A put-to-light system is a warehouse sorting method that uses illuminated displays to show workers exactly where to place each item. It is often used in e-commerce, retail replenishment, kitting, and order consolidation because it speeds up packing while reducing mistakes. Instead of reading long paper lists, the worker follows lights, numbers, and confirmation buttons at each bin.
This makes the station easier to learn and helps many orders move through the warehouse at the same time.
A typical system connects conveyor flow, barcode scanning, inventory software, LED modules, and human motion into one coordinated process. When an item or tote is scanned, the control system identifies which customer orders need that item and lights the correct bin locations with the required quantities. The worker places the items into the lit bins, presses confirmation buttons, and the software updates each order in real time.
The main engineering goal is to balance speed, accuracy, ergonomics, and system capacity so that workers, conveyors, and storage slots do not create bottlenecks.
Key Facts
- Put-to-light directs placement of items into order bins using LED indicators, quantity displays, and confirmation buttons.
- Throughput rate = completed orders / time, such as orders per hour.
- Pick or put accuracy = correct placements / total placements × 100%.
- Cycle time per item = scan time + travel time + put time + confirmation time.
- Station capacity depends on number of active bins, worker speed, conveyor feed rate, and software batching rules.
- A well-designed put-to-light wall reduces search time because the worker looks for illuminated locations instead of reading every bin label.
Vocabulary
- Put-to-light
- A warehouse system that uses lights and displays to guide workers to the correct bins for placing items.
- SKU
- A stock keeping unit is a unique code used to identify a specific product type in inventory.
- Order consolidation
- Order consolidation is the process of combining items from different picking steps into complete customer orders.
- Throughput
- Throughput is the number of units, orders, or tasks a system completes in a given amount of time.
- Bottleneck
- A bottleneck is the slowest part of a process that limits the overall rate of the entire system.
Common Mistakes to Avoid
- Counting lit bins instead of reading the quantity display is wrong because one illuminated bin may require more than one item.
- Ignoring confirmation buttons is wrong because the software may not update inventory or order status unless the worker confirms each placement.
- Placing items in the nearest empty compartment is wrong because put-to-light locations are assigned by the control system to match specific orders.
- Measuring only worker speed is wrong because conveyor feed rate, software batching, bin availability, and replenishment delays can all limit throughput.
Practice Questions
- 1 A put-to-light station completes 420 orders in 3.5 hours. What is its throughput in orders per hour?
- 2 A worker makes 1,200 placements in a shift and 9 are incorrect. What is the placement accuracy as a percent?
- 3 A warehouse manager wants to add more LED bins to a put-to-light wall. Explain why this may increase throughput in some cases but not in others.