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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
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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
Answer: Page 1.57 - Dr.V.jayakumar
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
Answer: Page 1.36 - Dr.V.jayakumar
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
Answer : Page 2.25 - Dr.V.Jayakumar
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
Answer : Page 2.2 - Dr.V.Jayakumar
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
Answer : Page 1.47 - Dr.V.Jayakumar
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
Answer : Page 2.42 - Dr.V.Jayakumar
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
Answer : Page 2.24 - Dr.V.Jayakumar
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
Answer : Page 2.41 - Dr.V.Jayakumar
• 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)
Answer : Page 2.35 - Dr.V.Jayakumar
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
Answer : Page 2.28 - Dr.V.Jayakumar
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
Answer : Page 2.8 - Dr.V.Jayakumar
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
Answer : Page 3.3 - Dr.V.Jayakumar
• 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
Answer : Page 3.13 - Dr.V.Jayakumar
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
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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)
Answer : Page 3.79 - Dr.V.Jayakumar
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.
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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)
Answer : Page 3.36 - Dr.V.Jayakumar
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)
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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)
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= 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)
Answer : Page 3.90 - Dr.V.Jayakumar
• 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)
Answer : Page 3.79 - Dr.V.Jayakumar
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)
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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)
Answer : Page 3.62 - Dr.V.Jayakumar
• 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)
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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)
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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)
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• 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
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• 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
Answer : Page 4.18 - Dr.V.Jayakumar
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
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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
Answer : Page 4.34 - Dr.V.Jayakumar
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)
Answer : Page 4.14 - Dr.V.Jayakumar
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
Answer : Page 4.3 - Dr.V.Jayakumar
• 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.
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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
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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
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Answer : Page 3.3 - Dr.V.Jayakumar
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
Answer : Page 3.3 - Dr.V.Jayakumar
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
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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.
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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
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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
Answer : Page 5.8 - Dr.V.Jayakumar
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
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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
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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
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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
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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)