ME6005 PROCESS PLANNING AND COST ESTIMATION L T P C 3 … · ME6005 PROCESS PLANNING AND COST ESTIMATION L T P C 3 0 0 3 OBJECTIVES: ... Subject: Process Planning & Cost Estimation

REGULATION: 2013 ACADEMIC YEAR: 2018-2019

JIT-JEPPIAAR/MECH/Dr.P.K.CHIDAMBARAM /IVth Yr/SEM 07 /ME 6005/PROCESS PLANNING &COST

ESTIMATION/UNIT 1-5/QB+Keys/Ver1.0

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ME6005 PROCESS PLANNING AND COST ESTIMATION L T P C

3 0 0 3

OBJECTIVES:

To introduce the process planning concepts to make cost estimation for various

products after process planning

UNITI INTRODUCTIONTOPROCESSPLANNING 10

Introduction- methods of process planning-Drawing interpretation-Material evaluation–

steps in process election-.Production equipment and tooling selection

UNITII PROCESSPLANNINGACTIVITIES 10

Processparameterscalculationforvariousproductionprocesses-Selection jigs and fixture

selection of quality assurance methods-Set of documents for process planning- Economics of

process planning-case studies

UNITIII INTRODUCTIONTOCOSTESTIMATION 8

Importance of costing and estimation–methods of costing-elements of cost estimation–

Types of estimates–Estimating procedure-Estimation labor cost, material cost-allocation of

overhead charges-Calculation of depreciation cost

UNITIV PRODUCTIONCOSTESTIMATION 8

Estimation of Different Types of Jobs –Estimation of Forging Shop, Estimation of

Welding Shop, Estimation of Foundry Shop

UNITV MACHININGTIMECALCULATION 9

Estimation of Machining Time –Importance of Machine Time Calculation-

Calculation of Machining Time for Different Lathe Operations, Drilling and Boring-

MachiningTimeCalculationforMilling,ShapingandPlanning-MachiningTime

Calculation for Grinding




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OUTCOMES:

Upon completion of this course, the students can able to use the concepts of process

planning and cost estimation for various products.

TEXTBOOKS:

1. Peterscalon, “Process planning, Design/Manufacture Interface”, Elsevier science

Technology Books, Dec. 2002.

REFERENCES:

1. Ostwalal P.F .and Munez J.,“ManufacturingProcessesandsystems”,9thEdition,John

Wiley, 1998.

2. Russell R.SandTailorB.W,“OperationsManagement”,4thEdition,PHI,2003.

3. Chitale A.V and GuptaR.C.,“ProductDesignandManufacturing”,2ndEdition,PHI, 2002

4. Adithan. M., “Process planning and Cost estimation”, New Age International (P) Ltd.2007




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Subject code: ME 6005 Year/ Semester : IV/07

Subject: Process Planning & Cost Estimation Subject Handler: Dr.P.K.Chidambaram

UNIT I – INTRODUCTION TO PROCESS PLANNING

Introduction-methods of process planning-Drawing interpretation-Material evaluation–steps in

process selection-Production equipment and tooling selection

PART * A

Q.No Questions

1.

Describe the factors should be considered for equipment/machine.(BTL1)

Technical factors: physical size of the work piece, machine accuracy, power of the machine

Operational factors: Batch size, capacity, availability

2.

Define product design. (BTL1)

Product design deals with conversion of ideas into reality and, as in other forms of human

activity, aims at fulfilling human needs.

3.

What designing includes in product design? (BTL1)

• Specifications

• Experimental and development work for the production of desired product ;

• Calculation of all estimates; and

• Issuing necessary instructions to the production department for production

4.

List the characteristics of a good product design. (BTL1)

• Repair ability

• Modular design

• Redesigning

• Miniaturisation

• Drawing and specifications

• Functionality

5

Illustrate the factors affecting tooling selection. (BTL1)

• The three basic factors that determine tool performance are:

• The tool material

• The tool geometry

• The use of cutting fluids

6

Define bilateral tolerance. Give the examples (BTL1)

Bilateral tolerance is tolerance in which variation is

permitted in both direction from the specified direction.

7

List factors consider for Economic analysis? Economic Analysis (BTL1)

• How much investment is needed to manufacture the new product?

• Who are the estimated production cost per piece?




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• What is the expected volume of sales?

• What will be the expected profit margin?.

8 Define process planning. (BTL1) (May 2017)

Bridge between design and manufacturing.

9

Define manual process planning. (BTL1)

In traditional process planning systems the process plan is prepared manually. The task

involves examining and interpreting engineering drawings, making decisions on machining

processes selection, equipment selection, operations sequence, and shop practices..

10

What are the process planning methods? (BTL3)

11

Define CAPP. (BTL3)

In order to overcome the drawbacks of manual process planning, The Computer Aided Process

Planning (CAPP) is used. 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 plants. In addition CAPP provides

interface between CAD and CAM.

12

List the drawbacks of Retrieval (variant)CAPP System. (BTL2)

The components to be planned are limited to similar components previously planned.

Experienced process planners are still required to modify the standard plan for the specific

component.

The retrieval CAPP system has the capacity to alter an existing process plan. That’s why it is

also known as variant CAPP system

The commercially available retrieval CAPP systems are Multi Capp and MIPLAN.

13

Define generative CAPP systems. (BTL2)

In the generative approach, the computer is used to synthesize or generate each individual

process plan automatically and without reference to any prior plan.

The human role in running the system includes:

(a) inputting the GT code of given part design (b) monitoring the function.

14 List the four stages of machine selection. (BTL1)

First-cut selection, Power/force analysis, Capacity analysis and Operational analysis

15

List out the advantages of Generative CAPP. (BTL2)

Generative CAPP has the following advantages

• It can generate, consistent process plans rapidly.

• New components can be planned as easily as existing components.

• 3. It has potential for integrating with an automated manufacturing facility to provide

detailed control information.

16 What are the factors should be considered for process? (BTL1)(Dec. 2016)

• Economic-considerations:




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• Production rate and unit cost of production.

• Quality and reliability aspects.

• Lower process rejection.

• Minimum set-up time.

17

List the process planning activities. (BTL1)

Drawing interpretation, Material evaluation & process selection, selection of machines, tooling

& work holding devices, setting process parameters, selection of quality assurance methods,

cost estimation, preparing the process planning documentation , Communicating the

manufacturing knowledge to the shop floor.

18 What are the general classification of engineering materials for manufacture? (BTL1)

Ferrous metal, Nonferrous metal, plastics, ceramic, composite

19

Write any four cutting tool material.(BTL1)( High speed steel, tool steel, boron nitride

,Cemented carbide, Diamond.

PART * B

1

What is process planning? Explain process planning activities.(13 M), BTL2

Answer : Page 1.7 - Dr.V.jayakumar

“An act of preparing a detailed work instructions - manufacturer and assembly a

components - finished product in discrete part manufacturing environments”. (4 M)

Process planning activities: (9 M)

Step 1: Drawing interpretation-

Step 2: Material evaluation and process selection-

Step 3: Selection of machines, tooling and work holding devices-

Step 4: Settling process parameters

Step 5: Selection of quality assurance methods-

Step 6: Cost estimation-.

Step 7: Preparing the process planning documentation-

Step 8: communicating the manufacturing knowledge to the shop floor

2

Explain the two approaches commonly used in CAPP system. (13M) ,BTL2

Answer : Page 1.16 - Dr.V.Jayakumar ,

The two basic approaches or types of CAPP system are ( 3 M)

• Retrieval(or variant)CAPP system

• Generative CAPP system

Retrieval CAPP system:( 5 M )

• In this system, a process plan for a new part is created by recalling,

• Identifying and retrieving an existing plan for a similar part making the necessary

modifications for the new part.

