• Title/Summary/Keyword: Forming error

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Tendency Analysis of Shape Error According to Forming Parameter in Flexible Stretch Forming Process Using Finite Element Method (유한요소법을 이용한 가변스트레치공정 성형변수에 따른 성형오차 경향분석)

  • Seo, Y.H.;Heo, S.C.;Song, W.J.;Kim, J.;Kang, B.S.
    • Transactions of Materials Processing
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    • v.19 no.8
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    • pp.486-493
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    • 2010
  • A shape error of the sheet metal product made by a flexible stretch forming process is occurred by a various forming parameters. A die used in the flexible stretch forming is composed of a punch array to obtain the various objective surfaces using only one die. But gaps between the punches induce the shape error and the defect such as a scratch. Forming parameters of the punch size and the elastic pad to prevent the surface defect must be considered in the flexible die design process. In this study, tendency analysis of shape error according to the forming parameters in the flexible stretch process is conducted using a finite element method. Three forming parameters, which are the punch size, the objective curvature radius and the elastic pad thickness, are considered. Finite element modeling using the punch height calculation algorithm and the evaluation method of the shape error, which is a representative value for the formability of formed surface, are proposed. Consequently, the shape error is in proportion to the punch size and is out of proportion to the objective curvature radius and the elastic pad thickness.

A Study on Correction of the Gear Tooth Profile Error by Finish Roll Forming (전조가공을 이용한 기어의 치형오차수정에 관한 연구)

  • Lyu Sung-Ki;Uematsu Seizo
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.4
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    • pp.159-166
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    • 2005
  • This study deals with the correction of gear tooth profile error by finish roll forming. First, we experimentally confirmed that the tooth profile error is a synthesis of the concave error and the pressure angle error. Since various types of tooth profile errors appear in the experiments, we introduced evaluation parameters for rolling gears to objectively evaluate profile quality. Using these evaluation parameters, we clarified the relationship among the tooth profile error, the addendum modification factor (A. M. factor), and the tool loading force. We verified the character of concave error, pressure angle error, tool loading force and number of cycles of finish roll forming by using a forced displacement method. This study makes clear that tool loading force and number of cycles of finish roll forming are very important factors that affect involute tooth profile error. The results of the experiment and analysis show that the proposed method reduces concave and pressure angle errors.

A Study on the Concave and Pressure Angle Error of Gear Finish Roll Forming (기어전조의 기어 형상 및 압력각오차에 관한 연구)

  • Jang, J.H.;Kim, J.S.;Bae, H.J.;Uematsu, S.;Cho, S.H.;Lyu, S.K.
    • Journal of the Korean Society of Safety
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    • v.23 no.4
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    • pp.13-18
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    • 2008
  • This study deals with finish roll forming by forced displacement can be conceived as a method of eliminating errors in conventional form rolling under constant loads. This method produces a high-precision tooth profile by low-speed form rolling when a high rigid screw or cam is used at the pressurized section. Tooth profile is decided in the beginning of roll forming and ${\delta}_{max}$ mainly increases if the number of roll forming process is increased. Gear class is improved by one or two class after roll forming if the gear has convex type error and pressure angle error in KS 4 class. If the gear have concave type error and pressure angle error and pressure angle error, gear class is not improved in theory, but improved a little in practice. In the finishing roll forming, it inevitably yields both the concaving of tooth profile and plastic deflection of addendum of teeth. Experiments show that the concaving and the plastic deflection are successfully reduced, the accuracy of tooth profile reaches to KS 0 class.

Numerical and Experimental Study for Improvement of Formability in Flexible Forming Process (가변성형공정에서 성형성 향상을 위한 해석 및 실험적 연구)

  • Heo, S.C.;Seo, Y.H.;Kang, B.S.;Kim, J.
    • Transactions of Materials Processing
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    • v.21 no.7
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    • pp.432-440
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    • 2012
  • In this article, the design of the flexible forming process considering die shape compensation using an iterative over-bending method based on numerical simulation was conducted. In this method, the springback shape obtained from the final step of the first forming simulation is compared with the desired objective shape, and a shape error is calculated as a vector norm with three-dimensional coordinates. The error vector is inversely added to the objective surface to compensate both the upper and lower flexible die configurations. The flexible die shapes are recalculated and the punch arrays are adjusted according to the over-bent forming surface. These iterative procedures are repeated until the shape error variation converges to a small value. In addition, experimental verification was conducted using a 2000-kN flexible forming apparatus for thick plates. Finally, the configuration of the prototype obtained from the experiment was compared with the numerical simulation results, which had springback compensation. It is confirmed that the proposed method for compensating for the forming error could be used in the design of flexible forming of thick-curved plates.

