Simulation in Large-scale Precast Operations

This document details a rationalisation study on the production of shop-prefabricated parts supported by simulation to analyse potential operating alternatives. The goal was quite specific: to improve productivity and so reduce production costs. Since the study was carried out while the workshop was fully operational, no changes that would have involved stoppages in workshop production could be considered. An initial model was designed reproducing the established method, with a production rate of 75 parts per shift. The results obtained were in good agreement with the real-life situation . Alternatives were analysed by making gradual changes to the initial model: assigning jobs to the workforce, homogenising the number of parts being processed during each of the successive stages, and altering working hours. The simulated production of the final model tested was 108 parts per shift, i.e. an increase in productivity of 44%. When this solution was implemented the model was shown to have been accurate, with the forecast production being achieved within only a few days with absolute regularity. Before the case is described, an overview of the path followed by Dragados in the process of adopting simulation as a tool for enhancing productivity is given. 1 SIMULATION AT DRAGADOS Dragados is a group of over 50 companies, the result of an intensive process of diversifying the main activity, construction. With annual sales of over 550,000,000,000,000 pesetas, Dragados carries out a major part of its activities abroad. In the August 1996 issue of the Engineering News Record issue on the Top 225 International Firms, Dragados was ranked number 54 as an International Contractor (included only contracts outside of their home country), number 37 as a Global Contractor (home and abroad) and number 8 as a Latin American Contractor. Throughout its history, Dragados has considered it vital to have a strong team of highly qualified technicians with solid know-how of the latest technologies and their operational application. This philosophy led to the formation of technical teams specialised in each area of the company's activities: in other words, specialisation by products. In parallel, the technical-development process was implemented in all departments, with production-line support groups being set up using generalist techniques. In the late 60s the Planning and Methods Unit (PMU) was created, with a view to enhancing the productivity of construction processes by the application of work-rationalisation techniques. Processes are designed by the product specialists. The generalist detects opportunities for improvement, using Work Study techniques to analyse and summarise the processes and handling highly detailed information: • Breakdowns of item cycles, measured in hundredths of a minute.. • Existing conditions between operations, not just in order. Also by the cyclical use of space. • Often, the summary is made on a Multiple Activity Chart, which basically amounts to a graphic simulation done by hand. When simulation software applicable to construction operations first became available in the early 1980s, the PMU recognised its potential as a tool for standard work processes and so began to implement computerised techniques. We may conclude that simulation was implemented to meet the operational needs of a pre-existing operational group with the basic mission of increasing productivity: the function exists; the tool is useful. The PMU performed tests on the available software , devising models of different construction processes , and decided to adopt the Microcyclone PC version of the MCYCLONE methodology. It was felt that any model must comply with two key conditions. First, it must provide an accurate reproduction of reality. This was achieved, to differing degrees of success, by all the software tested. It boils down how costly the specialist's learning is going to be.