Hello and welcome back to this Manufacturing
Systems Technology module 45.
.
We were discussing about the Toyota production
system and some it is components and we mention
that it is different than the American system,
the MRP Material Requirement Planning base
system, which is more a push base system.
So, let us today in this lecture first try
to have a schematic look out on what really
we mean by pull and push systems.
So, here you can see there are different processes
in a particular assembly or sub assembly of
a product and at the end, there is a finished
product here, but it goes through process
1, 2 and 3 and there is a flow, continuous
flow of raw materials from one side which
leads to the different processes and finally,
gives the finished product information.
So, there are two different kind of lines
that you can see, one is the solid line here
and there is another dotted line, a solid
line actually means the production flow and
the dotted line means the information flow.
So, basically what happens is that in this
kind of and this is called a push base system,
because this system is governed by a certain
plan which has been made for a time horizon
for looking at the market, looking at the
you know the customer inspiration and wants
and the probably the marketing has suggested
that so much product of a certain type x can
be absorbed by the market.
So, over a period of let say 15 days or 10
days or may be even 30 days.
So, there is a planning horizon which is there
and the marketing has suggested these requirements
and based one that now all the subsystem level
requirements are generated or all the small
components, which would typically go in to
sub assemblies which would again modularly
go into the final assembly they are generated.
So, this generation is spread as a production
plan all across the whole organization with
it is various departments and divisions making
different modules towards the final product.
Then, because of this plan there is a requirement
assessment and there is a material buying
or inventory buying, which formulates all
the way to the vendor and now this material
has a lead time aspect, it comes in and now
it is ready for the production to begin.
So, once this is happened, the material as
well as this information is forward post from
the raw materials stay to process one.
Now, what are the problems associated with
such a push based system that is why it is
called pushed base.
So, you are pushing the material from the,
in the forward direction all the way to the
finished products.
Now, supposing there is some snag in the process
2 which happens, because of which the process
2 stops producing the particular, you know
the particular component at this particular
level.
So, if the process 2 is stop producing; obviously,
the process flow happening from process 1
is still continuing, there is no stop to that
flow, because you are driving the process
1 on the bases of the push system, which already
has a planning horizon defined and therefore,
there will be a pile up.
Because, the process 2 is not able to absorb
any more and the process 1 is still sending
the material, so there is going to be a pile
up.
So, this is a natural consequence of a disbalance
which will happen because of the defect of
the process 2.
Obviously, in that system then you will have
to really make sure that the process 2 comes
to normalization within minimum possible times.
So, that this pile up is reduce etcetera,
but whatever you are doing here is very, very
waste full.
Obviously, then another issue is, that at
the end of the process supposing you are produced
30,000 parts based on the planning horizon
and supposing in between there is a need change
or the aspiration change of the customer and
the demand suddenly falls done, then what
you do with this finish products.
So, this is either all made shelled and the
right of marketing opportunity being initiated
for selling them off or in other words, if
that does not happen then the only other situation
is that you have describe some of the product
off or may be just retranslate that back into
another aspiration or another needs.
So, you will have to make the additional work
of disassembling things and trying to have
some of the components to suffice.
Normally the companies do not do that was
the product is produce, they will either shelf
it if not needed and then, wait for an opportune
time to give it to the customer.
But, then this buy and large suggested the
system, where there is many chances of flaw
or bottleneck as for as the intermediate processes
are concerned or as far as the costumer need
mapping or customer aspirations are concerned.
So, this is generally the disadvantage with
the push base system, which continued before
the TPS of Toyota Production System came into
the process and in fact, TPS for the first
time showed that this push system can be completely
converted into a lean pull system, where it
would be the customer requirement that would
be mapped at every stage and the information
would come based on that particular requirement.
So, you need not really over produce and if
the expectation changes and there is a need
map which is different from for certain time
horizon and then suddenly is able to change
within that you know horizon to some other
direction; obviously, the production flow
will also change in accordance with that and
then may be minimalistic stock at different
levels, because of that need change or need
mapping change.
