Abstract
The lean manufacturing concept is a systematic minimization of waste and non-value activities in production processes introduced by the Toyota production system. In this research, lean manufacturing is implemented in a cement production line. Value Stream Mapping (VSM) is applied to give a clear picture of the value chain in cement production processes and to highlight the non-value-added in the shop floor. To begin, the existing VSM is constructed based on the information and data gathered during visiting and observing the manufacturing process in the firm. As a result, the excess inventory between workstations was identified as a major waste generation, hence, the proposed VSM conducts further improvement and makes action plans to alleviate the unwanted activities. Then, the takt time to ensure smooth material flow and to avoid any occurring delay or bottleneck in the production line was figured out. The supermarket pull-based production control is suggested to be adopted in the future map. Two pull production strategies are selected in this case. The first is applying the Kanban system to control the level of inventory between workstations. The other is the CONWIP approach to control the amount of work in process to the entire production line. The outcome of the proposed models indicates a decrease of the none-value time from 23 days in the current state to about 4 and 2 days in Kanban and CONWIP systems respectively, so the CONWIP was suggested as most efficient. Some suggestions for further research are also mentioned.
Highlights
The cement industry is the most prominent building material industry, contributing greatly to the global and national economy and growth
It can be seen that the longest value of lead-time is about 23 days in the push production system, while in the proposed maps they are about 4 and 2 days for Kanban and Constant Work In Process (CONWIP) approaches respectively
The comparative results of non-value times in the cement production line for the proposed future maps is decreased by 50% in the scenario of CONWIP approach
Summary
The cement industry is the most prominent building material industry, contributing greatly to the global and national economy and growth. The lime materials for clinker make up about 90% of the cement mass, as gypsum material is added to it in proportions ranging from 3 to 5% to control the hardening and cohesion of the cement, which varies in terms of the added amount according to the type produced [1,2,3,4,5,6] This series of activities from the suppliers to the customers is known as the value chain. In order to ensure the sustainability of production and competitiveness with a view to improve the cement production line, production management principles should be implemented in this industry The purpose of these strategies is to make decisions to develop and improve the shop floor operations in cement factories. Authors in [18] demonstrated a numerical approach to study the cement manufacturing lines taking into account the supply chain management and its effect on Just in Time production. There is an opportunity to compare the outcomes of the proposed pull production systems which are Kanban and CONWIP strategies among the push production system
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