Function Structure Approach
Good morning and welcome back. We discussed functional decomposition in the last class. We found that a functional decomposition is basically to identify the small sub-functions needed in a product in order to meet the requirements of the product function as well as to meet the customer
satisfaction. And we found that there are different methods to do the functional decomposition
and one of the methods we discussed was FAST or the Functional Analysis System Technique.
As you can see here in this screen, the FAST method basically tries to identify all the functions
within the product, assuming that there is something provided as an input to the product and
something is coming out as an output. So, what is coming out as an output is considered as the
top level function of the product. And what is given as input is what you provide to the product
so that the product will be able to provide the output. Now, whatever is happening in between
these two lines is known as the product functions or the sub-functions needed in the product.
In FAST method, we try to identify this by asking the question, how or why. How something is
happening in the product, by trying to answer that, you will be able to get the critical path
function, which we mention as the critical path functions. And these critical path functions lead
to the sub-functions associated with each critical path function. So by looking at each one of
these, you will be able to get all the functions needed in a product. So, this was what we
discussed in the last class.And we saw that the relation, the main functions may lead to some unwanted functions in the
product which something like generate noise or generate heat and that will lead to additional
functions also, which may need to compensate for the additional, to compensate for the
unwanted functions. And then we will be having something like an objective project, objective
all time functions and one time function, like this we will be having additional functions also. By
this way, we will be able to get all the functions needed in a product, in order to meet the main
function or the top level function of the product. Once we identify this function, we will be able to create a function tree. A function tree is one,
you will be having a top level function at the top and then we will try to identify the main
functions needed in order to get the top level function. And then we go for the all sub-level
functions at the bottom level and then create a tree structure with all the lower level functions
coming at the lowest level of the tree. So any function decomposition will effectively lead to this
kind of a function tree and that function tree is needed to design the product at a later stage.
Because we will be able to identify what are the sub-functions needed, or what are the modules
needed in a product in order to meet this requirement. And then, under that what are the
functions that can be identified. This is an example of the function tree for an electrical
screwdriver which, when we do the functional decomposition, we will be able to identify all
these functions and then create the function tree. So this was what we discussed in the last class. Just to give you one more example about the functional decomposition or the function tree, so
this is an iron box, electric iron box. So we can see that in an electric iron box, the top level
function can be assumed to straighten out clothing. So that can be considered as the top level
function and you can have additional things also. And then, smooth out wrinkles will be the way
how you can straighten out the clothing. To smooth out wrinkles, you can see that there are many things that we need. One is that you
need to maintain the base plate temperature, you need to generate the steam and then you need to
exert pressure and you need to have a base plate which can actually provide the necessary pressure, temperature and then remove the wrinkles. So these are the functions that are needed.
And then you can actually divide this into smaller modules or the smaller functions.NAnd that will be getting as switch to base plate temperature, hasten heating, generate heat, and
make base plate temperature uniform. Unless you satisfy these functions, this function will not be able to provide the necessary outputs. If you have to maintain the base plate temperature, you
need to have some kind to switch the temperature, you need to have the heating control or the speed at which the heating takes place and how to generate the heat and how to make the
temperature uniform at the base plate. If you satisfy these functions, you will be able to satisfy this and if you satisfy this, you will be
able to satisfy this. So this is the way you can actually identify the functions needed in a product.
So, what is the importance of identifying this? Because if you are trying to design a new product,
a new iron box, and you find that in the existing product, there is a problem with the heating,
then you know out of this which function is the one that creates the problem.
And then you can take out that function and then try to identify a new method to satisfy that
function. Because this is only a function, how you actually provide that in the product depends
on what concept you are using. And therefore, you will be able to modify this function in order
to improve the product. So you do not need to improve all the functions in order to change the
product, you can see, identify which function is the one which actually creates the problem and
then you can, you will be able to modify it and then get a new product.
So this, the way, how we use the functional decomposition at a later stage to improve the design
of the product. Similarly to generate steam, what are the things you need? You need to store the
water, you need to generate steam, and you need to facilitate addition of water. So you can add
water, you have to store water and you need to convert that into steam. These are the
requirements of generating steam.
So this is the way how you will look at the functional decomposition and create a function tree
for a product. Okay, so that is about the first method of, I mean, we discussed about this FAST
method. And one important question you will be having is, how do you actually know that these
are the, where actually I need to stop, should I actually go further and then do the decomposition.
