8.A2 Power consumption - the total power rating in horsepower of all electric motors recommended for use in a given tool. When the power consumption is plotted against the weight, the data points fall into place quite well (Figure 8.Al). A curve fit is shown with a zero intercept which is quite close to the linear regression fit (which has a slight negative intercept). The results of this fit gives us: Specific Power Consumption= 3 W/kg = 3 kW/ton When the mass is plotted against the volume (Figure 8.A2), the trend which emerges is not quite as clear as that for specific power consumption. Most of the data points lie roughly along the lower curve which is again close to the linear regression fit. This fit approximates most of the mass-efficient machines studied, and is taken as the mean density of light machine tools: Mean Density= 500 kg/m 3 The three points substantially above the curve in Figure 8.A2 represent a family of very massive "Monarch" lathes. Their curve (1000 kg/m 3 ) is assumed as the upper density limit for light machine tools. It should be noted that even in the limit, the density is quite low (compare steel 8000 kg/m 3 ). VIII .A. 3: ROLLING MILLS Not much data is available on the mass and power consumption of rolling mills, and the volume of a complete mill is rather hard to define. What data is available (mostly from reference (8.Al)) tends to confirm the results found above. The following data from reference (8.Al) is shown in Figure 8.A3: Mass Power Power/Mass Mill (Metric tons) (Kilowatts) (kW/ton) Blooming Mill 1150 5000 11000 2.20 950 4000 9000 2.25 800 2700 5000 1.85 Shaping Mill 6000 9400 1.57 Intermediate Mill 8000 13200 1. 65
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