Sheet Metal Bending Process Research Articles

Error compensation and path planning for sheet metal bending process based on improved modeling algorithms

Error compensation and path planning for sheet metal bending process based on improved modeling algorithms

Yüksek Mukavemetli Çeliklerde Geri Esnemenin Kalınlık Azaltma Yöntemi ile Telafisi

The sheet metal bending process plays an important role in sheet metal production and springback is an unintended consequence of this operation. If the bending die process is performed without knowing the amount of springback, it is difficult to produce parts within acceptable tolerance values. The springback behavior of the part to be bent also affects the size of the bending die. In particular, in the case of a 90° U bend die, the manufacturing cost of the bending die with the springback compensation method is high. Therefore, it is important to estimate the springback value at the design stage. In this work, the estimation of the amount of deformation to avoid springback value was performed using the thickness reduction method for high strength sheet metal. According to this study, the thickness reduction method can be used effectively in springback compensation. The estimation of the measurement accuracy at the design stage reduces the cost of the bending die and it is possible to produce parts within tolerance limits without much experimentation. The results showed that thickness reduction at the 0,2 t value was suitable to eliminate the springback value in the U-bending process. It has been found that experimental, empirical and finite element results are close to each other.

Effects of processes parameters on spring back, wrinkles and cracks in different flanging processes: A Review

Flanging is an important type of sheet metal bending process. In present review, an effort was made to explore the contributions of various researchers to drawn out the cause of defects in the flanging process. Several parameters such as geometrical, material and process parameters affect the formability of the flanging process. In straight flanging process, spring back (due to elastic recovery) is a major problem that affects dimensional and geometrical accuracy of a bent component. Several factors are responsible for springback such as – profile radius of punch and die, bend angle, thickness of sheet, clearance between punch and die, blank-holder force, Young’s modulus, n-value, yield stress, plastic anisotropy of materials, velocity of punch etc. In shrink flanging process, wrinkling is the prime concern that occurs due to the excessive compressive stress in the flange portion. It is mostly affected by mechanical properties of material (R-value, n–value etc.), geometry of the tools and blank, process parameters. In stretch flanging process, the effect of material parameters is found to be less as compared to geometrical parameters for crack initiation and thinning.

Development of a flexible tooling system for sheet metal bending

This article presents the design and development of a flexible tooling system for sheet metal bending. The flexible tooling system aims to reduce manufacturing disturbances and increase the efficiency of the forming process. First and foremost, the structural behaviour of the sheet metal is investigated using the finite element method for the numerical simulation of the three-point bending process. The analysis’ findings enabled the prediction of component reaction to loads, which are essential for the further optimization and enhancement of the tooling system’s flexibility. At the initial stage of the development phase, SolidWorks, the computer-aided design software, is utilized to visualise the flexible tooling system and improve the tooling connectivity design. Furthermore, the prototype is developed by integrating mechanical and electrical components, such as the Arduino Mega microcontroller, stepper motors, and digital stepper drivers. Automation is achieved by programming the Arduino microcontroller board and controlling the stepper motors’ movement to ensure precise displacement and speed control of the forming tools. The tooling system’s major qualities are its high flexibility, achieved through the implementation of two moveable support cylinders and the possibility of being further upgraded to a closed-loop forming system. The higher level of automation and optimization of the sheet metal bending process can lead to improved processing efficiency and help achieve the desired formed products with higher quality and the required geometric tolerance. It is expected that the development of a flexible tooling system will find widespread application in sheet metal bending processes, resulting in reduced material costs, rapid equipment set-up and higher processing repeatability.

Effect of material discontinuity on springback in sheet metal bending

ABSTRACT Origami-based sheet metal, a novel emerging technique, is explored in this paper. The process is similar to traditional process of making the Origami art from paper. Sheet metal forming is also considered as a paper with negligible thickness. Here the process was tried differently than traditional sheet metal-bending process. On the bend line, the material was removed intermittently. This process created the material discontinuity at the bend line. However, removing the material from the bend line opened the sections and it would not be able to use as a container to hold any liquid material due to leakage issue. Thus, in this paper, the material discontinuity was created by removing the small amount of material but not through. This can be called as blind material discontinuity. With change in thickness and width at material discontinuity four samples were created to see the effect on bending deformation and springback. In addition, die clearances and either MD will be faced on die or punch side was explored. From the results it was found that the lower thickness at material discontinuity and on die side would provide lower springback if the width of material discontinuity is higher.