Generative CAPP systems.( 5 M)

• To synthesize or generate each individual process plan automatically and without

reference to any prior plan.

• The human role in running the system includes:

(a) inputting the GT code of given part design (b) monitoring the function.




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3

Explain process, objectives and use of Process Selection. (13M), BTL2

Answer: Page 1.48 -Dr.V.jayakumar,

To establish the time - required for a qualified worker to carry out a specified job -

defined level of performance. (4 M)

Objectives of work measurement (5 M)

• To reduce or eliminate non-productive time.

• To fix the standard time for doing a job.

• To develop standard data for future reference.

Uses of work measurements (4 M)

• To compare the efficiency of alternate methods. When two or more methods are

available for doing the same job, the time for each method is found out by work

measurement.

• The method which takes minimum time is selected.

• Standard time is used as a basis for wage incentive schemes

4

Explain Drawing Interpretation in details. (13M) , BTL2

Answer: Page 1.24 - Dr.V.jayakumar

Information interpretation of an engineering drawing - Material of the component - produced

Weight of the component

Dimensions of the parts size and accuracy of the parts. ( 3 M)

Engineering drawing: Orthographic projection is the method of detailing a 3D object on a 2D

plane - different views viz front, top, right hand and left hand side views (3 M)

Types of drawing: (7 M)

Details drawings

• Single part drawings

• Collective drawings

Assembly drawing

• Single part assembly drawings

• Collective assembly drawings

Combined drawing

5

Explain Equipment and tooling selection in details. (13M), BTL2


Equipment Selection (5 M)

Technical Factors

• Physical size of the work piece

• Machine accuracy

• Surface finish

• Cutting forces

• Power of machine

Operational factors




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• Batch size

• Capacity

• Availability

Tooling selection ( 5 M)

• Constrains on tool selection

• Operating requirements for tool selection

• Factors affecting tooling performance

Tool selection methods ( 3 M)

• Evaluation of process and machine selection

• Analysis of machining operations

• Analysis of work piece characteristics

• Tooling analysis

• Selection of tooling

PART *C

1

Discuss the various Engineering materials for manufacture. (15 M) ,BTL2


Classification of engineering materials (6 M)

Ferrous material

Non-ferrous materials.

Polymers.

Ceramics.

Composites.

Properties and applications of engineering materials( 9 M)

Mechanical, thermal, magnetic, chemical etc.,

2

Explain the machine selection process and process selection method (Dec. 2016)( 15M),

BTL2

Answer: Page 1.36-Dr.V.jayakumar

Four steps of process selection (6 M)

Drawing interpretation, identification of critical processing factors, comparison of potential

manufacturing process, identification of suitable process.

Four Stages of machine selection (9 M)

First-cut selection, power/force analysis, capacity analysis, Operational analysis

UNIT II- PROCESS PLANNING ACTIVITIES

Process parameters calculation for various production processes-Selection jigs and fixtures

election of quality assurance methods-Set of documents for process planning-Economics of

process planning-case studies

PART – A

Q. No Questions




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1

List the functions of process planning. (M/J 2009) (BTL2)

• The systematic determination of the engineering processes and systems to manufacture a

product competitively and economically is a called operation planning.

• It is the stage between design and production.

• The plan of manufacture considers functional requirements of the product, quantity, tools

and equipment, and eventually the costs for manufacture.

2

What is Flow Chart? (BTL2)

Flow chart is one of the most commonly used for the collection and display of manufacturing

knowledge.

3

Define sequencing.(N/D 2012) (BTL1)

Sequencing is one of the process planning activities in which the order of the manufacturing

process is decided based on various factors.

4

What are the parameters required for calculation of various production processes?(BTL2)

• Size or dimensional requirements

• Tolerance requirements

• Surface finish requirements

• Production volume requirements

• Material requirements

5

Define – Manual Process Planning. (M/J 2013) (BTL2)

Process plan is prepared manually. Task involves examining and interpreting engineering

drawings, making decisions on machining processes selection, equipment selection, operations

sequence and shop practices.

6

List the factors affecting speed feed and depth of cut. (BTL2)

• The work piece material and geometry;

• The tool material and geometry;

• The processing time available as specified by production planning.

7

What is the use of quality assurance? (BTL2)

Identify and reduce the seven wastes of production which are overproduction, waiting,

transporting, inappropriate processing, unnecessary inventory, unnecessary motion and defects.

8

Write the factors to be considered for process and equipment selection. (BTL2)

• Production rate and unit cost of production.

• Quality and reliability aspects.

• Lower process rejection.

• Minimum set-up time.

• Functional versatility.

9

List the classification of machining process. (BTL2)

• Cutting Processes;

• Abrasive Processes;

• Non-traditional machining processes

10

What are the assumptions in break-even analysis? (BTL2)

The break-even analysis is based on the following assumptions :

• Selling prices will remain constant at all sales levels (i.e., quantity discounts are not

available).

• There is linear relationship between sales volume and costs.




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• It assumes that costs are classified into fixed and variable costs, ignoring semi-variable

costs.

11

Define break-even point. (BTL2)

• Level of sales at which total revenues, total costs are equal. It is a point at which the,

profit is zero.

• It is also known as "no-profit no-loss point".

• If a firm produces and sells above the break-even point, it makes profit.

• In case it produces and sells less than the breakeven point, the firm would suffer losses.

12

What are the methods of determination of break-even point? (BTL2)

• The algebraic method

• The graphical method.

13

What do you mean by Break-even point in terms of Sales Value? (BTL2)

. Break-even sales Fixed costs

(BEP in rupees) = 1 – Variable cost

Unit Selling price

14

Define contribution. (BTL2)

The difference between selling price and variable cost per unit is known as contribution or

contribution margin.

Contribution(C) = Selling price(SP) - Variable cost(VC)

15 Define P/V Ratio. (BTL2)

P/V Ratio = Contribution Sales

16

What do you mean by margin of safety? (BTL2)

Margin of safety is the difference between the existing level of output and the level of output at

BEP.

Margin of safety (in %) = (Sales - Sales at BEP) x 100 Sales

Greater value of margin of safety means higher profits to the firm.

If the safety margin is low, then the firm runs the risk of incurring losses.

PART - B

1 Explain work holding devices and elements of Jigs and fixtures. ( 13M) (Nov.16) BTL1

Answer : Page 2.21 - Dr.V.Jayakumar

It communicates - work holding device - tool engineer - detailed design - drawings -

manufacturing

Work holding device

To position - hold a work piece in a precise location - manufacturing operation

Types of work holding device can be classified:

• General work holding devices

• Specialist work holding devices (3M)

Jigs:

• Work holding device which locates / holds the work piece.

• It does not guide the cutting the tool.

Functions of jigs:

• To locate and position the work holding relative to the cutting tool.

• To clamp the work piece during drilling, reaming or tapping (5M)

Fixtures:

• Work holding device which only holds / positions the work piece.




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• It does not guide the cutting tool.

Functions of fixture:

• To locate and position and work piece relative to the cutting tool

• To clamp the work piece during machining, welding, inspection or assembly

Elements of jigs and fixtures

• Clamping elements

• Locating elements

• Tool guiding and setting elements (5M )

2 Discuss TQM and its Elements. ( 13M) , BTL2


Management approach of organization centred on quality, based on the participation - members -

aiming at long term success through customer satisfaction. ( 4M)

Elements/principles of TQM

• Top management commitment

• Focus on the customer

• Continuous Improvement

• Effective involvement

• Treating supplier as partner

• Establishing performance measures for the processes. (9M)

3 Explain various process of planning activities. (13M), BTL2


Process Planning Activities

• Analyse finished part requirements

• Determine operating sequence

• Select machines

• Material selection parameters

• Calculate processing time

• Document process planning ( 7M)

Reasons for documentation

• To provide a record for future job quoting, cost estimating, and standard costing systems.

