How to Make an Operation Bulletin (OB) for a T-Shirt and Calculate SAM & SMV

How to Make an Operation Bulletin (OB) for a T-Shirt and Calculate SAM & SMV

Creating an Operation Bulletin (OB) for a T-shirt is an essential task in garment manufacturing. It helps streamline the production process, ensure quality, and maintain consistency. In this blog, we’ll guide you through the steps to create an OB and calculate the Standard Allowed Minute (SAM) and Standard Minute Value (SMV).

What is an Operation Bulletin (OB)?

An Operation Bulletin (OB) is a detailed document used in the garment industry to outline the steps involved in the production of a specific item. It includes information on each operation, the sequence of operations, the machinery required, and the time allocated for each task.

Steps to Create an Operation Bulletin (OB) for a T-Shirt

1. Analyze the T-Shirt Design

• Understand the design and style of the T-shirt.
• Identify the components (e.g., front, back, sleeves, collar).

2. List All Operations

• Break down the production process into individual operations (e.g., cutting, stitching, hemming).
• Sequence the operations logically.

3. Determine Machinery and Tools

• Identify the machinery and tools required for each operation (e.g., sewing machines, hemming machines).

4. Assign Time to Each Operation

• Conduct time and motion studies to determine the time required for each operation.
• Record the time taken for experienced workers to complete each task accurately.

5. Create the Operation Bulletin Format

• Use a tabular format to list each operation, the machinery required, and the time allocated.
• Include additional columns for worker allocation, skill level, and quality checkpoints.

6. Gather Information

• ·  T-Shirt Style: Crew neck, V-neck, pocket details, etc.

• ·  Bill of Materials (BOM): Fabric type, thread color, trims (buttons, zippers).

• ·  Production Target: Number of t-shirts to be produced per day.

7. Breakdown of Operations

• Spread and Ply Marking (if applicable)
• Cutting Fabric Panels (front, back, sleeves, etc.)
• Bundling Fabric Layers (for some operations)
• Shoulder Seam Assembly
• Sleeve Setting
• Side Seam Assembly
• Collar Attachment (if applicable)
• Cuff Attachment (if applicable)
• Bottom Hemming
• Buttonhole Making (if applicable)
• Button Sewing (if applicable)
• Trimming Threads
• Quality Control Inspection

8. Prepare the OB Format (Table):

• Operation Description: A clear description of each sewing step.
• Machine Type: The type of sewing machine required (e.g., flatlock, overlock).
• SMV (Sewing Minute Value): The standard time allowed in minutes to complete one unit (t-shirt) at 100% efficiency. We’ll calculate this in a later step.
• Remarks: Any additional notes about the operation (e.g., specific stitch type, special instructions).

9. Calculate SMV (Sewing Minute Value):

SMV represents the average time a skilled worker takes to complete one unit (t-shirt) with normal effort under standard working conditions. There are established industry benchmarks for SMV based on stitch type, seam length, and fabric type. You can obtain these values from standard manuals or time and motion studies conducted in your factory.

10. Include Allowances:

• Basic Minutes (BM): The actual sewing time based on the SMV.
• Personal Allowances (PA): Time allotted for personal needs like bathroom breaks (typically 5-7% of BM).
• Fatigue Allowances (FA): Time allotted for recovery from physical exertion (typically 4-6% of BM).
• Delay Allowances (DA): Time allotted for unavoidable interruptions like machine breakdowns (typically 2-5% of BM).

11. Calculate Standard Allowed Minutes (SAM):

SAM = BM (1 + PA% + FA% + DA%)

12. Fill in the OB Table:

• Enter the operation descriptions.
• Specify the required machine type for each operation.
• Use industry benchmarks or time studies to assign SMV values for each operation.
• Calculate the Basic Minutes (BM) by multiplying SMV by the number of units (t-shirts) to be sewn in a minute (typically 1 unit/minute).
• Apply the allowance percentages to BM and calculate Personal Allowances (PA), Fatigue Allowances (FA), and Delay Allowances (DA). ·  Finally, calculate the Standard Allowed Minutes (SAM) for each operation using the formula mentioned above.

13. Additional Information:

• Include the OB title, style number, date, and person who prepared it.
• You can add a section for the target daily production output and the number of workers needed based on the calculated SAM values.

