Design and Development of Coupling for Unequal Torque System

Abstract

The problems occurs at the steel industries, as the overall subject of this paper is the frequent failure of output shaft of gear motor at the pay-off reel and design and development of new type of coupling which will operates according to the situation of the nature of the rotation of pay-off reel rotation and the nature of the rotation of the 4HI cold rolling mill and which will perform efficient working under maximum torque condition without fail. As the mechanism used in the coupling is a ratchet pawl mechanism which work is to provide only one directional rotation and restrict the other. Also the use of spring loaded inserts to, which when reverse motion required, mechanism to engage the coupling hence the newly designed coupling is best suitable as per the nature of the rotation of the pay-off and 4HI cold rolling mill. Keywords: Pay-off reel, 4HI cold rolling mill, Gear motor, Coupling, Ratchet and pawl mechanism. I. Introduction The gear motor is used in cold rolling mill to give motion to the Pay-off reel which is movable with automatic guide table also un-wrapping the coil and the beginning of the process. Pay-off is the standby unit to reduce feeding time of the coil to the cold rolling mill. A cold rolling mill, also known as a reduction mill or mill, has a common construction independent of the specific type of rolling being performed. Cold rolling occurs with the metal below its recrystallization temperature (usually at room temperature), which increases the strength via strain hardening up to 20%. It also improves the surface finish and holds tighter tolerances. Commonly cold- rolled products include sheets, strips, bars, and rods, these products are usually smaller than the same products that are hot rolled. Because of the smaller size of the work pieces and their greater strength, as compared to hot rolled stock, four-high or cluster mills are used. Cold rolling cannot reduce the thickness of a work piece as much as hot rolling in a single pass. Cold-rolled sheets and strips come in various conditions: full-hard, half-hard, quarter-hard, and skin-rolled. Full-hard rolling reduces the thickness by 50%, while the others involve less of a reduction. Skin-rolling, also known as a skin-pass, involves the least amount of reduction: 0.5-1%. It is used to produce a smooth surface, a uniform thickness, and reduce the yield point phenomenon. It is also used to break up the spangles in galvanized steel. Skin-rolled stock is usually used in subsequent cold-working processes where good ductility is required. Other shapes can be cold-rolled if the cross-section is relatively uniform and the transverse dimension is relatively small. Cold rolling shapes requires a series of shaping operations, usually along the lines of sizing, breakdown, roughing, semi-roughing, semi-finishing, and finishing. If processed by a blacksmith, the smoother, more consistent, and lower levels of carbon encapsulated in the steel makes it easier to process, but at the cost of being more expensive. II. Force analysis of shaft of gear motor The shaft of gear motor goes failure at the weakest section due to overloading, a tangential load act by the metal sheet i.e. torque of cold rolling mill that comes over the Pay-off reel up to 30000 Nm, self-torque 1281 Nm, and bending loading. Also it was found that casing of gear motor goes failure, i.e. it broke. The Gear motor is of 5.5KW and 41 rpm and that of Cold rolling mill driving motor is of 1000KW and initial rpm of motor is 200mpm i.e. meter per minute. The shaft of gear motor goes failure in duration of 1-2 months and each motor cost up to 60,000 Indian rupees. Due to periodic failure of gear motor, company changed the gear motor with separate gear box and motor. One of the reasons of failure is lack of concentration of worker while working. In Continuous process industry many types of roll are used for various applications; however process rolls used are classified in to two as working & conveying. Working rolls are used for changing the product being process. This included cold rolling mill, hot rolling mill rolls used for reduction of sheet thickness & shape. Printing press rolls used for transferring pattern to product. Corrugation rolls used for changing the profile of sheet. Conveying rolls are mainly having application of transferring product from one place to other. This type rolls are smaller diameter and are generally non driven to large diameter used for transferring sheets, paper, and textile products in continuous process industry. The gear motor is used in pay-off reel to wound the metal coil, that motor is connected with Pinch roll of pay-off reel by claw coupling. One lever provided for