Different factors can affect productivity and quality of knitted fabric produced on automatic knitting machines. For example, yarn input tension, cam setting and take down load can be mentioned. The interaction between these factors and their effect on loop length and the percentage of contribution of variables on final fabric quality and production efficiency is determined. It was observed from the results that the contribution of cast on modification has vital role in fabric quality and productivity improvement.. The main are power failure, maintenance, new design preparation, lubrication, and caston. The main aim of this thesis is to illustrate the contribution of Caston modification on productivity and quality. From the result obtained from calculation only from cast on modification the efficiency of the machine increased from 68.75% to 74%. There is 5.25% efficiency increment. Therefore, 3579 courses per day or 1,288,440 courses per year which is about 758 meter more fabric is produced compared to the casting the factories are following now. This research is done on cast on modification by replacing waste fabric feeding by direct knitting from the yarn and pulling down the loops formed during first knitting cycle toward the take down roller. It is achieved by using stiff steel wire of about 5mm in diameter and nylon threads. The metal rod should be removed after certain knitting cycle because it cannot pass between take down rollers without stopping the machine.