2) Pengendalian Aktivitas Produksi

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Departemen Teknik Industri FTI-ITB

TI-3122 Perencanaan dan Pengendalian Produksi

Pengendalian Aktivitas Produksi

Laboratorium Sistem Produksiwww.lspitb.org

©2003

TI3122-Perencanaan dan Pengendalian Produksi - Minggu 2 2


Hasil Pembelajaran

• UmumMahasiswa mampu menerapkan model matematik, heuristik dan teknik statistik untuk menganalisis danmerancang suatu sistem perencanaan dan pengendalianproduksi

• KhususMemahami konsep pengendalian aktivitas produksi danperhitungannya

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Production Activity Control (1)

• Function of PAC:To have activities performed as plannedReport on operating resultsTo revise plans as required to achieve the desired results



Production Activity Control (2)

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Scheduling for Batch Flow Lines

• Runout time is the period existing inventory will last given forecast usage

Rate (usage) DemandInventoryin Units

=R

Item Inventory Demand (unit per day)

R (in days)

Scheduling Priority

A 80 20 4 1 B 100 10 10 2 C 150 12 12.5 3 D 60 4 15 4



Job shop scheduling

• Scheduling is the assigning of starting and completion times to orders (jobs) and frequently includes the time when orders are to arrive and leave each department

• Sequencing is the assigning of the sequence in which orders are to be processed

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Priority Control

• Priority rules: for establishing the priority of orders

• Commond priority rulesFirst Come First ServedShortest Processing (operation) TimeShortest Total Processing TimeEarliest Due DateFewest OperationSlack TimeCritical Rasio



Queue Length Management

• Objective: to control lead time and work in process and to obtain full utilization of bottleneck workcenters

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Typical queue distribution (1)



Typical queue distribution (2)

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Operation Overlapping (Transfer batches)

• Technique to reduce the total lead time of production order by dividing the lot into two or more batches and linking at least two successive operation directly.



Calculation of minimum batch size (1)

• whereQ = total lot sizeQ1 = minimum size of first batchQ2 = maximum size of second batchSB = setup time of Operation BPA = processing time per unit, Operation APB = processing time per unit, Operation BTAB = transit time between Operation A and B

* assuming Q2 is to be at Operation B before Operation B is completed on Q1

ABABABB TPQSTPQQQQ

+≥+++=

21

21

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Calculation of minimum batch size (2)

• Thus,

• Example:Q = 100 unitsPA = 10 minutesPB = 5 minutesSB = 40 minutesTAB = 30 minutes

AB

BA

PPSQPQ

+−

≥1

6415960

5104010100

1 ==+−×

≥Q



Comparison of lead time without and with overlapping

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Operation splitting

• A production lot is divided into two or more batches and the same operation is then performed simultaneously on each of these sublots



Input/Output control

• Is an effective technique for controlling queues, work in process and manufacturing lead time

Planning the acceptable input and output performance ranges per time period in each work center

Measuring and reporting actual inputs and outputs (feedback)

Correcting out-of-control situations

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Single Work Center Proceess (1)

• Basic concept: ending WIP = beginning WIP + input – output




• Situation in control

Day 25 26 27 28 29 30 Input Planned (PI) 16 16 16 16 16 Actual (AI) 12 19 22 10 15 Cumulative Deviation (ICD) 0 -4 -1 5 -1 -2 Output Planned (PO) 16 16 16 16 16 Actual (AO) 17 15 17 18 15 Cumulative Deviation (OCD) 0 1 0 1 3 2 Work in process (ending) Planned (PWIP) 32 32 32 32 32 Actual (AWIP) 32 27 31 36 28 28

iiii

iiii

iiii

iiii

AOAIAWIPAWIPPOPIPWIPPWIPAOPOOCDOCD

AIPIICDICD

−+=−+=+−=

+−=

−

−

−

−

1

1

1

1

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• WIP reduction Day 25 26 27 28 29 30 Input

Planned (PI) 14 14 14 1. 13 2. 13 Actual (AI) 12 17 16 9 14

Cumulative Deviation (ICD) 0 -2 1 3 -1 0 Output

Planned (PO) 16 16 16 16 16 Actual (AO) 17 15 15 14 18

Cumulative Deviation (OCD) 0 1 0 -1 -3 -1 Work in process (ending)

Planned (PWIP) 30 28 26 23 20 Actual (AWIP) 32 27 29 30 25 21




• Inadequate input

Day 25 26 27 28 29 30 Input

Planned (PI) 16 16 16 1. 16 2. 16 Actual (AI) 12 12 13 12

Cumulative Deviation (ICD) 0 -4 -8 -11 -15 Output

Planned (PO) 16 16 16 16 16 Actual (AO) 15 15 13 13

Cumulative Deviation (OCD) 0 -1 -2 -5 -8 Work in process (ending)

Planned (PWIP) 20 20 20 20 20 Actual (AWIP) 20 17 14 14 13

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Principles of input/output control

• The planned output should be realistic and should represent labor and equipment capacity

• A planned or actual input greater that the realistic output will increase WIP, hinder production, and increase manufacturing lead time.

• All significant deviation from planned input and planned output indicate operational problems that must be identified and solved



Multiple Work Center

• Gateway work center controlManagement of the release of orders controls the input, queues and WIP at gateway work centers

• Downstream work center controlThe input and queues at downstream work centers are controlled by dispatching at upstream work centers in the process flow

• Final work center controlThe output of the final work centers influences shipments, due date

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Rate of flow

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