Press Frame Research Articles

Constructing the Meaning of Rsk Society : How Korean Press Frame the Swine flu Pandemic

Constructing the Meaning of Rsk Society : How Korean Press Frame the Swine flu Pandemic

Development of high pressure apparatus for X-ray microtomography at SPring-8

A new high-pressure apparatus has been developed for studies of synchrotron radiation-based X-ray microtomography at SPring-8 of Japan. The high pressure tomography apparatus at SPring-8 is a compact hydraulic press with a 0.8 MN capacity and is equipped with an opposed anvil device. It has two wide windows for X-ray access with a 160-degree opening in the equatorial plane to the compression axis. Radiographs are acquired over 180 degree rotation for reconstruction of 3D image, in which some shadows occur, because the press frame blocks a 20-degree angular region. 3D tomography image computed from radiographs obtained using the high pressure tomography apparatus has a reasonably good quality enough to measure physical properties of materials.

The Power of the Press: The Effects of Press Frames in Political Campaign News on Media Perceptions

This article discusses how the behaviors, roles, and standards of mainstream journalism are framed in political campaign news and empirically examines applicability and accessibility effects of so-called press frames on individuals' media perceptions, specifically on news information quality and negative aspects of content (cf. Kosicki & McLeod, 1990). Following previous work, we posited that journalists frame the press in three ways, called conduit, strategy, and accountability. Participants in a between-subjects experiment were exposed to a political campaign story about an exemplar “character issue” containing these frames. Regarding applicability effects, exposure to each press frame differentially prompted individuals to think frame-relevant propositions were salient in the story. Further, participants exposed to the strategy press frame interpreted the press as being significantly more negative than individuals exposed to the conduit or accountability frame; participants exposed to the accountability press frame interpreted the press as having higher news information quality than individuals exposed to the conduit or strategy frame. Regarding accessibility effects, only the accountability press frame prompted individuals to access prior beliefs about the news media to form opinions about negativity and quality. Implications for future study of press framing are discussed.

An Analysis on the Forming Load of AA 2024 Aluminium Alloy in Combined and Sequence Operation Process

This paper is concerned with the analysis of the forming load characteristics of a forward-backward can extrusion in both combined and sequence operation. A commercially available finite element program, which is coded in the rigid-plastic finite element method, has been employed to investigate the forming load characteristics. AA 2024 aluminum alloy is selected as a model material. The analysis in the present study is extended to the selection of press frame capacity for producing efficiently final product at low cost. The possible extrusion processes to shape a forward-backward can component with different outer diameters are categorized to estimate quantitatively the force requirement for forming forward-backward can part, forming energy, and maximum pressure exerted on the die-material interfaces, respectively. The categorized processes are composed of combined and/or some basic extrusion processes such as sequence operation. Based on the simulation results about forming load characteristics, the frame capacity of a mechanical press of crank-drive type suitable for a selected process could be determined along with securing the load capacity and with considering productivity. In addition, it is suggested that different load capacities be selected for different dimensions of a part such as wall thickness in forward direction and etc. It is concluded quantitatively from the simulation results that the combined operation is superior to sequence operation in terms of relatively low forming load and thus it leads to low cost for forming equipments. However, it is also known from the simulation results that the precise control of dimensional accuracy is not so easy in combined operation. The results in this paper could be a good reference for analysis of forming process for complex parts and selection of proper frame capacity of a mechanical press to achieve low production cost and thus high productivity.

A new approach to determine press stiffness

A new procedure is proposed for measuring press stiffness, including separated horizontal and vertical loading of the press frame. The load can be eccentrically positioned for measuring rotational stiffnesses. Two loading devices and corresponding measuring equipment for registration of press deflections are designed. The press stiffness is presented as a 6 by 6 flexibility matrix. The approach has been tested by measuring the stiffness of a 5.000 kN O-frame, ring element, hydraulic press, a 10.000 kN O-frame, pillar element, hydraulic press and a 10.000 kN O-frame, ring element mechanical press. Deflections in the size of 0.5 mm were identified.

