PROCESS PLANNING AND COST ESTIMATION

PROCESS PLANNING AND COST
ESTIMATION
Mr.A . FELIX SAHAYARAJ ME
ASSISTANT PROF
MECHANICAL ENGINEERING
KALAIGNAR KARUNANIDHI INSTITUTE OF TECHNOLOGY
COIMBATORE - 641402

process planning
• Activities involved to convert design into the
product.

Types of process planning
• Manual process planning
– Traditional approach
– Workbook approach
• Computer aided process planning
– Retrieval process planning (variant)
– Generative process planning

Traditional approach
• Manual
• Based on process planner experience and
intuition it will vary.
• Stages
Stage 1 process planner interpret product
drawing
Stage 2 refer manual
Stage 3  documenting routing sheet

Workbook approach
• Modified version of the traditional approach
• Referring workbook
• Workbook which contains predetermined
sequence of operation (standard procedures).

Advantages of manual process
planning
• Suitable for small scale industries.
• Highly flexible.
• Low investment costs.

Disadvantages of Manual process
planning
• Time consuming process.
• Need a skilled process planner.
• Possibilities for human error.
• Inconsistent process plan.

Computer aided process planning
(CAPP)
why we need to go for CAPP?
• Overcome the drawbacks of Manual process
planning.
• Reduce the routine work of manufacturing
engineer.
• Act as an interface between CAD and CAM.

Benefits of CAPP (2 mark)
• Productivity improvement.
• Production cost reduction
• Elimination of human error.
• Product standardization.

Approaches of CAPP
• Retrieval CAPP system (variant approach)
• Generative CAPP system

Retrieval CAPP system
• Concept similar parts will have similar
process plan.
• Process plan for a new product is created by
recalling, identifying or retrieving the existing
plan for similar product.

Retrieval CAPP system (procedure)

Advantages of retrieval CAPP
• Once a standard plan is produced, similar
plans can be produced using existing plan.
• Simple programming (when compared to
Generative type).
• Easy to learn and use.
• Commercially available retrieval CAPP systems
are  MultiCapp and MIPLAN

Generative Process plan
• In generative approach, the process plan were
generate process plan automatically without
any reference to prior plan.
• Concept the concept is based on decision
logics and pre-coded algorithms.

Components of Generative process
plan
Part description
Sub system (define
machining parameters)
Subsystem (define
sequence of operation )
database
Report generator

Advantages of generative CAPP
• Generate consistent process plan.
• New components can planned easily
• Integrating with an automated manufacturing
facility.
• Example APPAS,CMPP,EXCAP,XPLAN

Drawing interpretation
• First step
• Getting information from the drawing.
• Prepared by design department.
• Details required
– Material of the component, its designation
– Number of parts to be produced
– Weight of the component
– Dimensions of the part
– Dimensional and geometric tolerances
– Size and accuracy of the parts

Engineering drawing
• Universal language
• Projection
– Orthographic
– Pictorial
• Types of drawing
– Detailed drawing
– Assembly drawing
– Combined drawing

Detailed drawing
• Detailed drawing
– Single part drawing
– Collective single part drawing

Collective part detailed drawing

Assembly drawing
• Assembly drawing
– Single part assembly drawing
– Collective assembly drawing

Information on the drawing sheet
required
• Geometric and dimensions (complete dimensions)
• Material specifications (material code , example SS310)
• Notes of special material treatments (like heat treatment)
• Dimensional tolerances (upper limit and lower limit eg:
10±0.2)
• Geometric tolerances (straightness, flatness, roundness)
• Surface finish specifications (roughness and waviness)
• Tool references
• Gauge references
• Quantity to be produced
• Part lists

Material Evaluation
• Second activity of process planning.
• Material selection (done by design engineer)
– Choose the material
• Material evaluation (done by process planning
engineer)
– Check the chosen material for further process

Metals and their classification

Metals
• Based on iron content
– Ferrous(iron more)
– Non ferrous (iron content less)

Ferrous
• Ferrous
– Steels (carbon percentage less than 2%)
– Cast iron (carbon percentage more than 2%)

