Open-die Forging Research Articles

Dynamic Modeling and Analysis of Lifting Mechanism for Forging Manipulator

The kinematic and dynamic behaviors of lifting mechanism for a forging manipulator are investigated. The forward kinematic equations are established. Then, based on the modular approach combined with equivalent dynamic ideal, the dynamic equations are deduced. Moreover, all the equations have been verified by the simulation on a virtual prototype with the ADAMS software and the experiments on a forging manipulator. The results show that the calculated values are well in agreement with the real measurements. Finally, both kinematic and dynamic models are analyzed, and it is found that the force produced by the kinetic energy has very weak effect on the results in comparison with the gravity. The results provide the foundation of gripper’s position control in automatic open-die forging process.

Fe-Ni-Co 합금의 고온 변형 공정 변수와 미세조직 및 열물리적 특성의 상관 관계

Abstract High temperature deformation behavior of a Ni 30 Fe 53 Co 17 alloy, with its extraordinary low coefficient of thermal expansion less than 10x10 -6 K 1 at temperatures ranging from room temperature to 673K, was investigated by conducting a series of compression tests. From an empirical processing map, the appropriate working temperature-strain rate combination for optimum -forming was deduced to be in the ~1373K, 10 -2 s 1 region. This region has a relatively high power dissipation efficiency, greater than 0.36. Furthermore, open die forging of a 100mm diameter billets was performed to confirm the variation of thermo-physical properties in relation to microstructure. The coefficient of thermal expansion was found to increase considerably with increasing the open die forging temperature and decreasing the cooling rate, which in turn provides a drastic increase in the average grain size. Key Words : Ni-Fe-Co Alloy, High Temperature Deformation, Open Die Forging, Coefficient of Thermal Expansion

Analysis of Technological Factors in Open Die Forging by Comparison of Different Analysis Methods

The scope of this work is to study a forging process at room temperature and at macroscopic level. The mechanism of deformation is influenced by the friction and the reduction ratio, but the influence of the geometry of the billet (aspect ratio) needs also to be taken into account. The objective will be to compare the results obtained during a simulation with the code based on Finite Element Method (DEFORM 2D/3D), with those obtained by analytical methods in order to validate the numerical model. Taking into account that deformation is not uniform and the free surface suffers a phenomenon known as barrel-shaped, that is not covered by analytical methods, the data obtained will compared with those obtained with the FEM code ABAQUS. The aim of this comparison between analytical and numerical methods using two commercial codes instead one, is a proposed way to validate a Finite Element simulation when experimental data are not available or do not exist yet.

Study on the Deformation of the Prestress Frame of Open-Die Forging Hydraulic Press with Different Operating Modes

The deformation of the prestress frame of open-die forging hydraulic press is studied in the paper. Firstly, the computing formula of true prestressing force of frame is deduced, and then the finite element model of prestress frame is established. With the model, the deformation of prestress frame is studied when the press works under different operating modes including upsetting, elongating and saddle forging and the effect of different operating modes on the deformation are revealed. The main achievements include: The true prestressing force of frame can be gained with nominal prestressing force, section area and working length of tension rods, section area and length of columns. Under prestress, the stress of the field of up beam and down beam acted by the axial force of tension rods and columns is bigger, that of the other field is very small. Under working loads, up beam and down beam tend to open out, tension rods and columns tend to bend in, and the bending effect cause the stress of inner field of tension rods bigger than that of outer field and the stress of inner field of columns smaller than that of outer field. The deformation of down beam under saddle forging is different with that under upsetting and elongating. The stress of center field of down beam under upsetting and elongating is higher and that of front and back field of down beam under upsetting is higher. The main achievements of the study are useful to design the prestress frame of open-die forging hydraulic press and the research method can be used to study the prestress frame of other equipments.