• To have a record on hoe a part is processed in order to plan future parts with similar

design requirements in a consistent manner.

• To act as a vehicle for communication ( 6M)

4 What are the basic factors influencing process selection? Write down the process selection

of parameters ( 13M), BTL2


Factors influencing process selection:

There are a number of factors common to both the material and process selection decisions:

• the number of components to be made

• the component size

• the component weight

• the precision required




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• the surface finish and appearance required ( 4M)

The workability will also have a significant influence on the quality of the part, where quality is

defined by three factors,

• freedom from defects;

• surface finish;

Dimensional accuracy - tolerances (5M)

Process selection parameters:

• the material has been selected first, as opposed to manufacturing processes first, and

specified at the design stage;

• All the information contained within the design documents, that is, drawings, parts lists,

etc.

• Comprehensive and that all information required for manufactures can be derived

during the drawing interpretation. (4M)

5 Explain the Economics of process planning. ( 13M) BTL2


Manufacturing costs play an important part in the successful design and manufacture of a

product .Based on the model of added value, the manufacturing costume be less than the value

added to allow a profit to be made. ( 4M)

The types of decisions that can be made based on costs are: The type of material to be used

for a product.

• The type of manufacturing process to be used for a product.

• How many of a product to manufacture.

• Whether to make or buy in a product/part. ( 5M)

Financial information:

• Control

• Decision making

• Reporting and recording

• Cost elements of product selling price:

• Process plan (4M)

6 Discuss the selection of quality assurance methods. ( 13M), BTL2


The process planner provides the inspection criteria - accordingly the quality engineer decides

on the QA tools - techniques to be employed. ( 4M)

Process planner in this stage of selection of QA methods include: Identification of inspection

locations

• Identification of the most appropriate inspection and testing

• Identification of corrective action

Quality

Quality is fitness for use – Juran

Quality is conformance to requirements – Crossby ( 9M)

7 Discuss about documents required for process planning.(13M) BTL2


• Assembly and components drawings of the product and bill of materials

• Specification of various machine tools available in the catalogues of machine tools




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• Machining/machinability data handbook

• Catalogues of various cutting tools and tool inserts

• Charts of limits, fits and tolerances

• Tables of standard time for each operation

• Tables of standard cost

• Table of allowances

• Handbooks such as Design Date Hand book, tool Engineers Hand book, etc.,(13M)

8 What is inspection? Write briefly about different methods of inspection followed

industries. (13M)(Nov.17)) (Nov.16) (BTL2)


Function by which the product quantity is maintained (2M)

Methods of inspection:

• 100% inspection

• Sampling inspection (8M)

Types of inspection

• Inspection of variable

• Inspection of attributes (3M)

PART -C

1 Explain basic quality strategies and seven statistical tools of quality. (QA Tools) ( 15M)

BTL2


Detection strategy and Prevention strategy. ( 3M)

QA 7 Tools:

• Flow chart ( 2 M )

• Check sheet ( 2 M )

• Histogram ( 2 M)

• Pareto diagram (2 M)

• Cause and effect diagram (2 M )

• Control chart ( 2M )

2 The fixed costs for the year 2000-01 are Rs.6,00,000 variable cost per unit is Rs.40.Each

unit sells at Rs.160 Determine:

1. Break-even point a, in terms of physical unit, and b, in terms of rupees

2. If a sales volume of 5000 units has been expected, then what will the profit (or loss)

earned?

3. If a profit target of Rs.1,20,000 has been budged, compare the number of units to be

paid

4. The company sales 6500 units, calculate the margin of safety and profit (15M) BTL

3

Answer : Page 2.49- Dr.V.Jayakumar

QBEP = FC/SP-VC = 5000 units

BEP in Rupees = FC/1-(VC/SP) = Rs. 8,00,000 (3M)




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Profit( or loss) if Q = 5500 units

Sales volume = fixed cost + Profit

Contribution

Sales volume at Rs.7,25,000 = 6000 units (5M)

Margin of Safety When Q = 6500 units

Margin of safety = Sales – Sales at BEP / Sales

= 23.08% (7M)

3 From the following data calculate the BEP expressed in terms of unit and also the new

break-even point, if the selling price is reduced by 10 %.

Fixed expenses:

Depreciation – Rs.1,25,000

Salaries – Rs.1,00,000

Variable expanses:

Materials – Rs.4 per unit

Labour – Rs.2 per unit

Selling price - Rs.15 per unit (15M) BTL4


Fixed cost = Depreciation + Salary = Rs.2,25,000 (3M)

Variable cost = Material cost + labour cost = Rs.6 per unit (3M)

BEP = FC/(SP-VC) = 25,000 units (4M)

BEP when SP is reduced by 10%,

30,000 units (5M)

4

CAST STUDY

A Mild steel spindle is shown in figure, is required to be manufactured in a workshop.

Present the various activities involved in process planning.(15M) (BTL4)

Answer : Page 2.57 - Dr. V.Jayakumar




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• The given component drawing is carefully analysed to identify and list out the key

features of the part.

• The next step is identification of the operations involved and sequence of operation.

(7M)

• Based on the operations identified, the machines, cutting tools - measuring - checking

instruments are appropriately selected.

• Cutting speed, feed, depth of cut for the operations are to be appropriately selected from

the data book. (8M)




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UNIT-III INTRODUCTION TO COST ESTIMATION

Importance of costing and estimation –methods of costing-elements of cost estimation –

Types of estimates – Estimating procedure- Estimation labour cost, material cost- allocation

of overhead charges- Calculation of depreciation cost

PART- A

1 What are factors for calculating the probable cost of the product? (M/J 2009) (BTL1)

• Design time,

• Amount and cost of materials required,

• Production time required,

• Labour charges,

• Cost of machinery, overheads and other expenses,

• Use of previous estimates of similar parts,

2 Write the importance of cost estimating. (M/J 2009) (BTL 1)

Cost estimating is very important for all organizations, before starting actual production or

filling up the tenders because only accurate estimating can enable the factory - owner to make

vital decisions such as manufacturing selling policies.

3 Write the aims of cost estimation. (N/D 2009) (BTL 1)

• To establish the selling price of a product for a quotation or contract, so as to ensure

reasonable profit to the company.

• To determine the most economical process, tooling.

• To prepare production budget.

• To evaluate alternate designs of product.

• To initiate means of cost reduction in existing production facilities by using new

materials, new methods of tooling and processing.

4 List the functions of cost estimation. (N/D 2009) (BTL 1)

• Cost estimates are required to submit accurate tenders for getting the contracts.

• Cost estimates are required for the manufacturer to choose from various methods of

production the one which is likely to be most economical.

• Cost estimates are required for fixing the selling price of a product.

• Cost estimate gives detailed information of all the operations and their costs, thus

setting a standard to be achieved in actual practice.

5 List the types of estimates. (N/D 2011) (BTL 1)

• Fixing the selling price of the product.

• Help the contractors to submit accurate tenders for entering into new contract.

• Setting various standards for the purpose of comparison.

• Forecast the progress of production and cost of the order to keep control of any

variation of the material costs




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6 Write the importance of realistic estimates. (N/D 2011) (BTL 1)

• Over estimation

• Under estimation

• Realistic estimation.

Both the overestimation and underestimation are dangerous because both will ultimately lead

the enterprise to failure.

7 What are the components of a job estimate? (N/D 2012) (BTL 1)

• Before doing the cost estimation of a product, one should know the constituents of

estimation. Design cost,

• R & D cost

• Labour cost

• Drafting cost

• Materials cost

• Inspection cost

• Cost of tools

• Jigs and fixtures

• Overhead cost.

8 Define – Design Cost. (N/D 2012) (BTL 1)

The cost of design of a product is estimated by ascertaining the expected time for the design of

that product.

