2013-test01-chap00 preamble chap01 pd and rpd-with answers

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INDIAN INSTITUTE OF TECHNOLOGY, BOMBAYDepartment of Mechanical Engineering

Course : ME-617 Rapid Product DevelopmentInstructor : K.P. Karunakaran

Date : August 8, 2013 (Wednesday) 9:30PM

L-T-P-C : 3-0-0-6I Semester 2013-14

Duration : 60 min.Instructions: Write your roll number only on the question paper. Do not

reveal your identity in any part of the answer books. Staple the question paper at the top of the answer book while

submitting. Manage time efficiently as the question paper is too long.

Roll No

Marks /85

TEST - 1(Preamble; Product Development; Rapid Product Development)

Part A(1 mark each)

1. What MRP-I and MRP-II stand for? What did lead to this evolution?

MRP-I Material Requirement Planning

MRP-II Manufacturing Resource Planning

Initially managers thought that control of various materials (inventory of raw materials,

work in progress and finished goods) alone is enough. Subsequently, they appreciated the

need to control the other resources like machines and man power too. So, MRP-II that

encompasses all the resources was developed.

2. Expand PLM and ERP and distinguish between them.

Product Lifecycle Management

Enterprise Resource Planning

ERP is largely alpha-numericdata driven whereas PLM is largelygeometricdata driven.

There are efforts to combine them into one or at least create interfaces between them

since they have some data common such asBill of Materials (BoM).

3. Name the most user-friendly and the most system-friendly solid representations in thepopular CAD/CAM packages.

FBM

B-Rep

4. Which is the simplest volumetric representation?

Voxel

5. Name a solid representation of the hierarchical space decomposition type.

Any one of [Octree, Bintree, Lintree ...]


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6. The bounding box of a solid sphereis defined by (32, 59, 85) and (132, 159, 185). Express

the half spacedefining its B-Rep.

The radius and centre of the sphere are 50 and (82, 109, 135).

The half space is (x-82)2+y-109)2+(z-135)2 502

7. Mention at least two important features required to upgrade a surface model into B-Rep

solid model.

No point is duplicated. This results in proper stitching or water tight model; i.e., no

overlaps or gaps.

B-Rep has the additional topology of outward normal.

8. What are the two keywords that are implicit in the term Feature-Based Modeling and

describe its behavior?

Constraints. Parametric.

Due to these, it has the following benefits:

The Boolean operation is built in.

Only sketching is done. So ease of creation.

Constrained parametric definitions. So, editing is easy.

So a family of parts is designed with the same efforts of a single part.

Bi-directional associativity permits broadcasting of a change in one place throughout

the assembly and related parts.

9. Pick the correct statement. Storage of redundancy in B-Rep causes:

(a) increase in space complexity and decrease in time complexity(b)increase in space complexity and increase in time complexity(c)decrease in space complexity and decrease in time complexity(d)decrease in space complexity and increase in time complexity.

(a)

10. Pick the correct statement. The memory occupied by

(a)B-Rep is proportional to the sum of the areas of all its surface patches.(b)Exhaustive enumeration is constant.(c)Octree is proportional to the volume of the object.(d)CSG is very high.

(b)

11. Pick the correct statement:

(a)Octree is the most accurate solid representation.(b)Octree cannot handle non-manifold objects.(c)Feature details are lost in Octree.

(d)Octree can handle self-intersecting objects.

(c)


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12. Which group of solid operations will you not find in such a pure FBM package?

Boolean operations.

13. Which type of solid is Klein bottle?(a) Manifold solid

(b) Non-manifold solid

(c) Self-intersecting solid

(d) Virtual solid

(c)

14. Which solid representation is suitable to represent gradient objects like bones, bamboos

and stones whose properties such as composition and density vary throughout?

Spatial Decomposition. Specific representations like voxel, octree etc. are also correctanswers.

15. A CNC machine is a

(a) Scalar device (b) Vector device (c) Tensor device

(d) Raster device (e) Voxel device

(b)

16. The most popular display today is:

a. Storage tube with vector graphics b. Storage tube with raster graphics

c. Refresh tube with vector graphics d. Refresh tube with raster graphics.

(d)

17. Pick two correct answers. Double buffering is required for:

a. Storage tube with vector type monochrome displays

b. Refresh tube with raster type monochrome displays

c. Storage tube with vector type color displays

d. Storage tube with raster type color displays

e. LCD displays

(b) & (e)

18. Give a binary (i.e., in terms of high/low) comparison of laser and inkjet printers as per

the following table.

