THE INTEGRATED METHOD OF WAREHOUSE LAYOUT ...

Proceedings of the International Conference on Industrial Engineering and Operations Management

Bandung, Indonesia, March 6-8, 2018

© IEOM Society International

THE INTEGRATED METHOD OF WAREHOUSE

LAYOUT AND LABOR SCHEDULING TO REDUCE

OVERTIME

Fransisca Dini Ariyanti

Aurellia Victoria, Lidya Guestine, Noviana

Industrial Engineering, Faculty of Engineering, Bina Nusantara University

KH. Syahdan Street No. 9 Jakarta,11480, Indonesia

[email protected]; [email protected]; [email protected]

[email protected]

Overtime was indicated that warehouse management neither inefficient and ineffective. The case study

taken place in Indonesia popular cement board finished goods warehouse. The objectives of this study are

to reduce overtime, by re-layout of warehouse finished goods using integrated methods. The integrated of

Class-Based Storage Method, Dedicated Storage Policy, From-to-Chart Method for layout improvement

and Tibrewala, Philippe, and Browne Algorithm for scheduling warehouse operators. The results of re-

layout the finished goods warehouse are obtained that the space efficiency and the reduction of cycle time

from 3,33 minutes to 1,86 minutes and the overtime hours decreased after partial implementation. The result

obtained for the new labor scheduling of warehouse operator is needed to reduce 2 operators. The proposed

improvement will continue to be applied and it is expected to increase efficiency in the future.

Keywords: Class-Based Storage, Dedicated Storage, From-to-Chart, Cycle Time, Tibrewala, Philippe,

and Browne Algorithm

1. Introduction

1.1 The case study company

PT XYZ is an Indonesia pioneer company which produces 13 types cement board in different thickness. In a good

warehouse management, the layout of the finished good warehouse is a very important to support effective delivery.

The first problem found in PT XYZ is the layout of the finished good warehouse was messy and irregular. The finished

goods of many types which have been produced and ready to be delivered to customers will be placed in the finished

good warehouse. The finished products which passed the sorting stage are placed irregularly by the warehouse

operators and there is no barrier between one type product to another type. The best-selling product is scattered into

multiple areas and quite far from input or output (I/O) point. The finished products are also placed without following

the principle of first in first out (FIFO) so there is a possibility of expired or damaged then become rejected. The

second problem found in The PT XYZ is warehouse operators scheduling. Three shift warehouse operators work five

days follow with two off-days. In high customer demand season, warehouse management order operators an overtime

and replace the off-day into next week. Warehouse operators scheduling is less likely to anticipate the possibilities

that occur so the scheduling system has not been effective. In results, January 2017 the overtime spent 1083 hours.

2 The Literature Review Warehousing can be defined by three functions: (1) receiving goods from a source, (2) storing goods until they are

needed by a customer (internal or external), and (3) retrieving the goods when requested [1]. The successful warehouse

layouts must accomplish the following objectives, regardless of the material being stored: (1) maximize the use of

space; (2) maximize the use of equipment; (3) maximize the use of labor; (4) maximize accessibility to all items; (5)

maximize protection of all items. The objective of this case study is to increase the efficiency and effective warehouse

management thru reduce overtime. In order to reach the goals, several methods were combined. First, a combination

of Class-Based storage, Dedicated storage policy and From-to-Chart method to a re-layout warehouse. Secondly, the

2008

mailto:[email protected]







modification of Tibrewala, Philippe, and Brown Algorithm (TBP Algorithm) to calculated warehouse operator

schedule which accommodates 3 shifts per each day with 6 working days per week, where operators work 5 days per

week with 3 shifts and 2 days off on weekend according to company policy and 1 day after work on shift 3

2.1 Class-based storage.

Class-based storage is widely studied in the literature and applied in practice. It divides all stored items into a

number of classes according to their turnover. It divides stored items into different classes (using three classes is

common in practice) according to the ABC demand curve (see Fig.1.1). Class Based Storage Policy is an inventory

application known as Pareto demand curve (ABC curve) by observing the storage activity level with retrieval (S/R)

which is in warehouse 80% S/R activity from 20% items, 15% from 30% items, and 5% from 50% items. [2] Thus,

it can be classified into three classes ie A, B, and C which are sorted by S//R activity level from the highest to the

lowest level. To minimize time spent in warehouse to store and retrieval, a highly demanded item is grouped as A-

class items and are then stored in a warehouse region closest to the input-output point (I/O) point. Then Class B,

after that grouped as C-class items, rarely demanded items are stored in the region farthest from the input-output

point (I/O) point. [3]

Figure 1.1. An example of an ABC demand curve (source: Guo, X., 2016)

2.2 Dedicated storage policy

The dedicated storage policy assigns material to a predetermined location based on throughput and storage

requirements. All storage jobs of a given material are routed to the dedicated storage location. [2] Dedicated Policy is

the placement of products to the specified location depending on the type of items to be stored. The space requirement

can be calculated by the following formula:

Space Requirement (S) = "The maximum products can be stored per day " (1) "product storage capacity per slot"

Floor Area Requirement = Space Requirement x product dimension (2)

After calculating the number of products that stored per product line can be converted into the number of pallets, so

it can calculate the total number of pallets that need to be stored based on the product items.

