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Ch25-I044963.fm Page 123 Tuesday, August 1, 2006 3:36 PM
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Tuesday, August 1, 2006
Ch25-I044963.fm
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The dry machining, the MQL machining and the Wet machining are evaluated in this case study. Here,
the life of cutting tool is assumed to be extended to 2 times of original one. The analyzed results are
shown in Figure 3. The equivalent CO2 emission of wet machining is largest and one of dry machining
is smallest in this comparison. Using this system, this kind of comparison can be carried out easily
from NC program. Here, the detailed discussion is tried based on the analyzed results. The portion of
electric consumption is highest in the all factors, obviously. This causes due to the peripheral devices
of machine tool. This factor is also proportional to machining time. That is to say the high speed
milling in dry machining method may be superior machining from the view point of CO2 emission
because of the short machining time, although detailed analysis will be required.

• Electric
Dry L
snsumption
E3 Coolant
• Lubricant oil
Cutting tool
H Metal chip
0.00 20.00 40.00 60.00 80.00 100.00 120.00
Equivalent CO 2 emission g-CO 2
Figure2: Product shape Figure 3: Analyzed environmental burden results
Also, the equivalent CO2 emission of the MQL machining and the wet machining is larger than the dry
machining. As shown in the Figure 3, the equivalent CO2 emission of cutting tool is smaller due to the
mitigation of tool wear, but one of peripheral devices operated by coolant usage and one of coolant are
added and total one becomes larger. It is found, however, one of peripheral devices operated by
coolant usage is larger than one of coolant effect. Furthermore, equivalent CO2 emission of CH4 and
N2O is calculated using analyzed results of wet machining. These are related to environmental burden
of cutting fluid. Equivalent CO2 emission of them is less than 0.001 g-CC>2. In other word, CO2 is a
dominant environmental burden in machining operation about the global wanning.
Here, the production cost is evaluated using cost data. This analysis can be realized that equivalent
CO2 emission intensity data in equations (2)-(9) is changed to cost data. These equations are
constructed by considering the activities related to machine tool operation, hence this cost accounting
method correspond to activity-based costing (ABC) (Brimson, 1997). The cost due to electric
consumption has to be changed a little, because the basic rate of the electricity is considered. The
equation of the cost due to electric consumption is following. In this research. JPY (Japanese Yen) is
used as currency.

Ec = EbcxMT + ERY.CE (10)
Ebc: Basic rate of electricity [JPY/min] MI: Machining time [min]
ER: Electricity bill [JPY/kWh] CE: Electric consumption [kWh]
Cost data are searched by hearing the related companies. In these dates, the metal chip processing
value is minus and cutting tool disposal cost is 0, because metal chip becomes profit and cutting tool
disposal is carried out free fee in Japan, respectively. Using these data, same machining operations are
compared. Figure 4 shows the analyzed results of cost evaluation. As shown in the Figure, the dry
machining is largest, and the MQL machining and the Wet machining are almost same value. The dry
machining is best from the view point of environmental burden, but this is worst from the view point
of cost. So, adequate machining strategy has to be decided according to the situations. It is also found
that the reduction of electric consumption of the machine tool peripheral device and the cutting tool
consumption is effective from the view point of cost down and mitigation of global warming.