Capital cost Running cost Speed

Laser printer

Inkjet printer

Capital cost Running cost Speed

Laser printer High Low High

Inkjet printer Low High Low

19. Pick the correct statement in the context of CRT:


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(a)Creating any color involves suitable proportion of Red, Green and Blue inconjunction with Yellow. This process involves optical addition of the basic colors

and their subtraction from Yellow.

(b)The three electron guns corresponding to Red, Green and Blue emit electrons atdifferent velocities so as to create different excitements on the phosphor coating. This

differential excitement results in the phosphor coating emitting the desired color.(c)The electron guns for all the three colors are identical.(d)None of the above is correct.

(c)

20. Why is triangular approximation preferred to other faceted modelling such a

quadrilateral?

Uniquely defines a plane (even in finite precision computing).

21. How will you compare two numbers when they are (a) integers and (b) floats?

(a) Integers can be compared using the standard equality operator, say, ==.

(b) Floats cannot be compared exactly. They need to be compared only within a defined

precision. For example,if (fabs(a-b)< 0.001) {...}

22. Among the solid representation schemes, name the two most significant advantages of

spatial decomposition method over the other three types?

Ability to define the interior details

Operations such as Booleans are implemented as binary rather than geometric. So,they happen in trivial time.

23. What are the two reasons for the shortening of product life and hence the decreasing time

for product development?

i. Fast changing taste of the increasingly affluent customers

ii. Technological obsolescence.

24. What are the three design phases?

i. Conceptual designii. Configurational design

iii. Detailed design.

25. Distinguish between Geometric ModelingandReverse Engineering.

Geometric Modelingcreates the object from scratch whereas Reverse Engineeringcreates

the Geometric Model of the physical object(through digitizing). The ultimate goal in both

is the creation of the geometric model, i.e., virtual object.


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26. The figure shows how various costs vary

during the product development cycle.

Identify the curves depicting the three

different costs along with brief

explanations of their respective trends. Is

the cost instantaneous or cumulative?

Marketing cost: The two bulges are for market survey and advertising.

Design cost: Gradual rise and fall in expenses with the peak in the middle. Initially only

manpower and office expenses are required in discussions, visits and virtual/paper works

for design and testing. The middle bump is during prototyping and testing.

Production cost: Gradual rise and fall in expenses with the peak towards the end. This is

due to physical prototyping and productionizing.

27. What are the two distinct phases of manufacturing automation? What do you understand

by total automationin this context?

i. Automation of the process

ii. Automation of the process planning.

When both these exists, it is called total automation.

Part B(Marks mentioned against each question)

1. Distinguish between CAD/CAM and CAD/CAM/CAE. In the latter acronym, list


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activities under CAD, CAM and CAE. [3]

CAD in CAD/CAM = GM+CAE

CAD in CAD/CAM/CAE = GM

Note: GM stands for Geometric Modeling.

CAD Geometric Modeling, ReverseEngineering, animation, drafting etc.

CAM process planning, toolDevelopment, layout etc.

CAE Structural Analysis, Heat & FluidFlow Analysis, Kinematic Analysis,Dynamic Analysis, Design for

Xability (DFX), Optimization etc.

2. Name at least one package for each of the following activities: [5]

a. Seamlessly integrated CAD/CAM/CAE system

b. Pure FBM package

c. FEA

d. CFD

e. Kinematic analysis

f. Casting simulation

g. NC simulation

h. Enterprise Resource Planning

i. PLM software

j. Expert System Shell

Sl.

No.Activity Package

a. Seamlessly integrated CAD/CAM/CAE

system

NX, Catia

b. Pure FBM package Pro/E, SolidWorks

c. FEA ANSYS, NASTRAN,

d. CFD Fluent

e. Kinematic analysis Adams, 3DStudio, Maya,

Pro/Mechanica,

f. Casting simulation MoldFlow (for plastics), CMold

(for metal), AutoCAST (for metals)g. NC simulation VeriCut, VirtualNC

h. Enterprise Resource Planning SAP, BAAN, IFF, DEdwards

i. PLM software Windchill (PTC), TeamCentre

(formerly Metaphase (SDRC), I-

MAN (EDS)), Ennovia (Dassaults),

Matrix One (Dassaults), SAP PLM

j. Expert System Shell nExpert

3. Reproduce the following table and write the three representations in the increasing order

of topological information. For an axis-aligned unit cube in the first octant, fill the

geometric and topological entities corresponding to these representations. [4]

Representation Geometry Topology


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Representation Geometry Topology

Wire frame 8 corners, viz., p0=(0,0,0),

p1=(1,0,0), p2=(0,1,0), p3=(1,1,0),p4=(0,0,1), p5=(1,0,1), p6=(0,1,1),

p7=(1,1,1)

