Warehouse Design - Block Stacking
Posted on 18th July 2022
The simplest and most cost-effective storage option in a warehouse is block stacking. Block stacks can provide the main storage and picking operation, or supplement other areas. Block stacks can also be used for:
short term storage (such as cross docking), and
for oversized, unstable, or heavy items not suitable for racking.
This blog aims to guide you at a high level through the various stages I adopt when designing a block stack area.
Block stack areas are generally comparatively cheap to create when compared to racked alternatives. However, I would advise using contractors to paint the lines. Good quality location labels will also be required and fitted to:
the floor, or
suspended from the roof (with the addition of a check digit), or
fitted to posts.
Block stack operations do not always utilise the full height of a warehouse unless they are located below a mezzanine floor.
Floor Location Label
Section 1: The Product
One of the first things to consider is the product to be stored. Can the items be stacked safely? We will need to determine the stack heights for each individual Stock Keeping Unit (SKU).
We will also need to know the dimensions and weights of the items to be stored. We can then decide what type and specification of MHE is required.
Section 2: Data Analysis
The data analysis phase is required to determine how many block stack lanes are required, and what sizes of lanes are most suitable. I use a model I have created in an Excel spreadsheet to perform this analysis.
The first stage is to review the storage requirements at SKU level. This will be analysed using an average week’s stock holding, then this will be compared to a peak week. The model is also populated with annual sales volumes.
At this stage I can determine which items are fast moving using ABC Pareto analysis. In the layout design phase, the location allocated to the fast-moving “A” items is key to providing the most efficient solution.
To start designing the layout I usually specify 2 sizes of storage lanes within the model. The lanes would ideally be the same width but different lengths. The model will allocate storage lane size to each SKU based upon stock holding requirements and velocity.
Within the model each SKU will be allocated an overall number of lanes. I allocate
1 pick lane 50% utilised
1 put away lane 50% utilised,
the other storage lanes 100% utilised (note: not always possible if batches or date codes cannot be mixed some storage aisles.
So, if a SKU has 60 pallets to store and we store 10 pallets per bay, we will need 7 bays, 5 full lanes and 2 lanes at 50% utilisation.
The size of the lanes I set as a variable within a summary table in the model, I can quickly see the impact of making any changes. I generally have an idea of what the lane sizes should be at this stage, so I use the analysis to confirm my thoughts.
TH Comment: overall utilisation for block stack areas is generally between 50% and 60%.
Section 3: Layout Design
I create my layouts using AutoCAD. The layouts will show the location of building columns, receiving and despatch locations and picking areas if applicable. I usually generate more than one concept to review with my client, maybe with different lane sizes to maximise warehouse space.
As part of the review process we will also consider the time and number of MHE movements.
Section 4: Other Considerations
To conclude the process, we must consider the:
functionality and processes of WMS (Warehouse Management System)
picking and replenish process (if picking from block stack area)
The WMS allocation process
- Last in First Out (LIFO) or First in First Out (FIFO), or
- best before date, or
- if batch control is applicable.
Designing a fit for purpose Block Stack layout is not a straightforward process. We are looking to maximise the utilisation of the space available and to provide efficient operations.
Please do not hesitate to ask for advice. Of course, I would be very happy to provide a quotation to complete the work if required.
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