Estimated design cost = Estimated design time x Salary of designer per unit time.

9 What is Drafting Cost? (N/D 2013) (BTL 1)

After the completion of the design, the drawing has to be prepared by draftsman.

Drafting cost = Estimated time by draft man in preparing drawings x Salary of the draftsman

per unit time

10 Explain Overhead Cost. (N/D 2013) (BTL 1)

• Overhead expenses are those which cannot be charged directly to a particular product

manufactured.

• All expenses other than the direct material cost, direct labour cost, and direct expenses

are known, as overhead costs or indirect expenses.

• Administrative expenses, selling and distribution expenses are added to the overhead

costs.

11 Define – Costing .(M/J- 2010) (BTL 1)

Determination of an actual cost of a component after adding different expenses incurred in

various departments.

12 What are the aims of costing? (M/J-2011) (BTL 1)

The main aims of costing are

• Cost determination: To determine the actual cost of each component and cost of the

final product.

• For fixing selling price: To provide information to ascertain e selling price of the

product.

• Cost control: To analyse the expenses incurred in production that control can be kept

over them.

13 Write the common methods of costing. (BTL 1)

• Job costing or order costing




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• Batch costing

• Process costing

• Departmental costing,

• Operating cost method

• Unit cost method

• Multiple cost method

14 How to calculate the Job Costing or Order Costing?(BTL 1)

Finding the cost of each individual job or contract.

• Total cost for each order is obtained from the daily cost sheet

• Adopted in job order industries such as ship building, machine manufacturing,

fabrication, building contracts, etc.

15 Define Batch Costing.(BTL 1)

Form of job costing, instead of costing each batch of components separately, each batch of

components is taken together and treated as a job.

16 What you mean by Process Costing? (BTL 1)

• When a standard product is made which involves a number of distinct processes

performed in a definite sequence.

• Adopted in industries such as oil refining, chemical, paper making, paint, cement

manufacturing and other similar industries.

• Indicates the cost of a product at different stages as it passes through various

operations or processes or departments.

17 Define Departmental Costing.(BTL 1)

• Determining the cost of the output of each department separately for the manufacture

of the standardised products.

• This method is applied in industries like steel industry, automobile industry, etc.,

where each department is producing independently one or more components.

18 How to calculate Operating Cost Method?(BTL 1)

This method is used in firms providing utility services.

Example: In transport services, water works, electricity boards, railways, etc., cost is

determined on the basis of operating expenses.

That is, charges are made as passenger per km per m3 volume, per kilowatt-hour, tonne, etc.

19 Define Unit Cost Method.(BTL 1)

Adopted by the firms, which supply a uniform product rather than a variety of products such

as mines, quarries, etc.

20 Define Multiple Cost Method.(BTL 1)

Which manufacture variety of standardised products, having no relation to one another in cost,

quality and the type of. process, etc.

PART- B

1 Explain importance and objectives of costing and estimation.Nov.16,Nov17 (13 M) BTL2


• Process of forecasting the expenses that must be incurred to manufacture a product.

• All expenditures involved in design and manufacturing with all the related service

facilities such as pattern making, tool making as well as portion of the general

administrative and selling costs.

( 3 M)




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Importance of Estimating

• Estimating is of great importance to a concern because it enables the factory owner to

decide about the manufacturing and selling policies.

• It is obvious that too high estimates will not get jobs to the firm by quoting higher rates

according to overestimate whereas under estimating will put the owner to a loss and

will lead the concern to utter failure.

• So, estimation should be carried out accurately. The persons preparing estimates

should be highly qualified and experienced. (5 M)

Objectives or Purpose of Estimating • To establish the selling price of a product.

• To ascertain whether a proposed product can be manufactured and marketed

profitably.

• To determine how much must be invested in equipment.

• To establish a standard of performance at the start of project.

• For feasibility studies on possible new products. (5 M)

• To assist in long term financial planning.

• To prepare production budget.

2 Discuss estimation of labour cost, materials cost in detail. (13 M) BTL1


The total cost is made up of three main elements (5 M)

• Material.

• Labour.

• Expenses.

MATERIAL COST Material cost consists of the cost of materials which are used in the manufacture of

product. It is divided into the following: Direct Material Cost

Directly used for the manufacture of the product and become a part of the finished

product.

The procedure for calculating the direct material cost is as follows:

• From the product drawing, make a list of all the components required to make the final product.

• Calculate the volume of each component from the drawing dimensions after adding machining allowances, wherever necessary. (4M)

Indirect Material Cost

A few other materials are necessary to help in the conversion of direct materials into final

shape. Though these materials are consumed in the production, they don’t become part of the

finished product.

The indirect materials include oils, general tools, greases, sand papers, coolants, cotton

waste etc. The cost associated with indirect materials is called indirect material cost. (3 M)

LABOUR COST It is the expenditure made on the salaries, wages, overtime, bonuses, etc. of the




5- 19

employees of the enterprise. Direct Labour Cost

Direct labourers are one who actually works and processes the materials to convert it

into the final shape. The cost associated with direct labour is called direct labour cost. (6

M)

3 Explain the methods of depreciation. Nov.16 (13 M) BTL2

Answer: Page 3.69 - Dr.V.Jayakumar

Depreciation is the process of allocating the acquisition cost of the tangible asset less salvage value,

if any, in a system able and a rational manner over the estimated life of the asset. (4 M)

Methods of depreciation

• Straight line method

• Diminishing balance

• Annuity method

• Sum of years digits method

• Sinking fund method

• Insurance policy method

• Machine hour method

• Production unit method

• Revaluation

• Retirement method ( 9 M)

4 Briefly Explain the allocation of overheads. (13 M) (BTL2)


In Industries Producing Single Product The Total Overhead Costs May Be Simply Divided By

The Number Of Items Produced.

1. Allocation By Cost Proportion ( 7 M)

This Method Is Sub-Divided Into Three Categories :

Proportional To Prime Cost :

The Formula For Calculating The Percentage Of Overheads

Percentage of Overheads =

Total Overhead Cost/ Total Prime Cost *100

Proportional To Direct Labour Cost :

In This Method The Percentage Of Overhead Costs To Be Allocated Is Given By

Percentage of Overheads =

( Total Overhead Cost/Total Direct Labour Cost) *100

Allocation Proportional To Direct Material Cost :

According To This Method, The Percentage Of Overhead Cost Equals The Total Overhead

Cost Of The Factory Expressed As A Fraction Of The Total Direct Material Costs

Total Overhead Cost

Percentage Of Overheads =

(Total Direct Material Cost /Total direct Material Cost)*100

2.Allocation By Hourly Rate: ( 3 M)

This Method Is Again Sub-Divided Into Two Categories : By Man-Hour Rate :

The Rate Of Overhead Is Obtained By Dividing The Total Overhead Costs By The Total

Production Man-Hours Worked During That Period.




5- 20

Rate Of Overhead = By Machine Hour Rate

Total Overhead Cost For The Entire Factory/ Total Production On Man Hours Employed *100

In This Method The Overhead Costs Are Allocated On The Basis Of Fraction Of The Time

Used On Particular Machine In The Manufacture Of An Item

Rate Of Overhead Per Machine-Hour =

Rate Of Overhead Expenses For Specific Machine /No Of Machine Hours *100

3.Allocation By Unit Rate ( 3 M)

In This Method Of Allocation Of Overhead Costs, It Is Assumed That The Overhead

Expenses Are Proportional To The Total Output

Overheads Costs/Unit Produced =

Total Overhead Charges For Entire Factory/ No Of Unit Produced

5 Discuss the Cost of Product (Ladder of Cost). (13M) (BTL3)


Prime cost: = Direct material cost + Direct labour cost + Direct expenses.