Development and performance evaluation of a web-based feature extraction and recognition system for sheet metal bending process planning operations

ABSTRACT Sheet metal bending manufacturing companies require changeable and adaptable process planning systems to shorten the production cycle time and reduce operations costs. This is due to globalisation and the rapid change in market demands for sheet metal products. In light of this, this paper proposes a web-based feature extraction and recognition system. The system would ensure automated planning of various processes used by a bending machine to produce varieties of sheet metal products. The algorithms were implemented using C++ to produce the geometric and feature models used to extract, and recognise the bending features in various CAD files acquired from literature. Five (5) CAD files of various sheet metals were utilised to test the functionality of this system. The results from the feature recognition process have proven to be precisely what the user has designed and saved in the model file. Bend radius and bend angle. Finally, the developed system is able to transform a STEP file into a feature model and display the 3D CAD model within the least time. It is a cost-efficient standalone system that provides data storage, allows collaboration and data sharing. can be used anywhere where there is internet access.

A Study on the Effects of Temperature, Punch Radius and Punch Stroke on Forming Force When Bending SS400 Steel Plate

Sheet metal forming process is a basic deformation method in the mechanical field. In particular, bending deformation processing is a universal processing method which is widely used to form sheet metal parts such as aviation industry, shipbuilding, automotive and so on. During sheet metal bending process, the forming force is a very important output parameter that needs to be determined to ensure the load capacity of a machining equipment. This forming force magnitude will vary according to machining conditions, Geometric shapes of products, sheet materials, etc. This study examines the influence of technological and geometric parameters such as: work-piece temperature, punch speed and sheet thickness to bending force when forming V-shape of SS400 sheet material.

Deep Learning in Sheet Metal Bending With a Novel Theory-Guided Deep Neural Network

Sheet metal forming technologies have been intensively studied for decades to meet the increasing demand for lightweight metal components. To surmount the springback occurring in sheet metal forming processes, numerous studies have been performed to develop compensation methods. However, for most existing methods, the development cycle is still considerably time-consumptive and demands high computational or capital cost. In this paper, a novel theory-guided regularization method for training of deep neural networks (DNNs), implanted in a learning system, is introduced to learn the intrinsic relationship between the workpiece shape after springback and the required process parameter, e.g., loading stroke, in sheet metal bending processes. By directly bridging the workpiece shape to the process parameter, issues concerning springback in the process design would be circumvented. The novel regularization method utilizes the well-recognized theories in material mechanics, Swift's law, by penalizing divergence from this law throughout the network training process. The regularization is implemented by a multi-task learning network architecture, with the learning of extra tasks regularized during training. The stress-strain curve describing the material properties and the prior knowledge used to guide learning are stored in the database and the knowledge base, respectively. One can obtain the predicted loading stroke for a new workpiece shape by importing the target geometry through the user interface. In this research, the neural models were found to outperform a traditional machine learning model, support vector regression model, in experiments with different amount of training data. Through a series of studies with varying conditions of training data structure and amount, workpiece material and applied bending processes, the theory-guided DNN has been shown to achieve superior generalization and learning consistency than the data-driven DNNs, especially when only scarce and scattered experiment data are available for training which is often the case in practice. The theory-guided DNN could also be applicable to other sheet metal forming processes. It provides an alternative method for compensating springback with significantly shorter development cycle and less capital cost and computational requirement than traditional compensation methods in sheet metal forming industry.

Development of springback tester and the effect of forming speed on the springback of four sheet metal bending processes

With the current increasing emphasis on issues of energy saving, emission reduction, driver and passenger safety in automotive industry, lightweight bodywork is an effective measure to reduce vehicle energy consumption. And also, high-strength bodywork structure can improve automobile safety performance because of its high impact absorption energy, and high fatigue resistance. In sheet metal forming, springback is a main defect with using high strength steel. Aiming to investigate sheet metal springback phenomenon for high-strength steel, a multi-funtional springback test machine is built. The testing machine can perform four types of springback tests: V-bend, U-bend, stretchbend and drawbend, and all these tests have been carried out to investgate the effect of springback factor in sheet metal forming processes for example forming speed. The research found that the springback angle of U-bend and drawbend increase with enlarging speed, however, V-bend and stretchbend show the opposite trend.