So when will I know that I do not need to do further decomposition of the function?
And to do that, we will actually have something called a functional common basis. We will try to
answer these questions - small easily solved sub-functions by having something called as a
functional common basis. So this is a set of well-defined function verbs and flow nouns. So we
have function verbs and flow nouns. And then, that can represent the products across product
domains known as functional to common basis.Across the domains, we will be able to use this functional common basis and then, we know at
what level we will be able to stop. Because if you can actually represent it as a simple verb and a
noun and that is a well understood function, then we do not really need to go further down for
decomposition. So this is the purpose of having a functional common basis. And moreover, it is
irrespective of the domain.So it can be an electrical product, or a mechanical product, or a hydraulic product. We use this
common basis to represent and therefore it does not really matter what is the domain, we can still
use the same kind of a verb and a noun to represent the function. And we know that with some
experience, we will be able to know that, okay, oh this is something which is commonly
available and we do not need to go further decomposition.And the advantages are basically a common vocabulary. So as I told you, independent of the
domain, you can have a common vocabulary of functions. And then, you can have a robust
vocabulary for expressiveness of designers. It is very robust, so that any designer will be able to
understand and represent the function using this vocabulary. And across domains, you can
compare the products and functions and level of detail that when reached, stops the
decomposition process.When we can actually reach that level, then this says that you do not need to further decompose.You can actually, if you can actually represent it in that, in a common functional basis, that
shows that you do not need to further decompose it because it has already reached a stage where
we have the required functions or required decompositional stage achieved. This is the purpose
of having a functional common basis.Let us see some examples of this common basis. For channeling of something whether it ischanneling of a material, energy or whatever it is, we use the terms called imports, exports,
guide, transfer, receive, etcetera. So transfer power, or get material, export material or import
material, receive material. These are the ways in which we can represent the channeling of
material, energy or whatever it is.Similarly, to support we will say the stop, stabilize, secure, couple, mix - for connection, for
connecting of two objects or two substances, you can have a couple solid or couple liquid or
whatever it is. So you can actually mix liquid, couple solid etcetera. Then you can have
branching of energy or materials, we can say separate or distributed. So separate solid and liquid,
or separate larger size and small size grains etcetera. And then provision is, store, supply, extract.
Control is, actuate, regulate, change, and convert. Then sense, indicate, display, measure
etcetera. For signals, we use sense signals or display signals or measure signals. These are the
common terminology you will be using. If you use this kind of terminology, then actually it is a
common basis or functional common basis. The basic functions are actually expressed using
these functions. So basic functions are expressed using these terminologies.
These are the verbs which can be used to represent the basic function. So once we reach the level
of this detail, then you know that okay, there is no need to further decompose it. That is the
purpose of using a functional common basis. Whenever you do a functional decomposition, you
need to ensure that you are using this terminology and then you know where actually you have to
stop once you reach the required level of detail.Okay, so that is about the functional common basis, and now we know that one of the functional
decomposition methods is known as the FAST. And there, in the first we take a few examples,
we did not use the functional common basis but here after, in all the methods we will be using
the functional common basis to identify the functions. Now in the FAST methods, the function
analysis system technique, we try to find out a critical path function.Between these two lines, we identified that the outside is input and this is the output, and
whatever is there in the critical path is known as a critical path function. So this FAST method is
useful when you have one critical path function or one critical path. So some of the products or
most of the products will be having more than one critical path. It may be doing two or three
things simultaneously, and all the three may be critical in that particular product.
So for such products, this FAST method may not be a suitable one. We need to have a better
method or more robust methods which can actually take care of all the products or products with,
across the, products having multiple critical path, or there are multiple critical path and then
there are multiple kinds of materials going inside and it is not a very simple product, it is a much
more complex product.For such products, we cannot use the FAST method and therefore, we need to go for a robust
method which we call it as the functions structure approach or function structure method. Or
sometimes it is known as a flow method also. So the functional decomposition using flow
methods. So this is the most commonly used method. Whenever the product is slightly complex,
and there are more than one critical path, then you can always go for a flow method.