Displacement Behavior of Wood in Boss Forming Using Open-Die Wood Forging

Biomass materials such as wood are attracting renewed attention as alternative fuels in order to help resolve environmental resources caused by the use of fossil fuels. In this study, the possibility of products being processed from wood bulk was investigated by means of boss forming using open-die forging. Additionally, the difference in formability and deformation behavior during forging was investigated by changing the experimental conditions, such as the moisture content of the wood billets used, the forming pressure, and the forming temperature. The experimental results showed that wood had enough liquidity to be forged, and that two sudden and large increases in displacement occur during forging. Finally, the conditions governing these displacements were summarized from these results

The Numerical Simulation of Conductive Body Forming Process and Mould Design

T2-copper conductive body is a important part used in high voltage switch, it has poor machining process due to the complex shape. Through Deform numerical simulation, conductive body was formed by open-die forging and closed die forging. In the open-die forging simulation，heat transfer coefficient between blank (880°C) and open-die (200°C) is 11, the surrounding environment temperature is 20°C, friction factor is 0.3. The main open-die forging process parameters is: outer draft angle α=6.5°; inner draft angle β＝10°; bridge width b＝5、8、11mm. punching skin and cylindrical blank. Simulation results show that forging can meet the requirement while properly adjusting mould parameters. The main size of closed-die forging working parts is designed according to the conductive body graph, no draft angle and ring blank of external diameter Φ111mm and inside diameter Φ93mm with the same volume of conductive body. The simulation results shows that forging can be formed using open-die forging, and it is difficult to form product by the process of the closed-die forging for ring blank because of the restriction of solid state metal liquidity, many regions of the filling is not sufficient. Open-die forging and casting blank-closed die forging are both used in actual production. The casting blank-closed die forging is a more reasonable forming process compared with the open-die forging as metal volume of distribution is solved, higher utilization rate of material, more simple process in following work and the like. To make it more suitable for practical production, appropriate adjustments of some parameters was made in the mold design process based on the numerical simulation. Keywords: open-die forging; casting blank–closed die forging; numerical simulation

Study on the Pretightening Assembly Moving Beam of Open-Die Forging Hydraulic Press

The FE model of the pretightening assembly moving beam of open-die forging hydraulic press is built with FE simulation software ABAQUS in the study. With the FE model, the force status of pretightening assembly moving beam is studied. Then the pretightening force of assembly moving beam is further studied and the computing method of pretightening force is given. The main achievements of the study include: Under pretightening, the stress of main moving beam is very low and that of guild sleeves is also lower than the allowable stress. Under center loading, the stress of the center field of main moving beam is higher and that of guild sleeves is almost same to that of pretightening. Under eccentric loading, the stress of same deviation field of main moving beam is higher and the effect of pretightening force on the stress of main moving beam is very small. The stress distribution of guild sleeves with different pretightening force is same and the effect of pretightening force on its strength is very low. The pretightening force of tension rod can be computed with the force of press, the allowable eccentric value of the workpiece, the distance between up guild section and down guild section of guild sleeve and the quantity of tension rods. The results of the study are very useful to design and install the pretightening assembly moving beam of open-die forging hydraulic press.

STUDY AND APPLICATION OF OPEN DIE FORGING CAPP SYSTEM BASED ON PROCESS KNOWLEDGE

This paper discusses concepts and methods related to CAPP (Computer Aided Process Planning) system based on process knowledge. The CAPP system framework module of Open Die Forging facing industry is proposed. This module can realize the fusion of retrieval type, derived type, and creative type, etc. CAPP functions, reasons and makes decision based on knowledge and, develops the optimal process route, and process card. In this paper, the main functions of the system are introduced based on developments of open die forging CAPP system in recent years.

The Technological Optimization of Closed Multiple-Ram Forging for Draw Rod

Draw rod is one of the main mechanical parts of vehicle steering system，which is required extremely high quality. At present the way to produce the draw rod is machining after common open-die forging. This technology will produce big flashings，damage the metal’s fibrous structure and reduce the material utilization. In this essay, we will use the technology of closed multiple-ram forging to produce it. We will utilize numerical simulation on several blanks through numerical simulation combined with experiments. In this way, the defects that some parts of the blank are folded and cannot fill well during forming process can be effectively avoided. Besides, there will be free of flashing and the draw rod forgings do not need to be cut. The weight of the original blank will be about 3.5 kg after being optimized, down by 36.4 percent compared with that of original material about 5.5 kg. And we will make different settings for the loading way of the plunger chips during the forming process, then compare with the simulation results and ultimately find out the best loading way. At last, we will verify the feasibility of such an optimal technology through experiments on the material-lead.

