Earticle

The objective of this study is to optimize the diameter of tubular shaft yoke and solid shaft yoke, which are the core components of Al IMS for xEV. The processes of both products were designed totally 6 steps to manufactured the shaft part and the yoke part. The diameter of solid shaft yoke and tubular shaft yoke were changed from 20mm to 25mm and from 30mm to 35mm, respectively. Al 6082 was applied to the material of both products. The friction condition between die and material was employed Oil_Cold (Aluminum) with reference to the library in the program. The results were analyzed and compared in terms of effective stress, effective strain, and nodal velocity characteristics. The effective strain value for manufacturing the yoke part was higher than the shaft part because its part has a complex geometry. The value of nodal velocity was also higher with high effective strain region. However, in 6 stage process of tubular shaft yoke, although it had the high effective strain value, the nodal velocity value was the lowest due to the piercing process. The effect of shaft part diameter on effective stress in the tubular shaft was difficult to observe, however, in the solid shaft yoke, when the shaft part of one increased, the effective stress value was increased due to the larger yoke size.

The objective of this numerical study is to investigate the effect of shaft part’s diameter on the load distribution, under-fill, and metal-flow line characteristics in tubular & solid shaft yoke of Al-IMS. The outer diameter of tubular shaft yoke was changed from 30mm to 35mm, and the shaft diameter of solid shaft yoke was varied from 20mm to 25mm. In this results, the required load for production was linearly increased with increasing the tubular shaft yoke outer diameter. In the solid shaft yoke, the loads for the shaft part extending process were almost constant by 10,000kg, however, the loads for generating the yoke process, which were needed a lot of strain, were increased by 4,000kg with increasing the diameter of shaft part. The under-fill regions according to diameter of the shaft part were not observed in both products, and the metal-flow lines were also straight without folding phenomena.

Forged part made of Cold heading quality wire materials are used for automotive brake systems. The cost reduction of forged products is a major issue because of the strict shape change. A series of studies were conducted to minimize the cost of EPB spindle process among brake parts. In order to reduce the material cost, heat treatment-abbreviated material was applied and the formability on the processes was verified by the ductile fracture theory. In addition, the causes of shape fixation and die life degradation were analyzed using the numerical simulation. The process cost has been minimized by re-designing process, changing the product shape, and the die material.

The objective of this study was to investigate the optimal design on the tubular shaft and solid shaft for A-IMS of commercial vehicle. The tubular shaft and the solid shaft were designed by 6 stageprocesses and the results were analyzed by using a finite element analysis method. The coefficient of friction was set to Oil_Cold conditions as referred to the analysis library. It was found that the actual underfill phenomenon was not observed on the tubular shaft and solid shaft. The metal flow of the tubular shaft and solid shaft revealed that the folding phenomenon was not occurred, so there is noproblem in actual production. Principal stress and load characteristics of tubular shaft were higher than those of solid shaft since the tubular shaft have many deformation from stage 1 to stage 3.

In this study, as part of the paradigm shift for manufacturing innovation, data from the multi-stage cold forging process was collected and based on this, a big data analysis technique was introduced to examine the possibility of quality prediction. In order for the analysis algorithm to be applied, the data collection infrastructure corresponding to the independent variable affecting the quality was built first. Similarly, an infrastructure for collecting data corresponding to the dependent variable was also built. In addition, a data set was created in the form of an independent variable-dependent variable, and the prediction accuracy of the quality prediction model according to the traditional statistical analysis and the tree-based regression model corresponding to the big data analysis technique was compared and analyzed. Lastly, the necessity of changing the manufacturing environment for the use of big data analysis in the manufacturing process was added.

Recently, the automobile industry has continued to demand lighter materials owing to international environmental regulations and increased convenience. To address this demand, aluminum parts have increased in popularity and are mainly developed and produced through hot forging and cold pressing. However, because this method has low yield and low production efficiency, a new manufacturing method is desirable. In this study, the water capacity efficiency of an aluminum inner tie rod socket was investigated using cold forging that provided a high yield and excellent production efficiency. Mechanical properties were derived through tensile testing of 6110A aluminum materials, and critical fracture factor and process analysis based on experimental data were carried out. The optimized process was applied as a prototype using cold multi-stage forging, and based on the derived results, the formability, productivity, and material efficiency of aluminum inner tie rod socket parts using this cold forging process was verified.

