TABLE OF CONTENTS.......................................................................................................... 1

AUTOMATION ....................................................................................................................... 3

INTRODUCTION - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3

THE BIG PICTURE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4

PRACTICE PROBLEMS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 13

COMPUTER AIDED MANUFACTURING (CAM) - - - - - - - - - - - - - - - - - - - - - 14

FLEXIBLE MANUFACTURING SYSTEMS (FMS)........................................................... 15

OVERVIEW - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 15

COMPUTER COMMUNICATION TO SUPPORT FMS - - - - - - - - - - - - - - - - - 19

THE FUTURE OF FMS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 23

PRACTICE PROBLEMS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 23

AN EXAMPLE OF AN FMS CELL - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 25

THE NEED FOR CONCURRENT PROCESSING - - - - - - - - - - - - - - - - - - - - - - 36

PRACTICE PROBLEMS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 38

MATERIAL HANDLING...................................................................................................... 39

INTRODUCTION - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 39

VIBRATORY FEEDERS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 41

PRACTICE QUESTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 41

COMPUTERS IN THE FACTORY....................................................................................... 42

COMPUTER HARDWARE AND SOFTWARE - - - - - - - - - - - - - - - - - - - - - - - 42

IDEF MODELLING OF THE CORPORATION - - - - - - - - - - - - - - - - - - - - - - - 44

PRACTICE QUESTIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 48

INTEGRATION ISSUES....................................................................................................... 50

CORPORATE SSTRUCTURES - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 50

CORPORATE COMMUNICATIONS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 50

COMPUTER CONTROLLED BATCH PROCESSES - - - - - - - - - - - - - - - - - - - 60

PRACTICE PROBLEMS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 61

GROUP TECHNOLOGY (GT).............................................................................................. 63

OVERVIEW - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 63

SOME DETAILS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 63

IMPLEMENTATION - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 66

GT MACHINE CELLS - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 67

REFERENCES - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 67

COMPUTER AIDED PROCESS PLANNING (CAPP)........................................................ 68

OVERVIEW - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 68

CAPP SOFTWARE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 70

REFERENCES - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 71

PRODUCTION PLANNING AND CONTROL.................................................................... 72

OVERVIEW - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 72

SCHEDULING - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 73

SHOP FLOOR CONTROL - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 75

PLANNING AND ANALYSIS.............................................................................................. 77

FACTORS TO CONSIDER - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 77

page 2

Automation

• As machines are used in production, we need to consider how they are applied to the tasks.

• What? - By adding electronics, sensors, actuators, computers and mechanisms human capabilities

can be augmented to improve manufacturing.

• Why ? - In many cases there are valid reasons for assisting humans

- tedious work -- consistency required

- dangerous

- tasks are beyond normal human abilities (e.g., weight, time, size, etc)

- economics

• When?

hard automation

manual assembly

robotic assembly

manual

flexible

fixed

unit cost

constant production volumes

page 4

• Without production, a company has nothing of real value to sell.

• A company which is poor at production is guaranteed to go out of business eventually.

• Competition drives production, and every advantage counts.

• Automation can act as valuable weapons against competitors.

• Advantages of Automated Manufacturing,

- improved work flow

- reduced handling

- simplification of production

- reduced lead time

- increased moral in workers (after a wise implementation)

- more responsive to quality, and other problems

- etc.

How Computers Can Be Used in an Automated Manufacturing System

• Some Acronyms

CAD - Computer Aided/Automated Design - Design geometry, dimensions, etc.

CAE - Analysis of the design done in the CAD system for stresses, flows, etc. (often

described as part of CAD)

CAM - Computer Aided/Automated Manufacturing - is the use of computers to select,

CAD

CAE

CAPP PPC CAM

page 5

setup, schedule, and drive manufacturing processes.

CAPP - Computer Aided Process Planning - is used for converting a design to a set of processes

for production, machine selection, tool selection, etc.

PPC - Production Planning and Control - also known as scheduling. Up to this stage each

process is dealt with separately. Here they are mixed with other products, as

required by customer demand, and subject to limited availability of manufacturing

resources.

Factory Control - On a minute by minute basis this will split up schedules into their

required parts, and deal with mixed processes on a factory wide basis. (This is very

factory specific, and is often software written for particular facilities) An example

system would track car color and options on an assembly line.

Workcell Control - At this system level computers deal with coordination of a number of

machines. The most common example is a PLC that runs material handling systems,

as well as interlocks with NC machines.

Machine Control - Low level process control that deals with turning motors on/off, regulating

speeds, etc., to perform a single process. This is often done by the manufacturers

of industrial machinery.

• A Blessing and a curse

• Acronyms make it possible to convey exact technical meaning in a quick efficient way. But, they

also make it possible to confuse a subject with poorly defined terms

page 6

• There are many acronyms involved with this book, such as CAPP, CIM, CAM, CAD, CAE,

PPC, MRP, MRP-II, UNIX, DOS, CNC, DNC, etc.

• Using computers for design and manufacturing

• We computerize the easier tasks, which are tedious and mistake prone when done manually.

• In CAD we design product geometries, do analysis (also called CAE), and produce final documentation.

• In CAM, parts are planned for manufacturing (eg. generating NC code), and then manufactured

with the aid of computers.

• CAD/CAM tends to provide solutions to existing problems. For example, analysis of a part

under stress is much easier to do with FEM, than by equations, or by building prototypes.

• CAD/CAM systems are easy to mix with humans.

• This technology is proven, and has been a success for many companies.

• There is no ‘ONE WAY’ of describing CAD/CAM. It is a collection of technologies which can

be run independently, or connected. If connected they are commonly referred to as CIM

CAD / CAM

Computer

Aided

Automated

Assisted

Manufacturing

Management

Design

Development

Drafting Marking

page 7

• CAD/CAM involves the use of computers to make Design and Manufacturing more profitable.

• Parts of CIM use CAD/CAM techniques and products to try and make the factory fully connected

using computers.

• The essential difference is CAD/CAM provides the tools, CIM is the philosophy which is used

when organizing the computers, programs, etc. and all the information that flows between

them.

• Another way to think of CIM is that it allows the structure of an organization to be entered into

the computers.

• CIM focuses on connecting the various CAD/CAM modules.

• An FMS is made out of CAD/CAM components (and can be PART of a CIM system).

• The list below shows users of FMS in the U.S.A. The variety of applications illustrates that the

technology may be used by any industry. The companies employing the technology show confidence

in the technology. [Source -- find]

Company FMS location Product Main supplier

Aerospace: Engines

Avco Lycoming Stratford, CT Engine components Kearney & Trecker

Pratt & Whitney Columbus, GA Engine components

General Electric WIlmington, NC

Lynn, MA

Engine components Lodge & Shipley

Aerospace

Boeing Auburn, WA Aircraft components

Shin Nippon Koki

page 8

FMC

Corporation

Brea, CA

Aiken SC

Joints and Hoses

components for

military vehicles

and rocket

launch systems

Cincinnati Milacron

General

Dynamics

Fort Worth, TX Components for F-

16 aircraft

Westinghouse

Lockheed

Georgia

Marietta, GA Airframe parts White-

Consolidated

Vought Dallas, TX Aircraft fuselage

for B-1 bomber

Cincinnati Milacron

McDonnell

Douglas

Torrence, CA

St.Louis, MO

Aircraft components

Missile bodies

Cincinnati Milacron

Giddings & Lewis

Westinghouse

Electrical

Systems

Lima, OH Aircraft generator

components

Westinghouse

Equipment

Caterpillar East Peoria, IL

Decatur, IL

Tractor components

Cincinnati Milacron

Giddings & Lewis

John Deere Waterloo, IA Tractor parts Kearney & Trecker

Detroit Diesel Detroit, MI Piston engines Lamb Technicon

Ford New Holland, PA Sheet metal parts

for farm equipment

Trumpf

Ingersoll Rand Roanoke, VA Hoist equipment White-Sunstrand

Mack-Truck Hagerstown, MD Transmission

Housing and casting

kearney & Trecker

Machine Tool

Company FMS location Product Main supplier

page 9

• The table below indicates the countries which are using the FMS technology. The countries with

Cincinnati

Milacron

Mt. Orab, OH Parts for plastics

Processing equipment

Cincinnati Milacron

Mazak Florence, KY Parts for machine

tools

Mazak

White-

Sunstrand

Belvidere, IL Machine tool parts White-

Consolidated

Other Industries

Allen-Bradley Milwaukee, WI Motor starters kearney & Trecker

Borg Warner York, PA Compressor components

Comau

Federal Mogul Littiz, PA Bearings

G.E. Medical

Systems

Milwakee, WI Parts for medical

equipments

Trumpf

Mercury Marine Fond Du Lac, WI Outboard motor

crankcase and

block

Kearney & Trecker

NY Air Base Watertown, NY Brake Systems

OMC-Evinrude Milwakee, WI Outboard motor

parts

Swedish Machine

Group

Onan MInneapolis, MN Electrical switchgear

for generators

Trumpf

Remington Arms Ilion, NY Firearm parts

Union Special Huntley, IL Sewing machine

bodies

kearney & Trecker

Westinghouse Electric

Corp.

