Cost per Component, Production Rate and Profit Rate Criteria:

The machining cost per component is made up of a number of different costs. The total cost (C) of making one component (excluding material cost) is given by

or,

C = C₁ + C₂ + C₃ + C₄                   ---------------------(2)

 (Fixed charges are not taken into account because they will not affect optimization.)

where,

C₁ = non-productive cost per component (cost of loading and unloading the component, idle time costs and other non-cutting time costs),

C₂ = cost of machining time, C₃ = tool changing time cost, C₄ = tool cost per component, T = tool life,

T_ac = tual cutting time;

T_ac /T number of tool (or cutting edge) changes per component,

T_c = chining time,

T_d = me required to change a cutting edge,

T_l = sum of all non-productive times,

x = cost rate including labor and overhead cost rates, and

y = tool cost per cutting edge.

For a brazed tool tip, the cost / cutting edge

--------------------- (3)

For the throw away tips,

------------- (4)

From Eq. (1), it is evident that cost per component can be reduced by decreasing the loading time, unloading time, idle time and tool changing time (by employing improved fixtures, jigs, inspection gauges, tool holder, etc). Improved tool materials and tool geometry which give longer tool life values and hence would reduce the number of tool replacements and grinding costs. Increasing the cutting speed has opposing effects on the cost per component because C₂ decreases while the total tool costs (C₃+ C₄) increase (Figure 10.1). The production rate is inversely proportional to the production time per component. The total production time per component (T_t) is given by

 --------------- (5)