Manu Supp Syst

8/10/2019 Manu Supp Syst

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PROCESS PLANNING AND

PRODUCTION CONTROL

1. Process Planning

2. Other Manufacturing Engineering Functions

3. Production Planning and Control

4. Just-In-Time Delivery Systems

5. Lean Production

©2013 John Wiley & Sons, Inc. M P Groover, Principles of Modern Manufacturing 5/e



Process Planning Defined

Technical staff function concerned with planning themanufacturing processes for economical production

of high quality products Deciding appropriate processes and their

sequence

Determining tooling requirements

Selecting equipment Estimating costs




Process Planning and

Manufacturing Engineering

Process planning is usually the principal function withinthe Manufacturing Engineering Department of a

company In addition to process planning, the scope of

manufacturing engineering also includes:

Problem solving and continuous improvement - staff

support to operating departments Design for manufacturability - manufacturability

advisors to product designers




Traditional Process Planning

Traditionally, process planning is accomplished bymanufacturing engineers who are familiar with the

particular processes in the factory and are able to readengineering drawings

Based on their knowledge, skill, and experience, theydevelop the processing steps in the most logical

sequence required to make each part Some details are often delegated to specialists, such as

tool designers




Details in Process Planning

Processes and sequence - process plan should brieflydescribe all processing steps used on the work unit in

the order they are performed Select equipment to be used - try to develop process

plans that utilize existing plant equipment

Otherwise, part must be purchased, or new

equipment must be installed in the plant Specify what tools, dies, molds, fixtures, and gages are

needed




Process Planning for Parts

Processes needed to manufacture a given part aredetermined largely by the material out of which the

part is made and the part design itself The material is selected by the product designer

based on functional requirements

Once the material has been selected, the

choice of possible processes is narrowedconsiderably




Typical Processing Sequence

A typical processing sequence to fabricate a discretepart consists of:

1. A basic process2. One or more secondary processes

3. Operations to enhance physical properties

4. Finishing operations




Basic process establishes initial geometry of part

Secondary processes transform starting geometry into

final part shape Property-enhancing processes

Finishing operations


Typical Processing Sequence



Examples of Typical

Process Sequences


Basic process SecondaryProcess(es)

Propertyenhancing

Finishingoperations

Sand casting Machining Heat treating Painting

Rolling sheet Blanking,bending

(none) Plating

Forging Machining (none) Painting

Extrusion (Al) Cut to length (none) Anodizing

Casting of glass Press, blowing Annealing Chem. etch



Example: Plumbing Fixture


Left: starting casting(basic process)

Right: after machining(secondary process) tocreate accurate holesand threads (courtesyGeorge E. Kane

ManufacturingTechnology Laboratory,Lehigh University)



Process Planning: Basic Process

Process planning usually begins after the basicprocess has provided initial part shape

Example: machined parts begin as bar stock orcastings or forgings, and these basic processesare often external to the fabricating plant

Example: stampings begin as sheet metal coils

or strips purchased from the mill These are the raw materials from external vendors

for the secondary processes used in the factory




Typical routesheet for

specifying theprocess plan


Route Sheet



Process Planning for Assemblies

For single stations, documentation is a list of assemblysteps in the order in which they must be accomplished

For assembly line production, process planningconsists of line balancing - allocating work elements toparticular stations along the line

As with process planning for parts, any tools and

fixtures needed to accomplish a given assembly taskmust be decided, and the workplace must be designed




Make or Buy Example

Quoted price from a vendor = $8.00 per part for 1000units. Same part made in the home factory would cost

$9.00. Cost breakdown on the make alternative:Unit material cost = $2.25 per unit

Direct labor = $2.00 per unit

Labor overhead at 150% = $3.00 per unit

Equipment fixed cost = $1.75 per unitTotal = $9.00 per unit

Should the component by bought or made in-house?




Make or Buy Example -

continued

Although the vendor's quote seems to favor the buydecision, consider the possible effect on the factory if

the quote is accepted Equipment fixed cost is based on an investment

that has already been made

If equipment is idled, then the $1.75 fixed cost

continues even if the equipment is not in use Same is true of the $3.00 overhead cost which

consists of factory floor space, indirect labor, etc.