전ㆍ후방 캔 압출공정의 성형하중특성

This paper is concerned with the analysis of the forming load characteristics of a forward-backward can extrusion process. The analysis in this paper is extended to the selection of press frame capacity for producing efficiently final product at low cost. The possible extrusion processes to shape a forward-backward can part with different outer diameters are categorized to investigate quantitatively the forming load, forming energy and maximum pressure exerted on the die-material interface. The categorized processes are composed of combined and/or some basic extrusion processes. After the analysis of the forming load characteristics, the frame capacity of press suitable for a selected process could be determined along with securing the load capacity and with considering productivity. In addition, it is also suggested that different load capacities be selected for different dimensions of a part such as the wall thickness in forward direction. The work in this paper could be a good reference for analysis of complex extrusion and selection of proper frame capacity of press to achieve low production cost and thus high productivity.

Assessment of the elastic characteristics of an ‘infinite stiffness’ physical modelling press

Abstract The use of a ‘triaxial force and moment transducer’ for the assessment of the character of the forces and moments on dies during forming operations requires the use of a physical modelling press with ‘infinite stiffness’. The design and development of the press was attended to by finite-element (FE) analysis to arrive at an acceptable design. Three dimensional (3D) FE simulation was used to assess different structural configurations of the press frame, which was configured to increase the lateral and rotational stiffness about the vertical axis of the modelling press to an acceptable level. The simulation results illustrate the influence of the structural configuration and scale of the members on the horizontal and rotational stiffness of the frame. Cross-braces are an effective means of increasing both the horizontal and rotational stiffness of the frame. The 3D FE simulation and measurements taken on the modelling press compare sufficiently well to recommend the approach for the design and development of model forming presses. The magnitude of the press deflections suggests that the measurement of forming forces and moments would not be influenced by the character of the developed modelling press.

Process control in blanking

This paper summarizes the results of testing the performance of in-die sensors for controlling the stamping process. Piezo based as well as strain gage based in-die sensors were mounted at different locations within a progressive die. Furthermore, these signals were compared with load curves of press frame mounted sensors and the acoustic emission acquired from a triaxial acceleration sensor. The signals acquired from the different in-die sensors at the different mounting locations showed all the different phases of the process. It was shown that changing process variables such as punch-die clearance, material properties, stroke rate and punch-die alignment results in different load-stroke curves. Based on these results it could be concluded that in-die sensors provide the most detailed information about the process.

Computer-monitored hydraulic bulging of tubes

A hydraulic bulging machine with independent pressure and axial-force control has been designed and constructed. This machine consists of a horizontal press frame with two opposed hydraulic units at the ends of two sliding units carrying the die halves. Two sets of three hydraulic cylinders open and close the die halves containing the tube to be bulged. Once the die halves are closed, two differential pistons operating in two pressure vessels attached to the end plates move in and seal the tube. Then hydraulic pressure is applied to the tube through the central bore of one of the differential pistons. Thereafter, by actuating another hydraulic circuit, the pistons apply an axial compressive force on the tube. During the bulging process, the hydraulic pressure inside the tube and the axial force on the tube can be varied independently. When the bulging is complete, the tube is de-pressurized, the pistons withdrawn, the die halves opened and the bulged tube removed. Initially, a PLC was used to control the internal hydraulic pressure, the axial load, compression of the tube and the operating sequence of the process, but experiments conducted with this control system in place indicated that closer control of the process parameters was needed. Recently, a personal computer together with a data logger was used to monitor the axial force and the hydraulic pressure. Results of the bulging experiments conducted with this set-up are reported in this paper.

Dynamics and probabilistic fatigue analysis schemes for high-speed press machines

The dynamic behavior of a connecting rod (CR) is relatively more complicated than other major moving parts in a high-speed press machine. For various analysis and design reasons, the lumping mass method is traditionally used in an attempt to represent the original CR dynamically equivalently, but this representation of CR is usually inaccurate. This inaccuracy may eventually lead to undesirable dynamic unbalancing and associated vibration problems. In that concern, an ingenious varied-mass lumping method (VLM) fused with percussion concept is developed here to integrate the dynamics analysis and design of press machines in a highly mutually beneficial sense. The ramhead reactive force due to workpieces will eventually transmit to the press frame through CR, crankshaft and its center bearing. This wavy, yet periodic forcing function can be conveniently obtained by the above VLM scheme. Then, the fatigue survivability at particular points can be calculated with the aid of finite element method, transient analysis techniques, peak range pairing, S-N fatigue curves and/or family of S-N-P curves for material used.

