Keywords: manufacturing process, conveyor, simulation, optimization, design and analysis of experiments.

Chain conveyors constitute one of the types of material handling equipment in textile spinning production. There are many phases in the spinning production process. To prepare the fiber for spinning, very short fibers and foreign matter are removed, and the loose, fluffy fibers are then formed into a long sheet that is wound into a lap, which is fed into carding machine that untangles it into single fibers and forms into a sliver. During this process operators constantly monitor their machines, checking the movement of the fiber, removing and replacing cans of sliver, repairing breaks in the sliver, and making minor repairs to the machinery. With the aid of overhead chain conveyor, cans of sliver are transported from carding machines to drawing machines that combine slivers into roving. Robots or human material handlers are used in loading and unloading the cans while the conveyor is continuously moving at a constant speed. The main function of the conveyor system is to transfer empty cans from the drawing machines to the carding machines and deliver full cans of sliver from the carding to the drawing machines. When a full can passes the available drawing machine a robot automatically lifts it from carrier and loads it on the drawing machine. Similarly when a carrier with an empty can passes the carding machine a robot lifts a can from carrier and places it at the carding machine. The main point is that a conveyor system links the two processes together. As a linkage mechanism it is required to effect a smooth transformation of the output flow of one process area into the input flow of the next. However random product processing time and random changes in the product flow are the main contributors to the variation of the spinning production. In consequence the following undesirable situation often arises:

• at the loading points no vacant carriers will be coming by for some time just when vacant carriers are required;
• at the unloading points, no cans will be coming by for some time just when cans (full or empty) are required.

The goal of the present research was to develop a simulation model of the overhead monorail conveyor system and statistical methods for the analysis and multi-objective optimization of the manufacturing process. In particular we discuss problems involving functional dependence of the chain pull, drive power, time in system, length of queues and waiting times from the speed of chain, carrier steps and operational capacity of the served equipment.

We show how simulation and statistical analysis influence the design methodology of the chain accumulating conveyor system Aspects of experimental design in simulation and multiple response optimization of such systems are discussed. The report phase of this work is the determination of the optimum speed of the conveyor, the step of carriers and the total capacity of the technological machines for the criteria of minimum drive power, the time in system, the lengths of queues etc. No substantive published work has been located which deals with these fundamental issues.

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