Brief introduction to CAD and CAM – Manufacturing planning, Manufacturing control- Introduction to CAD/CAM – Concurrent engineering

ME6703 - COMPUTER INTEGRATED
MANUFACTURING SYSTEMS
© J.Jeevamalar, EGSPEC

UNIT I – Introduction (10)
 Brief introduction to CAD and CAM
 Manufacturing Planning, Manufacturing control
 Introduction to CAD/CAM
 Concurrent Engineering-CIM concepts
 Computerized elements of CIM system
 Types of production
 Manufacturing models and Metrics
 Mathematical models of Production Performance – Simple Problems
 Manufacturing Control – Simple Problems
 Basic Elements of an Automated system
 Levels of Automation
 Lean Production
 Just-In-Time Production.

Product Development Cycle

Sequential Vs
Concurrent Engineering
Vs

Implementation of Concurrent
Engineering

Computer-Aided Techniques
 CAD (Computer-Aided Design)
 CAE (Computer-Aided Engineering)
 CAPP (Computer-Aided Process Planning)
 PPC (Production Planning and Control)
 ERP (Enterprise Resource Planning)
 CAM (Computer-Aided Manufacturing)
 CAQ (Computer-Aided Quality Assurance)

Interface between CAD/CAM

Computer Integrated Manufacturing
 Computer Integrated Manufacturing (CIM) is the
manufacturing approach of using computers to control the
entire production process.
 In a CIM system functional areas such as Design,
Analysis, Planning, Purchasing, Cost Accounting,
Inventory Control and Distribution are linked through the
Computer with factory floor functions such as Materials
Handling and Management, providing Direct Control
and Monitoring of all the operations.

CIM Wheel

Computerized Elements of CIM
System

Elements of CIM

Activities of CIM

Benefits of CIM
• Manufacturing engineers are required to achieve the
following objectives to be competitive in a global context,
– Reduction in inventory
– Lower the cost of the product
– Reduce waste
– Improve quality
– Increase flexibility in manufacturing to achieve
immediate and rapid response to:
• Product & Production changes
• Process & Equipment change
• Change of personnel

 Application of Physical and Chemical processes to
alter the geometry, properties, and/or appearance of
a given starting material to make parts or products.
Overview of Manufacturing

Manufacturing Defined -
Economic Definition
Transformation of materials into items of greater value
by means of one or more Processing and/or
Assembly operations
 Manufacturing adds value to the material
 Examples:
 Converting iron ore to steel adds value
 Transforming sand into glass adds value

Manufacturing Defined -
Economic Definition

Production Quantity
Number of units of a given part or product produced
annually by the plant
 Three quantity ranges:
1. Low production – 1 to 100 units
2. Medium production – 100 to 10,000 units
3. High production – 10,000 to millions of units

Production
Systems
Batch
Production
Continuous
Production
Mass Production
Flow
Production
Job Shop
Production
Production Types

Types of Production Facility

 Variety of metrics used by successful manufacturing to
help managing company’s operations
Quantitative metrics used to:
 Track performance in successive periods (i.e. months
 & years)
 Try out new technologies & new systems to determine
company’s merits
 Identify problems with performance
 Compare alternative methods
 Make good decisions
Manufacturing Models and Metrics

Manufacturing Models and Metrics
 Manufacturing Metrics can be divided into 2 basic
categories:
1) Production performance measure
2) Manufacturing Costs

Production concepts and
Mathematical Models
Metrics that indicates Production Performance:
 Production Rate (Rp)
 Production Capacity (PC)
 Utilization (U)
 Availability (A)
 Manufacturing Lead Time (MLT)
 Work-In-Progress (WIP)

Metrics that indicates Manufacturing Costs:
 Labor & material costs
 Costs of producing products
 Cost of operating a given piece of equipment
Production concepts and
Mathematical Models

Operation Cycle Time
 Typical cycle time for a production operation:
Tc = To + Th + Tth
 where Tc = Cycle Time,
 To = Processing Time for the Operation
 Th = Material Handling Time (e.g., loading and unloading
the production machine)
 Tth = Tool Handling Time (e.g., time to change tools)

