8- shopfloor control

8/3/2019 8- Shopfloor Control

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COMPUTER INTEGRATED MANUFACTURING

SHOP FLOOR CONTROL

BY: MOHAMED NAEEM

HEAD CONSULTINGKINGSLAKE

[email protected]


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CONTENTS

What is shop floor control?

Order release module

Order scheduling module

Order progress module Factory data collection systems

Data input techniques

Automatic identification methods


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Shop Floor Control

This includes,

Releasing production orders to the factory

Controlling the progress of orders through various workcenters

Acquiring current information about order status

Simply it is managing the work in process.


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Shop Floor Control

Shop floor control is part of the factory informationcontrol system as shown below:

MPS, MRP, CRP

System

Shop floorcontrol

Factory ProcessesRaw Materials Finished Product


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Shop Floor Control

There are three modules of a typical shop floor controlsystem



Order progress module


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Shop Floor Control


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Order Release Module

Provides the documentation needed to processproduction through out the factory.

The document includes,

Route sheet

Material requisition note

Job cards to report labour time / record progressof job

Move tickets authorization of movements betweenwork centers

Part list for assembly purposes


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Order Release Module

Two inputs to order release module are,

Authorization to produce (derived from variousplanning functions MPS, MRP, CRP etc.)

Product structure and process planning information(from engineering and manufacturing database)


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Order Scheduling Module

Assigning the production orders to the various workcenters in the plan

Provides information about relative priorities of differentjobs.

Two problems are expected to be solved by thismodule,

The machine loading problem what are themachines to be loaded

The job sequencing problem in what order thejobs to be routed.


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Order Scheduling Module..

There are several priority basis used in scheduling

Earliest due date

Shortest processing time

Least slack time (slack = difference between the timeremaining until due date and the processing timeremaining)

Critical Ratio lowest critical ratio first

(Critical Ratio = time remaining until due date / process time remaining) Priorities are changed due to,

Change in demand

Equipment break down

Cancellation of an order

Defective raw materials


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Order Progress Module

Monitors the status of the various orders in the plant

Provide useful information to manage factory based oncollected data

Main reports used are,

Work order status report current work center, remaininghours, job is on schedule or not.

Progress reports how many orders completed, notcompleted etc.

Exception reports deviation from schedules over due jobsetc.


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Factory Data Collection Systems

This consists of paper documents, terminals and otherautomatic data collecting devices located in the shopfloor.

Such data includes

Completed quantity at each work center

Direct labour time expended

Parts that are scrapped

Parts requiring re-work

Equipment down time


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Factory Data Collection Systems..

The collection method could be on line or batch.

In an on line system,

Availability of current data

Changes in the shop floor is immediately updated

Real time

In off line system / batch system,

Delay in data processing

Not real time information

Off line systems are easy to implement


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Data Input Techniques Manual Process

The techniques include manual documents:

Job traveler

Documents move with the order

Recording labour time

Quantity completed / scrap etc.

Current information is difficult to get since it travels with the job

Employee time sheets

Each sheet /worker

Work details for the day Order number, operation number (as per route sheet)

Completed quantity, hours spent per day


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Data Input Techniques Manual Process..

Operation tear strips

Pre-printed tear strips can easily be separated from shoppacket

Operation completion / shift completion time, information such

as time, quantity completed are recorded and sent to theoffice.

Pre-punched Cards

Similar to tear strips

Order data available

Production data are entered


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Data Input Techniques Computer Terminal

Accuracy is an issue in the previous method andtherefore, key board based terminals could be used forthis purpose.

This includes,

One centralized terminal

Satellite terminals

Workstation Terminals


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Data Input Techniques Computer Terminal..

One centralized terminal Single terminal located centrally in the plant

Workers walk to the place to feed data

Not a convenient method for bigger plants

Loss in workers productive timeSatellite terminal Multiple data collection terminals

Number of terminals is decided based on the trade off betweeninvestment and inconvenient of workers movement

Work station terminal Data collection terminal at each work station

Worker movement time can be avoided

Justified when number of data to be collected is more


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Automatic Identification Method (AIM)

Sensor based methods that provides a means ofreading data that are coded.

Computer system interpret and process data

Reasons for using AIM are

Accuracy of data collection

Reduce time required to feed data to computers


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Automatic Identification Method (AIM)

The technologies available are,

Barcodes widely used method

Radio Frequency Signals similar to those used in wirelesstelevision transmission, but the communication in two directions.

Magnetic stripes attached to product Optical character recognition readable by optical sensor device.

Accuracy is lesser than the barcode method.

Machine vision system for automated inspection activitiesidentification based on geometry of the product.


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Bar Code Technology

This became popular method in retail sales and factory datacollection system.

Bar code consists of thick and narrow coloured bars separated bythick and narrow spaces.

Bar code reader scan decode the sequence of bars

The light emitted by the reader recognizes the bars and thespaces. Then this is converted to electrical signals as shown.


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Bar Code Readers

Contact bar code readers

These are hand held wands or light pens

The tip must touch the barcode or it must be very closer to it.

Mostly used on factory data collection system.

It allows worker to input data using the barcode and somestrokes of a key board.


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Bar Code Readers

Non-contact barcode readers

A light beam is used to read

The reader probe is located in certain distance from thebarcode.

Two classifications fixed beam and moving beam Fixed beam mounted beside the conveyors, the barcode

passes the beam and reading happens. This is used inwarehousing and material handling operation with largervolumes.

Moving beam use a highly focus beam of light, lasers areoften used to have highly focused beam. A scan is defined asingle sweep of the light beam through the angular path. Thiscan be stationary or portable.


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Bar Code Readers Moving Beam-Stationary


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Bar Code Readers Moving Beam-Portable


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Application of Bar Code in Production

Production worker just scan to bar code to indicate operationcompletion in the route sheet.


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We have learnt

What is shop floor control?



Order progress module Factory data collection systems

Data input techniques

Automatic identification methods