Optimal Design of Hydraulic System for an Industrial Press Machine [PDF]

In this paper, we present an optimal design of the hydraulic system for a class of industrial press machines. ... A hydr

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Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

Optimal Design of Hydraulic System for an Industrial Press Machine for Performance Improvement and Noise Reduction *1

Jiafeng Yao, 2 Baochun Lu, 3 Chris Zhang, 4 Michio Sadatomi

1

Kumamoto University, Japan, [email protected] Nanjing University of Science & Technology, China, [email protected] 3 University of Saskatchewan, Canada, [email protected] 4 Kumamoto University, Japan, [email protected] 2

Abstract In this paper, we present an optimal design of the hydraulic system for a class of industrial press machines. Such machines are expected to produce a large pressure on a work-piece and they are driven by a hydraulic system. Excessive vibration in the period where the press is changed from pressure holding to pressure relief is a common bottleneck problem with such machines. The vibration is closely related to the hydraulic system that controls a press head’s movement and is subsequently responsible for the property of work-pieces. In the present study, we proposed a novel design of the hydraulic circuit for pressure relief and applied it to a brick press machine and evaluated through simulation by AMESim software, which showed that the design is effective. Finally, the simulation results were validated in practical operation, which showed that, the violent vibration was decreased significantly and the noise level of the new machine is decreased from 80 decibel to 58 decibel. Keywords: Optimal Design, Hydraulic System, Pressure relief, Simulation, AMESim

I. Introduction A hydraulic press is a mechanical machine used for lifting or compressing large items. The force is generated through the use of hydraulics to increase the power of a standard mechanical level. This type of machine is typically found in a manufacturing environment. Invented in 1795 by Joseph Bramah, the hydraulic press is also known as the Bramah press. He used his knowledge of fluid mechanics and motion to develop this device. This invention significantly increased the compression power available, expanding the product groups and options available to other inventors. By applying hydraulics to a press, an entire class of machines was invented. There is a wide range of different hydraulic press machines, ranging from small table top units for hobbyists to huge machines used to create metal parts. The primary concept used to provide power to the hydraulic press is that the level of pressure in a closed system is constant. This type of press has pistons with a fluid inside that is displaced by the pistons' inward movement. The fluid forces its way back into the space by moving the piston outward. The 1

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

additional power is created through the movement of the fluid, which is confined to the system. In this paper, we present an optimal design of the hydraulic system for a class of industrial press machines. Such machines are expected to produce a large pressure on a work-piece and they are driven by a hydraulic system. Excessive vibration in the period where press is changed from pressure holding to pressure relief is a common bottleneck problem. It is noted that this period will be called ‘pressure switching” period in this paper hereafter. The vibrations are closely related to the hydraulic system for control of a press head’s movement as well as the property of work-pieces. One of the existing solution principles is to control the movement of the press head to produce a proper pressure profile. For instance, two methods based on this principle are available in [1, 2]. However, from our experience in designing and operating some press machine in practice with these two methods, it is found that they may not be satisfactory. For instance, a particular brick press machine has a noise level up to 80 decibels [3]. Fig. 1 shows its pressure profile during the pressure switching period. As it is shown in Fig. 1, there are four periods during the working process. There is a sharp drop during the period d-e (the 6th second), and this means that when the press head moves back, the pressure in the chamber drops abruptly, which is a source of impact vibration. The objective of this paper is to present a novel redesign of the hydraulic control system to reduce the vibration significantly. Since the pressure change of the hydraulic system is difficult to measure, we developed a simulation method by AMESim software to find out the source of hydraulic impact and validate the pressure relief effect of the new method. The evaluation criterion of the simulation results are the level of noise (actually, noise is come from the violent vibration of the hydraulic impact). To illustrate and validate the proposed design, we take a particular type of brick press machine as an example.

Figure 1.

The pressure profile in the pressure switching period (a-b: press head down period; b-c:

pressing period; c-d: pressing holding period; d-e: pressing relief period; Note: 1 MP = 10 Bar. This paper is organized as follows. Firstly, the proposed redesign in the context of press machine is described, followed by modeling and simulation of both the new design and old design. After that, results are presented and discussed. Finally, there is a discussion of conclusion, limitation and future 2

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

work.