Pittsburgh, PA Wire harness for

electrical equipment

Xerox Webster, NY Panels for copiers

Company FMS location Product Main supplier

page 10

the higher numbers of FMS systems are also a sample of the major economic leaders. [Ayres et

al, 1991, pg. 212, an estimate based on limited information] [ source - find]

Country FMS installed percentages

Austria 6 0.7

Belgium 6 0.7

Bulgaria 15 1.7

Canada 4 0.5

CSFR 23 2.6

Finland 12 1.4

France 72 8.2

FRG 85 9.7

GDR 30 3.4

Hungary 7 0.8

India 1 0.1

Ireland 1 0.1

Israel 2 0.2

Italy 40 4.5

Japan 213 24.2

Netherlands 8 0.9

Norway 1 0.1

Poland 5 0.6

Romania 1 0.1

Singapore 1 0.1

South Korea 4 0.5

Spain 2 0.2

Sweden 37 4.2

Switzerland 6 0.7

Taiwan 5 0.6

page 11

• Driving forces of CIM/FMS are shown in the figure below[ source - find]

UK 97 11.0

USA 139 15.8

USSR 56 6.4

Yugoslavia 1 0.1

Country FMS installed percentages

Satisfaction of

primary needs

Quality/price

differentiation

Specific

features

of goods

Geographical

spread of

production

Demand

differentiation

More variety

in basic goods

production

Shorter lifecycle

for goods

Increase of

control cost

increase of

inventory cost

imperative for

higher quality

of product

(fewer defects)

Joining of

technological

operations in

one working

station

Computerized

control

Low level of

responsibility &

motivation

Relatively high

wage rates of

unskilled

Substitution

of machines &

computers for

human labor

Demand for Computer Integrated Flexible Manufacturing

DEMAND FACTOR

Return from

mass to batch

production

workers

Worker boredom

& dissatisfaction

unattractive

traditional

workplaces

SUPPLY FACTOR

Traditional Manufacturing

LABOR FACTOR

page 12

• We should aspire to meet the ideals of CIM when designing CAD/CAM technology

• CIM architectures contain,

- Computing Hardware

- Application Software

- Database Software

- Network Hardware

- Automated Machinery

• CIM benefits,

- Optimizes data flow in company

- Simplifies sharing and translation of information

- Reduces careless errors in data

- Allows checking of data against standards

- Promotes use of standards

• CIM modules,

- Customer Order Entry

- Computer Aided Design (CAD) / Computer Aided Engineering (CAE)

- Computer Aided Process Planning (CAPP)

- Materials (e.g., MRP-II)

- Production Planning and Control (Scheduling)

- Shop Floor Control (e.g., FMS)

page 13

• Reference model for enterprise related CIM [find source]

1. CAD and CAM are,

a) Integrated production technologies.

b) The best approaches to manufacturing.

c) Part of CIM.

d) None of the above.

(ans. c)

2. FMS systems are,

a) faster than robots.

b) a good replacement for manual labor.

c) both a) and b)

d) none of the above.

(ans. d)

Organization

Units

Staff and

Qualification

Hardware

Networks

Data Storage

Application

Systems

Data

Functions

Enterprise

Technical Fields

of Development

non technical

Fields of Development

page 14

• CAM is the use of computers for any part of manufacturing.

• The competitive world of manufacturing is requiring that computers now be used in a production

environment to make things faster and more precise.

• Some basic roles of computers in manufacturing are,

- Prepare product designs for shop floor production

- Schedule jobs into machines in the factory

- Track inventory, work in process, etc.

- Control workcells

- Control of processes

• When these functions happen automatically, and don’t require human intervention, we tend to

say they are part of a CIM system.

• Basically any device that can be controlled or interfaced to a computer, and be used in automated

manufacturing.

• These devices include,

- robots

- NC machines

- PLCs

- material handling

page 15

• An automatic materials handling subsystem links machines in the system and provides for automatic

interchange of workpieces in each machine

• Automatic continuous cycling of individual machines

• Complete control of the manufacturing system by the host computer

• Lightly manned, or possibly unmanned

• Characteristics of application,

- Medium product mix

- Medium production volume

- Allows fast changeover on products

• Various measures of flexibility,

- Able to deal with slightly, or greatly mixed parts.

- Variations allowed in parts mix

- Routing flexibility to alternate machines

- Volume flexibility

- Design change flexibility

• Major historical developments,

- Weaving Looms with paper tapes,

- NC machines with paper tapes

- Hard wired NC machines

- Computer controlled NC machines (CNC)

- Direct Numerical Control (DNC)

• Components of FMS Systems,

- Robotics

- Material Handling / Transport

- Machines

- Manual / Automated Assembly Cells

- Computers

- Controllers

- Software

page 16

- Networks

- Interfacing

- Monitoring equipment

• Humans are not without function in an FMS cell,

- loading and unloading workparts to and from the system

- changing tools and settings

- equipment maintenance and repair

• Computers provide essential support in a workcell for,

- CNC - Computer Numerical Control

- DNC - Direct Numerical Control of all the machine tools in the FMS. Both CNC and

DNC functions can be incorporated into a single FMS.

- Computer control of the materials handling system

- Monitoring - collection of production related data such as piece counts, tool changes, and

machine utilization

- Supervisory control - functions related to production control, traffic control, tool control,

and so on.

• FMS systems are intended to solve the following problems,

- Production of families of workparts, often based on group technology

- Random launching of workparts into system is OK, because setup time is reduced with

FMS.

- Reduced manufacturing lead time - this is possible because FMS has organization, and

fast setup.

- Reduced work in process

- Increased machine utilization

- Reduced direct and indirect labor

- Better management control

• The most common problems in an FMS are,

- Scheduled maintenance

- Scheduled tool changeovers

- Tooling problems (failures and adjustments)

- Electrical Failures

- Mechanical Problems (e.g., oil leaks)

• Implementation Strategies,

- find and identify a champion (someone who will push for automation)

- spend time to educate workers and engineers on FMS

- invest in the planning stages

- look at others in industry

- use employee involvement from the start

- install in stages - don’t try to implement all at once

page 17

• Things to Avoid when making a decision for FMS,

- ignore impact on upstream and downstream operations

- allow the FMS to become the driving force in strategy

- believe the vendor will solve the problem

- base decisions solely on financials

- ignore employee input to the process

- try to implement all at once (if possible)

• Justification of FMS,

- consider “BIG” picture

- determine key problems that must be solved

- highlight areas that will be impacted in enterprise

- determine kind of flexibility needed

- determine what kind of FMS to use

- look at FMS impacts

- consider implementation cost based on above

• Factors to consider in FMS decision,

- volume of product

- previous experience of company with FMS

- product mix

- scheduling / production mixes

- extent of information system usage in organization (eg. MRP)

- use of CAD/CAM at the front end.

- availability of process planning and process data

* Process planning is only part of CIM, and cannot stand alone.

• Manufacturing requires computers for two functions,

- Information Processing - This is characterized by programs that can operate in a batch

mode.

- Control - These programs must analyze sensory information, and control devices while

observing time constraints.

• A CIM system is made up of Interfaced and Networked Computers. The general structure is

hierarchical,

page 18

• The plant computers tend to drive the orders in the factory.