So, that is how a pull system would work out.
.
So, now you have finished product which is
done by the customer in terms of a requirement
and this requirement now starts to go in the
backward direction, you have maintained a
stock in between all the processes 1, 2 and
3.
So, that you can address if the process and
that is the reason why assembly lines, they
are broad in that.
Assemblies are basically having a work in
process inventory which is semi complete and
the line would go at a certain rate of the
expectation and aspiration of the customer.
So, therefore, the customer has given a plan
and based on that plan of his requirements
or aspiration, the product information goes
back to the process 3 which already has a
semi finished inventory and is waiting for
the customer order, the whenever the customer
order comes the process 3 finishes the particular
work in process and sends it is product to
the customer and simultaneously, orders for
again some part from process 2.
So, that it can augment the vacancy or void
created in the process 3 so on and so forth.
So, now what is happening is that the information
about the requirements is really flowing in
the backward direction and the production
is flowing in the forward direction and there
is a complete need mapping now.
So, wherever there is an aspiration change
on a real time, you would be able to change
this information flow.
So, that exactly what is needed is delivered
and then the processes are definitely made
flexible enough.
So, that they can suddenly change to this
business pressure or business environment
and that is all about the design of the system
in place.
Obviously, it cannot be really a real time
change, there are limitations the individual
level processes have to be change.
It will take some time for changing the process
also, but the whole idea is that can it be
quickly arrested, so that there is minimalistic
pile up in between and that is how the philosophically
this system is designed.
And therefore, you have an information flow
in the backward direction and production flow
in the forward direction, which represents
the pull based system.
.
So, there are many advantages of a pull base
system and there are many modalities of a
pull base system.
So, advantages I think I have enumerated a
lot now, now let us look at some of the basic
engineering modalities associated with designing
such a system.
So, the central tendency or the central requirement
of such a system is the information flow and
the information flow happens through this
particular, you know item here which is known
as Kanban on our visible record, which talks
about how much material between what process
to what process at what particular time and
what is the type of the material in one single
go.
So, there are normally two different kind
of most commonly used Kanbans or cards, Kanban
cards.
One is called the withdrawal Kanban and others
called the production Kanban and I am going
to now individually start designing the system
with respect to the withdrawal Kanban and
the production Kanban.
So, you can see that the primary function
of a withdrawal Kanban is to pass the authorization
for movement of parts from work center to
another.
Once, it fetches the parts from the preceding
process and moves them to the subsequent process
it remains with them till the subsequent process
has consumed the particular part and when
the consumption is happened only then the
withdrawal Kanban has to travel back preceding
to the preceding process to fetch equal number
of parts which have been consumed and the
succeeding process and the cycle keeps on
continuing.
So, Kanban card releasing the material to
the next station, the next station consuming
that material and then releasing the Kanban
card back to the previous station and movement
the Kanban the previous station gets the card
it is start to produce that particular material
and sends it a head to the center two or the
succeeding center and the cycle of the card
and the production flow keeps on continuing
for a lean inventory mountainous between two
stations.
So, with the withdrawal Kanban it should have
the following information should be typically
what is the part number, what is the part
name, what is the lot size and the routing
process that is needed to fetch the part and
these all are given as a part of the information
on the Charlet describe our Kanban card really
looks like.
.
So, this how a withdrawal Kanban looks like
you have raw materials and other part types
use the manufacturing at the works center
you have the container capacity, which gives
you number of parts this is a part number
we will describes, what the part is and also
it describe what is the preceding works center
number and what is the stock location number
for this particular work center number that
this card has to going.
.
The production Kanban on the other hand is
something which whose main function is to
release and order to the preceding process
to build parts equal to the lot size specified
on the card.
If I just want to see what is the flow of
the withdrawal in the production Kanban and
their interactions let us look at this particular
case of two stations, one is the preceding
stage PPS1 and the subsequent stage SPS2.
So, these are two stations and there is a
stocking area in between, where there is some
little bit stock to absorb the you know the
flow irregularities between the subsequent
stage and the preceding stage which may happen
between.