II. Optimal design of the hydraulic circuit system for press machine A. The generic operation of press machine A working process of a manufacturing system such as brick product or powder metallurgy is described as follows (Fig. 2): (1) press head is in contact with the work-piece (Fig. 2a), (2) press head is further down to deform the work-piece (Fig. 2b), (3) press head holds up with the work-piece (Fig. 2c), (4) press head is slightly up (Fig. 2d), and (5) press head is up (Fig. 2e). The performance of a press machine, in particular vibration and impact behavior is closely related to the pressure profile (Fig. 1) and the property of the work-piece.

Figure 2.

Generic operation of press head.

The generic structure of a machine system is shown in Fig. 3. When Pu < Pl, press head is up; otherwise press head is down. A control system is associated with the fluids in the upper chamber and the lower chamber. The fluids are represented by their flow rates (vu, vl), respectively. For the press machine, hydraulic systems are commonly employed to implement the control system, because they can generate high power with a high degree of compliance when the head interacts with the work-piece.

Figure 3.

Generic structure of press. 3

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

B. Proposed design for pressure relief of hydraulic system Two principles are widely used in the hydraulic control system for pressure relief. The first principle (Principle 1) is to release fluid from the upper chamber gradually and continuously using a throttle valve, and Fig. 4 shows a conceptual design which follows the first principle. In the hydraulic system, during the press action, high pressure is generated in the hydraulic cylinder. After that, the oil could run through the throttle valve to relieve the impact during the pressure change. This method is easy to control but the potential disadvantage is that pressure relief from the upper chamber may be too slow such that the pressure in the lower chamber may be accumulated to a level larger than the pressure in the upper chamber, leading to the head going up quickly and causing vibration [4].

Figure 4.

Pressure relief method with a throttle valve.

The second principle (Principle 2) is to release the fluid by a pressure valve group, and Fig. 5 shows a conceptual design which follows the second principle. The pressure valve group can relieve the pressure gradually because when the pressure is high, the oil can flow through the two valves in succession. The main problem is, pressure relief from the upper chamber is not smooth, i.e., the pressure of the upper chamber decreases sharply and also brings about a little impact [1]. In this paper, we proposed a new principle (Principle 3), which combined Principle 1 and 2 due to their complementary behavior, as shown in Fig. 6. The combination of the two was such that the second principle provides a main regulation of fluid while the first principle provides a varying regulation. In particular, a throttle valve and a check valve were added in the design. The throttle valve was used to adjust the flow rate according to different working conditions and the check valve was to prevent the backlash of the oil. 4

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

Figure 5.

Figure 6.

Pressure relief method with a pressure valve group.

Proposed principle for pressure relief (P: Oil Entrance Port; T: Outlet Port; C: Controlling

Port). A conceptual design for the proposed principle is shown in Fig. 7. A remote control port of relief valve (valve 2) is connected with P2 (P2 has a low pressure, as it is connected to a relieving valve), through a throttle valve (valve 3) and a check valve (valve 4). The opening velocity of relief valve (valve 2) can thus be adjusted by regulating the port of valve 3. It is also noted that the relieving velocity of the cavity can be adjusted correspondingly. The pre-setting pressure of valve 2 should be greater than the working pressure; in this way, valve 2 can also serve as a safety valve. This pressure-relieving loop is particularly designed for the dual-pump and double-circuit hydraulic system which suits a large flow-rate brick press machine. 5

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

Figure 7.

Conceptual design of the proposed principle.

III. Modeling designs based on Principle 1 and Principle 3 A. Case study by a Particular Brick Press Machine A particular brick press machine which was supplied by a company in China is taken for case study. This machine has a four-column cylinder structure with two opposite pressing directions (Fig. 8). The structure of the two pressing systems is the same, so we only consider the upper pressing system. The machine has a dual-pump and double-circuit hydraulic system that controls the press head.

Figure 8.

