Computer Aided Manufacturing - 2 Marks - All 5 Units

ME 2302 - Computer Aided Manufacturing

P.A. COLLEGE OF ENGINEERING AND TECHNOLOGY

PALLADAM ROAD, POLLACHI - 642 002

DEPARTMENT OF MECHANICAL ENGINEERING

ME 2302

COMPUTER AIDED MANUFACTURING

TWO MARK QUESTIONS WITH ANSWERS

ACADEMIC YEAR 2012 - 2013

Prepared By

Mr.M.Mohan Prasad M.E., MBA

PA College of Engineering and Technology, Mechanical Department 1


UNIT - 1 CAD/CAM INTERFACE

PART- A

1. What are the activities of CAD?

CAD activities include product design, engineering analysis and drafting

2. What are the activities of CAM?

A CAM activity includes process planning, NC part programming, production

scheduling, and computer production monitoring and computer process

control.

3. In what way CIM differs from CAD/CAM?

A CIM includes all of the engineering function of CAD/CAM, but it also

includes the firm’s business functions that are related to manufacturing.

4. List few of the current trends in manufacturing engineering

a. Group technology

b. Rapid prototyping

c. Concurrent engineering

d. CAPP

5. What is group technology?

Group technology is a manufacturing philosophy in which similar parts are

identified and grouped together to get the advantages of similarities in both

design and manufacturing attributes.

6. List out any four benefits of GT?

a. Setup time and cost for MHS is reduced

b. Standardization of tooling and setups

c. Production scheduled are simplified

7. What is meant by part family?

Part family is a collection of parts which are similar either because of

geometric shape or because of similar steps that are required in their

manufacture.

8. Write the various methods of part family formation

a. Visual inspection

b. Production flow analysis

c. Part classification and coding system



9. What is meant by PFA method?

Production flow analysis is a method for identifying part families and

associated machine groupings that uses the information contained on

production route sheets rather than on part drawings.

10.What are the steps involved in PFA?

a. Preparation of route sheets

b. Preparation of PFA charts

c. Cluster analysis.

11.What are different types of coding structure used in part coding schemes?

a. Hierarchical codes

b. Attribute codes

c. Hybrid codes

12.List out some of the coding system commonly used in industries?

a. Optiz

b. MICLASS

c. DCLASS

d. CODE

13.What is the basis for forming groups in group Technology?

The groups are formed based on the similarities of part design and part

manufacturing attributes.

14.Define process planning.

Process planning can be defined as “an act of preparing a described

processing documentation for the manufacture of a part or assembly”

15.Write the various approaches in process planning.

a. Manual process planning

b. Computer aided process planning

16.What are the components of generative CAPP systems?

a. A part description

b. A sub system

c. Database

d. A report generator

17.Why the retrieval CAPP system is called as variant CAPP system?

A retrieval CAPP system has the capacity to alter an existing plan. That’s why

it is known as variant CAPP system.



18.List any two commercially available retrieval CAPP systems.

a. Multi CAPP

b. MIPLAN

19.List any two commercially available generative CAPP systems.

a. APPAS

b. CMPP

c. EXCAP

d. XPLAN

20.What is meant by concurrent engineering?

Concurrent engineering deals with carrying out the design and manufacture

activities at the same time while designing the product.

21.What are the objectives of concurrent engineering?

a. Decreased product development lead time

b. Improved profitability

c. Close integration between departments

d. Improved product quality

22.What is meant by QFD?

Quality function deployment is a planning tool used to identify and carry the

customer’s voice through each stage of product development and

implementation.

23.What are Taguchi methods?

Taguchi methods focus on design and attempt to determine the best

combination of design parameters which results in superior performance of

the product.

24.What is rapid prototyping?

Rapid prototyping is a term used to describe number techniques which rapidly

produce solid physical models of components and products using 3D

computer data.

25.What are the various techniques used in rapid prototyping?

a. Stereo lithography

b. Selective laser sintering

c. Fused deposition modeling

d. Soldier

e. Laminated object manufacturing



UNIT - 2 FUNDAMENTALS OF CNC MACHINES

PART- A

1. Define NC system?

NC is defined as a form of programmable automation in which the process is

controlled by alphanumeric data.

2. What is MCU?

MCU is a hardware system which reads, interprets and translates the program

of instructions into mechanical action of machine tool.

3. List out any four advantage of using NC?

Increased flexibility.

Reduced setup time.

Production of complex part.

Elimination of special jigs and fixtures.

4. What are the limitations of using NC?

Relatively high price.

More complicated maintenance, a special crew is desirable.

Highly skilled and properly trained programmers are needed.

5. What are all the problems encountered with NC system?

Part programming mistakes.

Non-optional speeds and feeds.

Problem with punched tape and tape reader.

Problem with controller and management information.