Prime cost is also called as direct cost.

Factory cost: Factory cost = prime cost + factory expenses.

Factory cost is also named as works cost.

Office cost = Factory cost + Administrative expenses

Total cost = Manufacturing cost + selling and distribution expenses.

Selling price = Total cost + Profit

Profit = Total cost – Loss

Making price (or) catalogue price: Some percentage of discount allowed to the distributors of product is added into the selling price. (6M)




5- 21

6 A manufacture is making 100 units of an item per hour and incurs the following

expenses;

Direct material cost = Rs.35

Direct labour cost = Rs.200

Direct expenses = Rs.75

Factory on cost = 150% of labour cost

Office on cost = 30% of factory cost

Find out the selling price for a profit of 15% of the selling price (13M) (Nov. 16) (BTL3)

Answer : Page 3.66 - Dr.V. Jayakumar

Prime cost for 100 units = Direct material + Direct labour cost + Direct expenses

= 35+200+75 =Rs.310

Factory on cost for 100 units = 150% of labour cost

= (150/100)*310 = Rs.465 (5M)

Factory cost for 100 units = Prime cost+ Factory on cost

= 310+465 = Rs.775

Office on cost for 100 units = 30% of factory cost

(7M)




5- 22

= 30/100*775 = Rs232.50 (5M)

Total cost for 100 units = factory cost + office cost

= 775+232.50 = Rs.1007.50

Total cost/unit = 1007.50/100 =Rs.10.08

Profit = 15% on the selling price(given)

Selling price/item = total cost/unit + Profit/unit

Selling piece/unit = 110.08/0.08 = Rs.12.76 ( 5 M)

7 A CNC Machine was purchased for Rs.1,25,000 on 15th June 1995, the erection and

installation cost was Rs.10,000.the CNC machine is to be replaced by a new one on 14th

June 2010.If the estimated scrap value is Rs. 25,000,what should be the rate of

deprecation and deprecation fund on June 14th 2002.

If after 9 years of running ,some machine parts are replaced and the estimated

replacement cost is Rs.4,000,what will be the new rate of depreciation.(13M) (BTL3)


• Total cost (TC)= Machine cost+ Erection and Installation costs = Rs1,35,000

Rate of deprecation(D):𝑇𝐶−𝑆

𝑁 rupees = Rs.7333.33 (4 M)

• Deprecation fund collected up to 14th June 2002

73333.33*7 = Rs.51,333.33 (3M)

• New rate of deprecation (D’):

After 9th year, the book value of the machine=

Initial capital cost(C) – Depreciation cost for 9 years =Rs.69,000.03

Replacement cost = Rs.4,000

New book value C’ = 73,000.03

D’ =𝑐′−𝑠

𝑛′ = Rs. 8000

New rate of depreciation per year = Rs.8000 (6M)

PART - C

1 Explain expenses in detail. ( 15 M) (BTL4)


Expenses:

Apart from material and labour cost - several other expenditures such as cost of special layouts, designs, etc. (4 M) Direct Expenses

As chargeable expenses – include any expenditure other than direct material or direct

labour incurred on a specific cost unit.

(2 M)




5- 23

Indirect Expenses (Overheads)

• Production expenses

factory on cost - production overhead - factory overhead - work on cost -works overhead (2

M)

• Administrative expenses (2

M)

• Selling expenses

Spent towards securing orders - finding or retaining markets for the products

manufactured.

• Distribution expenses (2

M)

Paid for the distribution of the product - expenditure made on holding finished stock -

packing cost - dispatching them to the customer.

• Finished stock storages.

• Loss of packing.

• Loading, unloading charges, freight and warfare.

• Expenses of transportation and vehicles.

• Salaries of dispatch clerks and labourers. (3 M)

2

Calculate prime cost, factory cost, production cost, total cost and selling price per item from

the at a given below in table for the year 2012-13

Sl.No Particulars Expenses

in Rs.

1. Cost of raw material in stock as on 01.04.2012 25,000

2. Raw material purchased 44,000

3. Direct labour cost 14,000

4. Direct expenses 01,000

5. Factory/work overheads 09,750

6. Administrative expenditure 06,500

7. Selling and distribution expenses 03,250

8. Number of items produced 00,650

9. Cost of raw material in stock as on 31.03.2013 15,000

Net profit of the items is 10% of the total cost of the product (15 M) (BTL 4)


• Stock of material cost as on1/4/12 + raw material purchased+ stock of raw material as

on 31/3//13

= Rs 50,000 (3 M)

• Prime cost/item: prime cost for 650 units = direct material cost+ direct labour cost+

direct expenses

= Rs 65,000 (3 M)

• Prime cost/item = Rs.100 (3 M)

• Total cost = production cost+ total selling cost = Rs. 84,500

• Total cost/item = Rs.130 (3 M)

Selling price/item = total cost/item + Profit/item = Rs 143 (3 M)




5- 24

UNIT – IV PRODUCTION COST ESTIMATION

Estimation of Different Types of Jobs - Estimation of Forging Shop, Estimation of Welding

Shop, Estimation of Foundry Shop

PART *A

Q.No Questions

1

List the types of forging operations. (BTL 1)

• Upsetting

• Drawing Down (Fullering)

• Setting Down

• Bending

• punching

• Drifting

• Swaging

2

Define – Process Costing. (M/J 2013) (BTL 1)

When a standard product is made which involves a number of distinct processes performed in

a definite sequence.

It is adopted in industries such as oil refining, chemical, paper making, paint, cement

manufacturing and other similar industries.

3 Define Shear Loss.(BTL 1)

3 Explain methods of costing in detail. Nov.16 (15 M) (BTL1)

Answer : Page 3.22-Dr.V.Jayakumar

Methods of Costing (3 M)

• Process costing (3 M)

Standard product is being - performed in a definite sequence.

• In oil refining, chemical manufacture, paper making, flour milling, and cement manufacturing etc., this method is used.

• The object i.e., record and trace cots for each distinct stage.

• While costing, the by-products of each process should be considered.

• Job costing or order costing (3M)

Finding the cost of each individual job or contract. Absorbed on jobs on the basis of actual costs incurred or on predetermined costs.

• Materials requirements and prices to arrive at the direct material cost.

• Labour hours and rates to determine labour costs.

• Overhead costs.

• Percentage added to total cost to cover profit.

• Batch costing

• Form of job costing - component separately.

• Maintaining job cost sheets - sheets on which the cost of each component can

be transferred - finished product can be calculated. ( 3M)

• Hybrid costing systems

• Do not fall nearly into the category of either job costing or process costing

• Use some features of both main costing systems. (3M)




5- 25

Blank required for forging a component is cut from billets or long bars. During sawing, the

material equal to the product of thickness of sawing.

4 Define – Unit Cost Method .(M/J 2012) (BTL 1)

Which supply a uniform product rather than a variety of products such as mines and quarries.

5

Write the formula of manhour and machine hour rate. (BTL1)

Man-hour rate = Total overheads/Total direct man hour spent

Machine-hour rate = Total overhead/total productive machine hour

6

What is meant by materials cost? (N/D 2010) (BTL 1)

The cost spent for manufacturing of the product.

It consists of direct material cost and indirect materials cost.

7

What are the analyses used for overhead expenses? (BTL 1)

• Factory expenses,

• Administrative expenses

• Selling expenses, and

• Distribution expenses

8

What is Scale Loss? (M/J 2012) (BTL1)

In the forging process, heated work piece reacts with oxygen from air forms a thin film of

iron oxide on the outer surface of the wok piece. This thin film of iron oxide is called scale.

9 Define – Direct Labour Cost. (N/D 2008) (BTL 1)

Direct labour cost can be charged labour directly to the job under preparation.