A particular brick press machine was supplied by a company in China with a four-column

cylinder structure and two opposite pressing directions. The hydraulic control system for the press machine is shown in Fig. 9. Note that the machine of Fig. 8 is 6

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

based on Principle 1 (for brevity, in the following, this machine is called old machine). In the old machine, there are two charging valves in the upper and lower cylinders, respectively.

Figure 9.

Hydraulic control system of the old machine based on Principle 1. (1: upper cylinder; 2, 7:

charging valves; 6, 8-11: solenoid directional valve 4: lower cylinder; 5: throttle valves; 12,13: overflow valves; 14: check valve; 15: pressure gauge; 16: gear pump; 17, 18 : motor; 19: piston pump. Y means solenoid valves). At initial time, solenoid directional valves 12 and 13 are in the state of “normally open”, so two pumps 16 and 19 start up with no load. A working circle of the machine is shown in Fig. 10.

Figure 10.

One operation cycle of solenoid valves.

In Fig. 10, there are seven actions of the press machine, and each action is controlled by the solenoid valves. One working circle is described as follows: When the upper cylinder moves downward, charging valve 2 is open to fill oil into the upper cylinder to drive the upper cylinder move more rapidly. Likewise, 7

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

charging valve 7 is open when the lower cylinder goes upward. When the two cylinders reach the pre-set position, directional valve 6 places on right, the two cylinders are connected, and the charging valves are closed. The system can get a higher pressure, and then the pressing process starts. After pressing, the upper cylinder goes upward by hydraulic force, and the lower cylinder moves back by gravity of itself. Since the pressure change in the hydraulic system is difficult to test, we will simulate this working process of hydraulic system by AMESim software. AMESim stands for Advanced Modeling and Simulation Environment for Systems Engineering, it offers a complete 1D simulation suite to model and analyze multi-domain, intelligent systems and to predict their multi-disciplinary performance. The components of the model are described by analytical models representing the hydraulic, pneumatic, electric or mechanical behavior of the system [5]. B. Modeling for the old machine based on Principle 1 The goal of modeling is to develop a model to calculate the pressure profile in the pressure switching period. In the modeling, we neglected the noise factors as well as the influence of the dynamic characteristics of pipeline and fluid elastic modulus. Furthermore, we employed a modeling tool called AMESim. Set up the simulation model of the whole system shown in Fig. 11 based on the hydraulic system working principle 1 [6 - 8]. In this model, the lower cylinder is simplified as one cavity, and the up cavity of the cylinder is connected to the tank, since the lower cylinder goes back by gravity of itself. Considering the purpose of this simulation is to find out the source of violent vibrations and popping sounds, the simplification for the lower cylinder cannot affect the results.

8

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

Figure 11.

AMESim model of the hydraulic control system based on Principle 1. (BAP12: Cylinder;

MAS005: Mass Block; FORC: Press Force; UD00: Signal Source; Valve; TK10: Oil Tank; FP04: Hydraulic Oil Source;

CV005: Fluid Control One-Way

HSV34_01: Solenoid Directional Valve; OR003:

One-Way Throttle Valve; RV00: Relif Valve; PV022: Swith Valve; CV000: Check Valve; PM000: Motor; PU001:Hydraulic Pump). C. Modeling for the new machine based on Pricnciple 3 The improved hydraulic system based Principle 3 is given in Fig.12, (for brevity, in the following, this machine is called new machine) the optimized part is marked with a red arrow.

Figure 12.

Diagram of the optimized hydraulic system.

Compared with the old machine, one more relieving action was added in the new machine. The unloading relief valve only acts after keeping pressure and before the cylinder drawing back. Exactly, it acts on 6th second in this working process. That means the relieving loop unloads the high pressure gradually before the fluid direction changes. Based on the hydraulic system diagram, a model was established by AMESim. The model with relieving loop is shown in Fig. 13.

9

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

Figure 13.

The AMESim model with relieving loop

The relieving loop can be simplified as a pilot relief valve and a signal source. The improved part is labeled with a red arrow in Fig. 13 [9, 10].

