop stress induced in material,
σ hoop= p ×d
2 t
σ hoop= 107 ×0.02
2 ×3 ×10−4
σ hoop=333 MPa
Therefore, hoop stress generated is smaller that tensile strength of material. Hence the design is safe.
Other safety feature of proposed design

The variable displacement, pressure compensated pump used in the proposed design has a built
in relief valve that regulates the pressure inside the system. An extra relief valve is installed in
the pipes to act as a fail-safe feature. In case the pump malfunctions and continues to deliver
fluid exceeding the pressure rating of system, the extra relief valve installed in the system with
drain the fluid to sump.

Chapter 6
Result and Discussions
The work presented here describes feedback control system for hydraulic press actuation. The effect of
these modifications were analyzed in Simulink and the results were presented here. It was concluded that
the pump auto-regulates the fluid being pumped to cylinder thus reducing fluid power loss. The control
system modifies the input to actuator with feedback from rod position to match the required positions as
closely as possible. This reduces the vibrations in rod and further minimizes fluid power wastage.
The reduction in fluid power wastage flowing through relief valve to sump is clearly reduced as seen from
Figure 9 and Figure 15. The loss is minimized by a factor of 2.5. Further improvement to fluid power
waste minimization is expected by optimizing control system gain and is subject of future investigations.
In the literature about controlling and optimizing the fluid power and hydraulic press, which is presented
in the literature section of this report, it was observed that a similar feedback and control system was
employed to control the rpm of motor attached to the pump. This was made possible through a PID
controller circuit which took input from position as well as velocity of piston rod. This input was
compared with a predetermined position and velocity values, against time, and used to generate an error
signal which regulated the motor speed. The net effect was the optimization of on duty time of motor and
reduction in electrical power usage. Such a modification to hydraulic press cannot be included in
hydraulic circuit modification and hence was not considered in this report. Instead, use of variable
displacement, pressure compensated pump and feedback & control system to optimize valve opening was
considered and analyzed in this report.

References
ASME, n.d. ASME Process Piping Code. [Online]
Available at: https://www.asme.org/products/codes-standards/b313-2016-process-piping
[Accessed 04 04 2018].
Bapat.S.M. & Desai.Y.M, 2009. Design Optimization of A 30 Ton Hydraulic Press Machine.
International Journal for Research in Applied Science and Engineering Technology ( IJRASET ), pp. 24-
30.
Bickers, E., 2016. Hydraulic Cylinders and Cushioning Devices. [Art] (SlidePlayer).
Coelhoa, P. G., Fariab, L. O. & Cardosoa, J. B., 2005. “Structural Analysis And Optimization Of Press.
International Journal Of Machine Tools & Manufacture, Volume 45, pp. 1451-60.
Filters, B. B. W., 2018. Plastomatic RVT Pressure Relief Valve. [Art] (Big Brand Water Filters).
Fitzwater, L., Khalil, R. & Hunter, E., 2008. Topology Optimization Risk Reduction. Montreal. Canada,
American Helicopter Society 64th Annual Forum.
H.N.Chauhan & M.P.Bambhania, 2013. Design & Analysis Of Frame Of 63 Ton Power Press Machine.
Indian Journal Of Applied Research, Volume 3, pp. 285-88.
Parthiban, B., Eazhumali, P., S.Karthi & P.Kalimuthu, 2014. International Journal Of Research In
Aeronautical And Mechanical Engineering. Design And Analysis Of C Type Hydraulic Press, Volume 2,
pp. 47-56.
Prabaharan, M. & Amarnath, V., 2011. Structural optimization of 5ton hydraulic press and scrap baling
press for cost reduction by topology. International Journal of Modeling and Optimization, 1(3), p. 185.
Sachas, N., 2009. Root cause failure analysis understanding Mechanical failure. Plant maintenance
Recourses center home.
Sinha, S. & Murarka, P., 1988. Computer-aided design of hydraulic press structures. Mathematical and
Computer Modelling, 10(9), pp. 637-645.
Uys, P., Jarmai, K. & Farkas, J., 2003. Optimal design of Hoist structure frame. Applied Mathematical
Modelling, 27(12), pp. 963-982.