6. Define CNC?

CNC is defined as a NC system that utilizes a dedicated, stored computer

program to perform some or the entire basic NC functions.

7. Write the main functions of CNC?

Machine tool control.

In-process compensation.

Improved programming and operating features.

Diagnostics

8. What are the functions of diagnostic system in NC machine tools?

To identify the reason for a down time occurrence so that maintenance

personal should make repairs fast.



To alert to signs that indicate the imminent failure of certain component

which are considered unreliable

9. Write any four application of NC system?

Application are in aero equipment; printed circuit boards; coil winding;

automobile parts; and blue print of complex shapes.

10.List the differences between NC and CNC system?

NC system CNC system

1. Programming and

punched tape is read

every time

Only one time the tape is

read and stored.

2. Moderate manual work. Less manual work.

3. Medium flexible. More flexible

4. Part programming is

usedReprogramming is easy

11.List the differences between open loop and closed loop control system?

Open loop control system Closed loop control system

1. Feedback device is not used Feedback device is used

2. Low accuracy. Higher accuracy can be achieved.

3. Low maintenance is

required.

More maintenance is needed

4. Less expensive. Cost of the equipment is high

12.List any two advantages and disadvantages of open loop control system?

Advantages:

Low cost and less manual work.

Disadvantages:

Low accuracy.

Periodically adjustments are required to compensate backlash errors.

13.What is the function of a transducer?

Transducer is a device in which one form of physical quantity like speed,

velocity is converted into another form of physical quantity.



14.What are all the basic elements of closed loop control system?

a. Input parameter

b. Output variable

c. Controller.

d. Process.

e. Sensor.

f. Actuator.

15.Write the various types of MCU used in CNC machines?

Three types of MCU are

a. Housed MCU

b. Swing around MCU

c. Stand alone MCU.

16.Define DNC?

Direct numerical control system is defined as a manufacturing system in

which a number of machine tools are controlled by a computer through direct

connection and in real time.

17.List the main component of DNC?

Main component are

a. Central computer.

b. Bulk memory.

c. Telecommunications lines.

d. Machine tools.

18.Write the functions of DNC?

It will take some of the burden of the main computer.

Each satellite computer.

19.List out the types of CNC machine?

CNC machine can be classified as:

Machining centers

Lathe machines

Drilling machine

Turning centers

Milling machines

Gear shaping

CNC gear hobbling



20.Define the term “Basic unit length”?

The minimum possible incremental movement is called the Basic unit length

(BLU). The BLU might be on the order of 0.01 mm in typical machine tool

system.

UNIT - 3 CONSTRUCTION FUTURES OF CNC MACHINES

PART- A

1. Write the functions of sideways.

The functions of sideways:

a. To control the line of action of the carriage/table on which the

tool/work piece is held.

b. To absorb static and dynamic forces.

2. List out the characteristics of sideways used in CNC.

The sideways should have the following characteristics.

a. Good rigidity and damping capability.

b. Good wear and friction resistance.

c. Geometric and kinematic accuracy.

d. Ensure higher velocity of slide.

e. Protect against damage and sward.

f. Provision for adjusting the play

g. Position in relation to work area.

3. What are the different types of friction guide ways?

The different types of friction guide ways are:

a. Flat guide

b. Vee guide

c. Dovetail guide and

d. Cylindrical guide.

4. List the limitations of friction guide ways?

The limitations of friction guide ways ARE:

a. Surface to surface contact between the sliding members, which

leads to more amount of wear.

b. Large amount of friction and heat developed in the sliding parts.



5. Write the advantages of LM guide ways?

The following are the advantages:

a. To reduce the amount of wear

b. To reduce the friction.

c. To reduce heat generation

d. To improve smoothness.

e. Zero stick slip.

6. What is hydrostatic guide ways? State the classification of it?

The guide ways in which the surface contact between the sliding parts is

separated by a thin layer of fluid (oil or air) is known as hydrostatic guide

ways.

7. What is actuating system? Write the various types of actuating system used in

CNC?

Actuation systems are used to convert the rotational movement into

translation movement. The two types of actuation systems used in CNC are:

a. Screw and nut, and

b. Rack and pinion.

8. What are the advantages of ball screws sideways over conventional

sideways.

a. Ball screws have longer life.

b. Higher accuracy can be maintained.

c. Low frictional resistance and hence used for carrying heavier loads at

faster rate.

d. Low power requirement for driving.

9. What is meant by feed drive? List the different types of feed drives.

Feed drive is used to provide motion to the slide as per the motion

commands. Feed drives are classified as follows:

I. Servo motors,

a. AC servo motor,

b. DC servo motor,

c. Brushless DC servo motor

II. Stepper motors, and

III. Linear motors.



10.What is the function of ATC?

The function of ATC is to change the tool once the particular operation is over

and the next tool is automatically changed and positioned for machining

based on the tool sequence given in part program.

