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![Page 1: #8 STOPWATCH TIME STUDY - An Industrial Ergonomistdewihardiningtyas.lecture.ub.ac.id/files/2012/04/8_APK.pdf · –stopwatch, papan, kalkulator, form pengukuran kerja •Memilih operator](https://reader030.fdokumen.com/reader030/viewer/2022013104/5c922cf809d3f20e358c0a22/html5/thumbnails/1.jpg)
DEWI HARDININGTYAS, ST, MT, MBA
#8_STOPWATCH TIME STUDY ANALISA DAN PENGUKURAN KERJA
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METODE PENGUKURAN [WAKTU] KERJA
PENGUKURAN [WAKTU] KERJA
DIRECT INDIRECT
STOP-WATCH
WORK SAMPLING
STANDARD DATA
PMTS
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DIRECT VS INDIRECT TIME STUDY
• DIRECT TIME STUDY – Kelebihan :
• PRAKTIS, karena hanya mencatat waktu saja tanpa menganalisa gerakan-gerakan kerja.
– Kekurangan : • Dibutuhkan waktu
pengamatan yang lebih lama agar data AKURAT & TELITI.
• Biaya lebih MAHAL karena harus datang langsung ke lokasi pengamatan.
• INDIRECT TIME STUDY – Kelebihan :
• Waktu pengamatan relatif SINGKAT karena cukup merekam aktivitas kerja.
• Biaya relatif lebih MURAH karena tidak perlu berulang kali datang ke lokasi pengamatan.
– Kekurangan : • Terkadang tabel gerakan
kerja orang EROPA tidak cocok dengan INDONESIA
• Dibutuhkan KETELITIAN yang tinggi dalam membreakdown gerakan-gerakan kerja.
• Data waktu gerakan kerja harus disesuaikan dengan JENIS PEKERJAAN.
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• Element is a component of job or task that are logical divisions with easily identifiable starting and end points, and are repeated on a regular basis
• Cycle is the completion of the activities (elements) required to perform the job under study.
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D i r e c t T i m e S t u d y
STOPWATCH TIME STUDY : Elemen kerja berlangsung dalam waktu SINGKAT Waktu siklus kerja PENDEK Siklus kerja terjadi BERULANG-ULANG Waktu elemen kerja diukur dengan STOPWATCH
WORK SAMPLING : Elemen kerja berlangsung dalam waktu LAMA Waktu siklus kerja PANJANG Siklus kerja TIDAK BERULANG Mencari % kerja dan % delay (PROBABILITAS)
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LANGKAH – LANGKAH PENGUKURAN [WAKTU] KERJA
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1. Mengumpulkan informasi dan peralatan
• Tentukan TUJUAN dari pengukuran kerja!
• Melakukan pengamatan pendahuluan
(layout, lingkungan kerja, mesin yang
digunakan, dll).
• Menyiapkan peralatan :
– stopwatch, papan, kalkulator, form pengukuran kerja
• Memilih operator yang akan diamati dan mengkomunikasikan dengan supervisor (operator harus memiliki kemampuan NORMAL, bisa BEKERJA SAMA, dan WAJAR.
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2. Membagi operasi dalam elemen-elemen
• Purpose : easy to measure & line balancing
• Separate handling time (non-productive time) with operation time (productive time)
• Separate constant element with variable element.
• Every element must have an easily identifiable starting and ending point (breakpoints)
• Continuities between elements
• Elements times: 0.04min (short), 0.25min (reasonable)
• Relative frequency must be included
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3. Metode Stopwatch Time Study
• CONTINUOUS TIMING
Tombol stop-watch ditekan pada saat awal elemen kerja dan terus dibiarkan berjalan selama periode studi. Pengamat terus melihat jalannya jarum stop-watch dan setiap awal/akhir dari sebuah elemen kerja yang ada mencatat dan menuliskannya di lembar pengamatan. Waktu setiap elemen kerja akan diperoleh dengan cara “pengurangan” dan dilakukan setelah studi pengukuran kerja selesai dilaksanakan. APA KEKURANGAN-NYA???
• REPETITIVE (SNAP-BACK METHOD)
Jarum penunjuk stop-watch selalu dikembalikan ke posisi nol setiap kali satu elemen kegiatan selesai dilaksanakan. Waktu yang diamati dan dicatat akan merupakan waktu yang sebenarnya. Time study analyst akan bisa mendeteksi dengan mudah adanya variasi perbedaan waktu dari setiap elemen kegiatan. APA KEKURANGAN-NYA???