The flow method is applicable to all the domains, so it uses independent of the domains, you will
be able to use the same kind of functional common basis to represent the functions. So that is the
advantage of having flow methods. We call this a system approach also because in this approach,
we consider the product as a system, so we consider this as a system or we call, okay this is the
product.We assume that something is going inside to the product and something is coming out to the,
from the product, something is going into the product and something is coming out of the
product. And this is the black box where things happen inside. And as a user, we will not be
knowing what is happening inside the black box. We are not worried about what is happening
inside, right? So when I have this product, I do not really worry about what is happening inside.
I know that if I give an input, I will get an output. So for me, it is a black box. If I do not know
the technology inside, it is a black box. So the same way, we can assume that initially, okay, a
product is a black box, you give something as an input, and you get something as an output. So
for example, in the case of a washing machine, you put soap powder, water and then dirty
clothes, and then you switch on. So that is all. And you do not know what is going to happen,
how it is cleaning and all.And finally at the end, you will get clean clothes and then dirty water and other things like that.
So we can say that okay, for any product, you give something as an input and then something
comes as an output. Now, if we can actually find out what is happening to the input and how this
input is getting converted to an output, then we will be able to tell what is the function inside or
what are the functions happening inside.So, that is the approach taken in the flow method where we assume that there are many flows
taking place into the body, into the product and there are many flows coming out of the product
also. And then, these flows we assume that the one of the flows is basically energy. So, any
product or most of the products will be having some kind of energy as an input, say electric
energy or mechanical energy or human energy, some energy will be going inside the product.
And in addition to energy, there will be something called, some other input will be the material.
So we say that okay, there will be some materials going inside. Depending on the product this
material may change. In the case of a washing machine, you know the materials are soap
powder, water and then dirty clothes. So these are the materials which are going inside. Or in the
case of a toaster, it will be the bread for toasting that is going as an input to the toaster.
Same way, you will be able to identify the material, what are the materials going inside. For
example, you take the printer. If you take the printer as a product, what you are giving is an
input. That is all that is going on in the material. You get paper as an output also, right? So we
can get the materials, what are the materials going inside. Then, we assume that there is one
more input which we call it as the signal. Some signals will be going.
This signal is more like a control signal okay, you want it to be a switch on or off, the toaster, I
mean the toaster is on or off, printer is connected to the computer or not. So these are the signals
that will be going inside to the product in order to make the product do its function. Without this
signal, the product will not be able to do its function. That is known as the signal. It is
information given to the product in order to make it do its function. So that is the signal.
We assume that these are the three flows going into any product. Any product you take, you can
say that there can be 3 inputs, one is the energy, other one is the material, and other one is the
signal. And we assume that, because nothing stays inside the product, everything comes out. So
whatever energy you give, energy comes out, it is not staying inside. So there will be an energy
coming out, there will be material coming out and there will be signals coming out.
And this will be in a different form. The same, this is not the same material which is coming out.
The material may change its shape or size or its quality or whatever it is. So some material goes
inside and it comes out as something else. But it is material. So material is going inside and
material is coming out. Energy is going inside, energy is coming out. And signal is going inside,
signal is coming out. Now, once we assume that, this is a black box and these things are the,
these are the flows going inside and the flows are coming out.The question is, what is happening to this material, energy and flow, is the function of, functions
inside the product. So whatever happens to this material, energy and flow inside, these are, those
are the functions of the product. For example, okay, so material is, energy is normally
represented using a single arrow and material is represented using a double arrow in order to
make it distinguished from the other one - material and energy and signal is represented using a
dotted arrow.This is the energy, this is the material and this is the signal. So here, you get the energy outputs,
you get the material outputs and you get the signal outputs. Now, as a designer what we need to
look at is, okay, I am providing electrical energy here and then this is coming out as a sound or
heat, that is energy. So I am trying to give electrical energy as an input and it is coming out as a
sound energy and heat energy.What is happening to this energy, and how is it coming out as a sound or heat? So all those
things, what happens to this electrical energy inside this, are the sub-functions of the product. Or
we can decompose those functions which actually convert the electrical energy to sound or heat
using this. Similarly, what is happening to the mechanical energy, sorry the material? So I am
giving water and clothes.And then, how is it coming as dirty water? I am giving good water and soap powder, how is it
coming as dirty soap water? So, what is happening inside in order to convert this water into dirty
water? Similarly, I am giving dirty cloth, I am getting a clean cloth. So, what is happening to the
cloth inside in order to make it clean? All those things that are happening inside this box are the
functions of the product. So, this is the way we decompose the product functions using the
FLOW method or the function structure methods.Similarly the signal, we will be giving an on-off signal, and then finally you will be getting a
signal saying that, okay cloth is complete, and the washing machine, washing is complete. That
is a signal coming out. When you are giving a… on signal, you are getting output as either it is
an off, or it is some noise or whatever it is, you are getting a signal saying that it is complete.
