Pick to Light Systems: Advantages and Disadvantages

This page explores the advantages and disadvantages of Pick to Light (PTL) systems, a common architecture used in inventory management. We’ll cover the benefits and drawbacks of these systems.

Introduction:

Inventory management is crucial for effectively managing stock, covering everything from monitoring and control to storage and ordering. Pick to light and put to light systems play a significant role in improving the efficiency and effectiveness of this management. Let’s delve into the architecture, benefits, and drawbacks of pick to light systems.

Pick to Light System Architecture

Pick to Light (PTL) systems are utilized in order picking environments. They guide order pickers (both men and women) to the correct location quickly and easily using lights or LED displays. Each illuminated tag signifies a specific item at a particular storage location.

These light displays show the precise quantity of items within the bins on the rack, guiding the picker. The system requires confirmation upon item selection.

A related system, called Put to Light, works in reverse. Items are picked from the warehouse and brought to the Put-to-Light system. The picker scans or inputs the item, and all bin locations that require that item light up. The picker then manually distributes the items to each illuminated location and turns off the light after placement.

Pick to Light System Architecture

As shown in the figure above, a Pick to Light System architecture consists of the following:

• Rack with Multiple Pick to Light Units: As depicted in the figure below.
• Bar Code Reader: Used to scan items being picked or put to/from the rack.
• Controller: (Wired or wireless) managing the pick to light units.
• Router or Network Hub
• Remote PC: Running real-time material inventory management software.

Pick to Light Unit

The figure above illustrates a single Pick to Light Unit. It typically includes Up/Down buttons, a 3-digit display, an LED display, and an acknowledgement button. It may also be equipped with a Load cell or Force sensor to measure the weight of the materials placed in the bin above it.

Pick to Light units can communicate with the controller using either wired (RS232, RS485, RS422, Ethernet, Modbus) or wireless (GPS, Cellular, Wi-Fi) communication methods.

Benefits of Pick to Light Systems

Here are the key advantages of using a Pick to Light System:

• Paperless Picking: Eliminates the need for paper-based picking lists.
• Streamlined Order Fulfillment: Improves the overall efficiency of the order fulfillment process.
• Increased Picking Productivity: Drastically boosts the number of items that can be picked per unit of time.
• Improved Picking Accuracy: Reduces picking errors to below 0.1%, ensuring greater accuracy.
• Ease of Use: Pickers can be trained on the system quickly and easily.
• Strengthened Management Control: Facilitates online picking data control and provides easy alerts for material shortages.

Drawbacks of Pick to Light Systems

While Pick to Light Systems offer numerous advantages, they also have some drawbacks:

• Performance Dependence on Pick Size and Area: The system performs best when picks are smaller and the pick area is relatively compact, allowing pickers to concentrate effectively. Efficient management involves assigning pickers to specific racks.
• Security Vulnerabilities (Wireless Systems): Wireless Pick to Light systems are susceptible to noise and hacking. Wired systems are also vulnerable if connected to the internet. Firewalls and anti-malware software can mitigate these risks.
• Limitations of Wired and Wireless Technologies: Wired systems may face limitations associated with the physical medium used (RS232, RS485, Ethernet, etc.). Indoor wireless systems like Wi-Fi and Bluetooth have coverage range limitations. GPS is more effective outdoors than indoors.
• Controller Failure Impact: If the controller fails, the real-time inventory software will not receive accurate inventory information until the controller is replaced. Redundant or multiple controllers are recommended to prevent this. The controller should ideally support multiple wired and wireless technologies.