2.3 From-to-Chart method to re-layout warehouse.

To find out the most effective relationship between each area in finished good warehouse can using the From-to-

Chart Method. The method requires the number of movements between one area to another in a flow matrix

diagram.

2009




3. Methodology This research uses a case study approach. The observations were made in PT XYZ’s finished good warehouse. The

observations are also made to determine the problems that occur to propose the new optimal design layout of

finished good warehouse and the new warehouse operators scheduling system. The following is the sequence of the

research:

1. Determine the priority classification that supports the proposed design of PT XYZ's final product

warehouse layout, use of Class Based Storage Method.

2. Determine the area, width of road, and throughput that support the proposed layout design of PT XYZ's

final product warehouse, use of Dedicated Storage Method

3. Determine the design of an efficient and effective final product warehouse layout, use of the From-to-Chart

Method

4. Compare the cycle time between the current layout to cycle time after proposed layout is implemented.

5. Monitoring overtime warehouse operators.

6. Calculation of labor scheduling for non-staff workers using the TBP Algorithms.

4. Result and discussion 4.1 Class-based storage.

Based on 2016 turnover, 13 types cement boards in different thickness classified into class A which is the highest

demand and placed closest to the I/O point to minimize the time and movement activity. Then continued with

products in classification B and C

Product Name

Yearly

Demand

(sheet)

Cummulative

Demand

(sheet)

Percentage Percentage

Cummulative Classification

Cement board Internal

1.220 x 2.440 x 4 2.160.000 2.160.000 66,67 66,67

A Cement board Internal

1.220 x 2.440 x 6 324.000 2.484.000 10,00 76,67


1.000 x 1.000 x 4 119.000 2.603.000 3,67 80,34

Cement board External

100 x 2.440 x 9 112.000 2.715.000 3,46 83,80

B


200 x 2.440 x 9 112.000 2.827.000 3,46 87,25


1.220 x 2.440 x 8 108.000 2.935.000 3,33 90,59


1.220 x 2.440 x 9 72.000 3.007.000 2,22 92,81


300 x 2.440 x 9 56.000 3.063.000 1,73 94,54


1.220 x 2.440 x 5 54.000 3.117.000 1,67 96,20

C


1.220 x 2.440 x 10 54.000 3.171.000 1,67 97,87

Cement board Internal 500

x 1.000 x 4 51.000 3.222.000 1,57 99,44


1.220 x 2.440 x 12 10.800 3.232.800 0,33 99,78


1.220 x 2.440 x 15 7.200 3.240.000 0,22 100,00

Table 1. ABC Class of finished products

4.2 Dedicated storage policy.

To consider the placement of product area is using a dedicated storage calculation. Then calculating the expansive of

each area by knowing the number of slots required according to the optimum stock of each product. The size slot

determined is 6 meters x 2,92 meters and in one slot can patch 4 x 1 pallets with 5 pallets arranged which each pallet

accommodates 150 sheets of cement board products:

The space requirement (S) can be calculated as the following formula:

2010




S = 347 = 17,35 ≈ 18 slot 20

Floor area required = 18 x 6 x 2,92 = 315,36 m2

Based on the material handling (forklift) that used to retrieve the cement board pallets with P x L of forklift is 4,30

m x 1,90 m will be used to calculate the diagonal length of the forklift as follows:

Length of diagonal forklift = √(length of the forklift)2+(width of the forklift)2

Length of diagonal forklift = √(4,30)2+(1,90)2

Length of diagonal forklift = 4,70 m

Based on Indonesian Anthropometric Data on the width of the shoulder dimension which is D17 with percentile-95 is

45,51 cm ≈ 0,46 m and the allowance given is 10%, so the width of the aisle between pallets is 0,51 m.

After calculate the space requirement with Dedicated Storage, the efficiency of the warehouse can be obtained as

follows:

Remaining area = the available area – the used area

= 6.337,58 m2 – (1.645,95 m2 + 1.607,99 m2)

= 6.337,58 m2 – 3.253,94 m2

= 3.083,65 m2

% remaining area available = remaining area

spacious area x 100%

= 3.083,65

6.337,58 x 100 %

= 48,66 %

% the used area = 100% - 48,66%

= 51,34 %

4.3 Form-to-Chart

The attraction results of the proximity calculation reach on 7th iteration. In the first iteration obtained, there are 165

lines that connect between areas in the warehouse. Based on the 1st of the calculation of flow matrix in appendix

iteration 1 obtained total forklift activity as many as 14,813 movements. From the result of iteration 7, there is a flow

of 97 calculations by continuing calculations on the iteration. Based on the results of calculations in the last iteration

which is iteration 7, there was a total flow of 522 movements, from 2,327 which can be seen from the result of iteration

6 to 1.805. It shows that closer to the area with the greatest activity relation can minimize movement in each area.

