Research on the vibration model and vibration performance of cold orbital forging machines

The vibration of cold orbital forging (COF) machines is a major issue for the quality of forging parts. It is therefore necessary to investigate the vibration of COF machines and provide some effective methods for reducing the vibration. In this paper, horizontal and vertical dynamic models of COF machines are established. These dynamic models are then effectively verified by conducting experiments. By using dynamic models of the COF machine, the vibration performance of the COF machine is investigated. To investigate methods for reducing the vibration of the COF machine, the effects of some key parameters on the vibration of the COF machine are studied, which include the eccentricities and rotation angular speeds of the inner eccentricity ring and the outer eccentricity ring, the amplitude and frequency of external excitation, and the equivalent stiffness and equivalent damping between swing shaft and bearing. Investigative conclusions can be drawn: During the COF process, vertical vibration is more drastic than horizontal vibration. A larger absolute difference between the eccentricities of the inner eccentricity ring and the outer eccentricity ring contributes to reducing the horizontal vibration of the COF machine. A larger equivalent stiffness and a larger equivalent damping between the swing shaft and bearing, a smaller amplitude and a smaller frequency of the external excitation contribute to reducing the vertical vibration of the COF machine.

Static and Dynamic Analysis of a 6300 KN Cold Orbital Forging Machine

In cold orbital forging (COF) processes, large stress, displacement and vertical vibration of the COF machine are bad for the quality of the part and the fatigue life of the COF machine. It is necessary to investigate the static and dynamic performance of the COF machine and provide methods for reducing the stress, displacement and vertical vibration of the COF machine. In this paper, finite element analysis, theoretical analysis, numerical simulation and experimental analysis were applied to study the static and dynamic performance of a 6300 KN COF machine. The static and dynamic analyses were verified effectively by carrying out strain and vertical vibration test experiments. In the static analysis, the large stress and displacement positions of the COF machine were mainly distributed near the working table and the junction between the working table and the column. Large stress and displacement will be bad for the quality of the part and the fatigue life of the COF machine. Structural optimizations of the COF machine include ribbed plates on the working table and beam. This structural optimization method of the COF machine obviously reduced the stress and displacement of the COF machine. When the angular velocities of the eccentric rings were 8π rad/s, the vertical vibration of the swing shaft is a low-frequency vibration. The existence of absorber obviously reduced the vertical vibration of the COF machine.

Material Flow in Ultrasonic Orbital Microforming

Ultrasonic orbital microforming—UOM—uses the broadly understood idea of orbital forging but uses very different laws of physics. The only shaping force in this process is the inertia force resulting from the acceleration in the rotary motion of the workpiece. Micro specimen blanked from cold rolled aluminum sheet metal was used in the applied UOM process. Only the upper and lower part of the sample is deformed that gives about 70% of volume. The rest—the middle part—remains undeformed. The final shape of the product is influenced by the shape of the inside of the die in which the UMO process is carried out. However, this effect is not a direct one. The product shape does not repeat the shape of the interior of the die. The preliminary experiments with modular micro-die have been performed on the way of controlling the shape of deformed micro-objects. The microstructure analysis has been done as well as micro-hardness distribution.

Ultrasonic Orbital Microforming—A New Possibility in the Forming of Microparts

The demand for very small metal parts is growing rapidly due to the development of micromechanisms. In microtechnology, the dimensions of scale parts are below 1 + c mm, where c varies based on the process type. The “classic” processes usually cannot be simply scaled down, and tools require thorough structural changes. Microforming has been isolated from the area of “classic” metal forming and is governed by modified laws. The proposed new technological process ultrasonic orbital microforming (UOM) and its related phenomena are possible only on a microscale. UOM is a process that uses the broadly understood idea of orbital forging, which involves rolling on a closed road. This, however, is where the analogy ends. The UOM process uses completely different laws of physics. The process, the result of which is the axial-symmetrical micropart, consists of inducing a fast rotational movement of the billet by a punch that is vibrating at an ultrasonic frequency. The rotational speed is so fast that gyroscopic effect plays an important role. This work presents the concept of the process, preliminary research results, and their general interpretation. FEM-3d modeling of micro-orbital forming processes in geometrically similar conditions to the UOM process was also performed, obtaining shapes consistent with those obtained in the UOM.

Preform designing approach in cold orbital forging of flange gear

Flange gear has a complex geometry and its volume distribution along the axial direction changes suddenly. This makes it difficult to be formed by a single step using a simple cylinder workpiece and the preform is necessary. This research aims at proposing a preform designing approach in cold orbital forging of flange gear. A three-dimensional finite element model of cold orbital forging of flange gear is first constructed. Then, the cold orbital forging processes are simulated under different preform geometries and the insufficient filling and folding defects are studied. At last, the preform is optimized and the defects are eliminated. The experiments are also performed and the preform designing approach in cold orbital forging of flange gear is verified.

A Novel Cold Rotary Forging Method of Producing Multiple Racks Using One Set of Punch

When producing racks by cold rotary forging, the top punch and the rack teeth definitely intervene and thus the top punch has to be amended, which makes the technical designing processes difficult and complex (Han et al., 2016, “Cold Orbital Forging of Gear Rack,” Int. J. Mech. Sci., 117(10), pp. 227–242). In this study, a novel cold rotary forging method of producing racks is put forward to avoid the interventions between the top punch and the racks. Thus, the top punch need not be amended and the technical designing processes correspondingly become simple. In light of this presented method, a novel idea for cold rotary forging of producing multiple racks using one set of punch is motivated. The concrete researches are as follows: First, the mathematical models are developed and three kinds of key forging conditions in cold rotary forging of racks are calculated to avoid the interventions between the top punch and the racks. The first one is the condition that the top punch and the rack teeth do not intervene. The second one is the condition that the top punch and cylindrical surfaces of racks do not intervene. The third one is the condition that the top punch can be successfully constructed. On the basis of these three kinds of key forging conditions, the workpiece is optimized and the cold rotary forging processes of racks with constant and variable transmission ratio are examined using finite element (FE) simulations. The experimental researches are also conducted. The results show that for both racks with constant and variable transmission ratio, the obtained key forging conditions are effective and the presented cold rotary forging principles of producing multiple racks using one set of punch are feasible.