12 Edges: e0=[ p0, p1], e1=[ p0,

p2], e2=[ p1, p3], e3=[ p2, p3], e4=[p4, p5], e5=[ p4, p6], e6=[ p5, p7],

e7=[ p6, p7], e8=[ p0, p4], e9=[ p1,

p5], e10=[ p3, p7], e11=[ p2, p6],

Surface The above 12 Edges and

4 faces: f0=[ e0, e2, e3, e1], f1=[ e4,

e6, e7, e5], f2=[ e0, e9, e4, e8], f3=[

e2, e10, e6, e9], f4=[ e3, e10, e7, e11],

f5=[ e1, e11, e5, e8]

Solid In addition to the above 12 edges

and 6 faces, direction of material

will be given by through outward

normals corresponding each face.

n0=(0,0,-1), n1=(0,0,1), n2=(0,-

1,0), n3=(1,0,0), n4=(0,1,0), n5=(-

1,0,0)

4. Compare the traditional solid representations like CSG, FBM and B-Rep with spatial

decomposition methods. [2]

Traditional solid representations like

CSG, FBM and B-Rep

Spatial Decomposition Method

Exact Inexact

No need to specify universeand

resolution.

Universeand resolutionare to be

specified.

Geometric features are retained. Geometric features are lost.

Only the external surface of the object is

defined and the interior is assumed to be

homogeneous.

The entire object, i.e., its interior as well

as surface are defined. Therefore, suitable

for defining gradient objects. This is more

closer to reality.

5. Compare, in the form of a table, the vectorand rastertypes of computer devices in terms

of their principle of operation, accuracy, rendering capability, complexity in space andtime domains. Which one of these is popular and why? [4]

Feature Vector Device Raster Device

Principle

of

operation

Objects are created by the

movement of the tool (electron

beam, pen etc.) along the 2D

geometric entities.

The 2D geometric entities are

converted into a collections of dots

of different grey levels/colors and

stored. This is calledscan

conversion. Then, these are copied

to the corresponding pixels of the

screen.

Accuracy Accurate since there are no

staircases.

Suffers from staircase effect.

Rendering Shaded rendering is not Ideally suited for shaded


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capability possible.

Higher number of colors and

gray levels are not economical

since that many buffers will be

required.

rendering.

Higher number of colors and

gray levels are possible.

Spacecomplexity

Buffer size varies with picturecomplexity. The buffer here is a

series of vectors defined by (int x,

int y).

Buffer size is constant. It isindependent of the picture

complexity and depends only on

display accuracy. The buffer here is

a rectangular arrays that store (0, 1)

values.

Time

complexity

Refresh time depends on the

number of entities (actually sum of

their perimeters). Therefore,

flickering may happen when the

picture is more complex.

Refresh time is constant. It is

independent of the picture

complexity and depends only on

display accuracy. Therefore no

flickering occurs.

Raster. Time and space complexity is constant. Stairstep error is not a problem as we

have very high resolution today.

6. A monochrome display has 4 bit-planes. It has 16 pixels along X and 12 pixels along Y.

Draw a block diagram that shows the flow of the information stored in these planes onto

the screen. What will be the video memory required for such a display ignoring double

buffering? [5]

Video memory required = 16 x 12 x 4 = 768 bits = 96 Bytes.

7. Draw the block diagram depicting the steps in obtaining the display on the screen from

the CAD model. [3]


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Picture processing includes

Carrying out the viewing transformation for the given viewing conditions of zoom,

rotate and pan

Clipping for the window, Hidden line and hidden surface removal,

Shadow calculation,

Shading and rendering computations with respect to various lighting arrangements

and finally mapping to the screen coordinates. Saves the resulting data as a bit map in the computer's one of the display buffers while display

is created from the other (This is known as double buffering).

8. Explain double buffering. [3]

When the frame buffer is being written, if data is accessed from it to fill the screen pixel,

it will result in a mixture of the information from the previous and current frames.

Therefore, the user will not see anything clearly. Therefore, two buffers are required.

When one is being updated with a new frame, the other is accessed to update the screen

pixels. Then the two buffers are swapped in their role.

9. Which type of display requires shadow mask? Sketch its constructions and explain its

principle of operation. [5]

Display using Cathod Ray Tube (CRT) requires shadow mask.

Shadow mask is a grid of holes with 1/3 density of pixels as shown in the figure. The


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three beams corresponding to Red, Green and Blue merge at the shadow mask and

diverge. The distance between the shadow mask and phosphor screen is such that the

beams fall on the closest set of Red, Green and Blue phosphor dots. The shadow mask

thus ensures that the electron beam corresponding to any color will fall only on the

phosphor dot of that color.