• The plant floor computers focus on departmental control. In particular,

- synchronization of processes.

- downloading data, programs, etc., for process control.

- analysis of results (e.g., inspection results).

• Process control computers are local to machines to control the specifics of the individual processes.

Some of their attributes are,

- program storage and execution (e.g., NC Code),

- sensor analysis,

- actuator control,

- process modeling,

- observe time constraints (real time control).

• The diagram shows how the characteristics of the computers must change as different functions

are handled.

• To perform information processing and control functions, each computer requires connections,

- Stand alone - No connections to other computers, often requires a user interface.

- Interfaced - Uses a single connection between two computers. This is characterized by

serial interfaces such as RS-232 and RS-422.

Corporate

Plant

Plant Floor

Process Control

Mainframes

Micro-computers

Faster

Response

Times

More

Complex

Computations

page 19

- Networked - A single connection allows connections to more than one other computer.

May also have shared files and databases.

• Types of common interfaces,

- RS-232 (and other RS standards) are usually run at speeds of 2400 to 9600 baud, but they

are very dependable.

• Types of Common Networks,

- IEEE-488 connects a small number of computers (up to 32) at speeds from .5 Mbits/sec

to 8 Mbits/sec. The devices must all be with a few meters of one another.

- Ethernet - connects a large number of computers (up to 1024) at speeds of up to 10

Mbits/sec., covering distances of km. These networks are LAN’s, but bridges may

be used to connect them to other LAN’s to make a WAN.

• Types of Modern Computers,

- Mainframes - Used for a high throughput of data (from disks and programs). These are

ideal for large business applications with multiple users, running many programs

at once.

- Workstations (replacing Mini Computers) - have multiprocessing abilities of Mainframe,

but are not suited to a limited number of users.

- Micro-processors, small computers with simple operating systems (like PC’s with

msdos) well suited to control. Most computerized machines use a micro-processor

architecture.

• NC part program storage

• Distribution of the part programs to the individual machine tools

- include post processing for specific machine formats

• Production control

- decisions of part mix, rates, inputs to parts of system

- considers data like,

- desired production rate for parts per day

- number of raw workparts available

- number of applicable pallets

- routes pallets to load/unload area

- gives instructions to operator about desired parts via a data entry unit (DEU)

page 20

• Traffic Control

- Regulates materials transfer system to ensure parts are moved between desired workstations.

This may be problematic, depending upon the transportation system used.

Can act like a railway switch operator.

• Shuttle Control

- moves parts between stations and main conveyor

- coordinates actions between machines, and primary handling system

• Work handling system monitoring,

- monitor both work parts, and pallets.

• Tool Control

- tracks tools at each station (and reroute parts if necessary, or notifies operator to install

parts)

- tool life monitoring, and operator orders for replacement

• System performance monitoring and Reporting

- Generate management reports

• Part program file

- numerical control files for each part, and for each machine which may make a part

• Routing File

- A list of machines which the parts must be routed through for completion, including

alternates in some cases.

• Part Production File

- Production parameters for each workpart

- production rates

- allowances for in-process inventory

- inspections required

- etc.

- used for production control

• Pallet reference file

- a record of which parts a specific pallet is fixtured for

- each pallet is individually identified

• Station Tool File

- a file for each workstation identifies,

page 21

- codes of cutting tools at station

- used for tool control purposes

• Tool-life file

- keeps tool-life value for each tool in the system for comparison with maximum value.

• Utilization Reports

- summarize individual, and group efficiencies for stations.

• Production Reports

- daily and weekly reports of parts produced in the FMS

• Status Reports

- a snapshot of present conditions in the FMS system for,

- tools

- parts

- stations

- pallets

- etc

• Tool Reports

- list of tools at (or needed at) a workstation

- tool life status reports

page 22

• A Graphical Depiction of a Workstation Controller

Detail of Workstation Controller

Planning

Algorithm

Process

Plans

Simulation

Expert

Scheduling

System

Deadlock

Detection &

Avoidance

Error

Detection &

Recovery

Control

Logic

Status

Database

Planning Scheduling Control

Next action

To

equipment

From

equipment

Input

to

cell

Output

from

cell

page 23

• FMS systems which deliver directly into warehouse, and do not require labor

• The use of robots that have vision, and tactile sensing to replace human labor

• Technology will make 100% inspection feasible. Thus making faster process adjustment possible.

• Computer diagnosis will improve estimation of machine failure, and guide work crews repairing

failures.

• International coordination and control of manufacturing facilities.

• Customers have completely custom orders made immediately, and to exact specifications, and at

a lower cost

• Networks will tend to eliminate the barriers caused by international borders

• Standards will be developed which make installation of a new machine trivial

• Networking between manufacturers and suppliers will streamline the inventory problems

• Marketing will be reduced, as customer desires are met individually, and therefore do not need

to be anticipated by research.

• Finished goods inventories will fall as individual consumer needs are met directly.

• Better management software, hardware, and fixturing techniques will push machine utilization

towards 100%

• The task of Design and Process Planning will become highly automated, therefore reducing

wasted time on repetitious design, and discovering careless mistakes.

• Simplification of systems overall - MRP, MPCS, etc.

• More front end simulation

• Computing power increases - more sophisticated tools

1. What is concurrent (parallel) processing and why is it important for workcell control?

page 24

(ans. to allow equipment to do other tasks while one machine is processing)

2. What is meant by the term “Device Driver”?

(ans. a piece of hardware that allows a connections to a specific piece of hardware)

page 25

• A workcell has been constructed using one light industrial robot, and one NC milling machine.

Some automated fixtures are also used.

• All of the devices in the workcell are controlled from a single Sun computer. This is an engineering

workstation with UNIX. Thus, it is capable of multitasking (running more than one program

at once).

• Software drivers, interfaces, and applications have been developed, to aid in teaching and demonstration.

• The following pages will describe the interfacing in the workcell, as an example of the connection

between process control computers and a plant floor computer. A project in development

will be discussed for networking Plant Floor (and higher) computers.

page 26

Ethernet Ethernet

RS 232

Process Controllers

rocesses

Sun Computer (“Sunbane”)

Sun Computer (“RA”)

IBM PC Compatible

(Running CAM/CAM

Software)

CRS Robot Controller Dyna Controller Microbot Controller

DYNA NC

CRS Plus Robot Pneumatic Vice Milling Machine Microbot Teach Mover

Conveyor Belt

RS 232 RS 232

RS 232

FMS Cell Connection Diagram

page 27

• Workcell Layout

• Devices:

1 Sun Computer

2. CRS-Plus robot

• A five axis, articulated robot arm

• Communicates over an RS232 serial data line

• Interprets a language called RAPL

• Has 16 Digital I/O lines

• Uses a pneumatically controlled gripper

• The robot controller is 8088 based

3. DYNA-Mite Milling Machine

• A 3-axis 2.5D milling machine

• Uses a proprietary NC code

• Can be run locally, or remotely (over RS232 serial communication lines)

• Programs may be executed as they are entered, or when they are completely

ordered

• Can handle objects of dimensions 6” by 5” by 4”

• Can machine plexiglass, wax, aluminum, steel (at low feed rates)

4. Pneumatic Vice

Conveyor

Robot

NC Milling Machine

Robot Controller

NC Milling

Sun 3/60 Computer

Controller

Pneumatic Vice

gripper

Machine

Pneumatic Vice

Controller

page 28

• Has a maximum opening of 4 inches

• Has a maximum travel of 1 inches

• Controlled by a pneumatic solenoid

• Pneumatic solenoid controlled from CRS-Plus robot controller

5. Conveyor

• A former undergraduate student project

• Activated electronically by the CRS-Plus robot controller

6. Fixtures (for making customized keytags)

• These are highly specific to the task being performed

• Parts Feeder - Provides a structured environment so that the robot may easily

pick up the parts.

• Robot Gripper - Designed to provide a reasonable reach into the vice (and parts

feeder), and to firmly grasp the workpiece.