Compound stiffness modelling of an integrated open-die forging centre with serial–parallel heavy-duty manipulators

This paper presents a method for modelling the compound stiffness of an integrated open-die forging centre that consists of a forging press as well as a manipulator that handles the workpiece. Open-die forging has considerable differences to general machining processes due to the complex plastic deformation effects created by consecutive forging strikes. The manipulator must comply with the movement of the workpiece during forging. The stiffness of the integrated system mainly comes from two sources: the compliance of the manipulator and the elastic deformation of the workpiece during forging. First, the stiffness matrix of the workpiece is derived using the theory of mechanics of materials. Then, the complete Cartesian stiffness matrix of the manipulator is developed by using the conservative congruence transformation method. Finally, the compound stiffness model is constructed by combining these two stiffness matrices. A numerical algorithm is developed that is able to simulate the compliance motion of a programmed open-die forging process. Two numerical examples are presented to validate the proposed modelling method and numerical algorithm.

Simulation of programmed incremental open-die forging processes based on spread coefficient and geometric transformation

A typical open-die forging process, square bar drawing, is investigated, which is the most commonly adopted process in a programmed open-die forging system that includes press and co-ordinated forging manipulators. The simulation algorithm for the square bar drawing between simple dies is proposed based on the spread coefficient theory and geometric transformation. The geometry of the as-forged workpiece is modelled by using the concept of the Characteristic Point Set; the spatial motion of the workpiece is computed by using the norma-lized co-ordinate transformation; and the plastic deformation of the deforming part is described by using a geometric transformation based on spread coefficient and reasonable simplifications. The real-time simulation algorithm of the programmed forging process is then formed, which can be used in pass schedule design, providing codes for the coordination control of the press and the manipulator, and can be incorporated into the virtual reality integrated forging plant as the process simulation model.

Influence of mould design on the solidification of heavy forging ingots of low alloy steels by numerical simulation

Ingot casting of a 6-ton, heat-treatable Cr–Mo low alloy steel was simulated using finite element method in three dimensions. Effects of casting parameters including bottom pouring rate, mould slenderness ratio, mould slope, and height and shape of the hot top isolate on solidification behaviour and crack susceptibility during subsequent hot forging of the ingot were investigated. The simulation model was validated against experimental data of two different ingot mould designs. Influences of the casting parameters on the riser efficiency and possible crack formation in the intersection of hot top and ingot body during subsequent open-die forging of the cast steel ingots were discussed. Results showed that pouring the melt under a constant rate, reducing the mould slenderness ratio, and using a proper design for the hot top isolate would all improve the riser efficiency and thereby possibly reduce crack susceptibility during subsequent hot forging.

Coordinated kinematic modelling for motion planning of heavy-duty manipulators in an integrated open-die forging centre

An integrated open-die forging centre can realize programmed incremental forging processes to improve safety and efficiency; the centre consists of a forging press and one or two heavy-duty manipulators. This paper focuses on the coordinated kinematic modelling of the integrated system. First a newly designed serial—parallel forging manipulator is presented and the closed-form inverse kinematic solution is derived based on homogeneous co-ordinate transformation. Then the deformation of the forged workpiece is investigated by the spread coefficient method of plastic deformation theory, and the relation between the motion of the holding end of the workpiece and the movement of the upper die is formulated. Finally, the coordinated kinematic modelling of the integrated system is established, where the press and the manipulator are coordinated in movement. Simulation of a typical open-die forging process shows that the gripper of the manipulator should have good compliance abilities in horizontal and vertical directions during forging; however, it should have high rotation stiffness with respect to the transverse axis. The automatic programmed forging plan and coordination control strategy can be pre-designed based on this model.

The determination of steel cleanliness in the as-cast steel ingot 26NiCrMoV145

The content and the type of non-metallic inclusions in the as-cast ingot for open-die forgings made from 26NiCrMoV145 steel were determined. The standard methods for the determination of non-metallic inclusions are suitable only for the wrought steels, so a modified standard method for the determination of the non-metallic inclusions in the as-cast steel was performed. Analyzed samples were taken from three different positions on the ingot. The determination of the type of the non-metallic inclusions was made by EDS analysis. The content of the non-metallic inclusions was determined using an optical microscope.