Computer-Aided Process

Planning

During the last several decades, there has beenconsiderable interest in automating the process

planning function using computer systems Shop people knowledgeable in manufacturing

processes are gradually retiring

An alternative approach to process planning is

needed Computer-aided process planning (CAPP)

systems provide this alternative




CAPP Systems

Computer-aided process planning systems aredesigned around either of two approaches:

1. Retrieval systems2. Generative systems




Operation of a retrieval type computer-aidedprocess planning system


Retrieval CAPP System



Retrieval CAPP Systems -

continued

If the file does not contain a standard process planfor the given code number, the user may search thefile for a similar code number

By editing an existing process plan, or startingfrom scratch, the user develops a new processplan that becomes the standard plan for the newpart code

Process plan formatter may call other applicationprograms: determining cutting conditions,calculating standard times, or computing costs




Generative CAPP Systems

Rather than retrieving and editing an existing plan,the process plan is created using systematicprocedures that might be applied by a human planner

In a fully generative CAPP system, the processsequence is planned without human assistance andwithout predefined standard plans

Designing a generative CAPP system is a problem in

expert systems - computer programs capable ofsolving complex problems that normally require ahuman with years of education and experience




Other Manufacturing Engineering

Functions

1. Problem solving and continuous improvement

2. Design for Manufacturing and Assembly




Problem Solving in

Manufacturing

Problems arise in manufacturing that require technicalstaff support beyond what is normally available in the

line organization of the production departments Providing this technical support is one of the

responsibilities of manufacturing engineering

The problems are usually specific to the particular

processes performed in the operating departmentsand expertise is often required to solve them




Continuous Improvement

Project Areas

Cost reduction

Quality improvement

Productivity improvement Setup time reduction

Cycle time reduction

Manufacturing lead time reduction

Improvement of product design to increaseperformance and customer appeal




How Design Affects Process

Planning

Example: If the product engineer designs analuminum sand casting with features that can be

achieved only by machining Then the process planner must specify sand

casting followed by the necessary machiningoperations

The manufacturing engineer might advise thedesigner that a plastic molded part might bettersatisfy functional and economic requirements




Design for Manufacturing and

Assembly (DFM/A)

An approach to product design that systematicallyincludes considerations of manufacturability and

assemblability in the design DFM/A includes:

Organizational changes

Design principles and guidelines that should be

implemented during product design




Organizational Changes in

DFM/A

To implement DFM/A, a company must makeorganizational changes to provide closer interaction

between design and manufacturing personnel Often done by forming design project teams

consisting of product designers, manufacturingengineers, and other specialties

In some companies, design engineers must spendsome career time in manufacturing to learn about theproblems encountered in making things




DFM/A Principles and Guidelines

DFM/A includes principles and guidelines thatindicate how to design a given product for

maximum manufacturability Many of these principles and guidelines are

universal

Rules of thumb that can be applied to nearly

any product design situation In addition, DFM/A includes principles that are

specific to given manufacturing process




Benefits Typically Cited for

DFM/A

Shorter time to bring the product to market

Smoother transition into production

Fewer components in the final product Easier assembly

Lower costs of production

Higher product quality

Greater customer satisfaction




Concurrent Engineering

A modern approach to product design in whichcompanies attempt to reduce elapsed time to bring a

new product to market by integrating design andmanufacturing engineering, and other functions

Manufacturing engineering becomes involved early inthe product development cycle

In addition, other functions are also involved, such asfield service, quality engineering, manufacturingdepartments, vendors, and in some cases customers




Concurrent Engineering

All of these functions can contribute to a productdesign that performs well functionally, and is also

manufacturable, assembleable, inspectable, testable,serviceable, maintainable, free of defects, and safe

All viewpoints have been combined to design aproduct of high quality that will deliver customersatisfaction

Through early involvement of all interested parties,the total product development cycle time is reduced




The Production Planning

Problem

Any manufacturing firm must have a business plan,and that plan must include:

What products will be produced

How many and when

The manufacturing plan should take into account

Current orders and sales forecasts

Inventory levels

Plant capacity considerations




Aggregate Production Plan

Indicates production output levels for major productlines rather than specific products