• Vice Fixture - Designed to hold the workpiece at a level fixed height, and has a

location for drill through of the keytag. This part does not effect the travel

of the vice.

page 29

• Developed/Proprietary software in the workcell

Robot

Control

Subroutines

Vice

Control

Subroutines

Conveyor

Control

Subroutines

DynaMill

Control

Subroutines

Serial Communication Subroutines

CRS-Plus Robot Controller

DynaMill

Controller

CRS-Plus

Robot

Pneumatic Conveyor

Belt

DynaMill

Milling

Vice Machine

User

Interface

Device

Specific

Routines

on Sun

Serial

Interface

Routines

on Sun

Controllers

and

Operating

Systems

Hardware

Routines

on Sun

User Interface

(written with the Sunview Window Interface Library)

Programming

Module

High Level User Interface ( or application program)

Hardware and Controllers Supplied by Manufacturers (except Conveyor)

Low Level Device Drives and Communication Routines

proprietary Hardware

Purchased

Software

Written

or Built

page 30

2.1.4 - Example of Robot and Vice Software Driver Use

void demo()

{

static double a1, a2, a3, a4, a5;

crs_init();

crs_speed(40.0);

crs_open();

crs_close();

conv_on();

crs_xy_r_move(-5.0, -5.0, 0.0);

crs_xy_status(&a1, &a2, &a3, &a4, &a5);

conv_off();

crs_xy_a_move(a1+3.0, a2+2.0, a3);

crs_depart(-2.0);

crs_depart(2.0);

crs_home();

crs_r_move(0.0, 10.0, 0.0, 0.0, 0.0);

crs_speed(100.0)

vice_closed();

crs_a_move(-90.0, 0.0,0.0,0.0,0.0);

vice_open();

}

Set up Robot

Set speed to 40% of Maximum

Open the Gripper

Close the Gripper

Turn on Conveyor

Move Robot with relative

Cartesian Coordinates

Return Cartesian Position of

End Effector

Turn off Conveyor

Move Robot to absolute

Cartesian Position

Move robot gripper 2” forward

Move robot gripper 2” backward

Move robot to home position

Move robot in relative joint

coordinates

Close the Vice

Move the Robot in

Absolute Joint Coordinates

Open the Vice

page 31

• NC code Example (for the Dyna Milling Machine)

000 START INS 01

001 TD = 0.125

002 FR XY = 10

003 FR Z = 4

004 SETUP > zcxyu

005 GO Y -.625

006 GO Z -.125

007 GR a -180

008 ZERO AT

009 X .634

010 Y .5

011 GO r .125

012 a 90

013 GR a -30

014 > REF COODS

015 ZERO AT

016 X 1.50

017 Y 0

018 GO r .125

019 a 60

020 GR a -60

021 > REF COODS

022 ZERO AT

023 X 1.5

024 Y -0.3

025 GO r .125

026 a 0

027 GR a -90

028 GR X -1.3

029 END

2.00”

0.50”

0.50”

30°

0.20”R

Start Program in inches

Set Tool Diameter

Set Feed Rates

Set Absolute Zero Position

Move to Start Position

X

Y

Z

End Program

A

B

A

B

C

D

C

D

E

F

E

F

page 32

• An Example of the Dyna Mill Software Drivers

void demo()

{

char ret[100];

/* Initialize Dyna Mill and check for failure */

if(dyna_init() == NO_ERROR){

/* Send NC Program to Dyna Mill */

dyna_load(“/usr/people/cim/nc.code/test1.nc”);

/* Download program from NC Mill */

dyna_download(“/usr/people/cim/nc.code/test”);

/* Send program to mill 1 step at a time */

dyna_step(“/usr/people/cim/nc.code/test2.nc”);

}

/* Deinitialize mill */

dyna_kill();

}

page 33

• A User interface for Workcell Control

Robot Control

Subwindow

Vice and Conveyor

Controls

Dyna Mill Control

Subwindow

Key Tag Programs

Programming

Master Control

(Also uses Dyna Mill)

page 34

• Actual Communication with devices, via a report window

page 35

• Workcell Programming window

• Advantages:

• UNIX Based system allows easy control of cell in modes which are both parallel and/or

concurrent

• A blend of high level computers with low level devices allows for a very modular system,

with a variety of computing resources.

• Synchronization of processes is very simple.

• Allows rapid reconfiguration of the workcell.

• This workcell will perform all of the basic CAD/CAM/CIM functions.

• The hierarchical design of software tools has simplified the development of new applications.

• Disadvantages:

• Many Equipment manufacturers have not considered this type of control (they prefer

36

ware is made to be user interactive, and batch, but is not very friendly for software

applications.

• Requires technical people to operate the equipments.

• An individual computer is not powerful enough to control an entire factory. And, a single program

would be too complex. Therefore, there is a need for many computers and programs

which interact.

• The example below involves two programs. The first program will control the robot, and the

second will cut key tags with the NC machine.

• While the keytags are being cut, the robot program will move pegs around in the cell. This

requires that the control software be very complex, or that two programs be used.

• if two programs are used, then some communication is required for sequencing tasks in the work

cell.

• Concurrent tasks in the workcell use message passing between programs,

page 37

• Strategies for Concurrent processing, involve how the processes are split apart, and how they

communicate,

- Have a number of processes which communicate directly to one another (point to point).

This is synchronous and well suited to real-time control.

- Use a buffered message passing system. This allows asynchronous communication

between processes running at different speeds, which do not do real-time control.

- Remote Procedure Calls allows one program to run other programs remotely. This is

suited to well defined problems, but every program must have knowledge of the

other computers in the network.

Is

Another

Name

Left ?

Stop

Start

Is

Dyna Mill

Waiting for

Part ?

Yes

Load

Part

Is

Dyna Mill

Done with

Part ?

Yes

Unload

Part

Swap a

Peg

Start

Call for

New Part

Wait for

Part Loaded

Move to

Milling Position

Mill out

Keytag

Move to

Unload Position

Call for

Unloading Keytag

Wait for

Part Unloaded

Yes

messages

passed through

file #1

messages

passed through

file #2

Program #1 Program #2

No

No

No

page 38

1. What is concurrent (parallel) processing and why is it important for workcell control?

(ans. to allow equipment to do other tasks while one machine is processing)

2. What is meant by the term “Device Driver”?

(ans. a piece of hardware that allows a connections to a specific piece of hardware)

page 39

• Basic purpose is to provide automatic transfer of workparts between automated machines, and

interface with individual work stations.

• Basic layouts for material handling include,

- lines - stations arranged along a fixed part transfer path.

- batch - stations are grouped by function and batches of raw materials/WIP are brought in

batches

- job shop - individual parts are carried through one or more stages by one worker

- job site - equipment is brought to the work

• These transfer systems can also be categorized by their timing approach,

- synchronous - the entire line moves parts with a fixed period cycle. This is well suited to

mass production of similar products.

- asynchronous - parts are moved as completed or needed. Often buffers are required, but

this is more tolerant of problems than synchronous systems.

- continuous - the product flows by without stopping

• Basic Requirements,

• Random, independent movement of palletized workparts between workstations in the

FMS

- pallets can flow from any station to any other

- parts are mounted in pallet fixtures

- pallets can move independently to avoid interference

• Temporary storage or banking of workparts

- queues allow parts to wait for machines, thus increasing efficiency

• Convenient access for loading and unloading workparts

- easy to do manual load/unload.

- automatic loading/unloading of parts at workstations

- can load/unload from either side of system

• Compatible with computer control

• Provision for future expansion

- modular extensions to system are desirable

• Adherence to all applicable industrial codes

- safety, noise, etc.

• Access to machine tools

- allow unobstructed floor level access to each workstation

page 40

• Operation in shop environment

- must be reliable when exposed to metal chips, cutting fluids, oil, dirt, etc.

• Common type of Material handling systems

- power roller conveyors

- power and free overhead conveyors

- shuttle conveyors

- floor “towline” systems

- robots (in a limited sense)

- indexing (geneva mechanism)

- walking beam

page 41

• When small parts are hard to orient we can dump them in a vibratory feeder.

• The vibrations cause parts to ‘hop’ forward.

• Various cutouts, tracks, etc are added to sort parts.

1. What are pallets used for?

(ans. to acts as holders for work that is being transported)

2. List possible methods for guiding an AGV.

(ans. guide wire, vision, painted lines, chain)

page 42

• Considering CAD and CAM both start with C’s, computers are a dominant factor

• Hardware is much more advanced than software, and it is often less expensive.

