A short introduction to the process of line balancing in production/manufacturing environments that use many people on a line. This is a very valuable tool to allow people to increase capacity whilst reducing labour costs.

1. Optimising hand
lines
A guide to best practise in line balancing
Andrew Wilson
Finidhyn ltd.
17 March 2021
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2. Line balancing
Line balancing is a core skill in manufacturing. It is not always obvious
how this works, and sometimes it can seem contradictory. For example
it is not unknown to increase the labour on a line and see the “per-
packet” cost of the item plummet as the average speed of the line
increases. This is a genuine productivity and ef
fi
ciency improvement.
Hand-lines tend to need close management in order that they function
to there optimum. It is all too easy to set up a line with a standard crew
and just leave them alone. This is a sure
fi
re way to lose money.
Very simply a “hand-line” must be making product almost constantly
throughout a shift and be optimised, either for capacity or productivity.
Every minute and every bowl which does not get put into a slot on the
line is lost money.
It is therefore vital that each station is loaded with the correct amount
of work, and that the people servicing the line ensure that they have all
the materials necessary for them to do their job without moving off
station.
You will
fi
nd that if your staff on the line are uncomfortable, cold or
bored, they will seek any opportunity to get away from the line and do
something to warm up or overcome their discomfort. It is therefore
important that you do anything you can to ensure that they are happy,
warm and content to work for a full shift on the line.
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3. Setting a standard
The following points are to be used as a guide to setting the correct
standards for new products or existing products within your company.
You need to have been trained in order to take a standard, if you have
not been trained then please alert a manager, and seek guidance on the
subject.
Map out the number of different activities that take place in order to
create a product. For example:
Dinesting
Salad leaf
Onion
Red Peppers
Tomato
Tamping
Once you have identi
fi
ed the major operations, you need to arrange to
take a timing. A stop watch will be necessary for taking an accurate
timing. You will need to take at least 20 timings of each operation in
order to get an accurate average speed for each operation.
In order to get an accurate time for an operation, stand in clear view of
the end of the line and
fi
nd a
fi
xed point where an activity ends for the
operator in question.
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4. For example if an operator is depositing salad
you might want to pick the point at where the
salad is placed in the bowl as the
fi
nal point in
the timing loop. Focus on this point and nothing
else, and stop the watch when the salad is
deposited. A modern phone is ideal for this
operation as you can time a lap each time the
salad is deposited and the stop watch will then
continue timing, so there is no need to stop and
start the watch for each operation.
Before you start to take a timing, check that the line is running at the
correct speed by checking the number of packets per minute coming off
the end of the line.
Watch the production line for a minute before you start, to ensure you
can count adequately. Ideally you want the line to have settled down
into a regular rhythm where the operators are comfortable, it is no good
trying to do measurements if the operators are moving around on the
line or if the line is stopping and starting.
Once you are sure you can count accurately, start to count the chosen
operation and take timings. Remember you are looking for a minimum
of 20 readings. Taking more than 20 readings will not affect anything
and will only increase the accuracy of the data
you will use later to balance the line.
Work your way down the line measuring each
operation individually and storing your timings.
When you have a set of timings on your stop
watch or phone, it is worth writing these down
on a piece of paper with the time and date you
took the readings and the details of the product
you were timing and the station number on the
line and the item you were timing. This will allow
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5. you to remember what timings were for which product when you return
to the of
fi
ce.
Once you have collated all your readings, put the timings into Excel and
take an average time.
It is important at this stage to test the data you have recorded.
Sometimes you may have inadvertently recorded timings on the line
whilst the line is running slowly or whilst the line is using temporary
labour. These factors may lead to you recording a slow speed where a
higher speed would have been recorded if a permanent operator was
working on the line running at the right speed.
Make sure that you have captured all of your readings in Excel. It is
important to do this, as it is almost impossible to describe the difference
you have made to the line after you physically change the line layout.
One of the weird things about line balancing is that after you make the
changes, it all looks so normal you cannot describe the changes you
made.
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6. Line balancing
In the line balancing Excel spreadsheet you will
fi
nd a model which has
been designed to take all of the maths out of line balancing. If you
populate the spreadsheet in the correct way you will
fi
nd that line
balancing is quick and easy.

What the model does is allocate labour to positions on the line to
increase the throughput. When a cell turns pink, that will be a rate-
limiting-step. Clearly you cannot make a line run faster than the
machinery on the line as this on the whole tends to have a maximum
speed that it can run at. In the case of salad bowls the sealer will have a
maximum theoretical throughput which will be constrained by gas
fl
ushing. There is no point in adding any more labour once the rate of
the line is equal to the machine speed achievable.
You can see in the example above that the machine in position 7 is rated
at 30 packs per minute. Therefore once the speed at stations 1 and 2
reach 30, there can be no further bene
fi
t in adding people. Instead you
should look to see if some of the stations can be combined. Notice in the
model that stations 3,4,5,6, all have cycle time of 1.5 seconds or 40 per
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7. minute. By combining two of these stations, so for example, tomato and
cucumber become one persons job, you will load that station to 20 packs
per minute. This on the face of it might seem too slow, but you tend to
fi
nd that where people are “under-loaded” on t a line, they slow down to
the speed they need to operate at. You might
fi
nd that if you combine a
station like this that they are capable of achieving the 30 packs per
minute rate comfortably and you have reduced the labour cost of the
line.
Another thing to consider is that not all products have the same
ingredients and therefore do not require the same labour layout. If for
example you
fi
nd that a number of your products require less labour, it
might be worth scheduling these to be the last things you make in a
shift. This way you can send people home early once you move on to
these items. This way you incur less labour cost over the shift.
For further information and help is how to improve your process
performance contact Andrew Wilson MBA
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