How is
the production
capacity calculated
?
(Written
by : N.R. Jayaraman)
What will be the
ideal production capacity of a machine printing 40
ups per sheet ? How is it determined ?
Before we proceed further, be aware that the norms can be fixed only :-
- For those presses where the
same design is printed in millions
throughout the year.
- The press which is engaged
in the printing the same
design on long term contract through the
year.
- Even if there is change
in the design it will be
effected only after several days of
working with the same set of plates/
blocks.
- Those engaged in the
printing of Bank notes, Currencies,
Detergent wrappers, fast selling several
Consumer product labels and wrappers
in several thousands , Raffle tickets etc.
- The basic requirement for fixing
the norms are that the plant should have
regular long run print order and
not those printing short run copies
and irregular print orders.
- The norms can also be
not fixed for those which are
printing multi colour work with design change
every day.
The following
factors will determine the production
capacity.
- Rated speed of the machine
as suggested by the manufacturer
- Working hours per Shift - 8 hours
or more
- Whether over lapping shift
is in force
- No of shifts per day
- No of working days per
week
- No of days the unit
work per year
- No of declared holidays
per annum
The data shown under
are only illustrative for educative purpose
to show the methodology and figures not actual as every
unit will have their working pattern. Therefore the
working pattern of the press will have to
be taken into account before calculating the
actual figures. Let us presume the following:-
- Machine speed as suggested by the manufacturer :
10000 sheets per hour
- Working hours per Shift : 8 hour per shift
- Whether over lapping working is
in force : No
- No of shifts per day : Two
- No of workmen per machine (
This will be necessary to distribute
the work for faster moment of work )
- No of working days per
week : Six with weekly Off on Sundays
- No of declared holidays per
annum excluding holidays : 14
- No of days the unit work
per year :
- Declared : 14
- Sundays : 52
- Absenteeism caused non working 15
days per annum 365 - (14+52) -15 = 284
A) The
following factors will be considered
as non productive hours :
(1)
Make ready before actual production that
includes Fixing plates, loading of paper, color
setting, registration etc say about one hour (60
minutes) max. If the job is of regular run
which is continued for few days without
changing the plates or colors, then initial
setting time which includes ink charging, loading
of paper and other settings etc is 30 minutes
(2)
Machine to stop before Lunch, say 10 minutes .
(3)
Restart time after lunch say 10 minutes
(4) Machine
to stop before next shift working say 15 minutes
.
All these factors
thus takes away on an average one hour
per shift for regularly run work from the
shift hours.
- In view of the above the
non productive hours per
shift becomes approximately 1 hour in 8 hour
shift. Therefore we will have 7 hours
left for production activity.
B) Even
though the rated speed of the machine
is given as 10,000 sheets per hour by the
manufacturers they are only theoretical figures
and it will not be possible to
instantly start printing 10,000 sheets per hour the moment you
switch on the feeder. Every time the
machine stops and restarts for some reason or
the other, the speed of the machine comes
down before picking up the full speed
on restart and therefore the average
speed will be 75 % of the rated
capacity only. accounting to an average of
7500 sheets per hour on an average
.
During the process of printing due to
several technical problem s
connected to ink, paper , dust, and colour
adjustments one can expect the machine to
stop at least once every hour especially on
presses where blanket cleaning at certain
intervals will be inevitable. Every time when
this happens minimum 8- 10 minutes loss will
be there before restarting the machine.
- Therefore with minimum 8 times
stoppage and restart of the machine
per shift the loss of productive
hours will further be accounted to
one to 1½ hour on an
average.
Therefore we will be
left with the following no of hours
for production :
- 7 (See 'A' above)
minus further 1½ hour on an average ('B' above) leaving
5 hours and 30 minutes for production activity.
(C)
Again for unforeseen activities like blanket
change, plate change, packing adjustment, machine break
down repairs, week end cleanings, week beginning make ready time
etc another 10 % down time allowance is
added .
Therefore considering the above we will be
left with the following no of hours for
production:
- 7 hours (See
'A' above) minus further 1½ hour on an
average ('B' above) minus 10 % (
45 to 50 minutes) which will work out
as 4½ hours for actual production .
Therefore in 4½ hours
the machine can surely produce the
following quantity of production:
- 7500 sheets per hour X 4½ hours =
33750 sheets or 33750 ÷ 500 sheets = 67.5 reams in
ideal condition . The 67.5 reams
with 40 up images will be
equivalent to 1.35 million (67.5 Reams X 500
sheets X 40 Ups = 1350000 ups or 1.35 million)
per shift.
Taking the above figure
as targeted production the annual capacity
can be assumed as below:
- 33750 sheets per day per
shift X 2 shifts X 40 ups x 284 days
of working = 766 millions rounded to
750 million on the lower scale
and to 800 million on an upper
scale.