Takashi Jimma

Experiments into the cold roll-forming of straight asymmetrical channels

Abstract Methods of eliminating distortion such as twisting and curving in the forming of straight asymmetrical channels has been experimentally researched, using a tandem mill of eight stands, the twist forming stand of which has been specially designed to avoid the trouble of making different asymmetrical rolls for different asymmetrical channels. The correction effects of employing: an exit straightener; roll-pressure adjustment; transverse shift of the rolls; over-bend rolls; and a twist-forming stand were explored. The combination effects of each correction method were examined, and the correction mechanism established.

Effect of Rigidity of Die and Press on Blanking Accuracy of Electronic Machine Parts

Abstract Blanking accuracy is decided by the relative displacement of an appear die to a lower die in the blanking. Deformation of a die-set subjected to an accentric load in a press is analysed, and the bending moment M and the lateral force Q acting on the end of each guide post are expressed by the inclination θ and the lateral displacement DX of the upper die. In the experiment, a die-set of sub-guide construction is installed on a 1250kN straight side frame press and 100kN C-type frame press, and θ DX are measured user static loading and dynamic loading of 100sdm. The calculated M and Q using the measured θ and DX show that the M and Q acting on the guide post end are smaller on the straight side frame press than on the C-type frame press though the capacities of both presses are almost the same. The analytical method proposed in this paper can be used in the selection of a press suitable to a given die set and a given accentric load.

On high speed precision blanking of IC lead-frames using a progressive die

Abstract The factors affecting the dimensional accuracy of blanked IC lead-frames are discussed. Attention is focussed on the elimination of the residual stress in the material caused by roll-slitting. Improvement in the designing and manufacturing of the blanking tool is explained and the mechanism of vibration of the stripper in high-speed blanking is analyzed. A high speed precision press that has been developed in Japan is introduced. The effects of blanking conditions such as tool clearance, strip-holding force, lead-shape, and order of blanking are explained, using a newly proposed mechanical model.

Deep drawing of double cylindrical shells

Abstract Using the complex-potential method, an analytical technique in hydrodynamics, a plane-strain velocity field in the flange region of a double cylindrical shell is calculated theoretically: two sinks of equal strength are set at the center of each circular die cavity. Blank shapes are determined theoretically from the velocity field to obtain double cylindrical shells with flanges of constant width. Experimentation is carried out on cold-rolled steel sheet (SPCE) for three different punch intervals. It is found that: (i) the theoretical streamlines in the flange region are in good agreement with experimental ones; (ii) there exists an optimal punch interval — of about 1.8 times the punch diameter — which gives the deepest shell, the height of which is about half of the punch diameter (iii) the optimal blank-width for obtaining the deepest shell is 2.1–2.2 times the punch diameter; (iv) the above conclusions (i)–(iii) will also hold for other types of double-bowl shells in which twin non-circular shells are joined together.

Elimination of distortion near the cut-off edges of cold roll-formed large thick channels

Abstract Methods for eliminating the distortion of the cut-off flange edges of a steel channel-section of 4.5 mm wall thickness and 75 mm flange height are experimentally researched, using a punch-die apparatus or press-rolls. The principle of the methods is to compress the flange edge and cause new plastic deformation there, so that the residual stress which occurred during the cold rollforming forming process re-distributes, with reduction of elastic recovery during the subsequent dimensional length-cutting operation. Prototype production tests have been carried out and high accuracy products have been obtained.

Development in Cad for Cold Roll Forming

In order to estimate the number of roll passes necessary to form the light gage steels for general structure, relation between the shape factor and the number of roll passes for various sections is investigated by arranging the data collected from several companies. We can obtain a good relation for symmetrical, asymmetrical and wide profile section, and optimum downhill curve and optimum downhill height for pipes are obtained. Furthermore, allotment of roll bend angle at any stage was carried out under the hypothesis that the locus of the edge of the section on the horizontal plane was the modified cubic curve. The roll flower for deck plates, keystone plates and pipes designed by these data base agreed well with actual roll drawing.

Effect of bend-corner of lead on blanking accuracy of IC leadframe

Abstract An IC leadframe which is one of the important electronic machine parts is mass-produced using a progressive blanking die. As simulation of the IC leadframe, an L-shaped cantilever of 0.25mm thick and 0.5mm width is blanked and the influence of bend-corner on the accuracy of the product is discussed. The mechanical model (ref. 1) is used for explaining the accuracy. Lateral and vertical deflection and twist of the L-shaped lead model are explained as the result of the elongation and shrinkage along the blanked contour. The influence of the blanking order, corner radius, tool-clearance and strip-holding force on the blanking accuracy is made clear.

Deep Drawing of Shells Having Slopes in the Base

Abstract A deep drawing process of shells having two couples of slopes in the base is investigated as a model for three-dimensional sheet forming processes. The deformation behavior of rectangular blanks is experimentally examined in detail by using five punches having different shaped bases. Furthermore, a simple, plane-strain deformation field (no change in thickness) in the flange and the combination of simple shear and elongation in the inclined side walls are assumed to approximate the mode of deformation of the blanks. Based on this model, the strain distributions of the finished shells are predicted by the use of an energy method, and the degree of wrinkling is evaluated by the amount of the overlapping material along the ridges of the punches. The validity of this simulation method is discussed by comparing the experimental and calculated results.