AUTOMATED OPERATIONAL SCHEDULING SYSTEM FOR MULTI-STAGE PRODUCTION: MATHEMATICAL MODEL AND SOFTWARE IMPLEMENTATION

The purpose of the study is to improve the efficiency of production areas of multi-stage production with the possibility of rational use of equipment capacity and stocks of WIP inventory in the operation conditions of the automated operational scheduling system. Features of the considered problem regarding operative calendar planning are: necessity of processing raw materials at several stages according to the flow chart; an array of the equipment which demands division of work into three periods for each party; availability of planned and unscheduled equipment downtime; necessity to complete set of orders from several suborders; availability of incomplete production in a warehouse; restrictions in order and timing of orders. In the work, the authors construct a mathematical model with the use of multidimensional matroids with structured elements in the construction of free time scale for equipment loading. The research was carried out for a metallurgical plant at the cold strip production site...

A System to Determine the Optimal Work-in-Progress Inventory Stored in Interoperation Manufacturing Buffers

Continuous cost reduction is a subject of interest for almost every production company. The cost reflects the competitiveness and sustainability of the business. Many company costs are linked to the effectiveness of production. One such cost is the work-in-progress (WIP) inventory cost. The present article deals with the design of a system for calculating the optimal WIP inventory stored in a manufacturing buffer, which, in the long term, provides the lowest costs. The main goal of the article is to design a new system that allows for the calculation of the optimal capacity of interoperation manufacturing buffers and thus the calculation of the optimal WIP inventory, which influences the lead time and cost. The newly designed system consists of algorithms that describe various steps, many of which use mathematical models. The individual blocks of algorithms are described, and the proposed system is verified and validated by simulation of the production line in the automotive production company.

Work-in-Progress Inventory Control Case Study in Lean Management

Increasing the rate of converting raw material into finished product and delivering it on time is a main driver for each manufacturing industry to achieve continuous improvement in its business operation. This case study demonstrates the improvement of the work-in-progress inventory in a non-lean company seeking to adopt lean management. Introducing the value stream mapping (VSM) lean technique to identify the waste in the current production operation. A selection of lean tools such as Kanban card, supermarket racking and one-piece flow are applied to control and monitor the WIP inventory after justification of the factors (process cycle time, production facilities layout and facilities capacity allocation) that influence the change from the current production operation situation.The construction of the current VSM had identified the major waste in WIP inventory handling in the final fabrication process. The fluctuation of WIP inventory has been resolved by the implementation of supermarket racking; therefore, an improvement base for WIP inventory control has been established. Throughout this study, the lean management concept had been fostered into the production floor team and will continue developing to the organization.

Strategic WIP Inventory Positioning for Make-to-Order Production with Stochastic Processing Times

It is vital for make-to-order manufacturers to shorten the lead time to meet the customers’ requirements. Holding work-in-process (WIP) inventory at more stations can reduce the lead time, but it also brings about higher inventory holding cost. Therefore, it is important to seek out the optimal set of stations to hold WIP inventory to minimize the total inventory holding cost, while meeting the required due date for the final product at the same time. Since the problem with deterministic processing times at the stations has been addressed, as a natural extension, in this study, we address the problem with stochastic processing times, which is more realistic in the manufacturing environment. Assuming that the processing times follow normal distributions, we propose a solution procedure using genetic algorithm.

Research on Production Control Mode of Manufacturing System Based on Neuroendocrine Hormonal Regulation

With the developing control and configuration pattern of modern manufacturing system, the complexity of manufacturing system is enlarged and the operating environment is filled with uncertainty. Under the influence of many uncertain factors, reducing delivery time, due-date performance and low inventory become the important goals of production enterprise. This paper presents a bio-inspired manufacturing system control model, combining the knowledge of manufacturing system, biological control and control system. The relationship between response time and production rate of manufacturing system with different capacity is analyzed, production capacity controller is designed using PI and PD, and the control strategy differences of production rate deviation and overshoot is also discussed. Finally, an optimized design for the parameters of a two-layer work-in-process (WIP) inventory controller is analyzed, with the reference to the neuroendocrine regulatory mechanism. The simulation analysis shows that in bio-inspired manufacturing system made of organic manufacturing cells, the shorter the response time of production capacity is, the faster its production rate responses. With the combination of two-layer WIP inventory controller and traditional PID production capacity controller, the production system is more responsive and the production offset and overshoot are small when the unexpected external demand changes of manufacturing system occur.

A Simulation Study Of Economic Production Quantity Lot Size To Kanban For A Single Line Production System Under Various Setup Times With Average Work In Process (WIP) Inventory Cost As Performance Metric

The Setup time variable was evaluated for the two systems (Kanban and EPQ) against the performance measure of average WIP inventory cost. EPQ outperforms Kanban on average WIP inventory cost at setup times less than 8 minutes. The research helped clarify for practitioners whether EPQ might be more suitable than Kanban for their given situations.