Sample Operation Bulletin for a T-Shirt

How to Calculate SAM and SMV

Standard Allowed Minute (SAM):

• SAM is the time allocated for a task considering the standard time required by an average worker.
• It is calculated using time and motion study data.

Standard Minute Value (SMV):

• SMV includes the SAM and allowances for fatigue, personal needs, and machine delays.
• It ensures the worker has adequate time to complete the task without rushing.

Formula to Calculate SAM

SAM=∑Time for each operation (in minutes)SAM=∑Time for each operation (in minutes)

For the sample T-shirt: SAM=2.0+2.0+1.5+0.5+3.0+2.5+1.0+1.5+1.0+1.0=16.0 minutes SAM=2.0+2.0+1.5+0.5+3.0+2.5+1.0+1.5+1.0+1.0=16.0minutes

Formula to Calculate SMV

SMV=SAM+AllowancesSMV=SAM+Allowances

Allowances typically range from 10% to 20% of SAM.

For the sample T-shirt with a 15% allowance: Allowance=16.0×0.15=2.4 minutes Allowance=16.0×0.15=2.4minutes SMV=16.0+2.4=18.4 minutes SMV=16.0+2.4=18.4minutes

SAM & SMV Calculation

Understanding the T-Shirt Production Process

For this example, let’s break down the operations involved in manufacturing a basic T-shirt:

1. Front Panel Cutting
2. Back Panel Cutting
3. Sleeve Cutting
4. Collar Cutting
5. Front and Back Panel Sewing
6. Sleeve Attachment
7. Collar Attachment
8. Hemming
9. Quality Check
10. Packing

Step-by-Step Calculation

Time Study

Conduct a time study to determine the average time taken for each operation by an experienced worker. This is typically done using a stopwatch or time study software.

2. Calculate SAM (Standard Allowed Minute)

SAM is calculated by summing up the time taken for each operation.

SAM=∑Time for each operationSAM=∑Time for each operation

Using the times from our example:

SAM=2.0+2.0+1.5+0.5+3.0+2.5+1.0+1.5+1.0+1.0=16.0 minutesSAM=2.0+2.0+1.5+0.5+3.0+2.5+1.0+1.5+1.0+1.0=16.0minutes

3. Calculate Allowances

Allowances are added to the SAM to account for personal needs, fatigue, and machine delays. This percentage can vary but typically ranges from 10% to 20%. For this example, let’s use a 15% allowance.

Allowance=SAM×Allowance PercentageAllowance=SAM×Allowance Percentage Allowance=16.0×0.15=2.4 minutesAllowance=16.0×0.15=2.4minutes

4. Calculate SMV (Standard Minute Value)

SMV includes the SAM and the calculated allowances.

SMV=SAM+ Allowances SMV=SAM+ Allowances SMV=16.0+2.4=18.4 minutes SMV=16.0+2.4=18.4minutes

Real-Life Example Summary

Here’s a summary of the calculated times:

• SAM (Standard Allowed Minute): 16.0 minutes
• Allowances: 2.4 minutes
• SMV (Standard Minute Value): 18.4 minutes

Importance of SAM and SMV in Garment Manufacturing

Setting Production Targets

By knowing the SMV, you can set realistic production targets for your team. For example, if a worker is expected to work 480 minutes (8 hours) a day:

Daily Production Target=Working MinutesSMVDaily Production Target=SMVWorking Minutes​ Daily Production Target=48018.4≈26 T-shirts per worker per dayDaily Production Target=18.4480​≈26T-shirts per worker per day

2. Costing and Pricing

SMV helps in calculating labor costs for each garment, which is crucial for determining the final product pricing.

3. Efficiency Measurement

By comparing the actual production time with the SAM, you can measure the efficiency of your production process and identify areas for improvement.

Takeaway

Creating an Operation Bulletin (OB) for a T-shirt involves detailed planning and precise calculations. By following the steps outlined above, you can ensure efficient production, maintain quality, and optimize the use of resources. Calculating SAM and SMV accurately helps in setting realistic production targets and managing workforce productivity. Implementing a well-structured OB can significantly enhance the overall efficiency of the garment manufacturing process.

By mastering these techniques, you’ll be well-equipped to manage production processes effectively and contribute to the success of your garment manufacturing operations.