Vol.5 No.3 2012

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Research paper : Spinning process using robot technology (H. Arai)−151−Synthesiology - English edition Vol.5 No.3 (2012) value, the material is pressed onto the rotating mandrel. Meanwhile, the roller is controlled by feeding at a constant speed in the direction parallel to the rotation axis of the mandrel. The roller moves along the mandrel to press the material firmly against the mandrel. As a result, a product that has the same noncircular shape as the mandrel can be fabricated (Fig. 2).Initially, the roller was driven by ball screws in the spinning machine shown in Fig. 3 in our experiment. However, in forming the noncircular shape, it was necessary to move the roller in the radial direction very quickly along the surface of the mandrel. Therefore, we developed a new spinning machine where the roller was driven directly by linear motors (Fig. 4).[4] Since the responsivity to force control is high and the roller follows the mandrel shape quickly, the time required for forming can be greatly reduced. Also, shapes with noncircular cross sections can be formed by open-loop force control without using a force sensor.In synchronized spinning,[5] the forming roller is numerically controlled by synchronizing the roller with the rotational angle of the workpiece. The spindle is driven by a servo motor in which the rotational angle can be controlled. The spinning roller is moved back and forth in the radial direction according to the rotational angle of the workpiece, and the roller is moved so that the contact point between the roller and the workpiece tracks the desired cross-sectional form. The cross-sectional form is changed along the axial direction to form the entire workpiece into the desired shape. In this method, a noncircular cross-sectional shape can be formed without using a mandrel. This is particularly effective in forming a hollow tube with a noncircular cross section that is difficult to remove from the mandrel after forming. A prototype of a two-roller machine (Fig. 6) suitable for pipe forming by synchronized spinning was also developed.A prototype of the practical spinning machine for noncircular shapes was jointly developed with Daitoh Spinning Co., Ltd., a specialist manufacturer of spinning machines (Fig. 7, Table 1).[6] Both force-controlled spinning and synchronized spinning can be performed with this machine. Balanced-attraction linear motors, which cancel the magnetic attraction force between the iron-core coil and two magnetic track components, were employed to realize both increased propulsion and reduced friction. Steel sheets of 2 mm thickness and workpieces with diameters of 400 mm could be formed. Since its development, the machine Pushing force controlVelocity controlSpindle rotationSpinning rollerMaterialMandrelBall screwMaterialReduction gearMotorMotorMotory axisx axisForce sensorRollerMandrel Desired cross sectionDisplacementRadial directionSpinning rollerSpindle rotationCross section of blankReciprocal motionx Fig. 3 Experimental spinning machineFig. 5 Forming of non-circular shape by synchronized spinningFig. 2 Forming of non-circular shape by force-controlled spinningFig. 4 Linear motor driven spinning machine (experimental) and product sampleshttp://staff.aist.go.jp/h.arai/linspin_j.html

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