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A robotic palletizer is a type of palletizer that uses a robotic arm to pick, orient, and place individual products into a single stack or load. Representing the next generation of palletizers, robotic models offer advantages such as lower capital cost, versatility, and the ability to perform multiple tasks. However, their limitations in speed, product dimension tolerance, and robustness prevent them from entirely replacing traditional palletizers in all applications.
Like any other type of palletizers, robotic palletizers take advantage of the concept of unit load. Unit load refers to the assembly of materials combined for efficient handling. It is faster and more economical to move a large, single unit instead of several small individual items. Finished goods are not designed and built to be handled and shipped separately. These are usually placed in boxes, cases, trays, and crates that are then combined into a single unit supported by pallets or roll cages. The former ones are referred to as secondary unit loads, while the latter ones are tertiary unit loads.
Before the advent of automatic palletizing, manual hand stacking was used to organize products into pallet loads for storage and distribution. This method was labor-intensive and relatively slow compared to its output. Pallets and pallet handling became crucial logistics tools in the early 20th century, particularly during World War II, as the transport of heavier loads accelerated the need for enhanced material handling and storage capabilities.
The first mechanical palletizer was developed by Lamson Corp. in 1948. This early model was a row-forming palletizer, where materials were arranged in a row-forming area and then transferred to another area to be stacked in layers. This process was repeated until a complete stack was formed and ready to be placed on a pallet. This method laid the foundation for conventional palletizers.
Robotic palletizers emerged in the 1980s, featuring a robotic arm equipped with an end effector or product gripper. This gripper picks up products from a conveyor or layer table and positions them on the pallet. The end-of-arm tool can be a mechanical, suction, or magnetic gripper.
Automatic palletizers provide numerous benefits in packaging and production lines. They enhance manufacturing efficiency and remove the variability introduced by human labor, which can slow down the plant's operational rate. The advantages of using palletizers often outweigh the initial investment costs. Key benefits of palletizers include:
Palletizers remove the need for manual labor in unitizing products. They are more efficient, capable of handling heavier loads, and operate at a faster pace. Unlike human workers, palletizers do not suffer from exhaustion or injury. With proper maintenance, they can operate reliably 24/7, minimizing potential bottlenecks in the packaging line.
As automated machines, palletizers have pre-programmed movements that are designed to handle products without causing damage. Unlike human operators, palletizers do not need to make constant decisions, which reduces the likelihood of errors and ensures more consistent product handling.
Properly designed palletizers help eliminate workplace threats and hazards associated with manual labor. Manual palletizing can involve risks such as falls, slips, trips, and crushing injuries. It also often leads to muscle strains from repetitive reaching and stacking, which can result in lower back injuries and long-term health issues for workers.
In most applications, especially in large packaging systems, the cost-benefit analysis of acquiring a palletizer usually shows positive results. Benefits include savings in operating expenses due to increased throughput, reduced product wastage, and lower labor costs.
Beyond the general benefits, robotic palletizers offer additional unique advantages. When considering the purchase of a palletizer, the key decision often revolves around choosing between robotic and conventional types. Understanding the pros and cons of each is crucial, as each has specific strengths that make it suitable for different applications. The table below provides a comparison of these two types of equipment.
