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Ch25-I044963.fm Page 121 Tuesday, August 1, 2006 3:36 PM
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Ch25-I044963.fm
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Electric consumption of machine tool (Ee)
The environmental burden due to the machine tool electric consumption is expressed by equation (2).
In equation (2), the electric consumption of the servo motors and the spindle motor is varied
dynamically according to the machining process, so the electric consumption of these motors are
calculated with considering the table weight, the friction coefficients of the slide way, the ball screw
lead, the transmissibility of the ball screw, the axial friction torque, the cutting force and the cutting
torque. Here, these are also predicted by cutting process model (Narita, et. al, 2002). This cutting
process model concept can be applied to square end milling operation, ball end milling operation,
turning operation and so on. Using these models, various cutting processes can be evaluated.
Ee = kx(SME+ SPE +SCE+CME +CPE+TCE1+TCE2+ATCE+MGE+VAE) (2)
k: CO2 emission intensity of electricity [kg-GAS/kWh]
SME: EC of servo motors [kWh] SPE: EC of spindle motor [kWh]
SCE: EC of cooling system of spindle [kWh] CME: EC of compressor [kWh]
CPE: EC of coolant pump [kWh] TCE1: EC of lift up chip conveyor [kWh]
TCE2: EC of chip conveyor in machine tool [kWh] ATCE: EC of ATC [kWh]
MGE: EC of tool magazine motor [kWh] VAE: Vampire energy of machine tool [kWh]
EC: Electric consumption

Coolant (Ce)
There are two types cutting fluid, so two equations are proposed for Ce evaluation. First, the water-
miscible cutting fluid is explained. The coolant is generally used to enhance the machining
performance, and circulated in a machine tool by a coolant pump until the coolant is updated. During
the period, some coolants are eliminated due to the adhesion to the metal chips, so the coolant is
supplied for the compensation. The dilution fluid (water) is also reduced due to the vapor. So, the
equation (3) is adapted to calculate the environmental burden. Second, the water-insoluble cutting
fluid is explained. In this case, the discharge rate is an important factor. Hence, the equation (4) is
applied.

Ce {(CPe + CDe)x(CC + AC)+fVAex(lVAQ+ Al¥AQ)} (3)
CUT: Coolant usage time in an NC program [s] CL: Mean interval of coolant update [s]
CPe: EB of cutting fluid production [kg-GAS/L] CDe: EB of cutting fluid disposal [kg-GAS/L]
CC: Initial coolant quantity [L] AC: Additional supplement quantity of coolant [L]
WAe: EB of water distribution [kg-GAS/L] WAQ: Initial quantity of water [L]
AWAQ: Additional supplement quantity of water [L]

Ce= CUTXCS x(CPe CDe) (4)
+
3600x1000
CS : Discharge rate of cutting fluid [cc/h]

Lubricant oil (LOe)
Lubricant oil is mainly used for spindle and slide way, so two equations are introduced. The minute
amounts of oil are supplied to the spindle part in an interval time. For the lubricant of the slide way,
the certain amount of the oil is also supplied by pump in an interval time. So, the following equations
are adapted to calculate the environmental burden due to lubricant oil. These equations can be adapted
oil-air lubricant and the grease lubricant.

LOe = Se + Le (5)