• There are four major functions which must be addressed when dealing with the application of a

computer system.

- Input

- Output

- Processing

- Storage

• An Example - If you are implementing a system on a shop floor with inexperienced typists,

input devices should be simple, like a mouse, or rugged like a touch screen. If the computer is

controlling a large machine, an emergency stop button is required. Disk drives may have problems

if there is vibration, or static. ETC.

• Software is expected to perform many tasks with more speed, and accuracy than a person. Software

will not perform a task better, Hence the term ‘Garbage in Garbage Out’

• The software has similar functions to the hardware,

- Input

- Output

- Processing

- Storage

• An example is software to be written to run on a Nintendo Game System. If this is the case, the

43

grams are stored in ROM chips in the cassettes), Output is visual and audio. Processing could

include trajectory calculations, collision detection and scenery drawing.

• Software is clearly distinguished from hardware by the lack of commitment when it is purchased.

Software undergoes updates, it may be adapted to suit new demands, etc., hardware is

often fixed.

• Computer software and hardware have both decreased in cost, keep in mind that the cost of software

and hardware are often both in the same cost range. (originally hardware was more

expensive (1940s-1970s) then software went through an expensive phase (1970s-1990s), but

the enlargement of commercial markets has brought economies of scale to both products.

• A Good Computer Rule to Remember

“If a problem cannot be solved by a human on paper (ignoring the time factor), then it cannot

be done by computer. The computer requires that a task is well defined, and

understood”

page 44

• IDEF is a diagraming method used to describe systems.

• developed by ICAM (Integrated Computer Aided Manufacturing)

• Three (3) levels of IDEF models:

• We will examine IDEF0 for modelling processes. Other models would be useful when designing

complex inofmration systems.

• IDEF serves to illustrate the relationship of all processes in a system in a graphical format

•Boxes represent activities or functions.

•Information or data needed to carry out the activities or products produced by the activities are

represented by arrows.

•A top down diagramming method is used.

•The model starts off with a single block that represents the entire system or process.

•The first block diagram is “expanded” to more detailed diagrams or processes.

•The collection of successively more detailed diagrams is the IDEF model

PROCESS

output, (O)

mechanisms, (M)

control, (C)

input, (I)

page 45

input t o output from

output from

to p level

input from

to p level

controls

(mechanisms, tools)

(mechanisms, tools)

controls from top level

to p level

to p level

input from

seco n d level,

first box

from to p level

(mechan isms, tools)

from seco n d level

output from

secon d level,

first box

(mechan isms, tools)

from th ird level

input from

th ird level,

second box

output from

third level,

second box

... e tc.

A0

A1

A2

A3

A11

A12

A121

A122

page 46

•This is the top level of the IDEF model.

•This box is labeled as A0 (“0” indicates the top level)

•Decomposing “A0” will produce another set of boxes and process flows.

PRODUCE

SOFTWARE

PRODUCT

User Requirements

System

Requirements

Successful

Software

Package

Product Development Team

Market

Research

Schedules

page 47

Successful

Software

Package

User R equirements

System

Requirements

Product D evelopment Team

M arket

Research

( )

P lan

Softw are

Product

Program and

Document

Product

M arket

Product

Product P lan

Tested P roduct

• This decomposed box from the top level shows more

detail than the previous level.

• The “( )” on the ‘System Requirements’ arrow indicate

that this control stops at box “A1” and is not passed to the

page 48

1. In the Shop Floor Production Model (SFPM), a PLC connected to a robot, NC machine and

safety systems would be considered,

a) Section/Area Control (Level 4)

b) Cell Control (Level 3)

Plan

Marketing

Strategy

Design

User

Interface

Organize

Programming

Activities

Design

Documentation

Product Development Team

User Requirements

Market

Research

Product

Plan

Schedules

documentation

specifications

writers and

programmers

marketing

staff

programmers

writers

design

specs.

user

profile

page 49

c) Station Control (Level 2)

d) Equipment Control (Level 1)

(ans. c)

2. In the IDEF0 diagram below,

a) there are more than 10 problems

b) there are 6 to 10 problems

c) there are 1 t o 5 problems

d) there are no problem

(ans. b)

3.Draw an IDEF diagram to describe how you study for, and write an exam.

process A

process B

process C

plans

schedule

director

progress

reports

page 50

• First consider the major functions within a company,

- Production

- Materials

- Process Planning

- Design

- Customer Orders / Service

- Marketing

- Accounting

- Management

• All of these functions generate and use common information which must be communicated

between departments.

• Since computers handle information, we must be aware of what we get, and what we produce.

• Previous paper based systems provided support for data transfer between departments, and provided

a good basis for the introduction of computers

• ASIDE: Computers can make a good system better, but they will always make a bad system

worse. This is because a system which is not well defined and poorly understood cannot be

programmed, or optimized.

• Characteristics of paper based manufacturing systems,

- Multiple copies of same information.

- Revising information is hard when multiple copies exist.

- Delays for the transfer of paper.

- Easy to lose paper.

- Paper is not interactive.

- Paper requires bulky storage.

• Computers overcome and reduce the problems above, but introduce some technological challenges,

- Creating programs to support corporate functions.

- Software to support interdepartmental communication and data sharing.

page 51

- Hardware to support the software.

• This figure below shows various departments, and the information flow [source - ???

Plant Functional E ntitie s

External E ntities

Customer

Customer

Accounting

Purchasing

Marketing

and S ales

Corporate

R & D

Marketing

and S ales

Transit

Company

Accounting

Marketing

and Sales

Supplier /

Vendor Process

Orders

1

Schedule

Production

2

Manage

Production

3

Assume

Quality

6

Manage

Product

Inventory

7

Manage

Product

Shipping

8

Manage

Product

Costs

9

Manage

R aw M aterial

and E nergy

4

Manage

Procurement

5

O rder

Invoice

Supplier

P erform ance

Supplier

D ata

Paym ent

Release

Purchase

O rder R eq

O rder R eq

Incoming

Commun ication

Long Term

Materia l and E nergy

Req u iremen ts

P arts

RM & Energy

In com ing

M ateria l and

E ne rgy R eqd

M aterial and

Energy Inventory

A pprovals

O rder

S tatus

K now

H ow

D ata

O rder

Request

QA

R esu lts

STD S

Perfo rmance

& Costs

C ost O B J Capacity

Schedule

Methods

R eqmts

QA R esult

Waivers

R eqmts

Confirm

Ship

Release

To S hip

Inventory B alance

R eservation

Pack O u t S ch ed u le

Inventory

Invoice and

Shipp ing

Documents

Invoice

Transport

O rder

Release Invoice

Shipp ing C ost

Accep ted

O rder

M FG

RM & Energy

C osts

Production

C ost

Credit L imit

and O ther P o licy

Sales

Forecast

Annual

Sales

Confirm

O rder

Production

O rder

Availability

page 52

• Requirements for interfacing corporate management and staff functional entities to the factory

[source - find]

MKTG

and

SALES

Human

RES

PURCH RD&E ACCT

CORP

MGMT

FACTORY LEVEL 0.0

Policies

External

Entities

Vendor

Contracts

Know-

How

Requirements

Manpow er M anufactuing

policies

Requirements

page 53

• Assumed functional hierarchy computer system structure for a large manufacturing complex

[source - find]

Operational and

Production

Supervision

Supervisor’s

Console

Management

Data

Presentation

Dedicated

Programmable

Logic Controllers

Plant Production

Scheduling and

Operational

Inter-area

Coordination

(Shop coordination)

Work Cell

(Direct Numerical

Control)

Work Station

(Computerized

numerical Control)

Plant

Management

Information

Supervisor’s

Console

Operator’s

Console

PROCESS

Management

Level 1

Level2

Level3

Level4

Sales

Orders

Communications

with other areas

Communications

with other

supervisory systems

Communications

with other

control systems

page 54

• Report interfacing to corporate management and staff functional entities from the factory

[source - find]

MKTG

and

SALES

Human

RES

PURCH RD&E ACCT

CORP

MGMT

FACTORY LEVEL 0.0

Corporate

External

Entities

raw material, energy

and spare parts

Requests for

information,

Status of

Production

Manpower

operational

performance

Policies

Cost

reporting

Performance reporting

performance

orders plant tests orders data and reqmts

page 55

• The Shop Floor Production Model (SFPM):

[ source - find]

The ISO Reference Model for Factory Automation adds a couple of layers

[ source - find]

Level Sub-Activity Responsibility

4 Section/Area

Supervise shop floor

production process

Supervising and coordinating the

production and supporting the

jobs and obtaining and allocating

resources to the jobs.

