Guide to Order Picking Systems in Warehousing: Complete Guide

According to a research paper by De Koster, Le–Duc, and Roodbergen, order picking has been identified as the most labor-intensive and time-consuming activity for most warehouses, which accounts for 55% of the total operating expenses. This means that the overall operational efficiency of a distribution warehouse is heavily dependent on how efficient its order-picking operations are. To streamline picking, different methods have been developed to cater to varying types of warehouses, product assortments, and order volumes.

Each warehouse or distribution center has different inventory moving and packaging strategies. In this article, we’ll explore order picking systems & look at the ongoing debate between Automation vs. Optimization and how businesses can choose the best path to improve their warehouse operations.

Types of Order Picking Methods

Piece picking

Piece picking is the simplest method, where a picker retrieves one product from the shelf for a single order. While suitable for small warehouses or low order volumes, this method can be slow and inefficient for larger operations. An order is complete when each of the products has been picked and packed for shipment.

Piece picking reduces errors in fulfilling orders but increases order fulfillment time as well as travel distance when workers handle this process manually.

Pros:

• Easy to implement and requires minimal training.
• Suitable for small or low-order-volume warehouses.

Cons:

• Highly inefficient for large warehouses.
• Increased travel time and picker fatigue.

Batch picking

Batch picking involves picking items for multiple orders simultaneously. This method reduces travel time since pickers retrieve the same SKU for several orders in one go. Rather than handling each order individually, the picker will pick one or multiple items for other orders, and bring them to a sorting area.

Pros:

• Reduces travel time.
• Increases picker productivity by consolidating orders.

Cons:

• More complex to manage, especially for large volumes.
• Requires efficient sorting after picking to avoid order mix-ups.

Zone picking

In zone picking, the warehouse is divided into zones, and each picker is responsible for a specific zone. Orders that require items from multiple zones are handed off from one picker to the next. Zone picking reduces traffic through aisles since the workers are only responsible for picking the inventory in their assigned zones. 

Pros:

• Reduces picker travel time within their zone.
• Increases efficiency within zones.

Cons:

• Requires coordination between zones to avoid delays.
• Not suitable for small warehouses with fewer zones.

Wave picking

Wave picking is a variation of batch picking where orders are grouped into waves based on shipping schedules or warehouse zones. This method improves scheduling and ensures that orders are picked and processed on time. Wave picking happens simultaneously in so-called ‘waves’ which are then processed, allowing for more efficient picking operations. Learn more about wave picking.

Pros:

• Helps meet tight shipping deadlines.
• Combines the efficiency of batch picking with better time management.

Cons:

• Can be complicated to manage and requires sophisticated software.
• Works best for large warehouses with time-sensitive shipments.

Cluster picking

Cluster picking involves picking items for multiple orders simultaneously. A picker collects items for several orders at once, grouping them into clusters and using a cart or tote system to keep them organized. This method is particularly effective when pickers need to retrieve small items from various locations for multiple orders. Learn more about cluster picking

Pros:

• Pickers collect items for multiple orders in one trip, minimizing walking distance & allowing more orders to be fulfilled in less time.
• When paired with software, cluster picking can be significantly optimized. reduces the chance of order mix-ups.

Cons:

• Requires effective organization and sorting to avoid errors during the picking process.
• Picking carts or totes with multiple compartments is necessary to manage different orders efficiently.

Case picking

Case picking involves picking a full case (or carton) of products for an order, rather than individual items. It is commonly used in warehouses that deal with bulk orders or large quantities of a single SKU. Learn more about case picking.

Pros:

• Faster than piece picking for bulk orders.
• Reduces handling time per order.

Cons:

• Not suitable for orders that require individual SKUs.R
• Requires efficient storage and handling of large cases.

Pallet picking

Pallet picking is used for bulk orders that require entire pallets of products to be moved at once. This method is common in warehouses that handle large quantities for retailers or wholesalers.

Pros:

• Highly efficient for fulfilling large orders quickly.
• Minimizes handling, reducing the chance of errors or damage.