11.What is machining center? Write the different types of machining centre. How

it differs from conventional CNC milling machines?

The centers which consists of multi function CNC machines equipped with

ATC which are capable of carrying out milling, reaming, tapping, boring,

counter boring and allied operations without operator intervention is called

machining centre.

Different types of machining centers are:

a. Horizontal machining centre,

b. Vertical machining centre,

c. Universal machining centre.

12.What are the functions of feedback drives?

The functions of feedback drives are:

a. To convert one form of physical quantity like speed, displacement, etc.,

into electrical signals.

b. This electrical signal is then compared with the reference signal to

check whether the desired motion of tool/worktable is achieved or not.

13.Enumerate the various feedback devices used in CNC system?

There are two types of feedback devices used in CNC system.

a. Position feedback devices (Example : Linear transducers, encoders)

b. Velocity feedback devices (Example : Tachogenerator)

14.What is the use of position feedback circuits and classify it.

Position feedback circuits are used to measure the position of the tool edge

with reference to the machine slide. They may be classified as:


Rotary transducers Linear transducers

a. Rotary encoder

b. Resolver

a. Glass scales with line gratin.

b. Ferranti system.

c. Binary coded system.


15.What are the different forms of Inductosyn? Where it is used and why?

Inductosyn are classified into:

Rotary encoder and Linear encoder.

Rotary form is used in precision servo systems on machine tools whereas

linear forma are used in automatic machine tool slide controls.

Reason: Inductosyn is a precision feedback device for the accurate

measurement and control of angles or distances with inductive coupling

between conductors separated by a small space.

16.What is a rotary type encoder? Where it is used?

An encoder is a rotary transducer that provides continuous or discrete signal

value of an angular or linear movement.

It is used in the CNC at the end of the slide screw directly or through gearing

timer belt.

17.What is the role of optical grating in CNC drive?

An optical grating is a glass strip marked with series of equally spaced

transparent opaque lines. They are used as transducers on machine tools.

This is used to measure the position of the table.

18.What is Inductosyn?

Inductosyn is a analogue type position back device which is used for the,

measurement of control angle and/or linear distance.

19.Write the various measures employed in CNC machine to minimize the

structural deformation.

To avoid the structural deformation, following precautions have to be

considered.

a. Providing a proper design mild steel structure having higher stiffness.

b. Use of ribs, braces and plates to increase the stiffness of machine.

c. Providing large heat removing surfaces.

d. Use of excellent coolants.

e. Reduction of ambient temperature by using air conditioning units

20.Write the salient features of tooling system?

The following features should be considered before the selection of tooling.

a. Rigidity to withstand higher cutting forces



b. Rigidity to transmit the spindle power at higher speed.

c. Perform variety of cutting operations.

d. To keep down time

UNIT - 4 PART PROGRAMMING FOR CNC MACHINE

PART- A

1. Define numerical control.

Numerical control is a form of programmable automation in which the

mechanical action of machine tool or other processing equipment are

controlled by a program containing alphanumeric data numbers, letters and

symbols.

2. How tapes are standardized? List some of them.

Tape standardization covers two important categories.

a. Physical dimensions, and

b. Character coding.

3. What are the different types of dimensioning system used?

a. Absolute dimensioning or baseline dimensioning system.

b. Incremental dimensioning or delta dimensioning system.

4. What is BIT? What is the use of it?

‘Bit’ is an abbreviation of “Binary digit” which can be 1 or 0.Uses in binary

coded decimal system.

5. What is block? Write the significance of it?

Block is the basic unit of a part program input to the control. It contains

adequate information for the machine to perform a movement and for

functions.

6. What Is G code? How G codes are represented?

It is the series of combination of ‘1’s and ‘0’s.It represents a number or an

alphabet or any symbol.

7. Write the different types of tape programming format?

The following are the types of tape programming format.

a. Word address format,

b. Table sequential format,



c. Fined block format.

8. Explain the functions of codes G28 and M30.

G28 = Mirroring

M30 = End of data.

9. State the function of post processor in CAPP.

Post processor is separate computer program which has been used to

prepare the punched tape for a specific machine tool.

10.List out some of the important NC languages.

a. APT

b. ADAPT

c. EXAPT

d. Compact II

e. PROMPT

f. CINTURNII

11.What are the four statements used in APT language?

a. Geometric statements

b. Motion statements

c. Post processor statements

d. Auxiliary statements.

12.How can you represent an APT geometric statement?

Symbol = Geometry/Descriptive data

Example: point, line, circle, plane

13.What are the different types of surfaces used for achieving continuous path

commands?

a. Drive surface, which guides the tool.

b. Part surface, on which the bottom of the tool rides.

c. Check surface, which stops the movement of the tool.

