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Industrial Robots in Warehousing and Distribution Operations

The warehousing and distribution industry is facing new challenges due to the increasing number of SKUs coupled with the need to provide more “direct-to-store” pallets. This need is causing disruption in an industry where product handling, depalletizing, and palletizing are typically done manually. Having a large number of SKUs and having to supply “direct-to-store” pallets requires an increase in labor, an increase in the quality of the labor, and is a physically demanding job. These new requirements also cause the distributor increased costs due to product damage and fines/penalties in shipping inaccuracies. To combat this, applying robots to key functions in the warehouse and distribution centers is needed now.


FANUC Robotics has successfully implemented robotic depalletizing and palletizing systems since 1982. Traditionally, these palletizing/depalletizing robots have been used in the food and consumer goods manufacturing arena for homogenous palletizing applications, such as building a pallet at the end of a production line with only one type of product on the pallet. But the warehousing and distribution arena often involves build-to-order custom pallets mixed with multiple SKUs, potentially of widely varying sizes and exterior packaging materials.

One major challenge to automating this process with a robot is mimicking the high-level decision process that human operators make with each placement of an item on the load, as they carefully fit each one to achieve the highest shipping density combined with pallet load stability and minimal product damage.

Another significant challenge is emulating the broad range of adjustability inherent in a pair of human hands. In the past 10 years, great strides in development of intelligent robots, software and tooling have been made to enable robots to meet the needs of the warehousing and distribution market for building these mixed unit load pallets. FANUC Robotics has focused our developments for the warehousing arena on the Receiving/Replenishment and Order Fulfillment/Shipping areas. These are prime target areas where robots can provide a considerable benefit.

In the Receiving/Replenishment areas of a warehouse, robotic layer handling is employed to break down homogeneous pallets and either build mixed layer pallets (to go to shipping and be sent directly to stores) or to place a layer of product to a singulator to transport individual items to storage (for subsequent delivery to a palletizing operation in Order Replenishment / Shipping). In the Order Replenishment /Shipping areas, the robots palletize “direct-to-store” pallets, usually involving Mixed Item Palletizing (MIP). Building a “direct-to-store” pallet normally consists of multiple SKUs on a pallet, and potentially, orders for multiple stores on the same pallet. Note that Mixed Item Palletizing (MIP) is a generic naming convention. This type of application is often times referred to as Mixed Case Palletizing (MCP), Mixed Load Palletizing (MLP), and Random Order Palletizing (ROP). Beware that there may be subtle differences, so you will need to investigate the user requirements and the available application solutions on the market to ensure you have what you need.

Layer handling is a straightforward process and a relatively simple application for an industrial robot. It involves a robot equipped with layer handling tooling to accommodate the various products to be handled. Simplified robot programming enables the robot to either build mixed layer pallets or place a layer to a singulator. The mixed item palletizing operation to create “direct-to-store” pallets is considerably more complex, but is the largest robotic opportunity to solve the problems facing the industry such as eliminating the notoriously bad ergonomic issues of manual palletizing, reducing product damage, and improving order accuracy.

What is a Good Pallet?

Pallet Stacking

Before we discuss robotic mixed item palletizing and the associated state-of-the-art technology, we need to define a “good pallet.”

In our investigation of warehousing requirements, a good “direct-to-store” pallet has the following attributes:

  • Uses the Full Available Height

    • Maximizes the allowable height for end-user store requirements and shipping.

  • Very Dense

    • Maximizes the Pallet Footprint

    • Minimizes Air Gap

    Good Pallet Example

  • Has the Correct Sequence

    • Reverse Stop/Drop sequencing may be required

      • Involves Mixing Multiple Orders on a Single Pallet

      • Palletizes orders on a ”first on - last off” basis

      • Designed to reduce the amount of work that the delivery person has to do.

      • Challenges most algorithms, making it more difficult to hit high density targets.

    • If no pre-defined sequence — Maximizes Density

  • Is Conveyable!

