How to Balance a Traditional Sewing line?

Today I will teach you how to do line balancing in the apparel manufacturing. 

You know that a number of operations are involved in making a garment. In bulk garment production, generally a team works on an assembly line (Progressive Bundle system) and each operator does one operation and passes the garment another operator to do next operation. In this way garment reached to end of the line as a completed garment.  In the assembly line after some time of the line setting, it is found that at some places in the line, work is started to pile up and few operators sit idle due to unavailability of work.

When this situation happens in the line it is called an imbalanced line. Normally it happens due to two main reasons –

  • variation in work content (time needed to do an operation) in different operations
  • operator’s performance level. To meet the production target, maintaining smooth workflow in the line is very important. So it is very important to know basics of quick line balancing.

How to balance an imbalanced line has been explained in the following. 

The main job in line balancing is to eliminate or reduce WIP (work in process) at bottleneck operations. To do that you have to know which operations are a bottleneck in the line. Through capacity study and target setting, you will find existing bottlenecks in the line.

Tools required:
i)                     Stopwatch
ii)                   Spreadsheet or Calculator

Step 1: Capacity study:
List down all operations (with operator name) as per operation sequence in a paper. Using stopwatch cycle time (time study) for each operation for five consecutive cycles. With average cycle time calculate the hourly capacity of the operators. (i.e. operation cycle time 30 seconds and total allowances are 20% then capacity is 100 pieces per hour). Draw a line graph with per hour capacity data.

Step 2: Target setting:
With the above capacity data set your target output per hour from one line. Normally, it is calculated using following formula (Target per hour= Total no of operators X 60 /garment SAM). Check current hourly operator production report. Draw a straight line with target output data on the line graph. 

Step 3: Identification of bottleneck areas: 
Now go to the capacity study table and compare each operator’s capacity with the target capacity.  Each individual operator whose capacity is less than the target output is bottleneck operation for the line. It is impossible to improve imbalanced line’s output without improving the output of the bottleneck operations. A bottleneck operation is like a weak link chain.

Step 4: Eliminate bottlenecks from the line: Now to eliminate bottleneck areas use following methods which suit best to your situation but don’t jump without trying initial steps.
  1. Club operations where possible. Where there is higher capacity than the target output, give that operator another operation with less work content. Considering machine type and sewing thread colors. 
  2. Shuffle operators. Operations that have low work content use low performer there. And where work content is higher use high performers.
  3. Reduce cycle time using work aids and attachments. To assist the operator in handling parts during sewing, positioning cutting and disposing of the finished task, work aids, guides or attachment can be used. Think of that if possible provide the operator work-aids. It will reduce operation cycle time.
  4. Improve workstation layout and improve methods. Most important area for improving output from a particular operation is using best workstation layout and best method of work. There is always a chance that through improving the method of bottleneck operations you can do line balancing.
  5. Add more operators to bottleneck operations. Adding one additional machine in the easy task than others. Before adding one more machine compare the cost-benefits of putting an additional machine into the line. It can be simplified compared to estimating machine productivity in both cases.
  6. Do extra work at bottleneck operations. At lunch break and Tea break when each operator of the line goes for a break, bottleneck operator can continue work to feed next to his operator. Later he can take the break. At the end of the day tell this operator to work for one hour extra to reduce the WIP.
Important things to keep in mind:

Conduct Time Study hourly basis and check the output of each operator. Once you have eliminated one bottleneck, you will find a new bottleneck operation. Follow the same methodology to improve line balancing.

Also Read: How to do Line balancing using Operator Skill History?

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