DMAIC Project: Improving Warehouse Lead Times
Baseline (Define)
The warehouse stores pallet products in stacked lines, so-called mixed lines and mass lines. In mixed lines it is allowed to stack different products in the same queue, while in mass lines only one specific product may be stacked.
Many different products arrive in the warehouse every day, but on average, a particular product arrives only every few months. As a result, mass queues are less likely to be filled, as they are emptied one pallet at a time over a longer period of time, while any product can be added to mixed queues on a daily basis.
Process performance at the beginning (Measure)
Statistical calculations:
- 3 550 pallets were retrieved from mixed zones during the previous year
- The average search time for mixed lines is 485 seconds
- Target time 200 sec, so potential savings 285 sec per pallet or 3550*285/60/60 = Potential savings 281 man-hours per year
Improvement measures (Analyze & Improve)
Root cause:
The traditional thinking has been that empty space is expensive and therefore it is better to favour mixed-use buildings.
It is important to take into account the batch, as one batch may be slightly different from the previous one. It is therefore important that products are collected in FIFO order to ensure that batches are delivered out in order. This causes that when a pallet is needed from mixed lines according to FIFO, it is likely to be buried behind newer pallets. In this case, the pallets in front must first be moved to the side of the aisle and once the required pallet is found, the pallets must be moved from the aisle back to their proper location.
Solution:
The time spent in mixed zones has been measured, proving that empty space is not as "expensive" as previously thought.
During the project, an automatically updated report was built using Diver software, which shows which products should be kept in mass queues in terms of quantity. Based on this report, pallets of mixed lines were arranged in mass lines.
Results (Control)
Continuous improvement process
During this project, Diver created a model that contains enough information to allow warehouse workers to update mixed lines into mass lines themselves, under the guidance of a supervisor, if the warehouse space allows it.
lessons learned
Traditionally, it has been thought that empty space is expensive to keep, which is why there are so many mixed yachts in storage. In this project, however, the time "wasted" on mixed zones has been calculated and it has been found that mixed zones are very expensive because of the labour costs.
This project was a Lean Six Sigma Green Belt training exercise project, which the participant did as part of the training and received a Green Belt certificate at the end of the project.
If you are interested in learning how to improve your processes using Lean and Six Sigma, and obtain a Green Belt Certification at the same time, please visit the training link: Green Belt training.