    • Stable enough to survive the Conveyance System (normally to a stretch-wrapper) after the build operation.

These attributes must be weighted and prioritized according to:

  1. The industry targeted (beverage, grocery, consumer products, etc),

  2. The product being handled (cases, shrink-wrapped bundles, etc…),

  3. The transport system after the pallet build operation - oftentimes, direct fork truck handling.

Specific characteristics of the industry, product, and transport system will determine the correct combination and order of the build attributes in order for a successful system. One of the largest factors is conveyability.

What Makes a Pallet Conveyable?

Pallet Dimensions

Simply put, a pallet of product must have the ability to withstand the forces applied to it when it moves. This movement may be via a transport system (i.e., conveyor) to a stretch-wrapper or via a fork truck either to a stretch-wrapper or directly to a truck. In building a pallet, a mixed item palletizing (MIP) algorithm must take into account forces due to acceleration and deceleration of the pallet. The three basic pallet building principals are

  • Product Mass

  • Center of Gravity

  • Supported Base

MIP algorithms must analyze the pallet build and take these principles into consideration. The algorithm must be flexible enough to modify the build pattern to maximize the pallet build attributes desired. The MIP algorithm considers the stability of the resultant stack prior to placing each and every item. If stability of the pallet is deemed lower than the configured minimum, no other items are stacked on the pallet and a request is sent for a new pallet.

Creative solutions often optimize the entire system and allow for higher pallet builds. However, be careful to ensure that pallets built for optimal height and density do not sacrifice the overall stability and make the load impossible to transport. In addition, end user requirements must be considered. For example, when a build-to-order pallet arrives at a store and the stretchwrap is cut away: will the built pallet collapse and items fall to the floor? This could be a showstopper, but potentially could be avoided if stability is taken into account while the pallet is being built.

Mixed Item Palletizing Operational Modes

Automating the Mixed Item Palletizing (MIP) operation is extremely important to warehousing and distribution centers; this is the area that has the largest labor costs, greatest potential for product damage and where order inaccuracies from manual labor are most prevalent. This is where distributors will get the largest return on investment by automating with robots.

MIP automation demands an understanding of two fundamental operational modes that can be implemented. The two operational modes are:

  • Preplanned

  • Real-Time

In a preplanned mode, customer order data is analyzed well before the order is processed. The various SKU items in the order (perhaps multiple orders) are then picked, sequenced and delivered to the robot based on the results of the preplanning algorithm that defines optimal pallet build solutions. MIP workcell(s) then palletize the variety of SKU items in the customer order(s). Note that an MIP workcell is an island of automation usually consisting of a robot with its end-of-arm-tooling to handle the product, safety fencing surrounding the robot area, infeed conveyors (bringing in product), and outfeed conveyors (sending out mixed item pallet builds).

There are many algorithms on the market that can preplan for manual operations. For robotic building, the list of available algorithms is shorter since the preplanned build must consider the robot’s capabilities in terms of reach, robot tooling, and ability to place the product on the pallet when considering limitations of neighboring products and peripheral obstructions. All of these aspects must be considered by a preplanning algorithm to have a successful operation.

The Real-Time mode is where the MIP workcell(s) must determine the best location on a pallet for a variety of SKU items at the moment they are delivered to the robot. While doing this operation in Real-Time, the algorithm must also consider the robot’s capabilities in terms of reach, robot tooling, and ability to place the product on the pallet when considering limitations of neighboring products and peripheral obstructions This Real-Time mode is often referred to as a Random Order mode.

What Comprises a Mixed Item Palletizing Workcell?

As mentioned earlier, the robotic workcell is an island of automation, with an infeed conveyor (for product coming into the workcell) and an outfeed conveyor (for built mixed case pallets). There are three critical components of the workcell that must be carefully selected:

Palletizing Robot

  • Robots

  • End-Of-Arm Tooling (EOAT)

  • Software

The robots handle the products to the build pallet. The robots can be “stand-alone” robots or they can be mounted on robot transport units (RTU) and move between build pallets to allow for multiple build positions.