Analysis of distortion of coupled process forming to welding using fem-based virtual manufacturing with experimental verification

In this paper, the numerical model of coupled process forming to welding by means of FEM is developed in order to analyse the displacement. Simufact. Forming and Simufact. Welding are utilized to execute a thermomechanical FEM analysis of forming to welding coupled process. Prior to welding process, a sheet metal bending process is performed in order to bend the 2mm plate into a U-shaped geometry. The material used for this process is S235 low carbon steel along with filler material ER70s. Goldak’s double ellipsoid model is chosen as the heat source model for GMAW simulation. A series of sheet metal bending and GMAW experiment is executed in order to verify the distortion result produced by FEM analysis. ABB IRB 2400/16 is the assigned robotic welding equipment used in GMAW process while sheet metal bending machine SUNFLUID 800/2007 is utilized for sheet metal bending process. For the calibration model, a forming force between FE simulation will be compared with the forming force of experimental bending process. The final results have shown that the distortion result of FEM analysis of coupled process forming to welding shows a good agreement with the experimental coupled process.

Stress State Control by a Novel Bending Process and its Effect on Damage and Product Performance

Abstract The novel sheet metal bending process is designed to change the load path in order to control the damage evolution. The process superposes targeted radial stresses during bending and is therefore called radial stress superposed (RSS) bending. As material damage is strongly dependent on the load path, the setting of this property becomes possible in this process. Hence, the process principle, its features, and the tool setup are presented. Furthermore, numerical simulations are carried out with the aim to investigate the occurring deformation zone and the resulting radial stress superposition. Scanning electron micrographs prove that the evolution of voids is delayed. With the acquired knowledge to change the stress state during the bending process, the property “damage” can be controlled and finally reduced. This enhances the microstructure and lifetime performance of the bent product. The improved product performance is shown by a newly designed specimen for impact testing of bent products.

Stress State Analysis of Radial Stress Superposed Bending

Radial stress superposed bending is a sheet metal bending process, which superposes predetermined radial stresses. Stress superposition is mandatory to enable the reduction of the triaxiality in bending, resulting in delayed damage evolution and an improved product performance. The knowledge of the stress state is essential for damage-controlled bending as the triaxiality is the driving force for the void evolution. To control the stress state in radial stress superposed bending, an additional counter force responsible for the pressure in the outer fiber is applied. To predict the effect of the counter force on the radial stress and the triaxiality an analytical model is proposed. The prediction of the reaction forces in the system is required for the process design and for the calculation of the stress superposition. The stress state for plane strain bending with stress superposition is derived, and pressure calculations are made using the theory of Hertz. The model and the assumptions are verified in numerical and experimental studies for various counter pressures and bending ratios. Finally, a discussion of the load path depending on the transient counter pressure is carried out and experimental evidence for a inhibited damage evolution due to stress superposition is given.

Grain Size Effect on Saddle Phenomenon in V-Bending Process of Thin Sheet Metal

The ability for predicting the springback on sheet metal bending processes is identified as an important feature of the ability for predicting the final geometry of sheet metal parts. The grain size effect makes the difficult on application of traditional design method in processing. As through tool and processing design, to understand the effects of grain size effects is an important and powerful way to effectively compensate for and eliminate the springback. In this paper, 99.5% pure iron specimens were annealed at different temperature to obtain the specified grain sizes. The effects of different grain sizes on the saddle after V-bending of the thin sheet metal were investigated. The results show that at the same thickness of specimens, the grain size has no significant effect on the saddle height. However, with increasing the thickness of the specimens the saddle will also be more prominent protruding height. The concave side of bent specimen is against the compression force and its grains structure tend to a round shape, whereas the convex side is against the tensile force and its grains structure tend to a flaky shape.

Position deviation of bending point in asymmetric V-die bending process with HSS trapezoid sheet

The prediction of the deviation of bending point in asymmetric V-die bending is extremely needed for practical application. An analytical model and a series of experiments are performed to characterize high strength steel (HSS) sheet metal parts fabricated by asymmetric V-die bending dies and trapezoid sheet. The proposed strategy uses an elementary bending theory to develop a basic model to predict the position deviation of bending point of asymmetric V-die bending process and to test its viability for a trapezoid sheet. Accordingly, a series of experiments obtained good agreement with the calculations. The effects of die radius on deviation in the bending point were experimentally tested to identify the behavior of position deviation in sheet metal bending processes. The experimental results show the important role of contact friction on deviation change; however, its value, i.e., friction coefficient, is always difficult to be determined in calculation. In conclusion, the interactive effects of process parameters are complex and show the important roles of die radius and sheet width on deviation change. The results of this study can be considered when developing process design guidelines for asymmetric processes in HSS sheets.

