Showing papers by "Satoshi Kitayama published in 2017"

Multi-objective optimization of injection molding process parameters for short cycle time and warpage reduction using conformal cooling channel

Abstract: In this paper, cooling performance of conformal cooling channel in plastic injection molding (PIM) is numerically and experimentally examined. To examine the cooling performance, cycle time and warpage are considered. Melt temperature, injection time, packing pressure, packing time, cooling time, and cooling temperature are taken as the design variables. A multi-objective optimization of the process parameters is then performed. First, the process parameters of conformal cooling channel are optimized. Numerical simulation in the PIM is so intensive that a sequential approximate optimization using a radial basis function network is used to identify a pareto-frontier. It is found from the numerical result that the cooling performance of conformal cooling channel is much improved, compared to the conventional cooling channel. Based on the numerical result, the conformal cooling channel is developed by using additive manufacturing technology. The experiment is then carried out to examine the validity of the conformal cooling channel. Through numerical and experimental result, it is confirmed that the conformal cooling channel is effective to the short cycle time and the warpage reduction.

Multi-objective optimization of variable packing pressure profile and process parameters in plastic injection molding for minimizing warpage and cycle time

Abstract: Process parameters in plastic injection molding (PIM) such as the packing pressure, the melt temperature, and the cooling time have a direct influence on the product quality. It is important to determine the optimal process parameters for high product quality. In addition to the product quality, high productivity is required to plastic products. This paper proposes a method to determine the optimal process parameters in the PIM for high product quality and high productivity. A constant packing pressure during the PIM is conventionally used, but the variable packing pressure profile that the packing pressure varies in the packing phase is adopted as the advanced PIM. Warpage and cycle time are taken as the product quality and the productivity, respectively. Then, these are simultaneously minimized and the pareto-frontier between them is identified. Numerical simulation in the PIM is so intensive that a sequential approximate optimization using radial basis function is adopted. It is found through the numerical result that the variable packing pressure profile can improve both the warpage and the cycle time, compared with the conventional PIM approach. In order to examine the validity of the proposed approach, the experiment is carried out. It is confirmed through the numerical and experimental results that the proposed approach is valid for minimizing the warpage and the cycle time.

Optimization of blank shape and segmented variable blank holder force trajectories in deep drawing using sequential approximate optimization

Abstract: Blank holder force (BHF) is one of the important process parameters for successful sheet metal forming. Variable blank holder force (VBHF) that the BHF varies through the forming process is recognized as an advanced forming technology. It has also been reported that segmented VBHF (S-VBHF) is valid to a complex shape forming, but the optimal S-VBHF trajectories are rarely discussed and used. In addition to BHF, blank shape has an influence on the product quality. The blank shape minimizing the earing is still an important issue in sheet metal forming. Simultaneous optimization of both S-VBHF trajectories and blank shape is one of the crucial issues in industries. This paper proposes a method to simultaneously optimize both the segmented VBHF trajectories and the blank shape. Numerical simulation in sheet metal forming is so intensive that a sequential approximate optimization (SAO) using a radial basis function (RBF) network is adopted for the simultaneous design optimization. Based on the numerical result, the experiment using the AC servo press (H2W300, Komatsu Industry Corp.) that can conduct the optimal S-VBHF trajectories is carried out. It has been confirmed from the numerical and experimental result that the proposed approach is valid.

Numerical and experimental case study on simultaneous optimization of blank shape and variable blank holder force trajectory in deep drawing

Abstract: This paper shows a case study for a simultaneous optimization of blank shape and variable blank holder force (VBHF) trajectory in deep drawing, which is one of the challenging issues in sheet metal forming in industry. Blank shape directly affects the material cost. To reduce the material cost, it is important to determine an optimal blank shape minimizing earing. In addition, VBHF approach is recognized as an attractive and crucial technology for successful sheet metal forming, but the practical application is rarely reported. To resolve these issues, the simultaneous optimization of blank shape and VBHF trajectory is performed. First, the experiment to identify the wrinkling region is carried out. Based on the experimental results, the finite element analysis (FEA) model is developed. The validity of the FEA model is examined by using the FLD. Numerical simulation in deep drawing is so intensive that a sequential approximate optimization (SAO) using a radial basis function (RBF) network is used for the numerical optimization. Based on the numerical result, the experiment using the AC servo press is carried out. It is found from the experimental results that the successful sheet metal forming is performed. In addition, it is confirmed from the numerical and experimental result that both the material cost and the forming energy are simultaneously reduced by using the design optimization technique.

Simultaneous optimization of blank shape and variable blank holder force of front side member manufacturing by deep drawing

Abstract: This paper presents a method to determine an optimal blank shape minimizing earing for a front side member. In addition, variable blank holder force, meaning that the blank holder force (BHF) varies through punch stroke, is adopted. Blank shape directly affects the material cost, and it is important to determine an optimal blank shape minimizing earing that is trimmed out. BHF also have an influence on the product quality. Large BHF leads to tearing, whereas small BHF results in wrinkling. Variable BHF (VBHF) approach is recognized as one of the advanced manufacturing technologies, but it is difficult to determine the optimal VBHF for successful sheet metal forming. To determine the optimal blank shape and VBHF simultaneously, design optimization is performed. Numerical simulation in sheet metal forming is so intensive that a response surface approach is valid. In particular, a sequential approximate optimization that the response surface is repeatedly constructed and optimized is used to determine the optimal blank shape and VBHF. Front side member provided from NUMISHEET 2011 (BM3) is used for the numerical simulation. It is found from the numerical result that the proposed approach can drastically reduce the earing. In addition, the maximum thinning is much improved, compared with other results reported in NUMISHEET 2011.