Production Rate (Rp)
 In manufacturing, the number of goods that can be produced during
a given period of time. Alternatively, the amount of time it takes to
produce one unit of a good.
 For manufacturing and construction, a higher production rate can lead
to a decrease in quality.
 Usually expressed in hourly rate
 Consider 3 types of production – Job Shop, Batch Prod & Mass
Productions

In Batch Production, time to process one batch of Q work
units is
Batch time, Tb = Tsu + QTc
where;
Tb = batch processing time (min)
Tsu = setup time to prepare for the batch (min)
Q = batch quantity (pc)
Tc = operation cycle time per work unit (min/cycle)
Assuming one work unit is completed each cycle, thus Tc
also has units of min/pc
Production Rate (Rp) – Batch Prod.

By dividing batch time with batch qty:
 Average production time per work unit for the given
machine, Tp = Tb /Q
 Production rate, Rp = 1/Tp
 The average production rate for the machine, Rp = 60/Tp
Rp = hourly production rate (pc/hr)
 Tp = average production time per work unit (min/pc)
 60 = constant to convert minutes to hours
Production Rate (Rp) – Batch Prod.

 In Job Shop Production, when Q =1;
 The production time per work unit, Tp is:
Tp = Tsu + Tc
 Tsu = Setup time to prepare for the batch (min)
 Tc = Operation cycle time per work unit (min/cycle)
 If Q > 1, revert to batch production case
Production Rate (Rp) – Job Shop Prod.

The machine production rate is determined by taking the
reciprocal of Tc,
Rc= 60 / Tc
Where,
 Rc = theoretical or ideal production rate / cycle rate
(cycles/hr)
 Tc = ideal cycle time (min/cycle)
 60 = constant to convert minutes to hours
Production Rate (Rp) – Mass Prod.

Production Capacity
Production Capacity defined as: the maximum rate of output
that a production facility is able to produce under a given set of
assumed operating conditions
PC = n Sw Hs Rp
Where,
PC = weekly production capacity of the facility (output units/wk)
n = no. of work centers working in parallel producing in the
facility
Sw = no. of shifts per period (shift/wk)
Hs = hr/shift (hr) Rp = hourly production rate of each work center
(output units/hr)
 Work center manufacturing system in the plant typically
consisting of one worker & one machine

Utilization
Utilization = amount of output of a production facility relative to
its capacity
U = Q / PC
U = utilization of the facility
Q = actual qty produced by the facility during a given time period (i.e.
pc/wk)
PC = production capacity for the same period (i.e. pc/wk)
Utilization can be assessed for the entire plant/any other
productive resources (i.e. labor)
It is often defined as the proportion of time that the facility is
operating relative to the time available
Usually expressed in %

 Availability = a common measure of reliability for equipment
 Especially appropriate for automated production equipment:
A = MTBF / MTBF - MTTR
A= availability (typically in %)
MTBF = mean time between failures (hr)
MTTR = mean time to repair (hr)
 MTBF indicates the average length of time between breakdowns of
 equipment
 MTTR indicates the average time required to service the equipment &
put back into operation when breakdown occurs
Availability

Manufacturing Lead time (BATCH)
 Manufacturing Lead Time, MLT = total time required to
process a given part or product through the plant
Simplified form:
MLT = average Manufacturing Lead Time for a part/product (min)
no = no. of separate operations (machines)
Tsu = setup time for operation
Q = qty of part/product
Tc = operation cycle time
Tno = non-operation time

Work-In-Process
WIP = work-in-process in the facility (pc)
A = availability
U = utilization
PC = production capacity of the facility (pc/wk)
MLT = manufacturing lead time (hr)
Sw = no. of shifts per week (shift/wk)
Hsh = hours per shift (hr/shift)

Costs of Manufacturing Operations
 Fixed costs - remain constant for any output level
 Variable costs - vary in proportion to production
output level
 Adding fixed and variable costs
TC = FC + VC(Q)
where
TC = total costs
FC = fixed costs (e.g., building, equipment, taxes)
VC = variable costs (e.g., labor, materials, utilities)
Q = output level

Fixed and Variable Costs

Manufacturing Costs

Basic Elements of an Automated
System

Brief introduction to CAD and CAM – Manufacturing planning, Manufacturing control- Introduction to CAD/CAM – Concurrent engineering

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