Cost per cut is the benchmark in sawing machine purchase
KASTO Ltd
Unit 5,
Garamonde Drive
Wymbush, Milton Keynes
MK8 8DF
Map
Tel. 01908 571 590
Fax. 01908 566 106
sales@kasto.uk.com
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Cutting to length is often regarded as a preliminary operation in the life cycle of a product and not a value-added process, so there is a tendency for manufacturers and stockholders to skimp on the purchase of a saw. However, the questions every saw owner should ask are, "what is the total cost per cut?", or, "how much does it cost to cut an area of one square metre?", after all expenditure has been taken into account. It is not enough to consider only the price of a machine. The total cost of ownership (TCO) has to be taken into account, including consumables, operator wages and service over the lifetime of the machine, in addition to the capital cost. Only then can proposals from different sawing machine vendors be evaluated properly. Improved cutting performance, increased output, better quality of cut and a greater degree of automation have led to significant improvements in bandsaw technology, utilisation and efficiency in recent years. This has happened in parallel with the development and increasing use of carbide rather than bimetal bandsaw blades.
Illustration 1 compares the cutting performance of a traditional bandsaw with that of a KASTOtec AC4, designed for cutting with tungsten carbide tipped blades. The material was 300 mm diameter 42CrMO4V alloy steel. It shows that the performance of KASTO's carbide machine is 2.5 times higher, cycle times are reduced by 36 per cent and the total processing time of the sample order is reduced from approximately 58 hours to 20 hours. Such performance can only be achieved with a stronger, more powerful and robust bandsaw, with improved vibration damping characteristics and better dynamics regarding cutting and idle times. This in turn dictates a higher price compared with traditional bandsaws. The question whether or not the more expensive machine TCO approach includes all operational costs In addition to the price of the bandsaw, a TCO analysis must include all operational costs over the lifetime of the machine. Since some costs for floor space, energy, and swarf disposal are comparable for all machines, for the sake of clarity they will be disregarded in the following calculations. Thus the only costs to be considered will be: Machine utilisation requirements, investment, depreciation and interest charges Tool costs, idle times ctory supplies - coolant Service costs and maintenance Labour costs The normal depreciation period for a KASTOtec AC4 is 10 years, so this was used to calculate interest payments which were added to the capital cost of the bandsaws. A carbide bandsaw blade costs 280 Euro and has in this calculation a lifetime of one week when operated over a single shift. Since production saws, especially machines with automatic material feed, are often cutting around the clock, three bandsaw blades are necessary per week. Over the course of a year with 220 working days in three-shift operation, tool costs are 36,960 Euro. Factory supplies play only a secondary role; coolant is lost due to evaporation, sticking to chips, vapourising or vacuuming and about 35 litres per week are needed, which costs 620 Euro per year when using coolant concentrate mixed in a 1 : 10 ratio. Machine availability and maintenance are of great importance for every company. Particularly during production cutting or in steel distribution, maintenance contracts are recommended, which guarantee quick exchange of wear parts and spares. In this example, service costs were averaged over several hundred machines and an typical travel time for the engineer was taken. Over a period of 10 years, service and spares cost approximately 33,500 Euro. Based on the machine investment, service costs represent just over four per cent, about double the amount suggested by the VDMA (the German Association for Machine and Plant Manufacturers). The reasons for the disparity may be a combination of harsh operating conditions, frequent personnel changes and poorly trained operators. Personnel costs, in spite of higher automation, should not be underestimated as a cost factor. This example is based on multiple machine operation. Assuming that 20 per cent of the personnel costs are for setting-up, cut piece removal from and order entries relating to any given saw, the costs amount to an annual total of 26,400 Euro per saw, based on 220 working days and three-shift operation.
Illustration 2 shows that over the first 10 years of a KASTOtec AC4 bandsaw's life, machine investment represents only 15 per cent of the total costs, compared with a massive 48 per cent for tooling costs and 32 per cent for labour. Other cost elements are coolant (1 per cent) and service (4 per cent). In respect of the latter, speed and quality of service are important, as if spares are missing or not fitted correctly, the result is machine downtime and lost production. Total costs: KASTOtec AC4 compared with conventional machine
Comparing all lifetime costs of the KASTOtec AC4 with those of a conventional bandsaw, illustration 3 shows that a traditional machine requires around 50 per cent less investment and 43 per cent less in high-speed steel bandsaw blades due to the machine's shorter operating life. So taking into account just these two factors, the machine is around 30 per cent cheaper. Nevertheless, investment in a more expensive, high performance machine is justified from both technological and economic standpoints. First, a carbide bandsaw can cut tough materials up to a tensile strength of Rm =2000 N/mm˛, which cannot be sawn with traditional machines or blades. Second, the carbide saw has a more efficient cutting performance, resulting in shorter cycle times. Third, longer band life requires less frequent band changes and therefore reduces labour costs and machine downtime.
A productivity comparison shows that over a period of 10 years, the carbide machine cuts 2.6 times more material than a traditional machine (illustration 4). If one converts the total cut surface to cost per square metre, it shows that the figure for the KASTOtec AC4 is 48 per cent lower than for the conventional machine, or nearly half!
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