Design optimization of initial blank shape and segmented variable blank holder force trajectories in deep drawing

Abstract: Blank shape minimizing earing, which is trimmed off after forming, is an important issue in sheet metal forming. In addition, blank holder force (BHF) have an influence on the product quality. Recently, variable BHF (VBHF) that the BHF varies through punch stroke is recognized as one of the advanced forming technologies. Furthermore, segmented VBHF will be valid to complex shapes for successful sheet metal forming. However, the optimal segmented VBHF trajectories and the optimal blank shape minimizing the earing are unknown in advance, and consequently the trial and error method is widely used to determine them. To resolve above issues, in this paper, a simultaneous design optimization of the blank shape and the segmented VBHF trajectories is performed. Numerical simulation in sheet metal forming is so intensive that a sequential approximate optimization using a radial basis function network is adopted to determine them. Based on the numerical result, the experiment using AC servo press is carried out. It is confirmed from the numerical and experimental result that the proposed approach is valid.

Multi-objective optimization of process parameters in plastic injection molding using variable pressure profile

Abstract: Process parameters in plastic injection molding (PIM) such as packing pressure, melt temperature and cooling time have a direct influence on the product quality and it is important to determine the optimal process parameters for the high product quality as well as the high productivity. This paper proposes a method to determine the optimal process parameters in the PIM for high product quality and high productivity. In particular, the variable packing pressure profile that the packing pressure varies through the packing phase is adopted as the advanced PIM. Warpage and cycle time are taken as the product quality and the productivity, respectively. Therefore, a multi-objective optimization of the process parameters using the variable packing pressure profile is performed. Numerical simulation in the PIM is so intensive that a sequential approximate optimization using radial basis function is adopted. It is found through the numerical result that the proposed packing pressure profile can improve both the warpage and the cycle time. Based on the numerical result, the experiment is also carried out. It is confirmed through the numerical and experimental result that the variable packing pressure profile is an effective approach for the warpage reduction and the short cycle time.

Optimum design of cross-sectional sizes for thin steel plate columns considering buckling using the finite strip method and evolutionary computing

Abstract: An optimum design method for determining the cross-sectional sizes of thin steel plate columns used for steel framed house was developed to maximize their buckling strength under a constraint of constant volume using evolutionary computing and cold forming. Buckling analysis was performed by finite strip method (FSM) that can analyze the buckling loads of local, torsional, and total buckling within less computational time. Differential evolution (DE) was used for the optimization algorithm because it is a fast and reliable method for non-linear, non-convex, and multimodal optimization problems. In this research, an optimum design method is proposed, which combines DE and FSM to achieve an efficient global optimum design considering comprehensive buckling modes. This method was applied to overcome the optimum design problems of the thin steel plate columns with a lip channel cross-section. Normal axial compression capacity (Nc) of the column under a constant volume was maximized by considering design variables such as web height, flange width, and lip length of the cross-section. The search performance of the optimization method was evaluated by obtaining an objective function (1/Nc), which was calculated at the lattice points of the design variables. The optimum design point obtained by the optimization method included a global minimum point of the objective function surface, hence ensuring the validity of the proposed method. Furthermore, the optimum design problem was solved under the deformation constraint by considering connection to the wall panels for the column length of 1000 mm, 2000 mm, and 3000 mm. Optimum designs with the open profile cross-section was obtained for all the abovementioned column length. The optimum designs obtained by the proposed method can be used for practical purposes because of their open profiled cross-section and can be produced by cold forming. 1 座屈解析に進化計算を適用した 薄板軽量形鋼の断面寸法最適設計 坂本 二郎*1,小林 佳介*2,北山 哲士*3,清水 信孝*4 Optimum design of cross-sectional sizes for thin steel plate columns considering buckling using the finite strip method and evolutionary computing Jiro SAKAMOTO*1, Keisuke KOBAYASHI*2, Satoshi KITAYAMA*3 and Nobutaka SHIMIZU*4 *1 Institute for Frontier Science Initiative, Kanazawa University Kakuma-machi, Kanazawa-shi, Ishikawa 920-1192, Japan *2 Graduate School of Natural Science and Engineering, Kanazawa University Kakuma-machi, Kanazawa-shi, Ishikawa 920-1192, Japan *3 School of Mechanical Engineering, Kanazawa University Kakuma-machi, Kanazawa-shi, Ishikawa 920-1192, Japan *4 Nippon Steel and Sumitomo Metal Corporation 20-1 Shintomi, Futtsu-shi, Chiba 293-8511, Japan Received: 16 August 2017; Accepted: 19 September 2017