Steels
• Steels
– low alloy steel (percentage of alloying element is less
than 5 %)
• Low carbon steel (mild steel) (carbon percentage less than
0.25%)
• Medium carbon steel (0.25 % to 0.6 % )
• High carbon steel (more than 0.6 %)
– High alloy steel (percentage of alloying element is
more than 5 %)
• Tool steel
• Stainless steel (chromium content is more than 12 %)

Cast Iron
• Cast iron (carbon percentage more than 2 %)
– Grey most widely used
– White hard and brittle
– Malleable  highly malleability
– Spheroidal Graphite cast iron (SG cast iron) high
ductility.

Non ferrous materials
• Non Ferrous materials (iron content low)
Example Aluminium, Copper, Lead, Tin, Zinc,
Nickel, Titanium, Magnesium
• Properties
– Light in Weight.
– High electrical and thermal conductivity.
– Better resistance to corrosion.
– Ease of fabrication.
– Colour.

Polymer
• Polymers a substance which has a
molecular structure built up chiefly or
completely from a large number of similar
units bonded together.

Ceramics
• Ceramics A ceramic is any of the various
hard, brittle, heat-resistant and corrosion-
resistant materials made by shaping and then
firing a nonmetallic mineral, such as clay, at a
high temperature.

Ceramics Properties
• Ceramics are strong, hard and brittle.
• Can be used at high temperature.
• They are good thermal and electrical
insulators.

Ceramic Example
• Alumina
• Silicon Carbide
• Silicon nitride
• Sialons

composites
• Composites composites are the
combination of two or more materials having
superior properties than the original
materials.

Material selection process (procedure)

Material evaluation method
• Steps
– Shape and geometry considerations
• Dimension
• Size
• Surface finish
– Material property requirements
• Mechanical
• Physical
• service
– Manufacturing considerations
• Interchangeability
• Quality assurance
• Ease of manufacturing and assembly

Steps in process selection
• Process method of shaping, joining and
finishing
• We need to choose right process.

Factors in process selection
• Material form
• Component shape and size
• Economic consideration
• Dimensional and geometric accuracy
• Surface finish
• Batch size
• Production rate

Steps in Process Selection
• Drawing interpretation (process-shape matrix)
• Identification of critical processing factors
(process material matrix)
• Comparison of potential manufacturing process
(compare)
• Identification of suitable process (select)

Production equipment and tooling
selection
• Selection of production equipment (machine)
• Selection of tooling (tool)

Factors consider Production
equipment selection (machine)
• Technical factors
– Physical size
– Machine accuracy
– Surface finish
– Cutting force
• Operational factors
– Batch size
– Capability
– availability

Stages in tooling selection
• Evaluation of Process and tooling selection
• Analysis of machining operations
• Analysis of workpiece characteristics
• Tooling analysis
• Selection of tooling

Process Planning Activities
• Process parameter calculation for various
production process
• Selection of jigs and fixtures
• Selection of quality assurance methods
• Set of documents for process planning
• Economics of process planning
• Case studies

Process Parameter calculation for
various production process
• Process Parameter
– Cutting Speed
– Feed and Feed rate
– Depth of Cut

Cutting Speed
• Cutting Speed Relative speed between tool
and workpiece
• Unit mpm

Cutting Speed
• Factors affecting cutting speed
– Nature of cut
– work material
– Cutting tool material
– Cutting fluid application
– Purpose of machining
– Kind of machining operation
– Capacity of machining tool
– Condition of the machine tool

Turning problem
• Turning a rod of 60 mm diameter and the
maximum spindle speed is 500 rpm. calculate
the cutting speed in m/min.

Feed and Feed Rate
• Feed distance through which the tool
advances into the workpiece
• Feed rate rate at which cutting tool
advances the workpiece.
• Unit mm/rev or mm/min

Feed rate for turning and boring

Depth of Cut
• Depth of cut thickness of material removed
in one cut.
• Depth of cut is always perpendicular to feed
direction
• Unit mm

Speed, feed, and depth of cut
https://www.youtube.com/watch?v=NN3vOblJQ
Q8

Selection of Jigs and Fixture
• Work holding device to position and hold the
work piece in precise location while
manufacturing operation.
• General work holding devices
– Vices
– Chuck
– clamp
• Special work holding devices
– Jigs
– fixtures

Jigs and Fixture
• Jigs
– Which locate and hold the workpiece and guides
the tool
• Fixture
– Which locate and hold the workpiece and does
not guide the tool.