Cons:

• Not suitable for smaller, more varied orders.
• Requires material handling equipment like forklifts.

Multi order picking

Multi-order picking allows pickers to collect items for several orders at the same time. Both cluster picking and batch picking are multi-order picking methods. They involve fulfilling multiple orders in a single picking session, which helps increase efficiency by reducing the number of trips pickers need to make through the warehouse. However, they differ in how orders are handled during and after picking:

• Cluster Picking: The picker gathers items for multiple orders, but keeps them separated in compartments (or clusters) during the picking process. This ensures that each order is already organized, reducing or eliminating the need for sorting after picking.
• Batch Picking: The picker focuses on gathering similar items for multiple orders without separating them during the picking process. The items are sorted into their respective orders after the picking session is complete.

Automated robot picking

Automated robot picking uses autonomous mobile robots (AMRs) or automated storage and retrieval systems (AS/RS) to handle picking tasks. Robots navigate through the warehouse, collecting items and transporting them to packing areas.

Pros:

• Reduces labor costs and increases picking speed.
• Operates continuously, reducing downtime.

Cons:

• Expensive to purchase and maintain.
• Only suitable for high-volume operations.
• Long implementation periods

Manual Picking

Manual picking is still widespread in warehouses where automation hasn’t yet been implemented. Workers manually retrieve items from shelves, either based on printed lists or instructions from handheld devices.

Pros:

• Low upfront cost compared to automation.
• Highly flexible and adaptable to various order types.
• Workers can adapt to a variety of roles
• Can be enhanced with software optimization solutions, such as WMS plug-ins.
• can easily scale up or down depending on operational volumes.
  
  

Cons:

• Training new workers to understand warehouse layouts, procedures, and technology can take time
• Dependency on workforce availability

Which of These Methods Is Best Suited For You?

Automation vs. Optimization

As warehouse operations grow more complex, many businesses are faced with the choice of investing in automation or optimizing their existing processes. Both approaches have their merits, but they come with distinct pros and cons.

Automation: A Growing Trend with High Costs

Automation, particularly hardware such as robotics, is transforming warehouse operations by increasing picking speed and reducing manual labor. However, there are notable drawbacks to consider:

• Big Investment: Robotics and other hardware automation systems are expensive to purchase and maintain.
• High Maintenance Costs: requires regular maintenance and repairs, which can be costly and cause operational downtime if not properly managed.
• Long Implementation Periods: Implementing automated solutions can take time, often involving complex integration and retraining of staff.
• Dependency on Technology: Automation introduces a reliance on hardware making the warehouse vulnerable to technical difficulties that could halt operations.
• Limited Flexibility: adapting hardware automation to new processes or changes in order patterns can be difficult.
• Upfront Disruption: requires restructuring warehouse layouts and workflows, leading to temporary disruptions in operations.

Despite these challenges, automation is ideal for large-scale operations that require high-speed order fulfillment and can absorb the upfront costs.

Optimization: Speed of Implementation and Immediate ROI

On the other hand, optimization focuses on improving existing manual picking processes using software enhancements. This approach is often more practical for warehouses that rely on manual labor.

• Faster Implementation: Software optimization solutions can be deployed quickly, since they function as add-ons to existing systems - Warehouse Management Systems (WMS), Order Management Systems (OMS), or ERP systems.
• Lower Costs: These software tools are less expensive than investing in robotics or other hardware solutions. They leverage current infrastructure, reducing the need for additional capital expenditure.
• Faster ROI: Optimization shows immediate improvements in productivity. Real-time data insights and advanced picking algorithms offer visible results right away.

Many warehouses continue to rely on manual picking, and software automation can greatly enhance these operations without the significant investment required for hardware automation.

Conclusions

The choice between automation and optimization will depend on your warehouse’s size, budget, and operational needs. Whether you opt for robotics or choose to fine-tune your current processes, the key is to continuously evaluate and improve your picking methods to meet the growing demands of your supply chains.