10. What is the minimum number of triangles required to define a sphere of 20 unit diameter

with a maximum permissible deviation of 0.5 unit? Your answer can have an error of

5%. [5]

Note: There are deviations in 3D (spherical bulge) and 2D (circular bulge). One has to decide

which is dominating. The 2D deviation in the circle is 1.561 which is much more than the

allowed deviation of 0.5. So, this circle shall be approximated by a hexagon rather than a

triangle. Even then, the deviation becomes 0.781 which is higher than the permissible value.

11. a. Describe the STL format briefly. [2]b. What are its storage inefficiencies? What are its other limitations? [2]

c. What is the reason for its success in spite of being an inefficient representation? [1]

(a)

STL format is a planar approximation of the object boundary in the form of triangles.

STL file is an unordered collection of triangles. Each triangle is represented by not only

the three corner points (9 float values) but also its unit outward normal (3 more float

values). Topology is not explicitly available. A valid STL file defining a valid solid will

have the following characteristics:

It is a water-tight model void of any overlaps or gaps between the triangles

An edge will not cut another edge

An edge will be shared by two and only two faces


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A face will be surrounded by three and only three faces

In the beginning it was in ASCII format. However, only binary format is popular in view

of large number of triangle.

(b)Two storage inefficiencies are:

i. The same point is repeated several times in the file as this is simply an unordered set of faces.This not only increases the size of the file but also leads to defects such as gaps, overlaps,intersecting edges etc. as the same point may be interpreted as different points at the floatingpoint precision.

ii. Normal is also a redundant storage as it can be calculated from the three vertices that aregiven in a particular order.

Other limitations:

This is an inexact representation. For acceptable accuracies, the file size is much larger than its exact form even in binary

format. This is an unordered set of faces. Topology is not explicitly available. It has to be extracted.

(c)

Sheer simplicity.

12. Calculate the normal [nx, ny, nz] for the following triangle given in STL format: [3]

facet normal nxnynz

outer loop

vertex 1.495970 3.611590 -3.117449

vertex 2.764192 2.764192 -3.117449

vertex 0.830200 2.004281 -4.504845

endloop

endfacet

facet normal 0.350493 0.524550 -0.775887

13. Compare the behavior of competition with the way a python deals with its prey. List at

least four features of business environment that are analogous to breathing. [2]

When a python captures an animal, it tightens it a little every time the animal exhales

leaving less and less room for subsequent breathing till the prey finally dies of

suffocation. The cycles similar to breathing occur in organizations also; [i] the inventory

of raw materials, work in progress and finished products fluctuate, [ii] cash flow

fluctuates, [iii] machines fail, [iv] manpower attrition and so on. Whenever each of these

reaches a low level, the competitors loose no time to take away the market share just as

the python does. Therefore, organizations can never remain complacent with their current

performance.

14. Present the characteristics of the industrial scenario in the past and presently in the form

of the following table: [3]


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Feature Past Present

Economy based on

the type of Govt.

rotection

Type of Competition

arket is dictated byn(Profit, Price, Cost)

Definition of quality

One word to define

the attitude

Feature Past Present

Economy based on the

type of Govt. protection

Protected economy Open economy

Type of Competition Local Global

Market is dictated by Seller Buyerfn(Profit, Price, Cost) Price = (Cost + Profit) Cost Profit = PriceCost

Definition of quality Conformance to design Customer delight

One word to define the

attitude

Complacence Competition

15. Name each of the four project types with an example for each in the respective cells: [2]

Product

Market/

Applications

Existing New

Existing 1 2

New 3 4

Product

Market/

Applications

Existing New

Existing

Updating Replacement:

Annual release after taking care

of customer feedback and

minor improvements.

Supplementing:

Cell phone with camera, radio

etc.

New

Adaptation:

European car for India and vice

versa

Diversification:

An automotive company

starting an IT division

16. Explain the significance of Figure 1 in the context of product design: [2]

Design options are more in the beginning and they diminish with time. So, the later a

design error is recognized, the costlier it is to rectify.

17. Explain the significance of Figure 2. Is the cost instantaneous or cumulative? [2]

While the actual expenditure is less in the early stage, we commit drastic amount which

actually gets spent after quite some time. Any outside changes occurring during this gap


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may affect the fate of the project.

The cost is cumulative.

Figure 1 Figure 2

2013-test01-chap00 preamble chap01 pd and rpd-with answers

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