Jigs and Fixture animation
• https://www.youtube.com/watch?v=5m5HqE
y_Jqs

Functions of jigs and fixtures
• Chris Strikes Long Raining Sixes
• Clamping exert force to press the workpiece
• Supporting supporting machines
• Locating position the workpiece
• Resist forces
• Safety factors

Reason for using jigs
• Reduce the effort of setting workpiece
• Reduce production cycle time
• Semi skilled labour employed
• Reduce the cost of inspection

Factors considering during selection of
jigs and fixture
• Physical characteristics of tool and workpiece
• Type and capacity of machine
• Study of safety and ejecting devices
• Required level of accuracy

Types of jigs and Fixtures
• Types of Jigs
– Drill Jig
 drilling, tapping, chamfering, spot facing, reaming
countersinking
– Boring Jig
• Types of Fixture
– Turining, milling, grinding, broaching, boring,
taping, welding, assembly

Selection of quality assurance
methods
• Quality is fitness for use (Juran)
• Quality assurance maintenance of a desired level of
quality
• Selection of quality assurance methods for critical factors
• Critical factors
– Dimensional tolerance
– Geometry tolerances
– Surface finish

Steps involved in quality assurance
• Identification of inspection location
• Identification of most appropriate inspection
technique
• Determination of frequency of testing
• Evaluation of inspection and test data
• Identification of corrective data

Quality
• Quality Assurance Strategy
– Detection Strategy
– Prevention Strategy

Statistical Quality Control
• Descriptive Statistics mean, median, mode
• Statistical process control using control
charts
• Acceptance sampling samples are taken to
decide quality

Control chart
Attribute Vs Variables

Inspection and measurement
• Maintain the product quality
• Stages
– Pre-production inspection
– Inspection during production
– Post production inspection

• Types
– 100% inspection
– Sample inspection

• Inspection of attributes (surface finish,
accuracy)
• Inspection of variables (with quantitative
numbers)

Factors to be considered while
Selecting measuring instruments
• Accuracy
• Linearity
• Magnification
• Repeatability
• Resolution
• Sensitivity
• stability

Set of documents required for process
planning

Economics of Process planning
• Process planner should have fundamental
knowledge on cost estimating, cost
accounting, various types of costs,
components of cost and calculation of cost of
the product manufacturing

Economics of Process planning
• Knowledge of costing will help process
planner and management for taking following
decisions
– Type of material to be used
– Type of manufacturing process
– Volume of product
– Make or buy decision
– Design of a product

Break even analysis
• It is graph plotted between sales and volume

Break even analysis
• Break even analysis it is a study of inter
relationships between sales, cost and
operating profit at various levels of output.
• Break even point no profit no loss
(revenue=cost)

Break even analysis
• To help in deciding profitable level of output
• To compute cost and revenue for all volumes
• To take decision regarding make or buy
• To take plant expansion decisions

Break even Point
• Algebraic method
• Graphical method

Process planning activities
• Step 1 Analyse (Drawing interpretation)
– Spindle have to be manufactured 60 mm dia and
130mm length
– Spindle consist of three concentric cylinder
– One internal thread and one external thread have
to be cut

– material of the component is mild steel
– Dimensional tolerance is 0.05
– Number of parts to be made = 200

• Step 2 Identification of operation involved
and sequence of operation
• First operation  turning from 60 mm
diameter to 50 mm diameter for 130 mm
length

• Second operation  50 to 40 for 110 length
• Third operation 40 to 35 for 65 length
• Fourth operation  drilling 10 mm dia for 45 mm
length
• Fifth operation internal threading
• Sixth operation external threading

UNIT 3
INTRODUCTION TO COST
ESTIMATION

Topics to be covered
• Cost Estimation (Estimation) Vs Cost Accounting
(Costing)
• Importance of Cost Estimation
• Types of estimates
• Elements of cost estimation
• Estimating procedure

• Importance of Costing
• Methods of costing
• Elements of Costing
• Estimate of labor cost and material cost
• Allocation of overhead charges
• Calculation of depreciation cost

Cost Estimating (Estimation)
• Process of determining the probable cost of
the product before the start of manufacture.