Table 2 Triangularized Matrix used From-to-Chart

2011




I B N D E

F G H L J

K A O V M

P Q R S T

UC

Figure 2. Calculation From-to-Chart Iteration 7

Figure 3. Current layout (left) vs Proposed

layout ( right)

17.5

0m

.

128

.36

m.

Siap Kirim 2

Siap Kirim 1

Kantor

A

B

C

A

B

C

Papan Semen Eksternal

300 x 2440 x 9

A

B

C

A

B

C


1220 x 2440 x 9

A

B

C

A

B

C


1220 x 2440 x 15

A

B

C

A

B

C


100 x 2440 x 9


200 x 2440 x 9

D

E

F

D

E

F

D

E

F

D

E

F

D

E

F

D

E

F

D

E

F

D

E

F


1220 x 2440 x 12

Penyiapan

Packing

Papan Semen Internal

1220 x 2440 x 4

Lokasi Transit


500 x 1000 x 4


1000 x 1000 x 4

Siap Rework

Rework

Sortir


1220 x 2440 x 6


1220 x 2440 x 8


1220 x 2440 x 5


1220 x 2440 x 10

A

B

C

A

B

C

5.8

4m

.5

.84m

.

12.00m. 12.00m.18.00m.

18.00m. 18.00m.

24.00m.

42.00m.

12.00m.

24.00m.

5.8

4m

.

114m.114.00m.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

AC

AD

AE

AF

AG

AH

AI

AJ

AK

AL

AM

AN

AO

AP

6.0

0m

.

Legenda:

Forklift

Pintu

Pallet

Meja dan Kursi

Kerja

Tanaman

Telephone

Document Shredder

Printer

Jalur Forklift

37.9

2m

.

128

.36

m.

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

D

E

F

D

E

F

D

E

F

D

E

F

D

E

F

D

E

F

D

E

F

D

E

F

A

B

C

A

B

C

5.8

4m

.5

.84m

.

12.00m.

5.84m.12.16m.18.16m.

24.00m. 24.00m.

26.64m.

5.8

4m

.

114m.114.00m.

AC

AD

AE

AF

AG

AH

AI

AJ

AK

AL

AM

AN

AO

AP

Legenda:

Forklift

Pintu

Pallet

Meja dan Kursi

Kerja

Tanaman

Telephone

Document Shredder

Printer

Siap Kirim

Kantor


300 x 2440 x 9


1220 x 2440 x 9


1220 x 2440 x 15


100 x 2440 x 9


200 x 2440 x 9


1220 x 2440 x 12

Penyiapan

Packing


1220 x 2440 x 4

Lokasi Transit


500 x 1000 x 4


1000 x 1000 x 4

Siap Rework

Rework

Sortir


1220 x 2440 x 6


1220 x 2440 x 8


1220 x 2440 x 5


1220 x 2440 x 10

8.7

6m

.8

.76m

.

Jalur Forklift

11.6

8m

.

4.80m. 5.84m.

6.00m.

C

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

2.92m.30.00m.

2012




4.4 Warehouse operator Scheduling System with the Modification of Tibrewala, Philippe, and Browne

Based on the current scheduling and the worker needed per day, the new scheduling of warehouse operator used the

modification of Tibrewala, Philippe, and Browne algorithm was calculated, the result on Table 3, show that there are

85 iterations which means 85 warehouse operators needed instead of 87. PT XYZ is advised to reduce two operators.

Table 3 The Number of Workers Day Off in PT XYZ

Day off The number

of workers

Monday

Sunday

14

Tuesday 14

Wednesday 14

Thursday 15

Friday 14

Saturday 14

Total 85

4.5. Discussion Result.

Proposed layout has been implemented step by step in PT XYZ. Cycle time comparison per product taking per pallet

using forklift with previous layout is 3,33 minutes and implemented proposed layout has been reduced cycle time to

be 1,86 minutes. Overtime was reduced during implementation period February 2017 to June 2017. The monthly

benefit of efficient and effective warehouse system for PT XYZ, among others are saving overtime cost 937 hours (

equivalent to IDR 38 million), reduce 2 operators ( equivalent to 8 million), reduce forklift distance and time.

Table 4 Reduced overtime

5. Conclusion, Research limitation and Future researchThis research has been proposed new warehouse layout. The implementation of new layout and warehouse

systems has been increased the warehouse performance. In June 2017, cycle time reduce to be 1,86 second, overtime

only 146 hours and warehouse empty space increase 48,66%.

