Four-Bar Linkage Mechanism in Papermaking and Its Replacement by Direct Servo Drive Technology in Roll to Sheeting Lines in a Paper Mill—Converting House

Till the 1950s & till Grashof law was applied, Roll to sheeting Equipment manufacturers were not able to develop Dual rotating Knives sheeters. Till then, it was either Guillotine shears with production speed limitations or a Single rotating knife with output defects. Dual rotary knife machines became successful only with the Adaptation of Four-bar linkage mechanisms (Double Drag link) for avoiding parallelogram defects, for achieving diagonal length and cut length accuracies of <  ±0.5 mm of the set lengths, and for achieving higher production speeds at 100 mtrs/min. New servo drive technologies in both AC and DC saw the emergence of machines with more accurate performance, at higher productivity, and the highest machine uptime availability.

This paper starts with the application—the principle of operation, the machine requirements with examples and method of implementation of the four-bar linkages employed, and the performances achieved including a brief on Mechanical transmission elements earlier employed with few illustrations. The paper also details the development and evolution of Low inertia DC Motor servo drive technology in the 1970s, finding its best application in the Sheeting equipment. Subsequent developments in AC servo drive facilitated extensive adaptation in the application with the giant strides AC drives and motion control algorithms post the millennium year 2000 AD. This in conjunction presents the Feed Forward control algorithm deployed in the application also is briefed including comparison with other algorithms with the main advantage of acceptance of Low MOI prime movers and higher MOI mismatch going up to 20:1, i.e., load MOI: Prime mover MOI in such applications. The effective use of technology had yielded the best accuracies to the tune of ±0.38 mm in a cut length, diagonal lengths with increased productivity rates to 350 mtrs/min.

The paper also compares various Cam profiles available for the application including trapezoidal, trigonometric, and quasi sinusoidal options Electro-mechanically supported with illustrations present to the audience for effective selection of apt profile. Links to videos depicting the application with a modern state of technology in Fine Paper, Paper board, and Corrugation, Steel industrial sectors are included in the paper.