Cost Accounting (Costing)
• Process of determining the Actual cost of the
product after the manufacturing.

Importance of cost estimation
• Important for all organizations.
• Important for deciding manufacturing and
selling policies.
• Problem
– Overestimating problem with competitive
prices
– Underestimating will lead to financial loss

Objective of cost estimation
• To establish selling price of product
• To verify the quotation by vendors
• To take make or buy decision
• To prepare production budget

Types of estimate
• Preliminary cost estimate
• Final Cost estimate

Preliminary cost estimate
• Based on incomplete data
• Less Accurate
• Suitable for new project
• Procedure
– With drawings
– Without drawings

Final Cost estimate
• Based on complete data
• Most Accurate
• Huge amount of money spent to make the
estimate

Classification of cost estimates based
on design level
• Conceptual phase (cost estimate accuracy
±30%)
• Preliminary design phase (cost estimate
accuracy ±20%)
• Detailed design phase (cost estimate accuracy
±10%)

Methods of Estimate
• Conference method
• Comparison method
• Detailed analysis method

Methods of Estimate
• Parametric Estimating
– Uses relationship between the historical data and
other variables
• Statistical Estimating
– Sampling or random sampling used in general
study for variable

Data Requirements for cost estimating

Data Sources for cost estimating

Possible Estimation
• Over Estimation
• Under Estimation
• Realistic Estimation

Cost of Research and Development

Importance of Cost Accounting
• Determining , classifying and analyzing the
cost and income of business firm
• Determining prices to be quoted to customers
• Forming basis for managerial decision
– To make or buy decision
– To introduce new product or drop on existing one

Importance of Cost Accounting
• Cost control through the accumulation and
utilization of cost data.
• Establishing standard for measuring efficiency.

Methods of Costing
1. Job costing
2. Batch Costing
3. Process costing
4. Department costing
5. Operating cost method
6. Unit cost method
7. Multiple cost method

Job costing
• Method is concerned with finding cost of the
individual job
• Suitable for job order industries (ship building,
machine manufacturing, fabrication, building
contracts)

Batch costing
• Method concerned with instead of costing of
separately, each batch of components is taken
together.
• Used to determine the cost of group of similar
products

Process Costing
• Method concerned with standard product
with number of distinct processes performed
in a definite sequence.
• Used in oil refining, chemical, paper making,
paint , cement manufacturing

Department costing
• Method is suitable for cost of output of each
department separately for the manufacture of
standard products
• Used in Steel industry and automobile
industry.

Operating cost method
• Method is suitable for company providing
utility services
• Example transport services, water works,
electric board,
• Cost is based on operating expenses (per Km)

Unit cost method
• Method is suitable for companies with the
uniform product
• Example mines, quarries etc.

Multiple cost method
• Method is suitable for companies producing
variety of standardized products, with no
relation between cost, quality and process.

Material cost
• Direct Material material becomes the part
of product
– Mild steel used for spindle
– Wood used for table
• Indirect Material used to convert the direct
material into finished product
– Greese, lubricating oil, coolant

Labour cost
• Direct Labour labour directly work on the
produt
– Welder, casting technician etc
• Indirect Labournon productive staff to help
the productive labour
– Supervisor, inspector, store keeper, watchman

Expenses
• Direct Expenses charged directly to the
particular job
– Design
– manufacturing
• Indirect Expenses other than material, labor
and direct expenses.(Overhead charges)

Overhead charges
• Factory expenses
– Cost fuel, power and internal transport
– Repair and maintenance
• administrative expenses
– Charge of higher officials
– Office rent, legal charges, audit fees
• Selling expenses
– Cost of sales manager
– Cost of advertising
• Distribution expenses
– Packaging and delivery
– Store keeper
– unloading

