Papers by Keyword: Servo Press

Abstract: Magnesium alloy castings are mainly formed by the die casting method, but this method has the disadvantage that product properties such as strength vary due to many defects inherent in casting. In this study, AZX912 (a flame-retardant magnesium alloy with 2% calcium added to AZ91D alloy) was semi-solid forged using a servo press and die cushion system to stabilize product properties. Experiments were conducted to refine the α-phase and reduce the yield point, and the stirring speed was changed and its effect was investigated. Observation of the microstructure of the molded product using an optical microscope showed that the average grain size of the α-phase became smaller as the stirring speed increased. Tensile tests were conducted on specimens cut from the compacts, and the yield point increased as the stirring speed increased. This is thought to be due to compliance with Hall Petch's law. The microstructure of the molded product was observed under an optical microscope and showed a three-layer structure with a dendrite shape in the upper part (about 5%), a grain structure in the middle part (over 90%), and a chill layer in the lower part (less than 5%). Comparison of the thickness of the chill layer showed that the thickness of the chill layer decreased as the solidus ratio increased.

Abstract: Materials resistance to edge failure during sheet metal flanging operations is known as stretch-flangeability. It is one of the important concerns in the current automotive sector. Stretch flangeability of sheet metal is estimated by hole expansion test and commonly it is represented by hole expansion ratio (HER). The objective of the present work is to comprehend the hole expansion deformation behavior of DP600 steel. Firstly, finite element analysis was performed to understand the stress state at the edge during the hole expansion test. Thereafter, the effect of stress relaxation was studied by conducting hole expansion tests (HET) in monotonic and interrupted mode. Considerable improvement in the HER was observed. The HER was found to increase with the pre-strain. The combined effect of friction and stress relaxation played a crucial role in delaying the edge failure, resulting in the enhanced HER.

Abstract: This paper deals with characteristics of hot forging of twin roll cast magnesium alloyswhich have relatively high aluminum content. High tensile strength magnesium alloys containing 9 to12% aluminum, such as Mg-9%Al-1%Zn, Mg-10%Al-1%Zn, Mg-11%Al-1%Zn, andMg-12%Al-1%Zn have been made by twin roll casting. A new experiment was performed for hotforging of high strength magnesium alloys with high aluminum content was performed. From theresults, using magnesium alloys with high aluminum content yielded less compressive deformationresistance than AXM403. It was also demonstrated that hot forging of magnesium alloys with highaluminum content produces small magnesium crystals (about six micro meters) and crystallizedsubstances. The mean grain size of the microstructure of Mg-12%Al-1%Zn forged at 623K was lessten micrometers although that of the Mg-9%Al-1%Zn was about thirty micrometers. The small betaphase which precipitates in the twin roll cast Mg-12%Al-1%Zn was distributed uniformly comparingto Mg-9%Al-1%Zn. From the result of microscopic observation of the forged products, it has beenrecognised that the Hall-petch rule between mean grain size of forged materials and Vickers hardnesshas been proved. The effects of the dynamic recrystallization on the microstructures of the twin-rollcast products seem to be different in terms of aluminum content. Due to rapid cooling of twin-rollcasting process process, the fabricated magnesium material could be used for hot forging. By applyinga servo press machine, a hot-forging experiment was performed with development of high strengthmagnesium alloys. A novel material that show higher hardness have been fabricated by usingtwin-roll casting process. It has also been clarified that the aluminum content affect precipitation ofbeta phase as well as grain size.

Abstract: The effect of pulsed (oscillating) ram motion control on lubrication was investigated in hot forging of stainless steel workpiece with oxide glass lubricant. During the retreat in the pulsed ram motion, the workpiece was re-lubricated by flow of lubricant through the gap between the workpiece and the die. A hot spike-type forging test on a servo press with pulsed ram motions was carried out to investigate the lubrication performance of the oxide glass. In the test, the workpiece with a temperature of 1223 K was extruded into the hollow part of the upper die together with oxide glass in a manner that combined pulsed and stepwise ram operations. The re-lubrication of the workpiece with oxide glass was confirmed by the test results showing 5–10% reduction in the forging load and 5% longer length of the backward extruded part of the workpiece under an appropriate pulsed ram motion.