Reducing production costs through net-shaped cold forging is an important aspect in the automobile industry. In this study, we intend to produce a net-shaped electronic parking brake (EPB) serration gear for automobiles, using multi-stage cold forging. These serrations are then assembled to the reduction gear of an EPB actuator. The forging process of the serrations and the cold forging design were verified through finite element analysis (FEA) in order to evaluate metal flow. The forging machine was selected by checking the load using FEA. Based on the FEA results, molds were designed, and parts were made using multi-stage cold forging to produce a net-shaped serration gear.

Conventionally design for multi-stage cold forging depends on the designer's experience and decision-making. Due to such non-deterministic nature of the process sequence design, a flexible inference engine is needed for process design expert system. In this study, A* searching algorithm was introduced to arrive at the vetter process sequence design considering the number of forming stages and levels of effective strain, effective stress, and forming load during the porcess. In order to optimize the process sequence in producing the final part, cost function was defined and minimized using the proposed A* searching algorithm. For verification of the designed forming sequences, forming experiments and finite element analyses were carried out in the present investigation. The developed expert system using A* searching algorithm can produce a flexible design system based on changes in the number of forming stages and weights.

This study deals with a series of experimental investigations on multi-stage cold forging of an outer race used for a constant velocity (CV) joint with six inner ball grooves. The multi-stage cold forging, which consists of forward extrusion, upsetting, backward extrusion, and combined sizing-necking including ironing, was used to produce a prototype of the outer race. The cold forging tools such as forging punches and dies required in this multi-stage cold forging were also designed and fabricated. For the combined sizing-necking, especially, the longitudinally six-segmentallized punches were developed to easily eject from the necked inner groove of the outer race with consideration of the operating mechanism. Spheroidized SCr420H billet was used in the experimental study. To verify the suitability of the proposed process, the obtained parts were obtained from each forging operation, and the geometries were compared with the target dimensions. It was confirmed that the outer race with six inner ball grooves was well forged by adopting the proposed multi-stage cold forging, and the dimensional accuracy of the forged outer race matched well with the requirements.

Conventional load monitoring in multi-stage cold forging fails to localize embossing pin breakage due to die symmetry. To address this, we propose a fault diagnosis system utilizing a piezoelectric sensor placed eccentrically on the wedge and multi-modal data fusion. This offset placement induces asymmetric signal patterns relative to defect location. By fusing force and acceleration data with machine learning models, we achieved 98.4% Macro F1-score in classifying 11 defect states. This study demonstrates a cost-effective solution for precise fault localization without additional sensors.

In manufacturing a tripod housing using multi-stage cold and warm forging process, a process modification example is presented for approaching net-shape forging. The process modification in this study is mainly performed on target shape improvement at warm upsetting, and the target layouts of the intermediate billets of the following warm backward extrusion and the cold sizing are also changed minutely. Using mechanical and thermal properties of C48P medium carbon steel bar, elasto-plastic finite element simulation of the warm upsetting is re-started based on the prior results from the ejection operation in the second forward extrusion, and then a series of numerical simulations related to the warm backward extrusion and the cold sizing processes are followed. The numerically predicted results in view of the deformed feature before and after the process modification are compared with the tripod housing prototypes produced experimentally. As a result, the forged configuration of the tripod housing by the process modification is revealed to be improved.

In multi-stage cold forging process, to enhance the productivity and product quality, in-site process monitoring technique by implanting sensors such as piezo-sensor and acoustic emission sensor has been continuously studied. For accurate analysis of the process, the selection of appropriate sensors and implantation positions are very important. Until now, in a multi-state forging machine, wedge parts located at the end of punch-set are used but it is difficult to analyze minute changes in die block-set. In this study, we also implanted sensors to the die part (die spacer) and compared signals from both sensors and found that sensing signals from die part showed enhanced process monitoring results.