Must be coordinated with sales and marketingplan and must consider current inventory levels

Must reconcile marketing plans for currentproducts and new products under development

against the capacity resources available to makethose products

High level corporate planning activity




Master Production Schedule

Converts the aggregate schedule into a very specificschedule of individual products

Lists the products to be manufactured, when theyshould be completed, and in what quantities

Products listed in the master schedule generallydivide into three categories:

1. Firm customer orders2. Forecasted demand

3. Spare parts




Controlling Production andInventory

Two alternative techniques for controlling productionand inventory:

For job shop and mid-range production ofassembled products:

Material requirements planning (MRP) andcapacity requirements planning

For high production: Just-In-Time (JIT) and Lean Production




Material Requirements Planning

(MRP)

Computational procedure to convert masterproduction schedule for end products into a detailed

schedule for raw materials and components used inthe end products

The detailed schedule indicates:

Quantities of each item to be ordered

When the order must be placed

When the order must be delivered to achievethe master schedule




Common Use Items in MRP

The master production schedule specifies the monthlyquantities of final products

Each product may contain hundreds of parts These parts are made from raw materials, some of

which may be common among the components (e.g.,sheet steel for stampings)

Some of the parts themselves may be common toseveral different products

Called common use items in MRP




Lead Times in MRP

The time that must be allowed to complete the jobfrom start to finish

Two kinds of lead times in MRP: Ordering lead time - time required from

initiation of the purchase requisition to receiptof the item from the vendor

Manufacturing lead time - time required toproduce the item in the company's own plant,from order release to completion




Inputs to the MRP System

For the MRP processor to function properly, it mustreceive inputs from several files:

Master production schedule

Product structure indicating subassemblies,components, and raw materials

Bill of materials file

Inventory records

Capacity requirements planning




MRP Output Reports

1. Order releases - authorize placement of orders

2. Planned order releases in future periods

3. Rescheduling notices, indicating changes in duedates for open orders

4. Cancellation notices - indicate that certain orders arecanceled due to changes in the master schedule

5. Inventory status reports6. Exception reports, showing deviations from

schedule, overdue orders, scrap, etc.




Capacity Requirements Planning

Concerned with determining labor and equipmentrequirements needed to meet the master

production schedule Also concerned with identifying the firm's long

term future capacity needs

Also serves to identify production resource

limitations so that a realistic master productionschedule can be planned




Short-Term Capacity

Adjustments

Employment levels – increasing or decreasingnumber of workers

Shift hours – overtime or reduced hours Number of work shifts – authorizing a second shift

Inventory stockpiling – to maintain steadyemployment during slow periods

Order backlogs – delaying deliveries to customers Subcontracting – contracting work to outside shops




Long-Term Capacity

Adjustments

Purchasing new equipment to increase capacity

Additional machines

More productive machines (latest technology) New types of machines to match future product

requirements

Building new plants to increase capacity

Closing plants not needed for future production




Shop Floor Control (SFC)

Concerned with releasing production orders,monitoring and controlling progress of the orders, and

acquiring up-to-date information on order status SFC is concerned with managing WIP in the factory

Most relevant in job shop and batch production,where a variety of orders must be scheduled and

monitored

Purchasing department is responsible for thisfunction among suppliers




Three Modules of a Shop Floor

Control System1. Order release

2. Order scheduling

3. Order progress They are implemented by a combination of computer

systems and human resources




Order Release

Generates the documents needed to process aproduction order through the factory

Documents are sometimes called the shop packet: Requisition to obtain starting materials

Route sheet

Job cards to report direct labor time

Move tickets to transport parts

Parts list for assembly jobs




Order Scheduling

Assigns production orders to work centers in thefactory

A dispatch list is prepared indicating which ordersshould be accomplished at each work center

Also provides relative priorities for the jobs, e.g.,by showing due dates for each job

Dispatch list helps the department foreman assignwork and allocate resources to achieve the masterproduction schedule




Order Progress

Monitors status of orders, WIP, and other parametersin the plant that indicate production performance