10

What are the factors considered for calculating the time required for a particular

job?(M/J 2009)(BTL 1)

• set up time

• operation time

• handling time

• machining time

• tear down time

• Miscellaneous allowances.

11

Define Flash Loss. (BTL 1)

When dies are used for forging, certain quantity of material comes out of the die at the parting

line of the top and bottom halves of the die. This surplus wastage material is called flash.

Flash is generally taken as 20 mm wide and 3 mm thick.

12

What is meant by Depreciation due to Accident? (M/J 2009) (BTL 1)

Accidents may occur in the industry due to hazard and facility operations.

This may cause damage to the machines, plants, buildings, vehicles or such other fixed assets.

13

Define – Production or Manufacturing or Office Cost. (N/D – 2013) (BTL1)

Cost of each item incurred in manufacturing the finished product, right from purchasing the raw

material to the point when the finished product is ready for sale.

Manufacturing cost = Factory cost + Administrative expenses

14 Define – Prime Cost. (M/J – 2009) (BTL1)

It consists of direct material cost, direct labour cost and direct expenses.

15 Define – Factory or Works Cost. (N/D -2010) (BTL2)

It consists of prime cost and factory expenses.

16 What are the factors considered for calculating the time required for a particular job?

(BTL 1)




5- 26

• Set up time,

• Operation time,

• Handling time, machining time.

• Tear down time,

• Miscellaneous allowances,

• Personal allowances, Contingency allowances Fatigue allowances,

• Process allowances, Interference allowances, Special allowances.

17

Define Tear Down Time. (BTL1)

Time taken to remove job, tools, and other auxiliary equipment from the machine after the

last element of operation has been completed.

18 What is shrinkage allowance? (BTL1)

Shrinkage is the reduction in volume during the cooling of the cast metal.

19

Define Personal Allowances.(BTL1)

Worker to fulfil his / her personal needs such as washing hands, going to the lavatory, getting

water, tea, coffee, etc.,

Usually taken as 5% for male and 7% for female worker of the total working time.

20

Define Fatigue Allowances.(BTL1)

Provide a workman an opportunity to recover from physiological and psychological effects of

fatigue caused by carrying out a specified task under specified conditions.

Excessive work, repeated work, poor lighting, poor ventilation, machine noises, visual and

mental strain, etc.

21

Define welding and list its types.(BTL1)

It’s the process of joining similar or dissimilar metals by the application heat

Types:

• Plastic/pressure welding

• Fusion/non-pressure welding

22

List the pattern allowances.(BTL1)

• Contraction/shrinkage

• Draft

• Machining

• Distortion

• Shake

23

Define casting and pattern.(BTL1)

The molten metals or alloys are poured in the moulds and allowed to cool. The object is

called casting.

Pattern is replica of the object to be made by casing process

PART* B

1

Explain estimation in forging cost shop in detail. (13 M) BTL2

Answer: Page 4.6 - Dr.V. Jayakumar

Process in which the desired shape and size of an object is obtained through the plastic

deformation of the object. (2M)

Estimation of materials loss:

• Shear loss

• Tong hold loss




5- 27

• Scale loss

• Flash loss

• Finding flash loss

Sprue loss and position and work piece relative (2 M)

Estimation of forging cost:

• Material cost

• Labor cost

• Overhead cost

Total forging cost: Material cost+ Labor cost+ overhead cost. (7 M)

Calculation of Material cost:

To calculate the gross weight:

• Gross weight = Net weight + Material loss in the process

• Material cost = Gross weight * Price of raw material per Kg

• The length of the stock to be used= Gross weight* (Density of material * cross-

sectional area of stock

• Labour cost: Forging time per piece in hours * Labour rate per hour in rupees

Estimation of forging time. ( 4 M)

2

Calculate the net weight and gross weight for the component shown in figure .Density of

material used is 7.86 gm/cc. Also calculate 1. Length of 14 mm diameter bar require to

forge one component.2. Cost of forging/piece if: Material cost = Rs.80 per kg; Labour

cost = Rs.15/piece. Overheads=150% of labour cost. (13M) (April 16) BTL3


Net Volume = Volume of (A+B+C+D)

3.14/4(d)2 = 56784 mm3

Net weight/piece = Net volume* Density = 0.466 Kg (4M)

Shear loss = 5% of net weight = 0.0223 or 22.3 gms

Scale loss = 6% of net weight = 0.0267 kg or 26.7 grms

Flash loss = volume of flash * density = 146.2 grms

Sprue loss = 31 grams

Total material loss = 0.251 kg (4M)

Gross weight = Net weight + Total material loss

= 0.446+0.251 = 0.697 kg




5- 28

Length of 14 mm diameter bar required to forge one component

Gross volume = gross weight/density = 697/7.86*10-6 = 88676845 mm3 (5M)

L = length of the 14 mm bar required

3

Explain estimation of welding shop. (13 M) BTL2


Joining similar or dissimilar metals by the application of heat. (3 M)

Welding can be done with or without application of pressure and with or without the addition

of filler metal. (5M)

Total welding cost: Direct material cost+ Direct labour cost+ Direct expenses+ overhead

expenses (5 M)

4 It is required to prepare a hexagonal bolt of 15 mm diameter and 25 cm length from a

bar sock of 1.8 cm dia. Calculate the length of bar stock required. 4.7

Calculate the net weight and gross weight for the component shown in figure .Density of

material used is 7.86 gm/cc. (BTL4) ( 13M)


Net volume of bolt = volume of bolt head + volume of bolt shank (2 M)

Volume of the bolt shank = 3.14/4(7.5)2*225 = 9,940.19 mm3. (5 M)

Net volume of a bolt = 13,593.69mm3 (6 M)

5

Explain various forging operations and its estimation of cost in detail ( 13 M) BTL2


• Forging operations (5M)

• Upsetting

• Drawing down

• Setting down

• Bending swaging

Materials losses in forging: shear loss, tong hold loss, scale loss (3M)

• Estimation of forging cost Material cost

• Labour cost

Overhead cost (4M)

6 Estimate the weldinf cost for making a lap welded joint shown in figure.




5- 29

The available data are given below:

• Length of joint = 1 metre

• Electrode diameter = 6 min

• Minimum arc voltage = 30 volts

• Current used:250 ampers

• Welding speed = 10 m/hr

• Electrode used = 0.35 kg/m of welding

• Labour rate = Rs40 per hour

• Electrode rate = Rs.55 per kg

• Efficiency of welding machine = 60%

• Connecting ratio = 0.5

• Overhead charges = 40% of direct charges (13M) BTL3

Answer :Page 4.61 - Dr.V.Jayakumar

To find electrode cost:

Cost of electrode per metre of weld = electrode used /metre 8 * electrode rare = 0.35 X 55 =

Rs.19.25 (3M)

To find labour cost:

Time required for welding 1 m length = 1/welding speed = 1/10 = 0.1X40 = Rs.4

To find power cost: we know that,

Power cost = (V*A)/1000 = t/60 * 1/ƞ * 1/r * C =( 30X250)/1000 * 6/60 * 1/0.6 * 1/0.5 * 8 =

Rs.20 (5M)

To find over heads:

Total direct cost per metre of weld = electrode + labour cost + power cost = 19.25 + 4 + 20 =

Rs. 43.25

Overhead charges = 40% of direct charges = (40/100)x43.25 = Rs.17.30 (3M)

To find total welding cost :

Total charges for welding one metre length of joint = direct cost+ overheads =43.25+17.30 =

Rs.60.55

Total welding cost = 60.55x2 = Rs.121.10 (2M)