This research was conducted only at Company PT XYZ, which is a popular cement board national company

in Indonesia. The findings of this study cannot be generalized to the whole cement board industry in Indonesia. Small

and medium-sized companies may have different layout and may even have different warehouse systems.

Future research can be done to find the difference warehouse system and layout between small and medium-

sized cement board companies in Indonesia.

References [1] Larson, et.al., A heuristic approach to warehouse layout with class-based storage, IIE Transactions, Vol 29, p.

337 – 348, 1997

[2] Zaerpour, Nima; de Koster, René B.M. and Yu, Yugang, Storage policies and optimal shape of a storage system,

International Journal of Production Research,, 51:23-24, 2013, 6891-6899, DOI: 10.1080/00207543.2013.774502

[3] Guo X., Storage Policies and Maintenance Support Strategies in Warehousing Systems, © Springer Science +

Business Media Singapore, 2016 DOI 10.1007/978-981-10-1448-2_2

[4] Aminia, E. F., Rahman, A., & Mada, C. F. . Penjadwalan Tenaga Kerja Tiga Shift Berkendala Libur Hari Minggu

dan Satu Hari Setelah Shift Tiga. Jurnal Rekayasadan Manajemen Sistem Industri Vol 1. 2013

Periode Work time

(hours)

Overtime

(hours)

January 2017 15,225 1083

February 2017 12,425 724

March 2017 12,425 458

April 2017 12,425 279

May 2017 12,425 267

June 2017 12,425 146

2013




[5] BPS, Indeks Harga Perdagangan Besar Bahan Bangunan / Konstruksi Indonesia, 2002-2017. Retrieved from

Badan Pusat Statistik: https://www.bps.go.id/linkTabelStatis/view/id/1458, 2017, April 3

[6] Freivalds, A., & Niebel, B. Niebel's Methods, Standards, and Work Design 12th Edition. USA: McGraw Hill

International Edition, 2009.

[7 ]Heragu, S. S. , Facilities Design: 4th Edition. USA: CRC Press: Taylor & Francis Group. 2016

[8] Jacobs, F. R., Chase, R. B., & Lummus, R. R. , Operations and supply chain management, 13th Edition. New

York: McGraw-Hill Irwin. , 2011

[9] Kumar, S. A., & Suresh, N. Production And Operation Management Second Edition. New Delhi: New Age

International (P) Ltd. , 2008

[10] Nahmias, S., & Olsen, T. L. Production and Operations Analysis: 7th Edition. USA: Waveland Press, Inc. , 2015

[11] Permana, I. H., Ilhami, M. A., & Febianti, E., Relayout Tata Letak Gudang Produk Jadi Menggunakan Metode

Dedicated Storage. Jurnal Teknik Industri, Vol.1, No.4, 272-277. 2013

[12] Pinedo, M. L., Scheduling Theory, Algorithms, and Systems Fifth Edition. New York: Springer International

Publishing. 2016

[13 ]Richards, G., Warehouse Management: 2nd Edition. USA: Kogan Page Limited, 2014

[14] Rocha, M., Oliveira, J. F., & Carravilla, M. A. Quantitative Approaches on Staff Scheduling and Rostering in

Hospitality Management: An Overview . American Journal of Operations Research, 137-145, 2012

[15] Sule, D. R. Manufacturing Facilites; Location, Planning, and Design Thrid Edition. New York: CRC Press. 2008

[16] Susandi, D., & Milana, L. Perancangan dan Pembuatan Aplikasi PenyusunanJadwal Kerja Dinas Jaga Perawat

IGD Menggunakan Algoritma TPB. Jurnal Metris, 16, 29 – 34 ,2015

[17] Tompkins, J. Facilities Planning. , USA: John Wiley & Sons, Inc. ,2010

Biographies Fransisca Dini Ariyanti is a lecturer in the Industrial Engineering Department at Bina Nusantara University, Jakarta,

Indonesia. She earned her Bachelor of Chemical Engineering from Diponegoro University, Indonesia and Master of

Industrial Engineering from University of Indonesia, Indonesia. She has taught supply chain-related courses and

published conference and journal papers. Her research interests include supply chain management, performance

management, and quality management.

Aurellia Victoria, Lidya Guestine, Noviana

Are students who graduated from Industrial Engineering Department at Bina Nusantara University, Jakarta, Indonesia.

They earned their Bachelor of Industrial Engineering from Bina Nusantara University, Jakarta. Their research interests

include Facility planning, supply chain management and service Engineering.

2014

https://www.bps.go.id/linkTabelStatis/view/id/1458

THE INTEGRATED METHOD OF WAREHOUSE LAYOUT ...

Documents

Transcript of THE INTEGRATED METHOD OF WAREHOUSE LAYOUT ...