Warehouse layout design and rack arrangements to optimize picking
Warehouse layout design affects all warehouse processes, from receiving to warehousing, picking, and delivery. Of all warehouse processes, picking takes up over 50% of a warehouse’s labor. This isn’t surprising considering that, despite warehouse technological advancements in areas like automated storage and retrieval systems, picking is still a largely human-led process. In this two-part article, I will explain how to configure the warehouse layout in order to minimize picking time. In this first part, I will focus on the different arrangements of racks in the storage space.
Why focus on picking?
In my article on “How to improve your efficiency with the right Route & Warehouse KPIs“, we saw that picking costs represent 50% of the overall warehouse expenses and storage represents 18%. So, when thinking about warehouse layout design it is logical to think of ways to optimize picking time and storage space usage.
Warehouse layout design – Rack arrangement considerations
There are three elements associated with a warehouse layout design that have an impact, not only on picking efficiency but also on warehouse processes related to moving products. They are:
- Arrangement of racks throughout the storage space
- Warehouse traffic flow along the storage area
- Space allocation of products
In this article, I will go over rack arrangement. The other two elements will be addressed in the second part.
Types of rack arrangement
The first variable that needs to be considered in a warehouse layout design to optimize pickup travel time is the way you place the racks throughout the warehouse. There are four typical arrangements commonly used: U-shaped, L-shaped, I-shaped, and fishbone. Figure 1 compares the layout of the U, L and I shaped layouts and Figure 2 shows a fishbone warehouse structure. Let’s go over each of these topologies.
A U-shaped warehouse product flow is the most common type of layout. In this configuration the shipping and receiving docks are located next to each other, offering shared utilization of dock resources such as personnel and material handling equipment. This layout also minimizes product handling, offering high cross-docking capability.
I-shaped and L-shaped layouts
An I-shaped and L-shaped warehouse product flow, also known as through flow, are similar in that the shipping and receiving areas are located on different sides of the warehouse. As a result, these require more available warehouse space than U-shaped layouts. These layouts can be beneficial for certain operations. For example, warehouses that require heightened security can benefit from the separate ‘in’ and ‘out’ areas. I-shaped and L-shaped layouts can also provide larger sorting and storage areas for both shipping and receiving docks as well as allowing isolated monitoring of each function.
The previous layouts are based on the hypothesis that the shelf aisles are parallel. However, many companies have decided to go against this assumption and work on a V-shaped layout resembling a fishbone structure that, in some instances, claims to have a reduction of up to 20% in pickup travel time.
Cross dock aisles
All of the four layouts described above assume continuous aisles without any disruption. However, actual facts have shown that breaking the aisles with crossroad paths decreases further traveling time, but at the expense of more storage area. Let’s illustrate this with a simple example in figure 3. Assumptions:
- The black spots are the picking bins
- Each rack space (rectangular shape) is 3×3 feet.
For this particular picking, you will be saving 80% of picking travel time which is also 80% of picking labor costs.
Now you know the different rack arrangements you can have when working on your warehouse layout design. But if you want to minimize picking time, we need to analyze the picking route options and select the arrangement-picking route combination that will yield the minimum travel time. Your storage allocation policy also has an important role in the picking route. All these combinations will be the subject of the second part of this issue.
I hope this article and its follow-up are helpful. I will continue to publish information related to Warehouse Management, distribution practices and trends, and the general economy. If you are interested in this article or want to learn more about Laceup Solutions, register to keep you updated on future articles.
You can also watch this video on the subject.