Components of cost
• Prime cost
• Factory cost
• Production cost
• Total cost
• Selling Price

Estimation of material cost
Procedure

Estimation of Labor Cost
• Cost spent on workers who directly involve in the
manufacturing operations.
• Formula
Labor cost= standard time * cost of labour per hour
• Estimator should have knowledge on
– Operations involved
– Tools used
– Machines used

Estimation of Standard time
problem

Estimation of Standard time (with allowances)
problem

Estimation of Standard time (with
allowances)

Calculation of Selling Price
Problem

Methods of finding Depreciation fund

Straight line method
• Amount of depreciation distributed over the
equal period of installments.
• Merit simple method (little calculations)
• Demerit this method does not consider
maintenance and repair charges

Diminishing balance method
(Reducing balance method)

Reducing balance method
Formula

Reducing balance method
Problem

Annuity method
• In sinking fund interest amount earned invested
on outside agencies but in this method invested
within company.

Sum of years digit method
Problem

UNIT 4
PRODUCTION COST ESTIMATION

• Estimation of Forging Shop
• Estimation of welding
• Estimation of foundry shop

Forging
• ForgingForging is a manufacturing process
involving the shaping of metal using localized
compressive forces.

Types of Forging
• Hot Forging
– Forging done above the Recrystallization
temperature
• Cold Forging
– Forging done below the Recrystallization
temperature

Forging process
• Hand forging
• Drop forging
• Press forging
• Machine forging

Forging operations
• Upsetting
• Drawing down
• Setting down
• Bending
• Punching
• Drifting
• swaging

Estimation of material losses in forging
• Shear loss
• Tonghold loss
• Scale loss
• Flash loss
• Sprue loss

Estimation of forging cost
• Material cost
• Labour cost
• Overhead cost

Estimation in welding shop
• Welding welding is the process of joining of
similar or dissimilar metal by application of
heat

Types of Welding
• Pressure Welding
• Non Pressure Welding

UNIT 5
MACHINING TIME CALCULATION

Estimation of machining time
• Machining time is the time which machine
works on the component.
• Eg: from the time tool touches the work to
tool leaves the work

Terms used
• Length of Cut
• Cutting Speed
• Feed
• Depth of Cut

Length of Cut
• Approach Length
• Length of workpiece to be machined
• overtravel

Cutting Speed
• Cutting Speed Relative speed between tool
and workpiece

Feed and Feed Rate
• Feed distance through which the tool
advances into the workpiece
• Unit mm/rev or mm/min

Depth of Cut
• Depth of cut thickness of material removed
in one cut.
• Depth of cut is always perpendicular to feed
direction

Importance of machining time
calculation
• Inorder to find out the machining cost
• Reduction of total manufacturing time, T
• Increase in MRR, i.e., productivity
• Reduction in machining cost without sacrificing
product quality
• Increase in profit or profit rate, i.e., profitability.

Calculation of machining time for
different lathe operation
• Turning
• Chamfering
• Facing
• Knurling
• Thread Cutting

Facing operation by lathe
• The process of reducing length of the material
is called facing
• This can be done by the single point cutting
tool

KNURLING
• KNURLING MEANS CREATING CROSS LINKED
PATTERN ON THE WORKPIECE BY LATHE
MACHINE.

Machining time calculation for Drilling

Machining time calculation for
Boring(formula)

Milling
• Milling is the removal of material from
workpiece by rotary multipoint cutting tool.
• Operations
– Face milling
– Slot milling or slab milling
– Profile machining or forming
– Keyway cutting
– indexing

Machining time calculation for milling
formula

Machining time calculation for milling

Determination of added table travel
• Face milling

Determination of added table travel
• Slot milling or slab milling

Shaping

Shaping (problem)

planning

Grinding
• Grinding is the process of metal removal by
abrasion.
• Methods of grinding
– Surface grinding
– Cylindrical grinding

Grinding (Formula)

Grinding (Problem)

PROCESS PLANNING AND COST ESTIMATION

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