Abstract: Blanking noise and blanking vibration are causes of pollution. At the same time, blanking vibration disturbs the high precision of a press work product, and shortens the life expectancy of the press machine and the press die. Recently, the use of a servo press has been developed to improve these problems, using low speed blanking and pulse vibration banking. However, these methods lengthen the blanking time, so it is necessary to control the servo press properly in the case of blanking. In this study, we describe a principle for the reduction of blanking vibration when using a servo press, and we propose an active vibration control method for the reduction of blanking vibration. We used a crank servo press of 450kN in an experiment, which has a pulse motion of 10Hz. We conducted a simulation and an experiment of blanking using an active vibration control method, which we named “counter pulse blanking.” We confirmed that counter pulse blanking is effective in reducing vibration as a result of the simulation and the experiment.

Abstract: Test results of axial shift of “technical ceramics - glass” parts in taper interference fit joint under axial loading are presented. The load-carrying capacity was tested under normal conditions; a servo press was used to load the test samples. The tested samples were assembled by thermal method.

Abstract: Servo press machine can enable us to high precision, but the dynamic behavior does not seem to be considered well. In order to improve the accuracy in manufacturing, it has been discussed effectiveness of reducing the elastic deformation of die structure on forming by mechanically compensating die structure which includes a servo die cushion system.

Abstract: With regard to the climate change as well as the shortage and increase in price of natural resources, efficient resource management becomes more and more important, also for production processes. More than half of the sheet metal used in the automotive industry is wasted. Considering the amount of energy and the added value associated to the discards, enormous savings are possible. The approach of this research work is to avoid waste during a forming process by means of a continuous process monitoring and a self-learning intelligent tool interacting with the servo press. The flexibility of the servo press, which is so far used to optimize the single press stroke, only, shall be exerted to respond on altering material properties of blank sheets and the thereby changing forming behaviour. The sample process includes a two-tiered bending process, in which a conventional punch performs the pre-bending in the first step and an independent servo axis the compensation-bending in the second step. If an inadmissible bending angle is measured after the second step, the servo press stops automatically and the additional servo axis performs a teaching-stroke to adjust the compensation angle. After that, the continuous process starts again. This paper presents the springback compensation strategy which uses flexible correction algorithms based on data of the on-line process monitoring as well as data of the previous bending steps. Finite Element Analyses are carried out to validate the strategy.

Abstract: The objective of this paper is to study performance of triangular elbow transmission mechanism for servo press. Then kinematics models are deduced and given. Kinematics curves along slider motion direction are drawn. Moreover, under the same driving condition, the effects of different link ratios on slider output motion are examined and compared with common six bar transmission mechanism in the article. Through motion curves comparison, it can be seen that this triangular elbow mechanism has significant force increasing effect and good quick-return characteristics. In addition, we carried on triangular elbow servo press virtual design and simulation. The case study provides more visual and reliable decision basis for designer. The results would be useful reference for optimization design of transmission mechanism.

Abstract: For the fabrication of lightweight components such as hollow components, we proposed a cold extrusion method for forming of deep holes that utilizes a punch with an internal channel for the supply of liquid lubricant using a servo press. The relationship between the punch ram motion and the punch wear in the proposed forming method is investigated by the finite element analysis in this study. The punch wear is determined by using the Archard’s equation. Although low friction at specimen–punch interface realizes in the forming with pulse punch ram motion (proposed forming method), the punch wear in the backward extrusion with pulse punch ram motion is 1.1–2.4 times larger than that with no pulse punch ram motion (conventional forming method). The influence of punch ram motion and friction on the punch wear is discussed.