PART C

1

Estimate the cost of manufacturing a high carbon steel spanner to be made by die

forging. The following data are available:

i Batch size = 500 pieces

ii Die cost per batch = Rs 500

iii Stock cutting charges = Rs. 100/batch

iv Set up and machine operation cost = Rs.200/batch

v Labour charges = Rs. 100/batc




5- 30

vi Density of steel = 8.5 gm/cc

vii Cost of high carbon steel = Rs. 70/kg

viii Losses = 24% of net weight (15 M) BTL1

Answer :Page 4.31 - Dr.V.Jayakumar

Net volume of spanner = Volume of (A+B+C+D)

Volume of A = (15*6)(120-20-16) = 7560 mm3

Volume of B = 3.14 r2 * thickness = 12566.37 mm3

Volume of C = 8043 mm3

Volume of D = 2400 mm3

Volume of E = 1600 mm3 (6M)

Net volume = 24168.85 mm3

Net weight = 0.2054 kg

Losses = 24% of net weight = 0.0493 kg

Gross weight = 0.2054 + 0.0493 = 0.2547 kg

Material cost = Rs.70 /kg

Total material cost = 70*0.2547 = Rs.17.83. (4M)

Labour cost =Rs.100 /batch

Labour cost = Rs.0.2

Die cost/piece = Rs.1

Stock cutting charge/piece = 100/500 = Rs.0.4

Total cost of manufacturing a spanner =

Material cost + labour cost + die cost + stock cutting charges + set up and machine operation

cost

= 17.83+0.2+1+0.20+0.4 = Rs.19.6 (5M)

2

In a production concern, the variable overhead charges are Rs.4 per article and the fixed

overhead charges per month are Rs.40, 000. It is estimated that 75,000 articles are

produced each month under normal conditions. Find

i The normal overhead cost per article

ii If the factory cost drops to 85% production, the overhead charges that are

unrecovered

iii If the production is increased to 135%,by what amount these charges will be

over recovered

(15 M) BTL3




5- 31


The overload rate per article is the same as that during normal conditions

Total overhead = Fixed overhead+ total variable overheads

= 40000+(4*75000) = Rs.3,40,000

Normal overhead /article = Rs.4.533 (5M)

Overhead charges unrecovered if production drops to 85%

New monthly production = 63750 article (5M)

Overhead charges over-recovered if the production in increased to 135%

Monthly production = 1,01,250 articles

Overheads to be over-recovered = Rs.13,966.25 (5M)

3

Find out the cost of wood required for making the pattern of a lathe centre. Figure gives

the finished drawing of lathe centre. The figure gives the finished drawing of lathe

centre. Wood is available at the rate of Rs.12000/m3.consider the pattern

allowances.(15M) BTL3


Volume of rough wood required

Part A:

length = 44.42+3+3 = 50.42 mm

Width = 54.5+3+3 = 60.5 mm thickness = width = 54.5 +3+3 = 60.5 mm

Volume of rough wood required for part A = (50.42*60.5*60.5) = 184549.8 mm3 (3M)

Part B: These are two in number

length = 10.08+3+3 = 16.08 mm

Width = 54.5+3+3 = 60.5 mm

thickness = 54.5 +3+3 = 60.5 mm

Volume of rough wood required for part B = 2(16.08*60.5*60.5) = 117713.64 mm3 (3M)

Part C:

length = 23.25+3+3 = 29.25 mm

Width = 42.38+3+3 = 48.38 mm

Volume of rough wood required for part C = (29.25*48.38*48.38) = 68463.26 mm3 (3M)

Part D:

length = 77.75+3+3 = 83.75 mm

Width = 54.5+3+3 = 60.5 mm

thickness = 54.5 +3+3 = 60.5 mm




5- 32

Volume of rough wood required for part D = (83.75*60.5*60.5) = 306545.94 mm3

Total amount of wood required

184549.8+117713.64+306545.94 = 677272.65 mm3 or 67727.65*10-9m3

Rate of wood = Rs.12000/m3

Cost of wood = 12000*67727.65*10-9

Rs.8.12 (6M)

UNIT-V - MACHINING TIME CALCULATION

Estimation of Machining Time - Importance of Machine Time Calculation- Calculation of

Machining Time for Different Lathe Operations, Drilling and Boring - Machining Time

Calculation for Milling, Shaping and Planning -Machining Time Calculation for Grinding

PART *A

Q.No Questions

1 What is tear downtime? BTL 1

Time taken for a complete batch taken for machining.Remove the tools, jigs and fixtures

from the machine and to clean the machine and tools after the operation has been done on

the last component of batch.

2 What are the elements of machining time? BTL 1

• Set-up time

• Handling time

• Machining time

• Tear down time

• Down time

• Allowances

3 What is setup time? BTL 1

Time taken for study the component drawing, install and adjust the tools, jigs and fixtures on

the machine.

4 What is machining time? BTL 1

Time taken for a work piece to when the tool leaves the component after completion of

operation.

Depends on the type and extent of machining required, material being machined, speed, feed,

depth of cut and number of cuts required.

5 What is downtime? BTL 1

Time wasted by the operator due to breakdowns, non-availability or delay in supply of tools

and materials etc.

6 Enumerate the estimation in milling and list the operations done on a milling machine.

BTL 1

It is a very versatile machine and employs a multipoint tool, called milling cutter, for

machining. The various operations done on a milling machine include facing, forming or

profile machining, slotting, and key way cutting, etc.




5- 33

7 List the process parameters for lathe. BTL 1

• Length of cut

• Feed

• Depth of cut

• Cutting speed

8 Define Cutting Speed. BTL1

Speed at which the cutting edge of tool passes over the job and it is usually expressed in

meters per minute. Its depends on the cutting tool material, the work piece material and the

operation.

9 What is unit operation time? BTL 1

Sum of handling time and machining time for a job. Time that elapses between outputs of

two consecutive units of production. It is also called cycle time

10 List the allowances in machining time. BTL1

• Personal allowance

• Fatigue Inspection or Checking allowance

• Tool sharpening/Tool change allowance

• Other allowances

11 What is length of cut? BTL1

Distance travelled by the tool to machine the work piece.

12 Differentiate the operation drilling, boring and reaming. BTL1

• Drilling: Producing holes in a material

• Boring: Enlarging or finishing an internal hole

• Reaming: Small amount of material from a drilled / bored hole for perfecting the hole

13 What is meant by turning operation? Write the equation to calculate the turning time

on time. BTL2

Reducing the diameter of the workpiece.

T= 𝑨+𝑳+𝑶

𝒇∗𝑵* Number of cuts required

T = Time required for turning in minutes

f = feed per revolution in mm

L= length of the job to be turned in rpm

O = Over travel in mm

A = Approach length in mm

14 How long it will take a 12.7 mm drill to drill a hole of 80 mm deep in brass plate. Take

the cutting speed as 75m/mm and feed as 0.175 mm/rev? BTL3

N = 1000 𝑆

3.14𝐷 = 1879.78 rpm

Time for drilling T = 𝐿

𝑓∗𝑁 = 0.243 min or 14.6 sec

15 Give the formula for calculating over-travel, when cutter diameter is bigger than width

of workpiece, during face milling. BTL3

Added table travel = 1

2[𝐷 − √𝐷 + 𝑤2]

D = cutter diameter

Width of work piece

PART* B




5- 34

1 Explain calculation of machining time calculation for lathe operation. (13M) BTL2

Answer : Page : 5.4 - Dr.V.Jayakumar

Machining time is the time for machine works on the component from the time taken the tool

touched the work to when the tool leaves the component after completion of operation.

