166 APPLYING EFFICIBNCY PEINCIPLES
represents at any point the net effect of the number of
pieces on the eflSeiency. At that value of N for which
the tangent to OLB is equal to the tangent of the angle
made by OKMF with the axis of N, the intercept has
its maximum value; and if the number of pieces in the
order exceeds this, the final efficiency will be decreased.
In many plants these considerations may be of no
importance; but in some cases, like those shoe factories
in which orders are sent through in certain definite
numbers of pairs and must bring through an exact
number, and in which any spoiled work causes considerable
trouble and delay, the size of order which will
produce maximum eflSeiency is of much importance.
What this size of order should be can be determined
only by sending through orders of various sizes and
keeping records of the results. It is impossible to keep
all the conditions, except the value of N, even approximately
constant until betterment is very far advanced;
but very much earlier it may be possible to determine
a working approximation to the most eflScient size of
the order. This is the more feasible because a glance
at Figure 7, Article 341, shows that the intercept KL
will vary only slowly on each side of the maximum
point.
161. Efficient equipment. This is the condition
against which an American plant is least likely to offend.
Having plenty of equipment and having it up to
date is a hobby of American manufacturers.
In fact, the national sins are to scrap equipment
while it is still valuable, thereby burdening the plant
with a perpetual fixed charge for the interest on the
value written off, and to have too much and too big and
expensive equipment, leading to idle equipment time
and excessive equipment burdens.