A project for a BAX Global 3rd party DC

The company and the warehouse

See the photos and accompanying description.

BAX concerns

The overriding objective is to reduce the total labor required to distribute the product.

Improve order-picking

BAX has expressed interest in using bucket brigades to coordinate their order pickers. But to use bucket brigades, BAX would have to change the pick-to-light control so that each worker could take a batch of boxes into one bay at a time (batch size to be determined later). The picker would announce the presence of the box by scanning both the box the bay. In response, the bay would light up to show any picks to be made for this box from this bay alone. After making those picks, the picker would repeat this process for each remaining box in his/her batch. When all boxes in the batch have have been completed in this bay, he/she moves the batch to next bay and process continues.

Under bucket brigades workers would scan more often: Currently, each box is scanned into a specified, fixed zone of 5 bays, for a total of 4 scans. Under bucket brigades, there would be more zones than workers. For example, if we specified that each bay is a zone then each box would be scanned into each bay, for a total of 40 scans. We could reduce this by specifying zones of two contiguous bays, so each box would be scanned into a pair of bays, for a total of 20 scans.

warehouse layout

Figure 1: The conveyor carries boxes in from the right, then up and down each aisle. The pick-to-light system is set up to manage 8 picking zones, 2 up and 2 down each aisle. Each zone consists of 5 bays of flow rack. Check-pack-ship is on the bottom left.

Under bucket brigades workers would probably walk less: Currently, each box that needs a pick in a zone requires walking most of that zone (to the farthest pick and back to the box). Therefore, if box bi touches ni zones, the total walking incurred by this box is the length of ni zones. Under bucket brigades, each batch will require walking the the entire length of the conveyor. Which is less? This can be answered only by looking at the data about what picks were assigned to each box and where each sku was located. If boxes typically visit many zones, then bucket brigades will be more efficient.

Bucket brigades would get the box builders involved in picking too. The first worker of the bucket brigade should start by assembling and labeling the boxes for an order, and then begin picking that order.

Currently, boxes are built in batches. But there are no economies of scale to be had because after the tape is applied along the seam, it is put down. Consequently, the tape has to be picked up again to build the next box, so it takes twice as long to build two boxes as to build one. This means that there would be no loss of efficiency if boxes are built as needed.

In fact, building boxes in batches creates inefficiencies. Currently, the newly built boxes are stacked in columns, which people must work around. In addition the columns most be slid gradually towards the point of induction of the conveyor, which is additional handling. And then the boxes must be unstacked. It seems more efficient to pick up folded boxes, apply labels, then build and tape each of the boxes and place them directly on the conveyor as needed.

Expected benefits of bucket brigades: Reduced WIP on conveyor; increased pick rates. More importantly, it would be possible to achieve greater flexibility in staffing line, because other workers could join or leave the assembly line as they were available. The people who are currently building boxes could become more involved in the picking.

Suggested approach: Look at a history of boxes, the skus assigned to them, and the storage locations of those skus. Then recreate the flow of boxes through the flow rack and measure the conveyor occupancy, required walking, and material flow under alternative ways of organizing the pickers.

It might be possible to implement an approximation of bucket brigades without changing the current system very much at all. Sequence the workers from slowest to fastest along the direction of material flow. Then establish the following protocol: When a worker has finished work in his zone, he should walk back and help his predecessor by picking currently lighted locations. This would help get more contribution from the faster pickers, who are now, perhaps, underutilized. However, by allowing two workers in a zone you would not be able to track productivity or errors of individual order pickers, because this information is currently gathered by zone.

Slot the carton flow rack

There are 40 bays of flow rack, divided into 8 zones of 5 bays each. All active skus are represented in the flow rack. The current stocking strategy is unknown, except that it attempts to spread picking throughout all the bays. Some busier skus have multiple lanes or are double-stacked.

The carton flow rack is 8 feet wide, 8 feet deep, and shelves range from 8 to 16 inches high.

Locations 41 through 50 are in pallet flow rack and are used to store oversize items that are picked separately.

Suggested approach: Use the carton-slotting software to slot the flow rack so that total labor (picking plus restocking) is minimized.

Expected benefits: Reduced restocks. It may also be possible to enhance picking by storing product so that more orders can bypass one of the aisles.


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