3 Cell

Coordinate shop

floor production process

Sequencing and supervising the

jobs at the shop floor production

process

2 Station

Command shop floor

production process

Directing and coordinating the

shop floor production process

1 Equipment

Execute shop floor production

process

Executing the job of shop floor

production according to commands

Level/Hierarchy

Area of Control Responsibility Basic Functions

6 /

Enterprise

Managing the corporation

Achieving the enterprise’s

mission

and managing the

corporation

Corporate management

Finance

Marketing and sales

Research and Development

5 /

Facility or

plant

Planning Production Implementing the

enterprise functions

and planning

and scheduling

production

Product design and production engineering

Production management (upper level)

Resource management (upper level)

Procurement (upper level)

Maintenance management (upper

level)

page 56

4 /

Section or area

Allocating and

supervising

materials and

resources

Coordinating production

and obtaining

and allocating

resources to jobs

Production management (lower level)

Procurement (lower level)

Resource management (lower level)

Maintenance management (lower

level)

Shipping

Waste material treatment

3 / Cell Coordinating multiple

machines and

operations

Sequencing and

supervising shop

floor jobs and

supervising various

supporting

services

Shop floor production (cell level)

2 / Station commanding

machine

sequences and

motion

Directing and coordinating

the activity

of the shop floor

equipment

Shop floor production (station level)

1 / Equipment Activating

sequences and

motion

Taking action on

commands to the

shop floor equipment

Shop floor production (equipment

level)

Level/Hierarchy

Area of Control Responsibility Basic Functions

page 57

• A LAN (Computer Network) Hierarchy for Shop Floor Control [source - find]

D evice

Level 6 :

E n terp rise

Level 5 :

F ac ility o r P lan t

Level 4 :

S ec tion o r A re a

Level 3 :

C ell

Level 2 :

S tatio n

Level 1 :

Equipment

S ec tion

C o ntro lle r A

S e ctio n

C o ntro lle r B

S ec tion

C o n tro ller C

s im ila r to A sim ila r to A

E nte rp rise LA N

Factory B ackbone LAN

S ec tion A LA N

C e ll A LA N C ell B LA N

C ell

C o n tro ller A

C ell

C o ntro lle r B

D evice

C on tro lle r A

D evice

C o n tro ller B

D evice

Co n troller A

D evice

C on tro lle r B

D evice

D evice

D evice

D evice

D evice

D evice

D evice

D evice

D evice

D evice

D evice

page 58

• Typical Architecture for Manufacturing Components [ update]

• Functional Breakdown of Control Architecture

Item Equipment Workstation Cell

EXAMPLES

Hardware

Lathe, Mill, T-10

Bridgeport Series I

IBM 7545 Robot

Robot tended Machine

Center, Cartrac

Material Handling

System

Variable Mission System,

Several Integrated

workstations

Controller

Hardware

Mark Century 2000,

Accuramatic 9000,

Custom-singleboard

system.

Allen-Bradley PLC-5,

IBM-PC, etc.

Windows NT, SUN

workstation, etc.

Type Controller

Single-board processors,

Machine tool

controller, Servo-

Controller, etc

PLC, PC, Minicomputer

PC, Microcomputer,

Super-MiniComputer

Language

Application

Assembler, Part programming,

Robot

programming, etc.

C, Ladder logic, Pascal

and other sequential

languages

C, LISP, FORTRAN,

and other high level

languages

Memory/Size

Requirements

8k-128k RAM plus

custom ROM,

EPROM, etc.

32M RAM, >1M Hard

Drive

128M RAM,

>1Gigabyte Hard

drive

Machines/

Interconnects

1-1 connect 1-many

1-[1,8] Machine tools,

1-[1-50] Material handling

1-many

1-[1-15] workstations

Equipment Workstation Cell

Planning Tool selection, parameter

specification, tool path

refinement, GMT code,

tool assignment to slots,

job setup planning

•Resource allocation jobs

•Batch splitting and equipment

load balancing

Batching, Workload balancing

between workstations,

Requirements

planning

Task allocation to workstations

page 59

• In all of these models we must consider the value of the information being passed. At the low

level control stages, information that is more than a few seconds old may be completely worthless,

while the same information at the higher level may be valuable for quality tracking

months later.

• We can draw part of a simple flow chart that illustrates a simple CIM system. The elements

shown include a PLC, NC machine, and stand alone sensors. These are all integrated by a single

computer running cell control software.

Planning Horizon

Milliseconds - Minutes Minutes - Hours/Days Hours - Days/weeks

Scheduling •Operation sequencing at

individual equipment

•Sequence equipment level

subsystems

•Deadlock detection and

avoidance

•Gantt chart or E.S. based

scheduling

•Buffer management

•Assignment of due dates to

individual workstations

•Look ahead ES/simulation

based scheduling

•Optimization based tech

•Batch sequencing

Control •Interface to workstation

controller

•Physical control (motion

control at NC and robot

pick and place level)

•Execution of control programs

(APT, AML, etc.)

•Monitor equipment states

and execute part and

information flow actions

based on states

•Synchronize actions

between equipment (eg.

robot & machine while

loading/unloading parts)

• Ladder logic execution

Organizational control of

workstations, Interface

with MPS, generation of

reports, etc.

Equipment Workstation Cell

page 60

• The nature of Batch processes,

- Batch processes deal with discrete quantities of raw materials or products.

- batch processes allow the tracking of these discrete quantities of materials or products

- batch processes allow more than one type of product to be processed simultaneously, as

long as the products are separated by the equipment layout.

- Batch processes entail movement of discrete product from processing area to processing

area

- Batch processes have recipes (or processing instructions) associated with each load of

raw material to be processed into product.

- Batch processes have more complex logic associated with processing than is found in

continuous processes

- Batch processes often include normal steps that can fail, and thus also include special

steps to be taken in the event of a failure.

• The nature of steps in a batch process,

CNC

Controller

Actuators,

Structure,

Sensors

NC NC Quality

Programs Status

Gauges

and Meters

Measurements

Cell

Controller

Operation Cell status and

plans quality reports

(IBM PC)

CNC

Controller

Actuators,

Sensors

page 61

- Each step can be simple or complex in nature, consisting of one or more operations

- Generally, once a step is started it must be completed to be successful.

- It is not uncommon to require some operator approval before leaving one step and starting

the next.

- There is frequently provision for non-normal exits to be taken because of operator intervention,

equipment failure or the detection of hazardous conditions.

- Depending on the recipe for the product being processed, a step may be bypassed for

some products.

- The processing operations for each step are generally under recipe control, but may be

modified by operator override action.

• A typical process step

1. List 5 industries that are well suited to integration, and 5 that are not. Indicate why you think so.

2. In an automated factory there as many as six levels of control. Discuss the equipment available

in the lab and how this relates to the 6 level model of factor floor control.

Bypass Step

Hold

at step

completion

Perform Step

Operation

Operator or

Recipe Bypass

Command

Operator or

Recipe Hold at

Completion

Operator

Abort

Command Command

Yes

No

Yes

Previous No

Step

Fault Detected

or Operator Abort

Next

Step

Fault Exit to

pre-defined step

page 62

3. Information drives an automated factory from the initial entry of geometry in CAD, to the final

production of parts with CAM. Discuss how data networks support this and the impact of open

network standards.

4.

The lab equipment (right now) only satisfies the first couple of levels. You can argue

that the ability to watch over the net is a supervisory function. Etc...

ans.

page 63

• Most product models use an exact definition of geometry, or other details

• It can be useful to have a more abstract representation of a part for some tasks,

- Storage and recall of designs

- Recall of process plans for similar parts

- Classification of designs for analysis of production

• GT is used to identify subsets or families of similar parts for the purpose of realizing common

features for improved design and process efficiency through standardization.

