“Only one operator is absent today.” It sounds like one-twelfth of a day's output.
On a line it is never one-twelfth. It can be nothing at all, or the whole day, depending on
which post the person was standing at. The absence is the same; the cost is not.
Why it depends on the post
The line balancing article showed that a line
makes only as many garments as its slowest operation. An absent operator lowers the capacity of
their own operation. If that operation had spare capacity, the line does not notice. If it
was the slowest step, or becomes the slowest step once the person is gone, the whole line falls
to its new speed.
A worked example
These figures are made up to show the sum. They are not a benchmark and not a claim about any
line or any unit. It is the balanced line from the earlier article: 12 operators on a shirt of
18 standard minutes, allocated and timed as below, everyone at the standard.
- Collar (3 minutes), 2 operators: 40 an hour.
- Sleeve (4.5 minutes), 3 operators: 40 an hour.
- Side seam (2 minutes), 1 operator: 30 an hour.
- Hem (1.5 minutes), 1 operator: 40 an hour.
- Cuff (3 minutes), 2 operators: 40 an hour.
- Buttons (4 minutes), 3 operators: 45 an hour.
The line makes 30 an hour, 240 in an eight-hour day. Now take one operator away, one post at a
time, and see what the line makes.
One absent, six different days
- Buttons: 2 operators left, 30 an hour. The line still makes 30.
Nothing lost.
- Sleeve: 2 left, 26.7 an hour. 213 in the day: 27 fewer,
11% down.
- Collar: 1 left, 20 an hour. 160 in the day: 80 fewer, a
third down.
- Cuff: the same, 80 fewer.
- Side seam: nobody left. 240 fewer, the whole day, unless
someone else can do it.
- Hem: nobody left. 240 fewer.
Twelve operators, one absence, and a range from nothing to the entire day's output.
The two operators who work alone, at the side seam and at the hem, are the ones the line can
least afford to lose.
What it costs in rupees
The profit on a garment in the
costing example is ₹258.41. Eighty
garments not made is 80 × ₹258.41 = ₹20,673. The whole day,
240 garments, is ₹62,018.
An absent operator is not paid, which saves their day. At the assumed ₹400 an hour that is
8 × ₹400 = ₹3,200. Against the collar loss, that is a saving of about 15%
of what was lost. The saved wage never pays for the garments.
Count the post, not the head
When you ask how many were absent, also ask which posts. One absent button operator and one
absent hemmer are the same number on the attendance sheet and very different days.
What a floater is worth
A floater is an extra operator who can work any post. Costed at the same ₹400 an hour, a
floater costs ₹3,200 a day. That equals the profit on 3,200 ÷ ₹258.41 =
12.4 garments.
- Cover a sleeve absence and 27 garments are saved: the floater earns back more than
twice their cost that day.
- Cover a collar absence and 80 are saved: six and a half times.
- Cover a button absence and nothing is saved: the day cost ₹3,200 and bought no
garments.
A floater pays for themselves on the days when a critical post is empty, and does not on the
days when it is not. How often that happens is a number only your own attendance records can
give.
What to do with it
- Mark the single-operator posts. Any post with one person on it is a post
where an absence stops the line.
- Train a second person for each, in turn, rather than one person for
everything. A person who can cover two posts is worth more than a faster person who can cover
one.
- Keep a month of attendance by post, not just by number. That is the
only way to know how often the critical posts are the ones empty.
What the sums leave out
- Made-up times, posts and wage. All are assumptions in the example. Use your
own.
- The supervisor moves someone. In practice a line rarely stops outright;
someone is borrowed from another post. That is the floater in everything but name, and the
post that lent them now has a gap.
- Profit understates the loss. Overhead and the wages of those who did come
are paid whether or not the garments are made, so each garment not made costs more than its
profit. The ₹258.41 is the smallest fair figure, not the largest.
- Everyone at the standard. A slow operator at the bottleneck costs the line
in the same way, every day, with no absence at all.
The efficiency calculator turns a day's output into minutes earned,
which is where an absent operator shows up on the
efficiency figure with no explanation attached.