IV. Results and Discussion A. Results of simulation Main parameters of the model in a working process for the old machine are as follows: Action cycle: 9 s; Piston travel: 0.6 m; Hydraulic pressure:13 MP. One working circle of the stroke of the upper cylinder is as Table 1: TABLE 1.

One working circle of stroke in upper cylinder No load

Down

Apply

Hold

Back

Time [s]

1

2

2

1

3

Distance [m]

0

0.3

0.1

0

0.5

We set the relieving time as 1 second, and the pressure was reduced from 13 MP to 3 MP. The simulation curves of the old machine are obtained by AMESim software. For the upper cylinder, here gives the curves of its displacement, hydraulic pressure and acceleration in Fig. 14 - 16.

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Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

Figure 14.

Displacement versus time of upper cylinder of the old machine.

Figure 15.

Figure 16.

Pressure versus time in upper cylinder of the old machine.

Acceleration versus time of upper cylinder of the old machine.

Fig. 14 - 16 described the working process of upper cylinder for the old machine. The abscissa represents time. Fig. 14 shows the displacement of the upper cylinder. As for Fig. 15, there is a sharp pressure drop on the 6th second, it means that, when the upper cylinder moves back after keeping pressure for 2 seconds (it is on the 6 seconds in the picture), the pressure drops abruptly. From Fig. 16, we can see that the acceleration at that time is high. Due to the compressibility of the hydraulic oil and 11

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

the elasticity of the mechanical part, a large amount of energy is stored in the hydraulic cylinder. As a result, the machine would produce violent vibrations and emit a popping sound when the directional valves acts. This phenomenon does a serious destruction to the brick press [11, 12]. Subsequently, the simulation curves for the lower cylinder of the old machine are shown in Fig. 17 - 19.

Figure 17.

Displacement of lower cylinder.

Figure 18.

Figure 19.

Pressure in lower cylinder.

Acceleration of lower cylinder.

Also we find that, on the 6th second, the pressure in the lower cylinder drops down sharply and the acceleration is up to 110 m/s2. That means an analogous incident is emerged in the lower cylinder, so it 12

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

is not necessary to analyze the problem more. Meanwhile, the simulation results of the upper cylinder for the new machine were obtained. For the consideration of impact, we pay attention to the pressure change and acceleration of the upper cylinder. So Fig. 20 and 21 describe the pressure change in the cylinder and acceleration of the cylinder.

Figure 20.

Pressure in upper cylinder after optimization.

Compared with the old machine, it can be concluded that there is a sloping decrease of the pressure in the upper cylinder from the 6th second to the 7th second, which means that the pressure does not drop immediately and impact is reducing. In Fig.16, we can see that the acceleration is reduced from 500 m/s 2 to 35 m/s2, it also means that the vibration and impact are decreased greatly.

Figure 21.

Acceleration of upper cylinder after optimization.

However, a side effect is brought about, that is, the processing period is extended one second. Since the whole period is 9 seconds, the new appeared problem can be neglected. Because the lower cylinder has a similar working condition and process as the upper cylinder, the simulation of lower cylinder is not repeated here. B. Experimental validation and practical application Fig. 22 is the photograph of an experimental prototype. In the beginning of the practical operation, we found an obvious drawback during the working progress. A lot of noise was generated, especially when 13

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

the cylinder changed directions. It was hard to find the problem since the pressure in the cylinder and velocity of the press head was difficult to measure. So we developed the simulation method to look for the problem.

Figure 22.

Photograph of an experimental prototype.

From the simulation, we found that, the hydraulic system had a large impact in the pipes when the valve changed directions mainly because the system is lack of a relief system. After analyzing two principles of pressure relief, we designed a new pressure relief method by combing the two previous methods, and then simulated it again. The results showed that the new method is quite useful. After that, we applied the new method to the prototype. Noise test showed that, the noise level of the new machine is decreased from 80 decibel to 58 decibel. Impact in the hydraulic system was decreased significantly, and the working life of the new machine was prolonged greatly. Meanwhile, the products made of the machine were stronger and smoother than before (Fig. 23).