The following factors are consider Length of cut: Approach length + length of work piece to

be machined + over travel

Feed: Tool advances into the work piece during one revolution (5 M)

Depth of cut: thickness of the layer removed

Cutting speed(N) (8 M)

2 What is the machining time to turn the dimensions given in figure? The material is

brass, the cutting speed with H.S.S tool being 60 m/min, and the feed is 7.5 mm/rev,

depth of cut is 3 mm/pass .(13 M) BTL3


Step 1: for turning from 60mm to 40mm and 95 mm long

Number of passes = D-d/(2*depth of cut)

=318.3rpm (5 M)

Time required for turning

T1={L1/(f*N1) }*number of passes

=0.159min

Step 2: for turning from 40mm to 30mm and 55m long

Number of passes=D-d/(2*depth of cut)

=477.46rpm (5M)

Time required for turning

T2={L2/(f*N2) }*number of passes

Total turning time T=T1+T2

=0.159+0.0307=0.1897 min (3M)

3 Find the time required cylindrical job of dimensions: minor diameter 30 mm, major

diameter 80 mm and length 120 mm from a given round bar of 80 mm diameter and 120

mm length.

Assume: cutting speed = 75 m/min

Maximum feed by compound rest = 0.05 mm/rev

Depth of cut should not exceed 4 mm. ( 13 M) BTL 4

Answer : Page - 5.29 Dr.V.Jayakumar




5- 35

Time for taper turning

BC=√BE2+EC2

=103.08mm

Number of cuts required=EF/depth of cut

From triangle EFC

sinØ=EF/EC

From triangle CBE

sinØ=BE/BC=0.2425 (6 M)

EF=100*0.2425=24.25mm

Number of cuts= 24.25/4= 6.0625 ,say 7 cuts

N=1000S/(3.14D)=298.41 rpm ( 4 M)

Time for taper turning= {length of cut/(feed* rpm)} *number of cuts

={103.08/(0.05*298.41)}*7

=48.36min ( 3 M)

4 A CI table of size 250 mm * 600 mm is to be ground by a wheel having 20 mm face

width, If the table moves 6 m in one minute and the feed is 1/4th of the width of the

wheel, find out the time required for grinding in three cuts. (13M) BTL3

Answer: Page - 5.81 Dr.V. Jayakumar

Time required per stroke =m 𝑙𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑡ℎ𝑒 𝑡𝑎𝑏𝑙𝑒

𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑡𝑎𝑏𝑙𝑒 =

600

6∗100 = 1/10 = 0.1 min (3M)

Given that, feed = 1

4 * width of wheel = 5 min

Number of strokes = 𝑤𝑖𝑑𝑡ℎ 𝑜𝑓 𝑡𝑎𝑏𝑙𝑒

𝑓𝑒𝑒𝑑 = 250/5 = 50 (5M)

Time required per cut = time per stroke * number of strokes =m0.1*50 = 5 mins

Total time required for 3 cuts = 5*3 = 15 min (5M)

5 Estimate the machining the required for manufacturing a shaft shown in figure. From a

mild steel stock of 26 mm diameter.Assume

Feed for turning operation = 0.2 mm/rev

Cutting speed form turning and knurling operations = 20 /min

Cutting speed for threading = 12 m/min

Depth of cut not to exceed = 3 mm

Number of cuts for threading = 5 (13M) BTL4

Answer: Page -5.35 Dr.V. Jayakumar




5- 36

First operation :

Turning from 26 mm Ɵ to 25 mm and 135 mm long.

N =1000 𝑆

πD = 244.85 rpm

Time for turning T1 = 𝐿

𝑓+𝑁 = 2.757 min

Turning from 22 mm to 16 mm and 25 mm long

N =1000 𝑆

πD = 289.37 rpm

Number of cutting = 𝐷−𝑑

2∗𝑑𝑒𝑝𝑡ℎ 𝑜𝑓 𝑐𝑢𝑡 = 1

Time of cutting T4 = 0.432 min (5M)

Second operation: knurling for 10 mm long

N =1000∗𝑆𝑘𝑛𝑢𝑟𝑙𝑖𝑛𝑔

πD = 254.65 rpm

Time for knurling T5 =0.196 min (3M)

Third operation: threading for 25 mm long,

Pitch = 2 mm

numbers of cuts = 5

N =1000 𝑆𝑡ℎ𝑟𝑒𝑎𝑑

πD = 238.73 rpm

Time for threading T6 = 0.262.min

Machining time: machining time required for manufacturing =

T1+T2+T3+T4+T5+T6 = 7.185 min (5M)

PART C

1 Estimate the time taken to prepare a job as shown in figure from M.S stock bar 4cm in

diameter and 7.5 cm long .Assume the following data: Cutting speed for turning and

boing operation =20 m/min. cutting speed for drilling operation =30m/min . Feed for

turning and boring operation=0.2 mm/rev. Feed for 20mm drill=0.23 mm/rev. Depth of

cut not to exceed 3mm in any operation. (15M) BTL4

Answer : Page -5.87 Dr.V.Jayakumar




5- 37

Step 1: Turning from 40 mm to 35 mm

Numbers of cut= D-d/ 2* depth of cut

= 0.833

N = 1000 S/3.11*D = 159.15 rpm (3M)

Time for turning T1 = L/f*N = 2.36 min

Step 2: Drilling a 20 mm hole

N = 477.46 rpm

Time for drilling T2 = 0.683 min (3M)

Step 3: Under cutting (boring) from 20 mm hole to 25 mm hole

N = 318.31 rpm

Time for boring T3 = 0.707 min (3M)

Step 4:

Under cutting(boring)from 20mm hole to 25 mm hole

N = 318.31 rpm

T3 = 0.707 min (3M)

Step 5.

Under cutting(boring)from 20mm hole to 30 mm hole me =

N = 254.65 rpm

T4 = 0.491 min

Total machining time = T1 + T2 + T3 + T4 = 2.36 + 0.683 + 0.707 + 0.491 = 4.241 min

(3M)

2 A t-slot is to be cut in a C.I. slab as shown in fig. estimate the machining time. Take

cutting speed 25 m/min, feed is 0.25 mm/rev. diameter of cutter for channel milling is

80mm.

Estimate the grinding time to finish a shaft from 38.5mm to 30mm diameter. Length of

shaft as 300mm. Assume the following data: 5.59

Width of grinding wheel=50mm; depth of cut in roughening operation= 0.785mm;

depth of cut in finishing operation= 0.05mm; cutting speed= 12m/min.

Assume 1mm on diameter to be finished ground and remaining rough ground. (15 M)

BTL4

Answer : Page – 8.75 Dr.V.Jayakumar




5- 38

Step 1: Cutting a channel of 20 mm wide and 35 mm deep along the 260 mm length

For slot milling, added table travel = √Dd –d2

Added tool/ table travel = 39.68 mm

Total tool/table travel = length of job + added tool/table travel = 299.68 mm ( 4 M)

rpm of the cutter, N = 1000 S/3.14*D = 100 rpm

Time for cutting slot, T1 = Total table travel

Feed/rev*rpm = 11.987 min ( 4 M)

Step II: Cutting T-slot of dimensions 60*20 mm with a T-slot cutter

Diameter of cutter = 60 mm

rpm of the cutter N = 132.63 rpm

Since diameter of the cutter = width of slob, therefore

Over-travel of tool = 0.5*Diameter of the cutter = 30 mm

Total tool/table travel = 260+30 = 290 mm ( 4 M)

Time taken,T2 = 8.746 min

Total time to cut the T-slot, T = T1+T2 = 20.733 min ( 3 M)

3 A cast iron table of size 250 mm*600 mm is to be ground by a wheel having 20 mm face

width ,If the table moves 6 m in one minute and the feed is 1/4th of the width of the

wheel, find out the time required for grinding in three cuts. ( 15 M) BTL3

Answer : Page -5.29 Dr.V.Jayakumar

Time required/stroke = length of table/speed of table = 0.1 mm

Feed = ¼*width of wheel = 5mm (5 M)

Number of strokes = width of table/feed = 50 ( 5M)

Time required per cut = time /stroke* number of strokes = 5 min

Total time required for 3 cuts = 15 min (5M)

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