Upgrade referred to in the art , the activities, the resources of a working system (machine, manufacturing site, single plant or plant road and so on) for a particular operation to set up, they (and so mold punch) to be fitted, for example, with the necessary tools, as well as the activities restore the equipment to the unequipped state.
Differentiation from one-time retooling
Setting up a machine tool or production system designed to be retrofittable from the outset is a regularly recurring process, in contrast to a one-time retrofitting, e.g. B. an internal combustion engine-powered vehicle on electric drive .
Business importance of arming
Machines are not used productively during setup. No product is created. This means that the investments (machines) do not produce any income during the setup . This is why this factor is considered in cost accounting and calculation .
Originally, setup was viewed as a relatively unchangeable part of the job time . In order to optimize the cost of set-up, engineers developed calculations early on to minimize the total costs. The first known solution to the problem was presented in 1913 by the American engineer Ford Whitman Harris . In German-speaking countries, Kurt Andler developed his own approach, which was also more precise than the Harris formula, but which he gave up in favor of the Harris formula, which became known in Germany as the Andler formula .
After the end of the Second World War , Japanese companies in particular were forced to work with unfavorably small batch sizes in favor of greater flexibility . Toyota in particular developed a production system under the leadership of Taiichi Ohno and Shigeo Shingō in which, among other things, set-up times were systematically reduced. According to Ohno, Toyota reduced the mean set-up time between 1945 and 1971 from three hours to three minutes. Along with other measures, the Japanese approach has now become the predominant production paradigm.
The concept of set-up costs is also difficult to narrow down based on the circumstances mentioned. The definition of set-up costs as the costs arising from set-up often leads in practice to costs posted to the set-up cost type . The costs of labor and the proportionate costs of the resources used can be directly assigned to the set-up. In many cases, the opportunity costs of the non-producing machine are also used.
Setting up in practice
Observable allocability is often used as a decision criterion for setup. Only those activities that can be directly assigned to a specific order are considered as setup. The gray area of the activities is, however, quite wide. In practice, various activities that can be factually assigned to set-up end in overhead costs and other activities that are not related to set-up are related to set-up. Most of the time, the set-up term under consideration is based on the primary equipment (for example a machining center , a nibbling machine or a deep-drawing press ). In simplified terms, only the downtimes of this equipment due to setup are viewed as setup time and the work steps occurring during this time as setup.
Like all time types, REFA divides the set-up time into basic, recovery and distribution time.
- Set-up time
- The basic set-up time corresponds to the working hours of people that are spent setting up.
- Human recovery time related to the preparation activities.
- Distribution time for the set-up activities.
Determination of set-up times
Determining set-up times is one of the most difficult tasks in working studies . On the one hand, there are seldom performed activities related to the number of repetitions in the production process. As a result, the exercise effect is quite low. On the other hand, the two-part division of the process between upgrading and dismantling and the problems with the separation between dismantling of the previous and the upgrading of the following operation make data determination more difficult .
Usually, setup time recordings are prepared through preparatory observations of the activities and discussions with the setup staff . It is usually not possible to determine the processes before the time recording, as the frequency of disruptions and the sequence of activities is too erratic. The lack of repetitions in the processes also reduces the probability of information and the comparability of process sections. A setup matrix is usually set up if it is of such importance. In a setup matrix, the known configurations of the machine are listed in the title column and line. At the point of intersection, setup processes from one known configuration to another known configuration are collected. Several similar setup processes can be recorded multiple times. Since the data acquisition is thus spread over relatively long periods of time, it can not be assumed that the system elements will remain the same . The procedure is staff-intensive, so that self-writing by the setup staff often replaces observation by working study people.
Because the teachings of Japanese engineers have found their way into the western world, the relative importance of set-up time considerations decreases at the same time, since the set-up time as a percentage of production time decreases. Thus the determination of set-up times may have become out of date at the beginning of the 21st century.
Sources and individual references
- REFA: Methodology of working studies: Part 1: Basics - 7th edition, 211–230 thousand. 1984, ISBN 3-446-14234-7
- REFA (1984) Methods of Work Studies , Part 2 Data Determination , Carl Hanser Verlag; ISBN 3-446-12704-6
- Wallace J. Hopp, Mark L. Spearman (2000) Factory Physics: foundations of manufacturing management ; 2nd ed., McGraw-Hill Higher Education; ISBN 0-256-24795-1
- Ford W. Harris (1913) How Many Parts to Make at Once ; Operations Research Vol. 38/6; Pages 947 to 950. 1990
- Georg Krieg (2005) New findings on Andler's lot size formula . Working paper, Catholic University of Eichstätt-Ingolstadt
- K. Andler (1929) Rationalization of Manufacturing and Optimal Lot Size , Munich, R. Oldenbourg
- Taiichi Ohno (1988) Toyota Production System: Beyond Large-Scale Production. Cambridge, MA :, Productivity Press (translation of Toyota seisan hoshiki, Tokyo: Diamond, 1978)