This study deals with multi-stage cold and warm forging for fabricating a tripod housing used as a torque member of inner constant velocity (CV) joint. The multi-stage cold and warm forging process is composed of warm forging operations such as primary forward extrusion, forward extrusion, upsetting, backward extrusion, and of cold sizing. C48P medium carbon steel round bar with a diameter of 55.0mm is selected as initial billet workpiece, and uni-axial compression tests are performed to evaluate the compressive strength under various temperature conditions. In order to consider a series of thermal effects during warm forging operations, each forging stage is subdivided into feeding, forging, and ejection. Numerical simulations based on elasto-plastic finite element method are sequentially carried out to verify process flow designed for the multi-stage cold and warm forging process. As a result, the primary designed process flow is shown to be applicable itself to fabricate the tripod housing, but to be necessary minor modification for realizing the near net-shape forged tripod housing.

This paper proposes a real-time Ram Tilt variation monitoring system to detect equipment abnormalities and stabilize production in multi-stage cold forging processes. As equipment wear progresses, misalignment often occurs, leading to product defects and tool damage. The proposed system utilizes dual distance sensors to capture micro-variations in Ram Tilt during reciprocating motion and calculates the Ram Tilt deviation (mm) through real-time processing. Data collected over one year from eight forging machines were analyzed using SPC ${\bar{X}}$-R charts, and abnormal control patterns were classified into three types: chronic instability, intermittent spike, and mean shift. The system was integrated with an MES to automatically stop equipment when deviations exceed thresholds, minimizing downtime and tool damage. Furthermore, the statistical independence between cycle time and Ram tilt (Pearson correlation coefficient r ≈ 0 ) was verified, proving its reliability as a condition indicator. The results demonstrate improved manufacturing reliability, including a 98% reduction in defect rates, and reduced operator dependence, suggesting potential applications in smart factory environments with low-volume, high-mix production.

Cold forging is a method in which molding is performed at room temperature. It has a high material recovery rate and dimensional precision and produces excellent surface quality, and it is mainly used for the production of bolted or housing products. The lifespan of cold forging molds is generally determined by the wear of the mold, plastic deformation of the mold, and fatigue strength. Cold forging molds are frequently damaged due to fatigue destruction rather than wear and plastic deformation in a high-temperature environment as it is molded at room temperature without preheating the raw material and mold. Based on the results analyzed through FEM, an effective mold structure design method was proposed by analyzing the changes in tensile and compressive stresses on molds according to the number of molds and reinforcement rings and comparing the product geometry and mold stress using three existing mold models.

The outer race of a constant velocity (CV) joint having six inner ball grooves has traditionally been manufactured by multi-stage warm forging, which includes forward extrusion, upsetting, backward extrusions, necking, ironing and sizing, and machining. In the current study, a multi-stage cold forging process is examined and an assessment for replacing and modifying the conventional multi-stage warm forging is made. The proposed procedure is simplified to the backward extrusion of the conventional process, and the sizing and necking are combined into a single sizing-necking step. Thus, the forging surface of the six ball grooves can be obtained without additional machining. To verify the suitability of the proposed process, a 3-dimensional numerical simulation on each operation was performed. The forging loads were also predicted. In addition, a structural integrity evaluation for the tools was carried out. Based on the results, it is shown that the dimensional requirements of the outer race can be well met.

We analyzed a sequence of multi-stage automatic cold forging processes composed of four axisymmetric processes followed by a non-axisymmetric process using rigid-plastic finite element based forging simulators. The forging sequence selected for an example involves a piercing process and a heading process accompanying folding or overlapping, which all make it difficult to simulate the processes. To reduce computational time and to enhance the solution reliability, only the non-symmetric process was analyzed by the three-dimensional approach after the axisymmetric processes were analyzed by the two-dimensional approach. It has been emphsized that this capability is very helpful in simulating the multi-stage automatic forging processes which are next to axisymmetric.

In this paper, finite element analysis of an automatic five-stage precision cold forging process of a yoke, a steering part of a passenger's car, is conducted with emphasis on spring back analysis at the yoke-forming stage and its experimental verification is subsequently made. An elastoplastic finite element method with MINI-element technique employed for the analysis of the entire process is explained. There is emphasis that the thin film of material formed between the punch and die in the stage may result to some errors especially in elastoplastic finite element analysis of spring back due to frequent remeshing. The numerical robustness of the spring back analysis in regards to remeshing is hence shown first through investigation into its effect on the predicted spring back. Experimental measurement of displacement due to spring back is carried out for comparison with the predicted results, and they are in a qualitative agreement with each other.