Custom EOAT


The EOATs handle products of different sizes, shapes and textures. The EOATs must be extremely reliable and able to pick a wide variety of SKUs. They must also impose minimal restrictions on MIP algorithm(s) - tooling restrictions will limit pallet build options and compromise the quality of the finished load.

The software is the brain of the operation: it determines the best pallet build scenario and directs the robot, with its EOAT, to place each product to the proper location on the pallet. The software must be able to build dense and stable pallets. In the real world, the software must also be intelligent to handle events that go wrong. For example, in a preplanned mode when product arrives at the robot out of sequence, the software must be able to handle the “Broken Play” by determining what has gone wrong and how best to continue placing product on the pallet. FANUC Robotics’ Mixed Case Palletizing (MCP) Software Suite has the capability to switch automatically between a Preplanned mode and a Real-Time mode. Without this capability, manual labor must intervene to complete the build, leaving the door open for product damage and order inaccuracies.

Mixed Item Palletizing Software

FANUC Robotics offers a Mixed Case Palletizing (MCP) Software Suite that provides for a Preplanned mode (whether it is a FANUC Preplanned algorithm or a third-party algorithm) and for a Real-Time Mode. There are many features of the software suite that are needed for any MIP application:

  • Ability to handle multiple Preplanning algorithms: choose the best algorithm for your application. Beverage, grocery, and general merchandise are three different industries where the pallet build attributes are different and may require a different preplanning algorithm to provide for the best MIP pallet build. Note that if your SKU content (aka, size variation) is small, a preplanning algorithm may not be needed.

  • Ability to control the functions of the robot and its tooling: the tooling needs to be flexible to accommodate the wide variety of products; therefore, the software must be able to control the many functions of the tooling that may be needed to do this. This may include control of servo-motion tooling that optimizes the size of the tooling for the appropriate size of the item to be handled, thus reducing pallet build time and increasing handling reliability (squeeze to a size and force).

  • Ability to interface to the robot’s surroundings.

  • Ability to monitor (Monitor Function) and report (Reporting Function) what is being built and what has been built in order to track and verify order accuracy

Palletizing Software View

These are the run-time aspects of the software, but there are other operational aspects needed to predict if a pallet can be built optimally for an order such as Virtual Pallet Build and Robot Simulation.

Virtual pallet processing determines the viability of the pallet build before product is sent to the MIP workcell and provides historical information after a pallet has been built, such as:

  • Order Distributions

  • Density Distributions

  • Height Distributions

  • Number of pallets

  • Palletizing results at various pallet heights

  • Results for actual customer orders

  • Analysis for any day

Virtual robotic palletizing with FANUC Robotics’ ROBOGUIDEĀ® simulation software determines if a pallet can be built. The simulation automatically generates the product sizes graphically and presents them to a virtual robotic workcell where the robot (with the appropriate EOAT) handles the product in the virtual world. The virtual simulation enables the robot to verify the sequences: from the product pick up, to the approach points, to the place points, to the away points, and finally back to the perch point ready for the next product. In doing all of this, the ROBOGUIDEĀ® virtual simulation analyzes the robot’s reach and motion to ensure that the pallet can be physically built.

Mixed Item Palletizing Software Versatility

In using a Preplanned operational mode, the product must arrive at the robotic workcell in the sequence needed to build a pallet optimally. However, sometimes products get out of sequence. The question arises: What do you do?

Most operations are forced to go to a manual mode and stack the products by hand. This can be done by having a smart MIP software package that is virtually stacking the pallet and can print out a pictorial (with product item list) of what has been palletized and what remains to be palletized. FANUC Robotics has this feature built into its MCP Software Suite (it also indicates what was stacked automatically and what needs to be stacked manually). Additionally, our MCP Software Suite also incorporates a special feature called the “Broken Play” option. FANUC Robotics’ Real-Time algorithm is how to handle the “Broken Play”, by automatically taking control and palletizing whatever is presented to the robot to the best available position on the pallet! This “Broken Play” option is unique to FANUC Robotics’ MCP Software Suite and will help increase uptime, reduce product damage and order inaccuracies since the human element is not introduced.