| Robotic Palletizer | Conventional Palletizer |
|---|---|
| Low investment cost for simple applications: For simple palletizing solutions, a robotic arm can be employed where speed is not a critical factor. Using a robotic arm eliminates the need for multiple conveying systems, turning mechanisms, stoppers, gates, and so forth. Thus, robotic arms are a cheaper option when they can cope with the required throughput. | Better tolerance with varying packaging types: Conventional palletizers form the unit load by turning and pushing the product to its desired location and orientation without the need to pick up and place the product. Thus, varying the packaging dimensions or packaging types will not affect the handling of the palletizer. If modification is needed, this can be done by adjusting the controls through its program. No hardware modification is needed |
| Ability to serve multiple lines: One robotic palletizer can be situated between two or more packaging lines. They can also accept multiple products with unique SKUs, each carried by individual lines. For one conventional palletizer to serve multiple lines, upstream product accumulation systems are used. Robotic palletizers eliminate this need which further cuts the investment cost. | Higher throughput: Most conventional palletizers are used for high throughput palletizing. This is because their actuators‘ movements are much simpler than that of robotic types. Moreover, they can easily transfer and orient multiple products at once. Robotic palletizers, on the other hand, are slow if their mode of operation is individually picking and placing products. They can only increase their throughput rate by collecting multiple products at the same time. |
| Versatile pattern forming: Robotic palletizers are better equipped to change pattern formation than conventional palletizers. Changing the pattern only requires reprogramming of the robotic arm‘s movement and the actuation of the end effector. There is no need to change its hardware. However, changing the palletizing pattern can cause negative effects on its throughput. | More robust and reliable: Conventional palletizers are fit to handle heavier loads than robotic palletizers with similar capacities. In a conventional palletizer, the bulk of the load is carried by a conveyor system that easily handles weights far above the pallet load. In contrast, robotic systems have loads that are concentrated at their joints. This is especially significant for robots with articulated arms. Moreover, the joints of a robotic arm perform more movements for a given operation. Fatigue due to dynamic mechanical stresses is more evident in robotic types. |
| Ability to perform secondary tasks: Robotic palletizers equipped with vacuum, magnetic, or custom end-of-arm-tools can perform additional tasks such as slip sheet dispensing, pallet placing, and wrapping. Aside from these additional functions, robotic palletizers can completely reverse their operation. This feature is seen on robotic palletizers-depalletizers. | Easy maintenance and servicing: Conventional palletizers are easy to troubleshoot. They have several actuators that perform distinct functions. Determination of which actuator failed is accomplished by simply observing the operation of the machine. In addition, conventional types have more hardwired components than robotic types. Servicing hardwired components requires less technical specialization. |
| More compact: Robotic palletizers are more compact than conventional types. They only take up the space required by the robotic arm and the staging platform for the palletized load. Conventional types have many different components such as conveyors, pushers, and ejectors; these are all required for accomplishing a single operation. This configuration takes up significant floor area and headroom. They also have multiple staging areas for layer forming. | Easy part replacement and sparing: Most conventional palletizer actuators are on the market. These actuators are more common since their application is not limited to palletizers. Large supplies are available because of the high demand. Most manufacturers of robotic palletizers use patented parts, which usually have limited suppliers. |
Robotic palletizers can be classified based on their configuration and construction. Different configurations are characterized by the palletizer's mode of operation. Robotic palletizers can operate individually or in conjunction with other units and may also perform tasks beyond palletizing. Below are some types of robotic palletizers categorized by their configuration.
This configuration is the most straightforward and widely used, featuring a single robotic palletizer. This single unit handles the palletizing task and may also incorporate additional functions, such as slip sheet and pallet dispensing, as well as stretch wrapping.
Single in-line palletizers can handle one or multiple palletizing lines, which may contain either the same or different product SKUs, depending on the design. They are typically equipped with articulated arms and custom end-of-arm tools.
Although this type of palletizer offers significant versatility, it tends to have a lower throughput.
This palletizer type adds another layer of versatility—depalletizing. Depalletizing is the inverse process—the individual items are disassembled and separated from the unitized or palletized load. This feature is useful in applications that require the unloading of products from mixed pallets. The depalletizing robot also sorts the goods according to the product SKU.
Generally, a robotic palletizer is designed to handle either palletizing or depalletizing, but not both functions simultaneously. A machine labeled as a palletizer-depalletizer indicates it can be programmed for both tasks. Palletizers are typically used in end-of-line processes for packaging and storage, whereas depalletizers are used for unloading and distributing raw materials like empty bottles, boxes, and cases. The advantages provided by palletizers are similarly realized with depalletizers.