Evaluation for Vibration Restriction of Punch Press by CAE.

A computerized numerically controlled C-frame turret punch press for sheet metal punching induces impulsive vibration and accompanying noise when punching. Actual study of the vibration and noise reduction has been mainly carried out by experimental analysis using actual machine structures. In recent years, the finite element method (FEM) has spurred remarkable progress in numerical analysis. In the analysis of actual complicated structures by the FEM, many natural frequencies and eigenvectors are obtained in the specified frequency range as a result of computer calculations. Important modes for the vibration restriction are usually picked out from the results of FEM analysis by professional engineers on the basis of experimental results. In this study, bending vibration of a C-frame turret punch press frame which radiates noise when punching was noticed. Then, a new evaluation criterion of the vibration which strongly influenced noise radiation, that is, "modal inertance between the load point and the response area", was developed. Examination of the modal inertance in comparison with the experimental results showed effectiveness in actual use. Furthermore, this evaluation criterion was applied to improve the actual frame structure of the C-frame turret punch press to acquire a much more restricted "vibration-free" structure and confirmed the criterion's effectiveness.

Effect of Rigidity of Die and Press on Blanking Accuracy of Electronic Machine Parts

Abstract Blanking accuracy is decided by the relative displacement of an appear die to a lower die in the blanking. Deformation of a die-set subjected to an accentric load in a press is analysed, and the bending moment M and the lateral force Q acting on the end of each guide post are expressed by the inclination θ and the lateral displacement DX of the upper die. In the experiment, a die-set of sub-guide construction is installed on a 1250kN straight side frame press and 100kN C-type frame press, and θ DX are measured user static loading and dynamic loading of 100sdm. The calculated M and Q using the measured θ and DX show that the M and Q acting on the guide post end are smaller on the straight side frame press than on the C-type frame press though the capacities of both presses are almost the same. The analytical method proposed in this paper can be used in the selection of a press suitable to a given die set and a given accentric load.

Improvement of equipment for close-tolerance forging and extrusion in Japan

Nowadays, there is heavy demand for net or near net shape forming in mechanical working technology, in which both heavy and light weight products have dimensional tolerances of about one thousandth of the sizes of the worked material. In this paper, the factors affecting the accuracy of the product are discussed generally, with emphasis being given to the achieving of high dimensional accuracy in hot forging and extrusion. The important factors are the temperature rise in the worked material and the working tools. To meet the demand for higher dimensional accuracy, it is very important in forging and extrusion that the press has high rigidity and that movable members should be guided with good dynamic accuracy. Furthermore, it is essential to be able to predict the deformation of the press frame and of the tooling and the temperature distribution within the tools and the worked materials.

Construction of liter-class large volume high pressure apparatus for materials synthesis

A belt type high pressure apparatus was constructed with a chamber volume of about 1000 cc and an hydraulic press to operate the apparatus. The maximum pressure generated in the chamber is 6 GPa for a first step and 10 GPa for the final goal. The 6 GPa apparatus (FB120) was designed by the use of high speed steel anvils and a cylinder core. To prevent plastic deformation of the inner wall of the core special cell and inner sleeve materials of smaller thermal conductivity were adopted. A 30 000 ton wire winding frame type press was constructed for this purpose. The design and analysis of the press frame deformation during wire winding is presented.

Noise Reduction on Mechanical Punch Presses

Noise emmission on punch presses is to a large extent avoided by reducing the impulse sound at the moment of breakthrough. At this moment a part of the strain energy stored in the press prior to fracture becomes available for radiation as sound. With an electronically controlled hydraulic element in the force-flow of a power press it is possible to avoid the rapid unloading of the press frame. At stroke rates up to 400 per minute a noise reduction of up to 10 dB(A) can be obtained.

Use of Standardized Copper Cylinders for Determining Load and Energy in Forging Equipment

The actual load and energy capacities of equipment must be known for adequately designing the forging process. In the present study, copper samples have been used to (1) determine the maximum production rate, or strokes per minute, of a mechanical press for various levels of forging energy, and (2) calibrate the strain-gage sensors attached on a press frame in order to measure forging loads. For both applications, the accuracy of the measurement technique is acceptable for practical production and engineering purposes.