So you will be getting, you will be giving an input and you will be getting an output. And this,
the relation between this input and the output and what is happening to this input as it passes
through the product are the functions in the product, and this is basically known as the black box
approach for functional decomposition or the flow method of functional decomposition. We will
take a few examples to make it clearer.As I mentioned we consider the product as a black box, and then consider the input as a flow,
there is a flow going into the input and, going to the product and there is a flow coming out of
the product. And this flows, we assume that these are the energy material and information or the
signal. Okay, and then the energy material and information, so information and signal I
mentioned it as signal, it is information, so that information in the form of a signal, you will be
getting the energy material and information going and then energy material and information
coming out.And what is happening to this energy? As the energy is going and then in this box, it actually
passes through many functions. Okay, transmit energy, convert energy and then generate heat, so
many things will be happening there. And finally coming out will generate noise or heat or
whatever it is, this will be coming. What are these functions, we need to identify. Similarly, the
material will be coming inside so we see, material is accepted, then transmitted or coupled or
mixed and then doing something, something and coming out.So there might be interaction, this may be coming here and this may be going here. So we need
to look at all this and then see what these functions are and how the material is coming out in a
different form. So this is what the flow method of functional decomposition is. Okay, now what
are these material energies, and I already explained it. So, information gives the internal decision
making capability. So, the information or the signal gives the internal decision making
capability.And the term signal is often used to express the physical form in which the information is
conveyed. So signal is the common form in which the information will be normally conveyed.
And signals are prepared, received, compared, combined, separated and transmitted or displayed
or recorded inside the product. The signal can actually be transmitted or recorded or displayed, it
can actually happen many things inside. We need to find out what is happening.
And the materials are the gas, liquid, solid, dust, raw material, work pieces, components or
anything can be a raw material going into the product. We have the energy, the energy is the
ability to make something happen. So electrical, kinetic, magnetic, heat etcetera, etcetera. So,
this is the way in which we try to identify the flow, flow into the product and then find out what
is the flow coming out of the product.Let us take a simple example of an electrical screwdriver and see how we can actually identify
the functions inside the product using the flow methods. So we will take this as the product,
electrical screwdriver. So the purpose of an electrical screwdriver is basically to loosen or tighten
the screws. So, we will write the main function, loosen or, so that is what we know, to fix screws
or remove a screw, that is basically the purpose of an electrical screwdriver.An electrical screwdriver is normally used by a human, so it is actually a hand operated electric
screwdriver. Okay, so that is the screwdriver we are talking about. So loosening or tightening
screws is the function. Now we need to see what the flows are going into the product. Okay? So
what are the flows that we can think of? So, it is an electric screwdriver. So the energy, first we
look at the energy. So of course, electrical energy is the one going inside, electric energy is there.
And then as I mentioned it is a human operated one, so human energy is also used in the process.
So it is not only electrical energy, we have human energy also. We call it the human energy,
what actually we apply as a user, what we apply is the human energy. So we can say that these
are the energy going inside. Now, what are the materials going inside? So we can actually see
what kind of materials are normally gone inside.So one maybe a tool bit, so we may have to have a tool bit in order to screw the bit. So a tool bit
will be used. And then maybe screws, we will be using screws too, to fix something. So the tool
bit and the screws may be the materials going inside. And then, what is the signal or the
information? So one information is that you want to tighten or release the screw, okay? You
want to loosen or tighten the screw, so that is the information. So maybe the status of the, the
screw, whether you want to tighten or loosen.Then whether it is on or off, whether the screwdriver is on or off, power supply is there or not.
So these are the information that will be going inside. And then, what are the things coming out?
