7 Ways to Reduce WIP from Bottleneck Operations

A bottleneck operation determines the hourly production of a sewing line. In a bottleneck operation garments are piled up compared to other operations in the line and produce the lowest number of garments. The efficiency of the line, as well as labor productivity, is affected by the work in process (WIP) level at bottleneck operations. By reducing WIP level at bottleneck operations labor productivity can be improved. In this article, 7 practical ways have been discussed that will help you to reduce WIP.

1. Method improvement 

For the method improvement, you first need to conduct method study for the bottleneck operations. Method study is the in-depth monitoring and analysis of the way an operator performs its task. Once the method study is done, look for better ways to save time and less effort by the operator. This could be done by improving work motions or providing work aids like gauges, folders, attachments, trolleys, movers, tracks or machine automation. As much time as you save through method improvisation from bottleneck operation, you will get better output, in turn, reduce WIP level. 

2. Share capacity

In the sewing line, you will easily find some operations with higher capacity than required for the line’s target production. Take few pieces from the bottleneck operation to a nearby operation that has a potentially higher capacity. 

Maintain this capacity sharing in a certain interval. If you don’t have a performance-based (individual or group) incentive scheme in that case normally operators don’t like to do other's work. Operators who had the potential capacity to share his/her capacity for bottleneck operations intentionally reduce his/her speed to balance the bundle completion time with the line speed.
However, if you like to use this method, you must be careful on the operator with which work is shared has the same type of machine as that of bottleneck operation and the operator has the right skill required for it. 
You can also utilize the spare capacity of the adjacent line’s extra capacity operations.

3. Add additional manpower or machine

This is the easiest way to increase production at bottleneck operations. I will suggest initially not going for this option and better try to improve work method. In case you find the potential capacity of the operator is too less than the target output of the line then consider adding an extra machine. 
Calculate the capacity of each machine capacity and demand from the bottleneck operation. According to it add an additional sewing machine. Following this, you can drastically reduce the WIP level. 
It must be kept in mind that your machine productivity may reduce in some cases. 

4. Improve workstation layout

The first and last movement (i.e. pick up and dispose of) performed by an operator in an operation cycle depends on the workstation layout i.e. where you placed cutting and where the disposal bin has been placed. 

A closer look at the workstation layout of the bottleneck operators will help you to find out whether the layout is following the principles of best workstation design.  mentioned by Hiba in his book Improving Working Conditions and Productivity in the Garment Industry: An Action Manual

  • Position material, tool, and controls within easy reach
  • Use jigs and other devices to save time and efforts

This could be relating to ergonomic issues like light, fan, seat adjustment, etc. Redesign workstation to reduce material handling time and get increased production. 

5. Better operator allocation 

Each operator has a different set of skill levels (operations they generally perform) and efficiency at work. So at the time of operator selection do it correctly as much as you can. Allocate high content jobs to highly skilled (matching to the job) operators. And for low-skilled operators select jobs that required low skill to perform and that have comparatively low work content. 

In this step, you have to check whether operator selection was done correctly or not. For example, if you have a grading system for operators then check if any ‘A’ grade operator is allocated on a low skilled and high capacity operation, and B/C grade operator to the bottleneck operations. If this be the case both the operators could be swapped to get more production out of the bottleneck.

6. Work for extra hours

If you find additional machine set up is not possible due to unavailability of machine or space and above steps don’t making much difference in WIP reduction then follow this step. You can work overtime (provided that your factory policy permits for working extra hours) to make enough pieces and create WIP for the following operations. 

7. Use time-saving tricks

A lot of time is spent by operators in material handling and associated jobs. Here a few time-saving tricks have been listed. These may be helpful to you. 
  • If the bottleneck operation is having sub-parts of operations, they can be bifurcated and given to helpers or other nearby operators. In this way, an operator can produce extra pieces and keep a smooth flow to the line. 
  • Use UBT machines for thread trimming instead of hand clippers or trimmers.
  • Check the previous operation if there is any quality issue due to which the operator is not receiving proper input to work on. This may reduce production and create bottleneck operations. 
  • The operator could be provided with extra bobbins and needles (depends on company needle policy) to save the winding time and requesting for new needle and receiving it.
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