Analysis of performance and the Overall Equipment Effectiveness (OEE) in a manufacturing company

The Overall Equipment Effectiveness (OEE) has become an index of efficiency in terms of the use of machinery, equipment and production resources. It allows entrepreneurs to learn where to look for modest losses, and can be used to eliminate them. The main purpose of determining the OEE is to confront the theoretical use of machinery with the actual one, using a relationship of three main elements: availability, use and quality. The purpose of the paper is to present the experience of the use of the OEE in optimization of production processes in a production company. The most important factor in analyzing the overall effectiveness index of the equipment is choosing the right method for collecting and processing data. The best-known method is filling in of a worksheet by line employees. An analysis was carried out in a production company, determining the SLE production line performance index and using Pareto analysis results, based on data from May 2014 to June 2015. The bestperforming component of the OEE is quality, the value of which has not dropped below 95% over the period considered.


Introduction
An elementary factor in assessing the production line is the efficiency and availability of the machines used. Machines determine the percentage of a fully productive production time, and in the literature these elements are referred to as effectiveness of the use of equipment and resources [1,2]. These factors are identified by a number of activities related to measuring and analyzing the production process in an enterprise, based on which the socalled equipment use index, i.e. the Overall Equipment Effectiveness (OEE) is calculated.
The Overall Equipment Effectiveness (OEE) has become an index of efficiency in terms of the use of machinery, equipment and production resources. It allows entrepreneurs to learn where to look for modest losses, and the information obtained can be used to optimize the production process. The main purpose of determining the OEE is to confront the theoretical use of machinery with the actual one, using a relationship of three main elements: availability, use and quality. The result of these three elements allows managers to detect minor errors in the use of resources and forms the basis for making rational decisions regarding production, quality control and the need to replace or service the equipment [3]. * Corresponding author: anna.szelag-sikora@urk.edu.pl It is very important to take care of all OEE elements, because a decrease in one contributes to a decrease in the value of the entire index [3].
The purpose of the paper is to present the experience of the use of the OEE in optimization of production processes in a production company.

Methodology
The selected production company has five bottling lines for beverages: for PET and glass bottles, and aluminum cans. Each of them produces beverages of different sizes and flavors, which triggers a great need for improved effectiveness. The production plant runs a welldeveloped production process control system, which facilitates swift and effective detection and elimination of deficits or waste. The lines work in a counter pressure system, using KANBAN cards. This is the method in which the order placed by the customer significantly affects the production process, i.e. activities performed at the end of the value stream report the needs to previous positions. The system's aim is to eliminate unnecessary overproduction and operational inventory [4][5][6][7]. For the calculation of the OEE, data on its main components was collected, i.e. availability, use and quality of production resources. To this end, information was obtained on: a) the manufactured volume, i.e. the quantity of finished products (pcs), b) downtime, i.e. total time spent on redundant operations and processes such as failures, washing, retooling and other operations related to downtime (h), c) operating time, i.e. the total duration of the production process (h), d) defective products, i.e. physically damaged (bottles) or qualitatively damaged (e.g. mold germs) (pcs), e) daily working time, 24-hour working time (3 shifts). The most important factor in analyzing the overall effectiveness index of the equipment is choosing the right method for collecting and processing data. The best-known method is filling in of a worksheet by line employees. It consists in recording properly defined deficiencies with an eight-hour operation mode, then calculating and analyzing them in the form of charts [1]. This method, although the easiest, has many disadvantages, e.g. reliability of production or the frequency of value processing. The second, more accurate method is filling digital sheets using appropriate software, e.g. OEE SPC, MES (Manufacturing Execution System)/SCADA cards. This involves filling out digital sheets, and then calculating and generating reports and results as printouts, or saving them on a computer [1].

Result
To assess the efficiency of the production line, two indexes describing it must be carefully analyzed. The first is the performance of the SLE production line, which was calculated for the bottleneck. For this purpose, the pre-prepared Pareto analysis was helpful. The time taken into account was the period from May 2014 to June 2015. Based on the available data, the SLE index was calculated. As a result, the following results were obtained (Table  1).  Table 1 summarizes the SLE results for the glass bottle production line, taking into account the assumed monthly target based on demand and sales forecasts. At this point, it should be emphasized that the carbonated drinks market in Poland is strictly seasonal. Therefore, the highest demand, and thus the highest production was observed in the spring and summer months, while the lowest production characterizes the cold seasons of the year. The winter season is also intended for production stops for repair and servicing. Therefore, the level of performance at this time is lower [8][9][10][11].
In the next step, the effectiveness of the use of machines and devices on the production line in question was analyzed using the OEE index.  Table 2 assembles the data necessary to calculate the efficiency index for using machines on the production line in question. Data collection consisted in reporting real information related to the analysis by machine operators. As can be seen, the OEE is mainly based on data on the largest losses on the production line. It was found that retooling operations take the most time, as compared to other non-production activities. For the analysis of the OEE, 24-hour work time in the four-brigade system was taken into account. Based on the above data (Table 2), calculations were made and the results obtained are presented below (Table  3). It should be emphasized that the OEE is a measure of the efficiency of production line resources, i.e. an index of the efficiency of machines and devices, while maintaining the appropriate quality of products [3]. The value of the OEE index for the enterprise in question is closely related to the effects of the SMED project, which was implemented in the enterprise's production line. The higher the OEE index, the lower the resource efficiency and effectiveness. To take a closer look at this relationship, the OEE index was analyzed after the SMED project was carried out on the production line. The set of data needed to calculate the OEE was assembled in Table 4.  Table 4 summarizes the most important information necessary to calculate the OEE for the period in question. The data were collected thanks to a group of dedicated production line operators, involved in the project during their shifts. The material for analysis was recorded in reports and then entered into the computer system (MS Excel).

Summary
The tests carried out, and the results obtained, present the character and individual indexes associated with the use of production machinery and equipment in the examined enterprise at bottling into PETs, glass bottles and cans. Based on the calculations, it was found that the best-performing component of the OEE is quality, the value of which has not dropped below 95% over the period considered. This turned out to be a great result for the company, considering the fact that the plant strives for the best quality of production.