Okay when we use this screwdriver, you will see that something, some energy will be coming
out. So what is this energy coming out? So one maybe, when you use this screwdriver, a lot of
noise will be produced. Sound energy is something which you can expect.There will be a sound energy and there will be vibration, vibration energy or mechanical energy.
And then there may be heat produced. So these are the energy that you can see. So the electrical
energy is converted to sound energy, vibration energy, mechanical… heat energy. So that is the
energy that you can think of. And then here, what is the material? So the tool bit may come out,
after you use, you can actually take out the tool bit from the screwdriver.Similarly, if it is unscrewing, then you will be getting the screw also as an output. So these are
the material that you can get out, or at the say output from the product. And then, the signal again, whether it is on or off you can get, and whether the status also determines whether the
screw is tight or loose, that information also can be obtained. You can see that in order to loosen
or tighten the screws, so we will be giving this as an input and then we will be getting this as the
output.Now, as a designer, we need to know how this electrical energy is, and human energy is used to
loosen or tighten the screws and then finally the bit and the screw comes out and this is
converted to sound and vibration, and then you get the signal also here. So what is happening
inside, as the flow goes to the product, into the product and it comes out, what is happening in
between or what is inside it is happening, we need to find out.And that can be done by following the flows. So, we will take electrical energy and then see
what is happening to electrical energy inside, and at what stage it is actually getting converted to
heat, noise or vibration. Similarly, at what stage the tool bit is going inside and what is
happening and how the tool bit is helping to fix a screw and then come out as a tool bit itself. So
these are the things that we need to look inside the product, in order to identify the functions. So,
let us look at that and then see how we can represent it.Okay, so we will get this as loosen or tighten screws. So, electricity and human force as the
inputs. And then screw the tool bit and hand, okay hand also as a material will be going inside.
And then loose or tight, or on or off will be the information. And we will be getting the tool bit
screw and hand heat, noise, vibration and loose or tight, or on or off as the material.
Now, we need to see what is happening inside. So what will we do? We will try to explore this
box and then see each input. We will see, okay, this is the electrical energy. So I will try, start
with electrical energy and try to find out what is happening to the electrical energy and the
forces, human force, electricity, screw, bit tool etc. Then I will try to see what is happening to the
electrical energy.So now, I can identify, okay I take the electrical energy and if I assume there is a storage power,
battery storage, then I will say that okay, I need to store, store electrical energy. So first I will
store in the battery, and then I will supply electricity to it, so I am using the functional common
basis, store electrical energy, supply electrical energy. And then I will say that I need to actuate
it, I need to switch on or off in order to make the product work.
Basically, I am actuating the electricity. So what I will say, I will actuate electrical energy. And
then I will say that okay, I switch on or off, but then I need to control the energy or control the
motion of the tool bit. If I have to go in a forward or reverse direction, I want to change the
speed, increase the speed or decrease the speed. I need to have some kind of control over the
power. So what I will do is regulate electricity.So I will be regulating it. And then what I will do after I regulate, I can actually convert this
electrical energy to mechanical energy. So, I will convert the electrical energy to mechanical
energy and then I will transmit, transmit the mechanical energy. Okay? So the electrical energy
is coming and then it passes, going through all these functions and getting converted to
mechanical energy and transmitted as mechanical energy. So that is what actually happened to
the electrical energy.When it is converting to mechanical energy, then there will be something called generate heat or
generate noise, so these are the unwanted functions. And then the noise goes as an output, heat
goes as an output. So you have the noise as an output and heat as an output. If you have a cooling
mechanism, then there will be transmit heat also because you are transmitting the heat to outside
the product, so there will be transmit heat.Normally, in the screwdrivers, you do not have any special mechanism for heat transmission, so
we will say that just heat is just coming out. You know that now the electrical energy is
converted to noise and heat because of these functions. That is what actually happens here.
Similarly, okay, now this has to happen, now we have to see the, okay the next one is basically
the material. So we consider the material going inside. Assume that the tool bit is consideredhere.We assumed that there was a tool bit going inside. So we need to do this tool bit so the tool bit is
taken, and then we will be using our hand also, so the hand also has a material which is going
inside, so the hand will be coming. You will say, using the hand, so you will be using the hand
for many things one is basically to actuate electricity and regulate electricity, we will be using
this, because we need to have the human hand to do this. So we will actually say that there is a
connection here.Similarly, we use the tool bit. So