And so let us see that what part of the cycle
does the withdrawal Kanban obey and what part
of the cycle does the production Kanban obey.
So, if I look at let say what is going to
happen in the stacking area, let say there
is a full container f which has some kind
of a withdrawal Kanban card given by the circular
figure here and place.
So, the movement this withdrawal Kanban is
putting this full container, the container
moves ahead and the container goes all the
way to the subsequent stage moment it comes
to the subsequent stage and the container
is to be used now by the operator in the subsequent
stage, he will pick this card the circular
card and keep it in a stacking bin at P2 location
here.
So, the container is separate and the card
has been kept at P2 location and now the container
is being used by the subsequent stage continually.
So, know whenever the empty container comes
out let say for example, there has been some,
there was another container which was been
partially use or it was just about to get
finished when this ordering was them by the
operator through the withdrawal Kanban means.
So, in that case the there may be some time
delay and there may be some waiting period
for this particular card and whenever that
is a bin which is empty at this station this
SPS2 station, this bin can be put with this
P2 card and sent back as an empty containers.
So, you can see that this P2 withdrawal Kanban
is going along, traveling along this empty
container all the way to the site E.
So, you have now an empty container here in
this stacking area.
So, now, there is a roll of production Kanban
will come into picture.
So; obviously, there is a production Kanban
card which is...
So, this replaces the card here that you can
see circular card which is the withdrawal
Kanban goes and fits into a full container.
And; obviously, the full container has this
rectangular card that you can see this card
actually is changed back to the empty container
and this rectangular piece of card is called
the production Kanban.
So, the circular is the withdrawal Kanban
and the rectangular is the production Kanban.
So, once I have said that this is the withdrawal
in a production Kanban in place.
So, your exchanging merely the full container
gets the withdrawal Kanban.
So, the circular moves up here and the rectangular
Kanban comes done to the empty container and
the empty container comes back or gets transported
back from the staking area all the way to
the preceding stage when this production Kanban
which it had carried along is actually leads
and there is a the movement it arrives there
is a production plan which comes into this
preceding stage, there is material processing
which starts happening etcetera.
The people start initiating the empty container
and make it full, but before that happens
you ensure that there is some kind of a one
bin or one lot in place which is already been
produce.
So, that the rectangular card now can be fitted
to that particular full bin or full container
from the preceding stage and the movement
there is a rectangular card on it, the full
container starts moving to the stocking area.
In the meantime, because you had this withdrawal
Kanban circular card fitted on this full container,
the full container would also starts moving
towards a subsequent stage.
So, therefore, the right side of the whole
process from the stacking area to the subsequent
stage as a cycling flow of the circular card
that is the withdrawal Kanban and the left
side of this process from the preceding stage
to the stacking area as a circular flow of
the rectangular card that is the production
Kanban.
So, this 
is the production Kanban side and this is
the withdrawal Kanban side and; obviously,
the cycling flow has to 
be maintained in a well balance manner and
that will determine the size of the stacking
area or 
as 
a metro fact how much mini Refer stock can
be kept at the preceding at the subsequent
stage.
So, the overall you know behavior and this
flow system is that the flow should be such
that the container capacity that is 
the intention of the git system should be
limited to one container, it is very difficult
to achieve that kind of a capacity.
But obviously, the minimalist approach would
be a better idea if you have instead of one
about five containers to do all this stock
balancing job between the PS, PPS1 and SPS2
you are very much there.
So, that is the essence of the lean manufacturing
and that is the 
way that is Kanban circulates and know I would
like to increasingly valuate you know a ways
and means based on a certain demand pattern
or 
a forecasting pattern or whatever how you
can maintain this over all 
flow balance with minimalistic inventory at
a certain level.
So, we will try to estimate and do some problem
examples how to actually calculate the number
of Kanbans which would be flowing in 
a system to keep the system in active state.
So, with this I will like to close on this
particular module and in the next module we
will probably do little bit of mathematical
analysis as 
to 
how 
to estimate this over all Kanban level.
Thank you 
so much.
