Historically, research by scientists and apparel experts established standardized times for tasks to ensure consistency in production methods. These studies resulted in synthetic data, which now allows garment manufacturers to accurately measure time values for every movement involved in an operation.
Methods for Calculating SAM in Garment
Manufacturing
There are two primary methods for calculating
SAM:
- Using Synthetic Data (Predetermined Time
Standards or PTS)
- Conducting a Time Study
Let's break down each method and explore how it works.
Method # 1: Calculating SAM Using Synthetic Data
This method uses predetermined time standards
(PTS) codes to estimate the time for each operation. One of the most common
references used for calculating SAM is General
Sewing Data (GSD), which provides time values for various sewing
motions.
Steps to Calculate SAM Using Synthetic Data:
Step 1:
Choose the Operation
Select the operation or task for which you want to calculate the SAM. This
could include actions such as stitching sleeve, attaching a zipper, or joining
collar etc.
Step 2:
Observe the Operator’s Movements
Stand by the operator side and observe the movements involved in the task.
Record every action, such as picking up materials, aligning the pieces, sewing,
and completing the task.
Common movements may include:
- Picking up parts with one or both hands
- Aligning the fabric on the table or machine
foot
- Re-aligning fabric layers (plies)
Each movement needs to be noted as document carefully
to avoid missing any important actions.
Step 3:
List and Assign Time Values
List all the movements involved in the operation and refer to synthetic data or
GSD codes to find the corresponding Time Measurement Units (TMU) for each
action.
For example, if you determine the total TMU
for an operation to be 400 TMU, convert this value to minutes:
- 1 TMU = 0.0006 minutes and therefore
- 400 TMU = 400 x 0.0006 = 0.24 minutes
(Basic Time)
Step 4:
Add Allowances
Now, add the necessary allowances to the basic time to calculate the SAM. These
allowances account for factors like breaks, machine downtime, and personal
time.
The formula for SAM is: SAM = Basic Time + Bundle Allowance + Personal
& Machine Allowances
Assuming:
- Bundle allowance: 10%
- Personal and machine allowances: 20%
Calculation:
- Bundle allowance = 0.24 x 10% = 0.024
minutes
- Personal & machine allowance = 0.24 x
20% = 0.048 minutes
Thus, the final SAM is: SAM = 0.24 + 0.024 + 0.048 = 0.31 minutes
Method # 2: Calculating SAM Through Time Study
Time study is a practical method to calculate
SAM by observing the actual time an operator takes to perform a task. This
method uses a stopwatch to track the time required for each operation across
multiple cycles.
Steps to
Calculate SAM Using Time Study:
Step 1:
Choose the Operation
Like in the previous method, choose the specific operation for which you want
to calculate the SAM.
Step 2:
Perform the Time Study
Stand beside the operator and use a stopwatch to record the time taken to
complete one cycle of the operation. A cycle refers to the time from the start
of the operation (e.g., picking up the first piece) to the next start (e.g.,
picking up the next piece).
For accuracy, conduct the time study over five
consecutive cycles. Discard any readings where the times seem abnormal or
inconsistent, and take additional readings if necessary.
Step 3:
Calculate the Average Cycle Time
Once you have recorded the cycle times for multiple operations, calculate the
average cycle time. This represents the average time the operator takes to
complete the task.
Step 4:
Apply Performance Rating
Next, you need to apply a performance rating to adjust the cycle time. The
performance rating reflects how efficiently the operator performs the task. For
example, if the operator's performance rating is 80% and the cycle time is 0.60
minutes, calculate the basic time:
Basic
Time = Cycle Time x Performance Rating
Basic Time = 0.60 minutes x 80% = 0.48
minutes
Step 5:
Add Allowances
As with the synthetic data method, you need to add allowances to the basic time
to calculate the final SAM.
- Bundle allowance: 10% = 0.48 x 10% = 0.048
minutes
- Personal & machine allowance: 20% = 0.48
x 20% = 0.096 minutes
The final SAM is: SAM = 0.48 + 0.048 + 0.096 = 0.624 minutes
Method # 3: Another way to simply calculate SAM through Time Study
SAM = Basic Time + Allowance %
Basic (Normal) Time = Observed Time * Rating Factor
= Observed Time * (Performance Rating / Standard Rating)
Observed time refers to the average cycle time recorded by the observer. If recorded in seconds, it should be converted to minutes by dividing by 60.
The Rating Factor is the performance rating divided by the standard rating (the standard rating is always 100). The performance rating reflects the speed of a qualified worker as observed by an experienced observer, considering factors such as the worker's workstation, work concentration, tendency to work, motion sequence, motion repetition, and overall consistency in performing the task in a defined manner. The performance rating can be higher or lower than the standard rating, i.e., above or below 100.
If the worker's performance exceeds the standard, the time should be reduced, and if the worker's performance is below standard, the time should be increased (see the example below). A shorter time indicates better performance, while a longer time indicates relatively poorer performance compared to the standard.
To calculate the SAM, add the allowance percentage to the Basic Time. Allowances can include machine allowances, personal allowances, fatigue allowances, and any other relevant allowances based on the work criteria.
Example:
Suppose the observed time is 35 seconds. Multiply it by the Rating Factor. If the work is performed at the standard level (as observed by the experienced observer), the performance rating would be 100. To calculate the Rating Factor, divide by the standard rating: 100 / 100 = 1. Since the rating factor is 1, it means the work is performed according to standard performance, so there's no need to adjust the time. Therefore, the Basic Time = (35 sec / 60) min * (100 / 100) = 0.583 min.
[If the performance exceeds the standard, the performance rating might be 85 to reduce the time (because less time indicates better performance). In this case, Basic Time = (35 sec / 60) min * (85 / 100) = 0.495 min. If the performance is below the standard, the performance rating could be 110 to increase the time (since more time indicates poorer performance). In this case, Basic Time = (35 sec / 60) min * (110 / 100) = 0.641 min.]
Finally, to calculate the SAM, add the allowance percentage to the Basic Time. For instance, if the total allowance is 14%, then:
SAM = 0.583 + (0.583 * 14 / 100) min or 0.583 * (1 + 14 / 100) min = 0.665 min.
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