• ACCUMULATIVE TIMING
Merupakan kombinasi cara pengukuran dengan metoda continuous dan snap-back (pengukuran dilaksanakan dengan menggunakan dua atau lebih stop-watch yang bekerja secara bergantian).
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THE R
ULES !!!
Don’t comment to the worker during the task
Stand (don’t sit) beside the worker
Write every event (even though it may seems not important)
Have a good position to observe
Stop the study if the worker seems to be under pressure and it affects his/her work
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PENGAMATAN!!!!
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Time Study Observation Sheet
Identification of operation Sandwich Assembly Date 5/17
Operator Approval Observer
Smith Jones Russell
Cycles Summary
1 2 3 4 5 6 7 8 9 10 t Nt RF t
Place ham, cheese,
and lettuce on bread
1
2
3
4
Grasp and lay
out bread slices
Spread mayonnaise
on both slices
Place top on sandwich,
Slice, and stack
t
t
t
t
R
R
R
R
.11 .44 .79 1.13 1.47 1.83 2.21 2.60 2.98 3.37
.04 .05 .05 .04 .06 .05 .06 .06 .07 .05 .53 .053 1.05 .056
.04 .38 .72 1.05 1.40 1.76 2.13 2.50 2.89 3.29
.07 .06 .07 .08 .08 .08 .07 .07 .10 .09 .77 .077 .077 1.00
.11 .12 .14 .12 .12 .13 .13 .13 .14 .14 1.28 1.28 1.10 .141
.93 .23 .55 1.25 1.60 1.96 2.34 2.72 3.12 3.51
.12 .10 .08 .09 .12 .10 .11 .11 .10 .10 1.03 1.03 1.10 .113
.33 .67 1.01 1.34 1.71 2.07 2.44 2.82 3.24 3.61
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4. Tes Kenormalan, Tes Keseragaman, Tes Kecukupan Data
TES KENORMALAN data pengamatan seharusnya berjumlah cukup besar (banyak) dan berdistribusi normal.
TES KESERAGAMAN data harus homogen dan diperoleh dari populasi yang sama.
TES KECUKUPAN data yang dikumpulkan telah cukup secara obyektif, dengan konsep statistik (derajat ketelitian dan tingkat keyakinan/kepercayaan yang diinginkan).
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Time measurement
– Measuring time of each element
– The number of observation of each element depends on the significance level and required level of accuracy
Determining Number of Cycles
Primary time study
(normally 5 to 10
observation)
Examination of the
required number of
observations (N)
Continue study up to N
observations
Re-checking the required
number of observations (n)
N>=n
End the time study
N=n
No
Yes
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Number of Cycles
To determine sample size:
n = zs
eT
2
where
z = number of standard deviations from the mean in a normal distribution reflecting a level of statistical confidence
T = average job cycle time from the sample time study e = degree of error from true mean of distribution
s = = sample standard deviation from sample time study
(xi - x)2
n - 1
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Number of Cycles : Example
• Average cycle time = 0.361
• Computed standard deviation = 0.03
• Company wants to be 95% confident that computed time is within 5% of true average time
n = = = 10.61 or 11 zs
eT
2 (1.96)(0.03)
(0.05)(0.361)
2
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Recommended number of cycles/observations
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5. Performance Rating & Waktu Normal
Normal time : Tn = Tobs (PR)
1) Waktu Pengamatan (Tobs)
2) TN < TObs untuk p < 1 (100%)
3) TN = TObs untuk p = 1 (100%)
4) TN > TObs untuk p > 1 (100%)
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WESTINGHOUSE RATING SYSTEM
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6. Menentukan Allowance
Allowance
Constant
Personal Needs Fatigue
Special
Avoidable Delays
Unavoidable Delays
More details in : Handbook of IE (Salvendy) : pp. 1409
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7. Waktu Standar dan Output Standar
TS = TN (1 + Apfd) OS = 1 / TS
Waktu Normal (TN) Allowance
Waktu Baku/Standard (TS)
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Let’s Try!
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• Given: A direct time study was taken on a manual work element using the snapback method.
• The regular cycle consisted of three elements : a, b, and c. Element d is an irregular element performed every five cycles.
• Determine
(a) normal time
(b) standard time for the cycle using Apfd = 0.15
E x a m p l e
Work element a b c d
Observed time (min) 0.56 0.25 0.50 1.10
Performance rating 100% 80% 110% 100%
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“Knowing exactly what you want to do,
and then seeing that they do it the best
and cheapest way.”
- Frederick W. Taylor-