• GT codes can be used to represent products using any combination of geometry, manufacturing

processes, and/or function.

• The advantages of such a system can be found in,

1. Product design - Group technology allows similar designs to be recalled on the computer.

Instead of starting from scratch again.

2. Tooling and setups - standard tooling can be developed for a part family, and then standard

setup procedures and times can be used.

3. Materials Handling - Factory floor layout can be updated to reflect part families, and

reduce part handling time.

4. Production and Inventory Control - The use of GT to set up standard production techniques

allows faster production, therefore less inventory, and Work in Process

(WIP).

5. Employee Satisfaction - Grouping of machines allows easier tracking of quality (and

achievement).

6. Process Planning - Standard plans can be developed for GT part families. The plans can

then be altered to fit, instead of producing a new process plan.

• Problems with GT systems are,

1. Not suited to a factory with widely varying products

2. Can have a long setup time, and debugging

3. There are no standard GT codes developed - each GT code application will probably be

unique.

4. A GT code may be hard for inexperienced users to read.

• The GT code is made up of a string of digits which identify specific attributes of a part.

page 64

• If the digits of a GT code are unrelated, it is a polycode, and each digit may be looked up independently.

• If the digits of a GT code are related, it is a monocode, and they must be looked up in sequence.

• It is possible to have a hybrid GT code which is a combination of polycode and monocode.

• When selecting what the GT digits represent, the guidelines are,

• They must differentiate products

• Must represent non-trivial features

• Only critical features should be encoded

• Function should be encoded

• Every digit should be significant

• Parts can be encoded using

- process flow

- tool axis

- tolerance

- function

- material

- shape.

• One example system is the popular Opitz code, developed in a German university by H.Opitz.

• This code uses a sequence of 5 digits, 4 digits, and 4 letters, such as ‘11223 4455 ADEA’

- The first five digits are the form code (identify shape). See the table for form codes.

- The next four digits are the supplementary code - used to represent non-form details such

as tolerances, materials, etc.

- The last four letters are the secondary code, used to represent production operation types,

sequences, or other functions chosen by the manufacturer.

• The Opitz code for a part is constructed from the first digit on, as shown in the tables below.

page 65

• Decision trees are developed to be specific to typical product line, or manufacturing facility.

• To develop one of these trees we draw a tree that shows alternate possibilities for a part, and then

number the options (care must be used to leave options not anticipated).

• Part of an example decision tree is given below. This can be expanded as it applies to a particular

manufacturer or industry.

deviation

w ith

deviation

special

flat

parts

long

parts

cubic

parts

special

nonro tational p a rts rota tional p arts

0

1

2

3

4

5

6

7

8

9

external shape

or external

shape elem ents

m ain shape

m ain shape

m ain shape

m ain shape

second digit - main shape

first digit - part class

third digit - rotational surface machining

fourth digit - plane surface machining

fifth digit - auxilliary holes, gear teeth, forming

4 digit supplementary code

internal shape

or internal

shape elem ents

rotational,

internal and

external shape

features

principal

bores

dimension

material

original shape of raw material

accuracy

1

2

3

4

plane surface

m achining

plane surface

m achining

auxilliary

gear teeth

holes

auxilliary

holes, gear

teeth & forming

auxilliary

holes, gear

teeth & forming

page 66

• GT should be used when there are a large number of parts that can be divided into groups based

upon geometry, function, and/or production.

• implementation is a multistage process,

1. Develop a GT code

2. verify the GT code by coding about 10-20% of the parts in the factory. A good random

sample of parts should be used for reliable results.

3. The results of the coding should be reviewed. If too many parts have the same GT code,

or there are not enough similarities between codes, then the code should be

revised.

4. The remainder of the parts should be coded.

5. An examination of all the parts for the factory will allow the identification of patterns in

production, or design. As a result standard production routings, or standard product

designs may be selected.

0: plate

1: bar

2: large rectangular

3: large round

4: purchased

5: in process

0: <= 1/8” thick

1: <= 1/2” thick

FORM GEOMETRY SIZE

2: <= 1” thick

3: > 1” thick

0: straight sides

1: contoured sides

2: mixed

0: <= 1/8” thick

1: <= 1/2” thick

2: <= 1” thick

3: > 1” thick

page 67

• After identifying part families, a standard set of production steps can be identified.

• After identifying standard production steps, the factory floor can be reorganized to reflect a

more rational layout of machines.

• Various ways to lay out machines for part families are,

- Single Machine Cell

- Group machine layout

- flow line design

• Single Machine Cells are suited to products which may be produced on a single machine, using

a single process. This can also involve bringing two machines together. Such as a grinder, on a

lathe.

• Group Machine Layout is suited to a small set of operations on a part which cannot be performed

on a single machine.

• Flow Line Design - when parts in a family have a number of processes with the same sequence,

this system may be set up with a transfer line.

Ullman, D.G., The Mechanical Design Process, McGraw-Hill, 1997.

page 68

• If we had an engine block, how would you manufacture it ?

• When deciding how to produce a product there are a number of factors to consider,

- Product geometry, material, tolerances, weight, etc

- Available processes/machine tools/skills

- Available tools and fixtures

- Inventory

- etc

• Requicha and Vandenbrande [1988] describe the process of process planning as,

“A process planner and a set-up planner (often the same person) examine a part’s blueprint

and consult various files and handbooks to produce a process plan. A plan

contains process specifications and information on fixtures and clamping devices

to be used, and on set-up of the workpiece on a machine tool. Set-up specifications

are typically conveyed through annotated sketches or engineering drawings.”

• A process plan will vary from factory to factory, but there are some basic elements to be found

on all. An example is shown below.

OPERATION SHEET

Part No.

Part Name

Orig.

Checked

Material

Changes

Approved

No. Operation Machine Setup Time (hrs.)

page 69

• Obviously a process plan is important when there is a high product mix, because it lets us know

were to send the parts, and what to do with them. In a high volume setting, a process plan lets

us decide exactly how something will be made before equipment is bought or moved.

• A Process Plan includes,

- Part routings (Indication of where to send finished parts)

- Bill of Materials (for each operation)

- Work Orders (A description of what operations to perform at a work station).

• Every company uses process planning. In smaller companies the process planner may also be

the craftsman who makes the product. In larger companies there may be large departments set

aside to perform this function.

• As the size of a company grows, and so do the possible methods for manufacturing, and process

planning become more difficult.

• A Diagram of the traditional Two-Stage Approach to Process Planning

• Depending upon who defines process planning, it may, or may not include operation planning.

• In their purest sense, the definitions are,

- Process Planning - Choosing the technological means whereby a feature(s) of a product

will be manufactured (eg. drilling, milling, or casting). Also known as high level

process planning.

- Operation Planning - Choosing the parameters of the operation which is used to create

the feature(s). (eg. feeds, speeds). Also known as low level process planning.

PART and STOCK specifications and drawings

Operation

Planner

CUTTER, FIXTURE and MACHINE TOOL

specifications and drawings

Set-Up

Instructions

Part programs

CL file/G-code

Set-Up

Planner

Process

Planner

Process

Specifications

Set-Up

Specifications

Part design

and stock

specification

process plan

page 70

• There are few successful process planning software packages available today.

• There are two main categories of process planners - Variant and Generative.

• Variant process planners use existing process plans, then allow a user to edit the plan for their

new parts.

• Generative process planners should create a new process plan, without the use of any existing

plans. This does not imply that the process planner is automatic.

• Some of the process planning steps used for machining operations are,

1. Interpretation of part design data

2. Selection of machining processes

3. Selection of machine tools, and fixtures

4. Machining optimization

5. Decomposition of machinable volumes

6. Selection of machinable volumes

7. Generation of precedence constraints

8. Sequencing of machinable volumes

• Most successful variant systems depend upon Group Technology.

• The basic variant approach to process planning with GT is,

1. Go through normal GT setup procedures

2. After part families have been identified, develop standard process plans for each.

3. When a new product has been designed, get a GT code for each part.

4. Use the GT system to look up which part family is the closest match, and retrieve the

standard plan for that part family.