Study the Effects of Spring Back on Sheet Metal Bending using Mathematical Methods

In this study mathematical analysis of spring back was done for optimization of sheet metal bending process. The influence of sheet metal thickness, sheet metal type, friction, tool radius and tool shape on spring back for Aluminium, copper, mild steel and High strength steels, sheet metal have been used as variable to conducted this study. Since, the effects of each variable on the formation of spring back on sheet metal forming are investigated the following way. This empirical result shows that increasing sheet metal thickness from 0.8 mm to 4.5 mm the spring back is reduced 16% and 20.35%. When increasing of sheet metal strength spring back increases because spring back of the sheet should depend on the yield strength of the material. As the materials yield strength increase the spring back after un-loading condition also increases. The effects of material type as shows that, using Aluminium sheet metal instead of high strength sheet metals spring back is reduced by 56.%. Also, for decreasing of the tool radius leads reducing spring back. Spring back of deferential die 12% lower than edge bending die. In addition to these, if increasing the friction coefficient from 0.01 to 0.50 the spring back also increases by 52% because of increasing of friction force and this force generates higher amount of spring back. Thus the effects of material type, tool geometry, working condition and the thickness of sheet metal types were studied and investigated. Since, ultimately utilizing and compensation of tool is considered for prevention of spring back and optimizing of sheet metal bending process as well.

Application of Multivariate Adaptive Regression Splines to Sheet Metal Bending Process for Springback Compensation

An intelligent regression technique is applied for sheet metal bending processes to improve bending performance. This study is a part of another extensive study, automated sheet bending assistance for press brakes. Data related to material properties of sheet metal is collected in an online manner and fed to an intelligent system for determining the most accurate punch displacement without any offline iteration or calibration. The overall system aims to reduce the production time while increasing the performance of press brakes.

Influencing the Forming Limits in Air Bending Using Incremental Stress Superposition

High springback and limited forming limits of modern high strength steels are a big challenge in manufacturing engineering. Both aspects are crucial in sheet metal bending processes. Different modifications of the air bending process have already been developed in order to reduce springback and also to increase the forming limits of materials. The innovative process of incremental stress superposition on air bending, developed at the IUL, is an alternative to conventional processes. Studies of this new process alternative show a positive effect on the considerable reduction of the sheet metal springback and extension of forming limits. Using the principle of incremental stress superposition leads to several advantages compared to conventional bending processes like die bending, bending with an elastomer tool, or three point bending. The bending force and, therefore, the consumed energy during air bending with incremental stress superposition are much lower. This paper presents the new process alternative and shows the latest investigation results.

Position deviation and springback in V-die bending process with asymmetric dies

Novel finite element analyses and a series of experiments are performed to characterize high strength steel sheet metal parts fabricated by asymmetric V-die bending dies. The proposed strategy uses a finite element analysis of elasticity–plasticity to simulate asymmetric V-die bending process and to test its viability for friction contact processes. Accordingly, a series of experiments obtained good agreement with the numerical simulation. The effects of process parameters (e.g., lubrication (contact friction), material properties, and process geometries) on deviation in the bending point were experimentally tested to identify the main parameters of position deviation in sheet metal bending processes. Moreover, effects of springback phenomenon on bending defects and on the precision of an asymmetric bent component are discussed. The results of this study can be considered when developing process design guidelines for asymmetric processes in high strength steel sheets.

Analysis of the Potential of Incremental Stress Superposition on Air Bending

Springback and limited forming limits of modern high strength steels are a big challenge in manufacturing engineering. Both aspects are crucial in sheet metal bending processes. Different modifications of the air bending process have already been developed in order to reduce springback and also to increase the forming limits of materials. A new method (the incremental stress superposition on air bending) has been developed. Studies of this new process alternative show a positive effect on the springback behavior. In order to investigate the potential of this process a comparison with other already established bending processes have been carried out. A possible process control to extend the forming limits has also been investigated.

Application of Incremental Forming in Sheet Metal Bending Process

Based on the thought of incremental forming, a new kind of sheet metal bending process has been described and investigated in this article. The software of the control system for the specific machine is developed combining motion control card and servo motors. Both single point and multi-points bending are taken into consideration from experimental and finite element analysis. Curved sheet and hyperbolic sheet metal are examined through experiments to extend the application for more smoothed and complicated curved sheet metal. The effectiveness of the process to deal with complex curved sheet metal is shown by all the experiments.