Management Stategic

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By Roberto Hutapea, SE, MM

Tujuan

layout peralatan dan proses produksi merupakan optimasi pengaturan fasilitas operasi sehingga nilai yang diciptakan oleh sistem produktif maksimum : efektif, meminimumkan biaya penanganan bahan dan jarak angkut, kesinambungan proses produksi, menyederhanakan proses dsb.

1.

Layout fungsional (job lot), yaitu pengelompokkan mesin, buruh dan peralatan sejenis pada suatu tempat, yang memiliki fungsi yang sama. Mesin serba guna, biayanya lebih murah. Proses operasi yang berbedabeda dapat berjalan lancar walau pun ada mesin yang rusak. Namun, biaya mesin serba guna per output lebih tinggi. Routing, scheduling, accounting memakan biaya karena dikerjakan secara terpisah. Proses ini lebih baik untuk memproduksi barang dalam volume kecil dengan macam produk yang banyak.







Lay-Out produk (garis), yaitu pengelompokkan mesin dan peralatan berdasarkan urutan proses produksi. Lay-Out kelompok, kadang diperlakukan sebagai lay-out yang terpisah, merupakan variasi dari lay-out produk : bagian dan komponen produk dikelompokkan menjadi semacam keluarga,. berbagai area / departemen dipisahkan. Lay-out posisi tetap menempatkan produk kompleks pada suatu tempat

 Project

(no product flow)  Job shop (jumbled flow)
• Produk A
• Produk B • Produk C
 Line

WC1 WC2 WC3 B WC4 WC5 WC6 C WC7 WC8 A

flow

X

• X WS1 WS2 WS3 WS4 WS5 Output • Keterangan: WS : Workstation (stasiun kerja)

 Specify

the sequential relationships among tasks using a precedence diagram. The diagram consists of circles and arrows. Circles represent individual tasks; arrows indicate the order of tasks performance  Determine the required cycle time ( C ) , using the formula C = Production time per day Required output per day (in units)

 Determine

the teoritical minimum number of workstations (Nt) required to satisfy the cycle time constraint using the formula Nt = Sum of tasks times ( T ) Cycle time ( C )  Select a primary rule by which tasks are to be assigned to workstations, and a secondary rule to break ties

 Assign

tasks, one at a time, to the first workstation until the sum of the task times is equal to the cycle time, or no other tasks are feasible because of time or sequence restrictions. Repeat the process for workstation 2, Workstation 3, and so on, until all tasks are assigned.  Evaluate the efficiency of the balance derived using the formula  Efficiency = Sum of task times ( T ) Actual number of workstation ( Na ) x Cycle time ( C )

 If

efficiency is unsatisfactory, rebalance using a different decision rule.

 The

model J Wagon is to be assembled on a conveyor belt. 500 wagons are required per day. Production time per day is 420 minutes, and the assembly steps and times for the wagon are given in Assignment : Find the balance that minimizes the number of workstations, subject to cycle time and precedence constraints.

Task

A
B C D E F G H I J K

Performa nce time (in second) 45 11 9 50 15 12 12 12 12 8 9 195

Description

Tasks that must precedence

Position rear axle support and hand fasten 4 screws to nuts
Insert rear axle Tighten rear axle support screws to nuts Position front axle assembly and hands fasten with 4 screws to nuts Tighten fronts axle assembly screws Position rear wheel #1 and fasten hubcab Position rear wheel #2 and fasten hubcab Position rear wheel #3 and fasten hubcab Position rear wheel #4 and fasten hubcab Position wagon handle shaft on front axle assembly and hand fasten bolt and nut Tighten bolt and nut

A B D C C E E F, G, H, I J

45 sec 11 sec A B

12 sec 9 sec F

C
12 sec G 12 sec H 8 sec J 9 sec K

50 sec D

15 sec E

12 sec I

Draw a precedence diagram.  Cycle time determine. Here we have to convert to seconds since our task times are in seconds 
C= Production time per day= 60 sec X 420 min = 25.200 = 50,4 sec

 Theoritical

minimum number of workstations (Nt) required (the...
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