Slotting by velocity is a warehouse design method that places products according to how often they are picked. Fast-moving items are stored near packing stations and shipping docks, while slow-moving items are placed farther away. This reduces walking or driving distance, which often makes up a large share of order picking time.
Good slotting improves speed, labor efficiency, safety, and customer service.
Velocity is usually measured from order history, such as picks per day, units per week, or order lines per month. Items are grouped into zones, often called A, B, and C zones, where A items are the fastest movers and C items are the slowest. The layout should also consider item size, weight, storage requirements, and whether products are often ordered together.
Because demand changes over time, slotting is not a one-time decision but a system that must be reviewed and updated.
Key Facts
- Pick velocity = number of picks per time period, such as picks/day or picks/week.
- A items are high-velocity products and should be placed closest to packing, shipping, and main pick paths.
- B items have medium velocity and are usually placed in middle-distance storage zones.
- C items have low velocity and can be stored farther from shipping because they are picked less often.
- Travel time = travel distance / travel speed.
- Total picking labor time = travel time + search time + handling time + packing support time.
Vocabulary
- Slotting
- Slotting is the process of assigning products to specific warehouse storage locations to improve efficiency.
- Velocity
- Velocity is the rate at which a product is picked, sold, or moved through the warehouse.
- Pick path
- A pick path is the route a worker or vehicle follows to collect items for orders.
- ABC analysis
- ABC analysis is a method of grouping items by importance or activity level, often with A as fastest, B as medium, and C as slowest.
- Travel distance
- Travel distance is the total distance a picker, forklift, or robot moves while completing warehouse tasks.
Common Mistakes to Avoid
- Using sales revenue instead of pick frequency, which is wrong because an expensive item may sell rarely and should not automatically get a prime slot.
- Putting all fast-moving items in one crowded area, which is wrong because congestion can slow picking and create safety risks.
- Ignoring product size and weight, which is wrong because heavy or bulky items may need lower racks, wider aisles, or special equipment even if they move quickly.
- Never updating the slotting plan, which is wrong because seasonal demand, promotions, and new products can change item velocity over time.
Practice Questions
- 1 A picker walks 240 meters to pick a slow-moving item and walks at 1.2 m/s. How many seconds of travel time does this trip take?
- 2 A product is picked 600 times in 30 days. What is its average pick velocity in picks per day, and would it likely belong in a fast-moving zone if the A-zone cutoff is 15 picks/day?
- 3 Two products have the same pick velocity, but one is heavy and often ordered with packing materials while the other is light and rarely ordered with anything else. Explain how these differences could affect their slot locations.