Design of equipment for manufacturing helically-coiled tubes and its automatic control system

A simple but accurate method for manufacturing helically-coiled tubes was proposed, and the manufacturing equipment and its automatic control system were designed. The main geometric parameters of helically-coiled tubes are determined exactly based on the theorem "three given points determine a circle" and the definition of the helix angle of helically-coiled tubes. The finished equipment primarily consists of the mechanical noumenon and the automatic control system. In this design, three die wheels A, B and C made of wearable steel are used to adjust the positions of the raw materials in order to determine the product geometric parameters expected in advance. Three servo motors working with precision linear sliding rheostat and PID closed-loop control functions drive the three wheels mentioned above in different directions. The parameter e determining the base circle diameter of coil diameter is obtained by adjusting the position of wheel C up and down, and the parameter e' determining the helix angle is obtained by adjusting the relative distance between wheel B and wheel A in the helical axis direction. The whole manufacture process is automatically controlled by a piece of software compiled by Visual Basic, including the processes of baiting and cutting, installing wheels and calibration, motor controlling, bending tubes, and product inspection etc. The design parameters for manufacturing helically-coiled tubes using SUS304 stainless steel or other similar materials are tube diameters of 6-50 mm, coil diameters of 100-700 mm and helical pitches of 10-50 mm. A total of fourteen finished products were selected as random samples for inspection. The result showed that the average working velocity was about 0.6 m/min; the root mean square errors (RMSE) of coil diameter and helical pitch of finished products were 3.85 mm and 0.97 mm, respectively; and the maximum roundness error of tubes was only 0.09 mm.