Application of Machine Learning to Predict Web-warping in Flexible Roll Forming Process (머신러닝을 활용한 가변 롤포밍 공정 web-warping 예측모델 개발)

  • Woo, Y.Y.;Moon, Y.H.
    • Transactions of Materials Processing
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    • v.29 no.5
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    • pp.282-289
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    • 2020
  • Flexible roll forming is an advanced sheet-metal-forming process that allows the production of parts with various cross-sections. During the flexible process, material is subjected to three-dimensional deformation such as transverse bending, inhomogeneous elongations, or contraction. Because of the effects of process variables on the quality of the roll-formed products, the approaches used to investigate the roll-forming process have been largely dependent on experience and trial- and-error methods. Web-warping is one of the major shape defects encountered in flexible roll forming. In this study, an SVR model was developed to predict the web-warping during the flexible roll forming process. In the development of the SVR model, three process parameters, namely the forming-roll speed condition, leveling-roll height, and bend angle were considered as the model inputs, and the web-warping height was used as the response variable for three blank shapes; rectangular, concave, and convex shape. MATLAB software was used to train the SVR model and optimize three hyperparameters (λ, ε, and γ). To evaluate the SVR model performance, the statistical analysis was carried out based on the three indicators: the root-mean-square error, mean absolute error, and relative root-mean-square error.

Statistical Study on Correlation Between Design Variable and Shape Error in Flexible Stretch Forming (가변스트레치성형 설계변수와 성형오차의 상관관계에 대한 통계적 연구)

  • Seo, Y.H.;Heo, S.C.;Kang, B.S.;Kim, J.
    • Transactions of Materials Processing
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    • v.20 no.2
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    • pp.124-131
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    • 2011
  • A flexible stretch forming process is useful for small quantity batch production because various shape changes of the flexible die can be achieved conveniently. In this study, the design variables, namely, the punch size, curvature radius and elastic pad thickness, were quantitatively evaluated to understand their influence on sheet formability using statistical methods such as the correlation and regression analyses. Forming simulations were designed and conducted by a three-way factorial design to obtain numerical values of a shape error. Linear relationships between the design variables and the shape error resulted from the Pearson correlation analysis. Subsequently, a regression analysis was also conducted between the design variables and the shape error. A regression equation was derived and used in the flexible die design stage to estimate the shape error.

Investigation of Shape Parameters for a Profile with Variable-cross Sections Produced by Flexible Roll Forming (가변롤성형 공정을 이용한 단면이 가변하는 프로파일의 형상변수 분석에 관한 연구)

  • Park, J.C.;Cha, M.W.;Kim, D.G.;Nam, J.B.;Yang, D.Y.
    • Transactions of Materials Processing
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    • v.23 no.6
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    • pp.369-375
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    • 2014
  • Flexible roll forming allows profiles to have variable cross-sections. However, the profile may have some shape errors, such as, warping which is a major defect. The shape error is induced by geometrical deviations in both the concave zone and the convex zone. In the current study, flexible roll forming was modeled with FE simulations to analyze the shape error and the longitudinal strain distribution along the flange section over the profile. A distribution of analytically calculated longitudinal strains was used to develop relationships between the shape error and the longitudinal strain distribution as a function of the defined shape parameters for the profile. The FE simulations showed that the shape error is primarily affected by the deviations between the distribution of analytically calculated longitudinal strain and the longitudinal strain distribution of the profile. The results show that the shape error can be controlled by designing the shape parameters to control the geometrical deviations at the flange section in the transition zones.

Study on the Error Compensation in Strain Measurement of Sheet Metal Forming (박판성형 변형률 측정 오차보정에 관한 연구)

  • 한병엽;차지혜;금영탁
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.05a
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    • pp.270-273
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    • 2003
  • The strain measurement of the panel in the sheet metal forming is essential work which provides experimental data needed to die design, process design, and product inspection. To measure efficiently the complex geometry strain, the 3-dimensional automative strain measurement system, which has high accuracy in theory, but has some 3∼5% errors in practice, is often used. The object of this study is to develop the error compensation technology to eliminate the strain, errors resulted when formed panels are measured using an automated strain measurement system. To achieve the study object, the position error calibration method correcting coordinates of the grid node recognized by a camera using error functions is suggested. Then the position errors were found by calculating the difference in the position of the cube node between real coordinates and measured coordinates in toms of node coordinates and the error calibration equations were derived by regressing the position errors. In order to show the validation of the suggested position error calibration method, finite element analysis and current calibration method was performed for the initial-blankformed.

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Study on the Compensation of Strain Measurement Error in Sheet Metals (박판 변형률 측정 오차의 보정에 관한 연구)

  • 차지혜;금영탁
    • Transactions of Materials Processing
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    • v.13 no.7
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    • pp.594-599
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    • 2004
  • In the sheet metal forming operations, the strain measurement of sheet panel is an essential work which provides the formability information needed in die design, process design, and product inspection. To measure efficiently complex geometry strains, the 3-dimensional automative strain measurement system, which theoretically has a high accuracy but practically has about 3~5% strain error, is often used. For eliminating the strain error resulted in measuring the strains of formed panels using an automated strain measurement system, the position error calibration method is suggested, which computes accurate strains using the grids with accurate nodal coordinates. The accurate nodal coordinates are calculated by adding the nodal coordinates measured by the measurement system and the position error found using the multiple regression method as a function of the main error parameters obtained from the analysis of strain error in a standard cube. For the verification, the strain distributions of square and dome cups obtained from the position error calibration method are compared with those provided by the finite element analysis and ASAME.