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Recently, a new manufacturing method called Origami-forming is developed, based on traditional Origami approach. In particular, the new method follows the same steps as Origami, applying for wider rank of material (soft and hard material such as aluminum, high tensile steel, etc), and folding by a reconfigurable robot system. This method is suitable for high-variety low-volume, because of the unnecessary of die and punches. However, achieving the goal is still a challenge for researchers. Bending of hard material causes springback, increase risk of cracking, and require large pressure. In this study, by mimicking from the traditional Origami that we should make crease line before folding, bending method by grooving at the bend-line is proposed to reduce the necessary force to constraint the blank and get a high limit of bending. Firstly, several shapes of groove are compared: half-circle, gauss distribution, half-haxegon and rectangle. Then based on the comparison, the optimization of the shape is investigated. Lastly, handling system is considered to find an effective way of grasping the blank.Copyright © 2015 by ASME

In order to produce the origami-based foldable structures, designers have to determine the industrial material type, the geometry of structures and dimensions etc. These structures may be deformed in proportion to the load at the first step, and show the property of spring. Next step, the deformation will become non-linear conduct. However, deformation mechanism in these structures cannot be estimated yet well. So, appropriate design for shock absorbers cannot be done easily. In this paper, by experiments and FEM analysis, we present the theory of deformation mechanism on origami based foldable structures, which are made of resin or metal, have many types of dimensions and geometry. This theory shows not only the relationship between dimensions of structures and spring constant but also the relationship between material constant and the load to fold structures.

In our previous study, we calculated the time course of parison length in the parison formation stage, but it could predict only the parison area swell. The next target in our study is to calculate the parison diameter and thickness swell. Annular extrudate swell simulation is necessary for the understanding of various kinds of swelling ratios in blow molding. We have examined three kinds of swells (outer diameter, thickness, and area swells) obtained from simulation results of annular extrudate swell, using the Giesekus model, and have developed a method of predicting parison outer diameter and thickness swell values. The predicted values of parison outer diameters are discussed in comparison with experimental data, and reasonable results are obtained by the proposed method. This prediction method could also be applied to the parison formation process using a parison controller. As a result, it is possible to predict approximately the whole process of parison formation by numerical simulation.

The simulation of the parison formation process in blow molding has been studied. The flow field was divided into two regions, namely, the extrudate swell region near the die lip and the parison formation region after the exit swell. In the swell region, we predicted the swelling ratio and residual stress distribution for high Weissenberg numbers for steady planar swell using the 1-mode Giesekus model. In the parison formation region, the flow is assumed to be an unsteady unaxial elongational flow including drawdown and recoverable swell and is modeled using the 10-mode Giesekus model. We calculated the time course of parison length and thickness distribution, and compared the calculation results of parison length with experimental data. It was found that the predicted values agreed rather well with the experimental values. The calculation results could especially predict the shrink-back, which is the phenomenon where the parison length becomes shorter after the cessation of extrusion, and it was found that this was caused by the recoverable swell of the parison, which depends on the tensile stress generation in the die. Various flow rates and die geometries were studied and confirmed the reliability and usefulness of the method.

The shrinkage degree ξ of polymer products must be considered when the molds are at the stage of designing. On the calculation of ξ, the descending temperature ΔT of polymer products after molding process and α (the coefficient of thermal expansion) are necessary.It was found that α has the typical distributions at the various layers along the machine direction (MD) and the traverse direction (TD), especially under HDPE melts flow in the dies. Consequently, α distributions should be predicted for estimation of accurate ξ of HDPE products. In this study, we have investigated the experimental data of HDPE α distributions under extrusion process and calculated the strain distributions by polymer melts flow analysis using finite element method. The following results were obtained.(1) The measured data of α (MD) distributions correspond to the strain distributions which generate along the flow direction within the inner and the outer die.(2) The measured data of α (TD) distributions correspond to the strain distributions which generate along the θ direction within the inner and the outer die.(3) The measured data of α distributions in this study showed the correlation between the strain distributions much better than the shear stress distributions.

In the blow molding process, pellets are melted and pumped by a screw device into an accumulator. By plunger extrusion, the polymer melt flows into an annular die and emerges vertically downward to form a parison.The shape of the parison (diameter, thickness, length) should be controlled by setting the molding conditions (shape of annular die, flow rate, temperature, polymer properties, etc.) to make a successful blow molding process. Therefore, a method for predicting dimensions of the parison is necessary to research the best molding conditions.We performed numerical studies of polymer melt flows in several types of real annular dies using the finite element method. The constitutive model for polymer melts that we used was the Giesekus model.It was found that the relationship between the measured swelling ratio of parisons in these annular dies and the normal stress difference at the exit dies from analysis results could be expressed by a function. The function was independent of the geometry of the die in this study. This function may play an important role for the prediction of shape of parisons.