Various techniques are available to collect datafrom factory operations

Called the factory data collection system

Techniques range from requiring workers tosubmit paper forms that are later compiled, tofully automated data collection techniques




Enterprise Resource Planning

(ERP) ERP is a computer-based system that organizes and

integrates all of the data and business functions of an

organization through a central database Accomplishes MRP, capacity requirement

planning, and shop floor control

Also accomplishes business functions such as

sales, accounting, distribution, and humanresources




Just-In-Time (JIT)

Delivery Systems A JIT system produces exactly the right number of

each component to satisfy the next operation justwhen that component is needed

Aimed at reducing factory inventories

Important component of lean production




Where to Apply JIT

Just-in-time procedures have proven most effective inhigh-volume repetitive manufacturing

Example: automobile industry Potential for in-process inventory accumulation

in this type of manufacturing is significantbecause both quantities of products andnumbers of components per product are large




Some Requisites for JIT to Work

Small batch sizes and short setup times

On-time delivery of defect-free components and

materials Reliable production equipment

Pull system of production control




Small Batch Sizes and Setup

Reduction A requirement for minimizing inventories is small

batch sizes and short setup times

Large batch sizes mean longer production runsand higher inventory levels

Long setup times are costly in both labor andlost production time

Long setup times also necessitate longproduction runs in order to justify the setups




On-Time Delivery, Defects, and

Reliability Small lot sizes and parts buffers in JIT require parts

to be delivered on time at downstream stations

Otherwise, downstream stations are starved Defective parts cannot be used in assembly

Promotes zero defects in parts production

Machines that break down cannot be tolerated in JIT

because of low WIP Requires high equipment reliability and preventive

maintenance




Three Categories of

Activities in Manufacturing1. Actual work activities that add value such as

processing steps that alter the product in a positiveway

2. Auxiliary work activities that support the value-adding work activities, such as loading andunloading a production machine

3. Wasteful activities that do not add value and do notsupport the value-adding activities, such asunnecessary handling of the product




Seven Forms of Waste in the

Toyota Production System1. Production of defective parts

2. Production of more parts than needed

3. Excessive inventories4. Unnecessary processing steps

5. Unnecessary movement of workers

6. Unnecessary handling and transport of materials

7. Workers waiting




Toyota Production System

The principal components of the Toyota ProductionSystems that were designed to reduce or eliminatethe seven forms of waste:

1. Just-in-time delivery system

2. Autonomation (Taiichi Ohno’s word)

3. Worker involvement




Key Features of Autonomation

Stop the process

Error prevention

Total Productive Maintenance




Stop the Process

Underlying principle: When something goes wrong, theprocess should be stopped so that corrective actioncan be taken

Applies to both automatic machines and manuallyoperated processes

Machines are designed with sensors that detectthe problems

Workers on the assembly line are empowered tostop the line when a problem occurs




Total Productive Maintenance

(TPM) JIT does not provide for inventory buffers when

breakdowns occur

TPM aims to minimize production losses by makingthe machines highly reliable to avoid breakdowns

TPM integrates the following programs:

Workers are responsible for minor maintenance

Emergency maintenance

Preventive maintenance

Predictive maintenance




Worker Involvement

Third component of lean production as practiced inthe Toyota Production System

Three aspects of worker involvement: Continuous improvement

Visual management

Standard work procedures




Continuous Improvement

Identified earlier in the context of manufacturingengineering functions

In lean production, continuous improvement projectsare carried out be worker teams

Projects focus on problems related to productivity,quality, safety, maintenance, and other issues ofinterest

Workers serve the team part-time while theyperform their regular duties




Visual Management

Underlying principle: The status of a work situation isusually obvious just be looking at it

If a machine is stopped, it is obvious thatsomething is not right

The entire interior of a plant should be visible

Obstructions such as work-in-process should

be kept to a minimum Andon boards show plant status

Worker training using pictures and diagrams




Standard Work Procedures

Work procedures and times in the Toyota ProductionSystem are standardized to increase productivity,balance workloads, and minimize work-in-process

Procedures document the work elements and theirelement times for each repetitive task performedby workers

For workers responsible for multiple machines, thesequence of elements is designed to minimize idletimes of workers and machines


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