14.List the motion command words used in achieving path commands.

a. GOLFT

b. GORGT

c. GOFWD

d. GOBACK

e. GOUP

f. GODOWN



15.What are the modifiers used with motion command words?

a. TO

b. ON

c. PAST

d. TANTO

16.List any four post processor statements.

a. COOLANT/ON,OFF,MIST

b. RAPID

c. TURRET

d. MACHIN

17.Write any four auxiliary statements.

a. INTOL

b. OUTTOL

c. CLPRNT

d. PARTNO

e. FINI

18.What are the identifications needed to store a tool library?

a. Tool dimension details and

b. Tool assembly details.

19.Difference between 21/2 and 3 axes machine.

a. 21/2 axis machining implies that the machine movements are in planes

parallel to the X-Y plane.

b. 3 axes machining implies that machine movements are in all the 3 axes

(X, Y and Z)

20.What is the role of computer aided part programming?

The role of computers in CAPP is as follows:

a. Input translation

b. Arithmetic calculations

c. Cutter offset compensators

d. Post processor.



UNIT - 5 COMPUTER AIDED PROCESS PLANNING AND DATA

BASE FOR CAM

PART- A

1. What is meant my process planning?

Process planning is the systematic determination of the methods by which a

product is to be manufactured, economically and competitively.

2. List the activities and associated with process planning.

a. Analysis finished part requirements

b. Determining operating sequence

c. Selecting “machines”

d. Selecting material parameters

e. Calculating processing times

f. Documenting process planning

3. What is meant by CAPP?

CAPP refers to computer-aided process planning. CAPP is used to overcome

the drawbacks of manual process planning. With the use of computers in the

process planning, one can reduce the routine clerical work of manufacturing

engineers. Also it provides the opportunity to generate rational, consistent and

optimal plans.

4. What are the basic approaches of CAPP?

a. Retrieval (or variant) CAPP system, and

b. Generative CAPP system.

5. Differentiate the underlying concepts of variant and generative CAPP

systems.

In variant CAPP system, a process plan for new part is created by

recalling, identifying and retrieving an existing plan for a similar part,

and making the necessary modifications for the new part.

Whereas the generative CAPP system automatically generates the

process plan based on decision logics and pre coded algorithms.

6. List the various components of a generative CAPP system.



A part description.

A subsystem to define the machining parameters.

A subsystem to select and sequence individual operations.

A database

A report generator

7. List some commercial variant and generative CAPP software systems.

Some of the commercial variant CAPP systems include CUTPLAN,

COMCAPP V, DCLASS, and INTELLICAP

Some of the commercial generative CAPP systems include AUTAP,

CMPP, GENPLAN, and LOCAM

8. What is CMPP?

The CMPP stands for computer-managed process planning. It is a

commercial generative process planning system capable of automatically

making process decisions.

9. Define the terms database and data model.

A database may be defined as a well organized collection of data that are

related in a meaningful way which can be accessed in differential logical

orders but are stored only once. A data model is a logical representation of a

collection of data elements/fields.

10.Define the terms ‘schema’ and ‘PBMS’?

The schema is a diagrammatic representation of the database

structure.

A database management system (DBMS) is the collection of software

which generates runs and maintains a database.

11.What is the use of data definition language (DDL) and data manipulation

language (DML)?

A data definition language is used to describe the schema, the

database definitions and the logical links between the data to the

DBMS.

A data manipulation language is used to describe only access or

retrieval transactions and to pass data to user programs.

12.What is data modeling?

Data modeling is a method of depicting graphically data groupings and the

relationship between groupings.



13.Classify data models.

a. Record - based data models

Hierarchical data models.

Network data models.

Relational data models

b. Object - oriented data models.

14.What is a hierarchical data model?

In a hierarchical database, fields or records area arranged in related groups

resembling a family tree, with lower - level records subordinate to higher -

levels.

15.What is a relational data model?

A relational data model relates or connects data in different files through the

use of a key field, or common data element.

16.What is an object - oriented database system?

An object - oriented database system uses “objects”, software written in small,

rescale chunks, as elements within database files.

17.What are data associations?

Data associations are the relationship between the attributes of an

entity.

Associations between attributes of an entity can be of three types.

One –to –one association,

One-to-many association, and

Many-to-many association.

18.List various relational database operators.

a. Union

b. Intersection

c. Difference

d. Product

e. Select

f. Project

g. Join

h. Divide

19.Write the purpose of data operators ‘select’ and ‘join’.



Select creates a relation by extracting specific rows from a specified

relation, usually by reference to particular attribute values.

Join builds a relation from the rows of two specified relations on the

basis of equal values in an attribute which is part of both constituent

relations.

20.List some important features of DBMS.

a. Data dictionary

b. Utilities

c. Query language

d. Data recovery

e. Report generator

f. Access security


Documents

Computer Aided Manufacturing - 2 Marks - All 5 Units