TOOL PATH DESIGN OF INCREMENTAL OPEN-DIE DISK FORGING USING PHYSICAL MODELING

A small-batch product of large-sized parts is usually manufactured using incremental open-die forging. In order to control the overall change in the shape of a part, it is essential to be able to predict the shape changes that occur during each step. This paper addresses shape changes of a material according to the forging path. Rapid prediction of metal flows for continuing incremental deformation using theoretical methods is difficult. Accordingly, instead of a theoretical approach, an experiment that tests the tendency of the metal flow for development of forming processes is required. For the sake of convenience, simulative experiments are carried out using plasticine at room temperature. In present study, the tool movement is dominant parameters to with respect to changing the shape of the workpiece.

Development of a Process Model for Online-Optimization of Open Die Forging of Large Workpieces

Development of a Process Model for Online-Optimization of Open Die Forging of Large Workpieces

研究速報 : Microstructure Simulation in Hot Open Die Forging by Using the Incrementa Formulation (Preliminary Report)

研究速報 : Microstructure Simulation in Hot Open Die Forging by Using the Incrementa Formulation (Preliminary Report)

Microforging technique for rapid, low-cost fabrication of lens array molds

Interest in micro-optical components for applications ranging from telecommunications to life sciences has driven the need for accessible, low-cost fabrication techniques. Many microlens fabrication processes are unsuitable for applications requiring 100% fill factor, apertures approximately 1000 microm with high numerical aperture, and scalability to large areas (e.g., tens of centimeters to meters) with millions of lenses. We report on a flexible, low-cost mold fabrication technique that utilizes a combination of milling and microforging. The technique involves first performing a rough cut with a ball-end mill. Final shape and sag height are then achieved by pressing a sphere of equal diameter into the milled divot. Using this process, we have fabricated molds for rectangular arrays of 1-10,000 lenses with apertures of 25-1600 microm, sag heights of 3-130 microm, interlens spacings of 250-2000 microm, and fill factors up to 100%. Mold profiles have a roughness and figure error of 68 nm and 354 nm, respectively, for 100% fill factor, 1000 microm aperture lenses. The required forging force was modeled as a modified open-die forging process and experimentally verified to increase nearly linearly with surface area. The optical performance of lens arrays injection molded from microforged molds was characterized by imaging the point spread function and was found to be in the range of theoretical values. The process can be easily adapted to lenticular arrays as well. Limitations include milling machine range and accuracy.

Analysis on Void Closure Behavior during Hot Open Die Forging

Internal voids have to be eliminated for defect-free in some open die forging. The FEM analysis is performed to investigate the overlap defect of cast ingots during cogging stage. The measured flow stress data were used to simulate the cogging process of cast ingot using the practical material properties. Also the numerical analysis of void closure is performed by using the DEFORMTM-3D. The calculated results of void closure behavior are compared with the measured results before and after upsetting, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the void closure were estimated into effective strain of 0.6 by the comparison of practical experiment and numerical analysis.

Finite difference method for analysis of open-die forging of sintered cylindrical billets

In this paper, an analysis of the upsetting of axisymmetric cylindrical billets of porous materials is made on the basis of plasticity theory. A newly established yield function for porous materials based on Shima and Oyane is used to simulate the open die forging of porous billets, taking into account the current state of porosity at each stage of deformation. The proposed theoretical model combined with the concepts of the slab method and a finite difference solution, provides with a valuable design tool allowing for a more precise evaluation of the process loading and the shape changes of the porous billets obtained during upsetting. The variation of radial distribution of radial stress ( σ r), normal pressure ( p), porosity ( f), radial strain ( ε r), mean strain and Poisson’s ratio for various value of initial porosity ( f 0) is predicted. It is observed that with an increase in initial porosity, the normal pressure, the radial stress, Poisson ratio, and the radial strain are decreased. The current porosity ( f) variation in the radial direction seems to be negligible but it increases with increasing initial porosity. It is of interest to note that for a given initial porosity, the radial stress and the pressure attain their maximum values at r = 0 (at center).