COMPUTER AIDED PRODUCTION PLANNING

& CONTROL

JAYESH SHARMAJOMY JOSEPH

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TRADITIONAL PPC SYSTEM

Forecasting

Production planning

Master scheduling

Reqmts. planning

Machine loading & scheduling

Dispatching

Production & assembly

Expediting

Purchasing

OutsideSuppliers

Inventory control

Shipping & warehousing

Quality control

Design engineering

Process planning

Estimating

Sales and marketing

CUSTOMER

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PROBLEMS WITH TRADITIONAL PPC

Plant capacity problems

Suboptimal production scheduling

Long manufacturing lead times

Inefficient inventory control

Low work centre utilization

Process planning not followed

Errors in engg. and manufacturing records

Quality problems

Capacity planning

Forecasting

Production Planning

Master schedule

MRP

SFC

Production & assembly

Purchasing

OutsideSuppliers

Inventory management

Shipping & warehousing

Quality control

Design engineering

Process Planning

Engineering and manufacturing

database

Sales and marketing

CUSTOMER

Cost planning and control

COMPUTER INTEGRATED SYSTEM

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KEY FEATURES OF CIPMS

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Engineering and manufacturing database

Material requirements planning

Capacity planning

Inventory management

Shop floor control

Cost planning and control

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1) Engineering and manufacturing database

Comprises all the information needed to fabricate the components and assemble the products.

It includesItem master fileBill of material fileRouting fileWork center fileTool file……

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Item master file

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Bill of material file

Component item numberParent item numberQuantity per parentUnit of measurePoint of usageParent operation numberScrap allowanceCurrent engineering change number

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Routing fileRouting numberFor each operation on the routing:

Operation numberOperation descriptionWork centerMachine numberDrawing numberTool numberNC tape numberStandard setup time

Standard labor run time per pieceStandard machine run time per pieceInteroperation timeOverlap pieces or hoursNumber of machines for split operationShrinkage Alternate option number

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Work center fileWork center numberDescriptionLocationDepartment numberNumber of machinesNumber of workersWork center efficiencyWork center utilizationNumber of hours per shiftNumber of shiftsMaximum daily hoursMachine rateLabor rateOverhead rateSetup rateQueue timeWait time

For each machine in work center: Machine number Machine description Last preventive maintenance date Next preventive maintenance date

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Tool file

Tool numberDescriptionStatus (in use, available, being repaired)Number of toolsSerial numberStorage locationCurrent assignment (work center, order number)Usage codeAccumulated use since last repairEstimated tool lifeDate of last tool repair

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2) Material requirements planning (MRP)

Output ReportsOutput Reports

MRP by period report

MRP by date report

Planned order report

Purchase advice

Exception reports

Order early or late or not needed

Order quantity too small or too large

Data FilesData Files

Purchasing data

BOM

Lead times

(Item master file)

Inventory data

Masterproduction schedule

Material requirement

planning programs (computer and

software)

Masterproduction schedule

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BENEFITS OF MRP

Customer service is improved

Reduction in lead time for each time horizon.

Reduction in work-in-process

Reduction in past-due orders

Elimination of annual inventory

Increase in productivity

Capacity constraints are better understood

Inventory turn-over increases

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"Perhaps the greatest requirement of all for successful MRP installation and operation is discipline. This includes the discipline to maintain accurate stock

records, the discipline to report accurately and in good time the completion of jobs and orders and to report to the system every event that MRP should be aware

of. Many successful MRP installations have padlock on the doors to the stockrooms."

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Closed loop MRP system

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Why closed loop MRP?

The common MRP (open loop) is static in the sense that problems with production machines, quality, labor, late delivery etc. make the output of MRP more or less irrelevant.

Manual updating is difficult and time consuming and error prone also.

Closed loop MRP handle this problem of updating.

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How closed loop MRP works?

Purchase and production activities control modules interfaced with MRP-module.

Dynamic updating of order status done by purchasing interface generates updated order status from which new planned order releases.

Shop floor interface updates MRP production status by collecting daily production and operator time-sheet data.

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Manufacturing Resource planning (MRP II)

Once an MRP system is in place, inventory data can be Once an MRP system is in place, inventory data can be augmented by other useful informationaugmented by other useful information

Labor hoursLabor hours

Material costsMaterial costs

Capital costsCapital costs

Virtually any resourceVirtually any resource

Then the system is called MRP II or Manufacturing Then the system is called MRP II or Manufacturing Resource PlanningResource Planning

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An extension of the MRP system to tie in An extension of the MRP system to tie in customers and supplierscustomers and suppliers

1.1. Allows automation and integration of many Allows automation and integration of many business processesbusiness processes

2.2. Shares common data bases and business Shares common data bases and business practicespractices

3.3. Produces information in real timeProduces information in real time Coordinates business from supplier evaluation Coordinates business from supplier evaluation

to customer invoicingto customer invoicing

Enterprise resource planning

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ERP modules includeBasic MRPBasic MRPFinanceFinanceHuman resourcesHuman resourcesSupply chain management (SCM)Supply chain management (SCM)Customer relationship management (CRM)Customer relationship management (CRM)

ERP systems can be integrated withWarehouse managementWarehouse managementLogisticsLogisticsElectronic catalogsElectronic catalogsQuality managementQuality management

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3) Capacity planning

Concerned with determining the labor and equipment resources needed to meet the production schedule.

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Capacity planning for short term adjustmentsinclude decisions on

employment levelsnumber of work shiftsovertime or reduced workweekinventory stockpilingorder backlogssubcontracting

Capacity planning for long term requirements

investing in more productive or new type of machinesnew plant constructionacquisitions and buyoutsclosing down or selling off

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4) Inventory management

The inventory management module of the CIPMS should accomplish two major functions.

Inventory accounting

Inventory planning and control

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Inventory accountingInventory accounting is concerned with inventory transactions and inventory records.Inventory transactions include

receiptsissuesreturns& loans

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Inventory planning and control

Many of the planning and control activities are accomplished by the MRP module. Other functions include• Determining economic lot sizes• Determining safety stock levels• Determining reorder points• ABC inventory analysis• Analysis of usage rates for lot size calculations• Automatic generation of purchase requests

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4) Shop floor control

The functions of a shop floor control system are

Priority control and assignment of shop orders Maintain information on WIP for MRP Monitor shop order status information Provide production output data for capacity control

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Software modules in SFC system

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4) Cost planning and control

It receives data from all other CIPMS modules and reduces them to a lowest common denominator :

money

Input source InputBill of materials Components & materials usedProcess route sheets Manufacturing operations

employedTime standards Operation timesLabor & machine rates Associated costMaterial quotations Material costAccounting data Overhead rates

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Cost control

Expected cost?

Actual cost?

Why difference?

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References

1)CAD/CAM, Mikell P. Groover2)Computer based production and inventory control, Spencer B. Smith

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