Pallet-storage in a unit-load warehouse

This is a project to accompany the course and the book Warehouse & Distribution Science, at the Georgia Institute of Technology, by John J. BARTHOLDI, III and Steven T. HACKMAN. Everyone is welcome to use the book and materials for educational purposes, as long as all copyrights remain intact.

The company data is copyrighted and proprietary. You may use it for the purposes of this course only. (If you would like to use it for something else, please contact me to discuss.)

Figure 1: Floor-storage in 4-deep lanes.

The boxes on the bottom are on the verge of being crushed

Figure 2: This sku is too heavy to stack higher but rack storage would make the space above usable.

Purpose

The layout of the warehouse is a big decision that limits operating efficiencies ever after, so it is important to get it right. This is easiest in a unit-load warehouse (pallet-in/pallet-out) because the labor model is so simple. Every pallet requires a forklift driver to carry it from receiving to a storage location and later from the storage location to shipping. The challenge is to configure the warehouse so as to get the maximum utilization of space and labor.

A 3rd-party transshipment warehouse

This 3rd party warehouse stores pallets for an assortment of customers, such as local manufacturers who outsource their warehousing or distant manufacturers looking to improve service to customers near the warehouse.

The warehouse generates revenue by charging for handling each pallet in and out; plus rent for each pallet-position-month. Management of the warehouse must in turn pay rent on the facility based on the area of floorspace; naturally they want as many pallet-locations per unit area as possible in order to maximize their opportunities to generate revenue.

Data files

Here is a list of the sku's in the warehouse and something about their stackability: You may use either this spreadsheetin Microsoft Excel format or this text file.

Figure 3: This sku would lose spaceif in rack because there would no longer be enough clear height to stack it 4-high.

It took two forklifts almost 10 minutes to move the top pallet

Figure 4: These pallets should go in rack. Here they are stacked too high in a vain effort to save floor space. Besides the danger, any savings in space is more than offset by the extra labor required to move the top pallets (one forklift must pull the pallet straight so another can insert forks).

Each row corresponds to one sku and the columns correspond to the following fields:

Owner of the pallet
Height of each pallet in feet
Maximum number of pallets on hand during the previous year
The maximum number of pallets that may be stacked in a column (without rack)

Questions

Design storage for the pallets described in the data file above. Specifically:

Which pallets can justify storage in pallet rack? Assume that the pallet rack will be configured to be three openings high and that each opening can hold a stack up to five feet (1.5m) high. You may stack pallets within an opening if they will fit.
For the skus that could not justify storage in pallet rack, what is the optimum lane depth, measured in number of pallets, for each sku considered separately? Assume the pallets are stored so that the pallet depth is 48 inches (1200 mm). Assume aisles of width 12 feet and reserve each column and each lane for a single sku. What is the optimal commonlane depth?