Schematically, the FANUC Robotics’ MCP Software Suite operates as shown in the following flowchart:

Mixed Case Palletizing Software

How does the patented MCP Real-Time algorithm work?

  • Evaluates a series of prioritized RULES to select and place each case

  • Each RULE covers a special condition (full layer, full region, adjacent height, stability, supported area, interlocking, combined similar product, combined space, etc.).

  • Remembers previous rule if appropriate (full layer will remember chosen pattern)

  • Provides configurable process parameters (which rules to use, pallet size, etc.)

  • Last rule is BEST SCORE

    • Evaluates each case available against every potential position on the pallet

    • Uses 20 different evaluations: Supported area, stability, size, adjacent height, etc.

    • Each evaluation is weighted or factored differently

    • Factors stability and supported area

    • Highest Score WINS!

How to Choose What Mixed Item Palletizing Software and Operational Mode is Right for You

Understanding your product mix and typical customer orders is important in determining the best solution for your operation. Pallet Optimization software suppliers and Mixed Item Palletizing suppliers can evaluate your product master list (SKU#, size, weight, etc.) and order data (orders for a peak and average day; consisting of order number, SKU #, quantity per SKU, etc.). These customer-specific attributes will allow these companies to determine their best algorithm to use and validate what operational mode you need. If product mix is low (physical size), the Real-Time algorithm may be your best choice, since its price and complexity are low. If your product mix is high (large physical size variations), the Preplanned algorithm with “Broken Play” may be the answer, but the associated costs and system complexity increase.

The Comparison Matrix below will give you a guide in the choices on the market. The matrix also illustrates key pallet build requirements you may have versus cost and complexity.

Palletizing Comparison


Warehousing and distribution centers are facing ever increasing customer demands for higher product mix, higher variety of products for each order, multiple store orders on the same pallet, aisle rules, and an unforgiving demand for accurate orders. To face this challenge, automating the warehouse and the use of robotic applications at key points in the warehouse are a necessity.

You are not alone — all warehousing and distribution centers are facing the same battles. The first companies to automate will be able to overcome the ever increasing costs associated with high labor content, an inconsistent labor pool, product damage, order inaccuracies, theft/security, and increased employee injuries.

In the past, there were very few choices for automation and greater limitations regarding which warehouse operations could be automated. The advancement in intelligent robotics has broken the barrier, making it affordable now. The choices, once limited, are now wide and far-reaching. At FANUC Robotics, we have developed software and hardware tools to enable customers and system integrators to tackle this formidable task. The MCP Software suite, available through FANUC Robotics, can allow you to choose the best robot, the best algorithm to meet your needs (either FANUC Robotics’ algorithm or a third-party algorithm), and the best End Of Arm Tooling to allow you to build mixed item pallets reliably.

Field-proven Mixed Item Palletizing solutions are now available:

  • Real time: smaller investment, good performance

  • Preplanned: larger investment, better performance

  • Preplanned + Real time = optimal solution --- Only available through FANUC Robotics

The warehouse/logistics market presents a significant new opportunity to software and hardware suppliers, so the costs and complexity will decrease over the next few years making affordability more enticing. The United States has started adding robots to warehousing and distribution centers only within the last 10 years (but concentrating implementation in only the last 3-5 years). However, US industry is beginning to implement mixed item palletizing at an increasing rate.


[1] D. DeMotte, M. Poma, and A. Monique. United States Patent: AUTOMATED PALLETIZING CASES HAVING MIXED SIZES AND SHAPES, US Patent # US 7,266,422 B1, 2007.

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