Minimum total cost and minimum time per piece are the boundaries of the high efficiency machining range. The graph is based on AISI Cold Finished Steel Bar Manual 1968 (what I trained on when I entered the market).
A relationship exists between the cutting speed and the cost per piece. A high efficiency machining range exists between the minimum total cost and the minimum time per piece.
Accountants and engineers agree: This is the “sweet spot” of our operations. Higher speeds permit quicker operating sequences, reducing time per piece; but higher speeds reduce tool life and increase downtime.
Plotting both total cost per piece and total time per piece, the chart shows that the high efficiency range exists between the two curves’ minima.
Minimum time per piece usually occurs at higher speeds than minimum cost, providing higher operating efficiency. If you have plenty of open capacity, you should aim for minimum part cost. If you are capacity constrained, perhaps lowest cost per part is not optimum for your shop.
Originally posted on PMPASpeakingofPrecision.com.