5. Edit the standard plan so that values now match the new design parameters, and add or

delete steps as required.

• Some benefits of the GT system are,

- It is well suited to medium to low product mixes

- It can be developed quickly for most companies

- Can be used with other CIM

- One program can be used in radically different industries

• Disadvantages are,

- GT codes can become obsolete quickly

- While it is fast to setup, it is slower for planning than generative systems

page 71

- More prone to error than generative systems

• These systems tend to get exact matches 2-7% of tries. A standard plan is used about 50% of

time.

• Each plan is made from scratch

• The generative systems are poorly developed at this point in time, and tend to be research systems,

or very limited domain

• These systems rely heavily upon the methods of Artificial Intelligence, or very complex algorithms.

• An example of a Generative system is the development of rules deciding which machines to use.

• Possible sources of input vary from system to system, but they are essentially,

- Interpret designs from CAD directly (very difficult)

- User defines features then answers questions about them

- The user does design directly on the CAPP system.

- The users creates a special product description file

• A rule example for a CAPP system called XPS-2 is shown below,

0010 EXECUTE MILL_HOLE FOR EACH BLIND_HOLE IF

BLIND_HOLE.DIAMETER GT 25.,

BLIND_HOLE.DEPTH LT 50. !

• This rule identifies the operation, the feature it is used on, and the two conditions for it to be

used. When rules are used, the number of rules in the system becomes very large.

• Advantages,

- Runs faster when planning

• Disadvantages,

- Requires a more extensive setup

Ullman, D.G., The Mechanical Design Process, McGraw-Hill, 1997.

page 72

• A design must be converted to a process plan before it may be produced.

• But, if we have thousands of process plans, and hundreds of customer orders, with dozens of

parts in each, which machines do we use when to make the products? What parts do we need?

• Traditionally jobs have been scheduled on a first come, first served basis. This resulted in a

lineup of various jobs waiting to be done at each work center.

• When jobs are not scheduled efficiently, we often will get jobs sitting half completed, while we

wait for simple parts to be processed. This costs money, wastes time, takes up floor space,

makes the customer unhappy, etc.

• Eventually computers were used to figure out how to schedule jobs so that parts were made

before they were needed, and so that work was done on time.

• As computers were used more it also became obvious that strict schedules were a nice idea, but

they don’t work. A schedule is only valid until the first breakdown.

• Newer control programs called Production Planning and Control (PPC) systems were used to

generate schedules, and fix problems that came up.

• Most systems, manual, and automatic either push, or pull the work through the factory. If the

work is pushed, then customer orders tend to drive the production. If the work is pulled, the

factory often tries to satisfy some continuous demand, and when things are about to run out,

more is produced.

• Regardless of which system is used, Scheduling is not exact, and never optimal, but you can get

a near optimal schedule with the right tools and methods.

• Some of the traditional Production, Planning and Control subject include,

1. Forecasting - Estimating the production demands using a horizon of a few month to a

few years for long range planning.

2. Production Planning - Matching needed production to available resources.

• Note: This is more of a CIM topic.

page 73

• We often know well in advance what has to be produced

• We can use computer programs to come up with a ‘near perfect’ schedule for all jobs, ahead of

time.

• These methods at the present time are not well enough developed to handle sudden disruptions

on the shop floor (See next section on Shop Floor Control).

• Schedules are often made up weekly

*************** ADD DETAILS FOR MRP I and MRP II

• This is one very popular approach to planning

• Uses Master Production Schedules to determine how much of each product should be produced

within given periods. Master Production Schedules are based on customer, or projected

demand.

• The elements used by MRP to plan are,

- Master Production Plan (Schedule)

- On-hand inventories

- Bill of Materials

- Current of Purchased and Manufactured Orders

- Rules for each part produced (including WIP)

• The rules about each step in production include,

- Lead time

- Order quantity per final part

- Scrap rate

- Buffer stock quantity

- etc.

• MRP then tries to determine quantities required using the data input from the users, and a set of

rules, such as,

- Fixed Order Quantity - Product are produced as required using a prespecified lot size.

- Economic Order Quantity - The cost of carrying inventory is weighed off against the cost

of setup for one production run.

page 74

- Lot for lot - Lots are produced as required, any batch size.

- Fixed-period Order Quantity - Produce parts to cover more than a single order.

• Lot sizes required are subtracted from available stocks.

• The required production quantities are used to order from suppliers, etc, while considering lead

times, and delays.

• You should note that this approach is concerned more with inventory minimization than with utilization

of machines.

• While this system can lead to easy production scheduling, it is susceptible to errors in BOMs,

routings, etc.

• Advantages,

- improved Customer Service

- better Scheduling

- reduced inventory

- reduced component shortages

- reduced manufacturing costs

- reduced lead times

- higher production quality

- less scrap, and rework

- higher morale in production

- improved communication

- improved plant efficiency

- improved competitive position

- improved coordination of marketing and finance

• MRP II (Manufacturing Resources Planning) - A closed-loop MRP system that, at a minimum,

includes detailed capacity analysis (see next section). Some MRP II systems include the business

plan in the closed-loop system.

• While MRP is concerned with determining how much should be produced, it is not concerned

with how to produce it.

• Capacity planners attempt to determine how to assign jobs to machines, people, etc.

• Information used by capacity planners includes,

- Planned orders (from MRP)

page 75

- Orders in process (order status)

- Routings, including setup and run time (from process plans)

- Available facilities

- Workforce availability

- Subcontracting potential

• There are some strategies used by the Capacity Planner to Assign jobs to machines,

- Splitting of lots (batches) across identical machines

- Splitting of lots to expedite a smaller quantity

- Sequencing of lots to minimize setup times

- Alternative routings that require different resources

- Loading a facility by weight, volume, etc. (eg. heat treating)

• After jobs have been assigned to machines, the capacity of the machines must be considered.

• No factory is perfect, and a schedule can become invalid at any time because of,

- Machine breakdown

- Sudden material shortage

- Workforce vacancy

- Tool breakage

- etc.

• What to do about it,

- Wait and See

- Try to find alternative production plans/parts

- Ask engineering for replan

- Bump other jobs

- ?????

• Instead of scheduling before production (MRP and Capacity planning), a manufacturer may opt

to do scheduling on the fly.

• Some of these methods include,

- Earliest operation due date - soonest date. This gives time until due, but ignores processing

time.

- Order Slack - soonest date minus processing time. This gives the amount of time to play

with.

page 76

- Shortest operation first - Do the quickest jobs first. This just clears out WIP faster.

• It is important to know what is happening on the factory floor.

• To do this we must pay attention to obvious problems like machine operation, and hidden problems

such as quality, and production quantities.

• Inspection covers a number of areas,

- Inspection of raw materials

- Inspection of manufactured product

- preprocess

- in-process

- post process

- Inspection of production process parameters

- tools

- fixtures

- production machinery

- Verification/calibration

- inspection fixtures

- Inspection gauges

- Inspection machinery

page 77

• There are a number of factors in a company which must be considered when evaluating the need

for CAD/CAM/CAE/CIM/etc systems. Some of these are listed below,

external

- company crisis

- markets Niche/Global/Home/ etc.

- competition

- customer requirements

internal

- corporate objectives, mission and culture

technological

- available technology

- research & development

success factors

- the role of management

- worker security

- corporate organization

- unions

- middle management

- worker motivation

- training / worker abilities

- cash

- purchasing

- design engineering

- etc.

• Current popular planning strategies include,

Cost management

- direct costing

- effective capital investments

- space utilization

Cycle time reduction

- continuous flow manufacturing and vendor supply

- pull manufacturing

- business and process reengineering

Market driven quality

- defining market needs

- first to market

page 78

- agile manufacturing

- 6 sigma quality

Automation

- process

- warehouse

- information

CIM

- simplifying and automated processes

- increased information access

• We can draw a chart that illustrates the issues that might be encountered,

Structure Infrastructure

Micro

Macro

fiscal/tax

monetary

trade

industrial

capital market

political structure

labor organization

culture

tradition

religion

values

social behavior

business market

plant/equipment

- capacity

- location

- process technology

vertical integration

measure and control workforce

vendors

management

capital budget

organization