Figure 23. Products made by the press machine.

V. Conclusions 14

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

This paper discussed the problem of vibration presented in common pressing machinery. One of the factors related to the vibration is the hydraulic control system. A new hydraulic circuit system was proposed. By means of a reliable modeling and simulation tool called AMESim, it can be shown that the design based on the proposed principle worked quite well in comparison with the design based on the old principle. A particular type of brick press machine was used to illustrate this research and used to verify effectiveness of the proposed principle. In particular, the noise level of the old machine is about 80 decibel. The new machine based on the proposed principle allows the noise level to be reduced to 58 decibel. One limitation of the work may be the neglect of the type of materials that are pressed. The current type of material is coal fly ash, which is quite compliance or less stiffness. For other types of materials, due to different compliances, the vibration suppressing behavior of the proposed control system needs to be examined, which is an ongoing future work.

Acknowledgment The authors would like to express their sincerely appreciation to Mr. Gang Li, student from Nanjing University of Science & Technology, and Mr. Xianchun Tian, Mr. Huaitong Jiang, Mr. Feng Yu, engineers from Jiangsu Tengyu Machinery Manufacture Co., Ltd., for their technical and experimental cooperate. Financial support from Jiangsu Tengyu Machinery Manufacture Co., Ltd. is also appreciated.

References [1] B.

Ewing, M. Kowalsky, “Compressive Behavior of Unconfined and Confined Clay Brick

Masonry”, Journal of Structural Engineering, vol. 130, pp. 650-661, 2004. [2] M. Murakawa, J. Mo, Y. Wakatsuki, N.

Koga, “Investigation of blanking noise reduction using a

hydraulic inertia damper”, Journal of Materials Processing Technology, vol. 112, pp. 205-213, 2001. [3] J. W. Yin, Q. J. Wang, T. H. Liu, “Development on two-way hydraulic press”, Journal of Shewngyang Architectural and Civil Engineering Institute, vol. 8, No.2, pp. 176-178, Apr. 1992. [4] S. Y. He, X. Ma, S. J. Zhong, “Research on the depressurized circuit of hydraulic press”, Journal of Tianjin Institute of Technology, vol. 16, pp. 94-96, Jun. 2000. [5] AMESim Tutoral Menual, LMS Enginnering Innovation, 2010. [6] Y. L. Fu, X. Y. Qi, “System modeling and simulation based on AMESim”, Beijing University of Aeronautics & Astronautics Press, Beijing, 2006. [7] W. J. Gideon, S. L. Jasper, “Simulation and experimental verification of solenoid valve characteristics for semiactive dampers”, International Journal of Vehicle Design, vol. 47, pp. 118-132, 2008. [8] R. Henderson, “Design, simulation, and testing of a novel hydraulic power take-off system for the Pelamis wave energy converter”, Renewable Energy, vol. 31, pp. 271-283, 2006. [9] M. A. Milad, S. N. Sinba, “Stress-strain characteristics of brick masonry under cyclic biaxial compression”, Journal of Structural Engineering, vol. 126, pp. 1004-1007, 2000. 15

Open Journal of Mechanical Engineering, Vol.1 No.3 (2013) pp 1-16 Available online at http://www.arpub.org/jme/

[10] W. Marquis-Favre, E. Bideaux, S. Scavarda, “A planar mechanical library in the AMESim simulation software, Part 2: Library composition and illustrative example”. Simulation Modeling Practice and Theory, vol. 14, pp. 95-111, 2005. [11] M. Reineh, M. Pelosi, “Physical Modeling and Simulation Analysis of an Advanced Automotive Racing Shock Absorber using the 1D Simulation Tool AMESim”, SAE International Journal of Passenger Cars- Mechanical Systems, vol. 6, pp. 7-17 , 2013. [12] L. J. Fu, J. H. Wei, M. X. Qiu, “Dynamic characteristics of large flow rating electro-hydraulic proportional cartridge valve”, Chinese Journal of Mechanical Engineering, vol. 21, pp. 57-62, 2008.

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