This robotic palletizer configuration uses multiple robots. In a layer-forming system, each robot is assigned a specific task. For example, a basic layer-forming setup includes two robots: one for assembling layers and another for stacking them. This division of labor enhances the overall throughput of the palletizing system.
The specifics of robotic palletizers, including the number and types of robots, programmed tasks, and additional features, vary between manufacturers. Some systems combine conventional and robotic palletizers into what are known as hybrid palletizers. In these setups, a conventional palletizer is used for layer forming, as it effectively handles incoming products from conveyor belts. Once the layers are formed, a robotic palletizer takes over to stack them. Robotic palletizers are particularly efficient in stacking due to their optimized pick-and-place movements.
Mixed palletizing describes the capability of robotic palletizers to handle various products and consolidate them into a single pallet. Mixed configuration robotic palletizers are typically high-end models equipped with advanced programming, custom end-of-arm tools, and sensors. They are highly versatile, able to make precise adjustments to their arm and tooling movements without requiring reprogramming. This adaptability allows them to accommodate different product profiles and determine their positions on the stack. Mixed configuration palletizers are particularly valuable in environments with high SKU diversity, including packaging, storage, and distribution lines.
Robotic palletizers can also be classified based on their construction, with each type distinguished by its range of allowable movements. These types vary in complexity, with more advanced models offering greater freedom of movement. Below are the four primary types of robotic palletizers categorized by their construction.
This type of palletizer, known as a Cartesian palletizer, features an end-of-arm tool that moves along three Cartesian axes—x, y, and z. Its structure includes beams and a telescopic mast driven by servo motors, geared rollers, rack and pinion, chain and sprocket, or lead screw mechanisms. Cartesian palletizers are relatively slow and best suited for products with consistent weights and sizes. Their end-of-arm tools are typically basic, making them ideal for straightforward pick-and-place tasks. As one of the more cost-effective options, Cartesian palletizers are suitable for single line speeds of up to 10 items per minute.
A gantry palletizer features an end-of-arm tool or end effector mounted on a beam that moves along one axis. This beam, in turn, moves on a second axis, enabling movement within the horizontal plane. For vertical motion, the end effector assembly often includes a telescopic or articulated arm that can extend or retract. Gantry palletizers are a subset of Cartesian palletizers, as they provide linear movement along the three Cartesian axes. While they are typically slower than Cartesian robots and tend to be larger and more expensive, they offer the advantage of handling heavier loads.
A SCARA-type palletizer features an arm that is flexible in the horizontal plane but rigid in the vertical direction, which is its "Selective Compliant" characteristic. Its articulated robot arm, resembling a human arm, consists of two links connected by a joint at their ends. This joint typically has a single degree of freedom, allowing the arm to extend or fold. SCARA palletizers are generally faster than Cartesian models and can handle multiple palletizing lines, achieving speeds of approximately 20 items per minute.
Articulated palletizers offer two additional degrees of freedom compared to SCARA palletizers, making them the most advanced type with a design closest to a human arm. Their end-of-arm tool is mounted on a wrist with one or two degrees of freedom. Unlike SCARA palletizers, articulated palletizers do not have a mast; instead, one arm is mounted on a swivel joint with a fixed base, allowing for greater flexibility in movement. Articulated palletizers are faster than SCARA models and can manage multiple production lines, handling approximately 25 items per minute.
End-of-arm-tools, columns, arms, and joints are some of the terms used in the previous chapters to describe the different types of robotic palletizers. Robotic palletizer components are more similar to robots used in automated assembly and manufacturing systems than those found in conventional palletizers. From a mechanical point of view, a robotic palletizer is an assembly of links and joints. These links and joints are specifically denoted by their role in the robotic system and their position in the assembly.
The columns and masts are the vertical components mounted on either a fixed base (in Cartesian, gantry, and SCARA types) or a rotating base (in articulated types). These columns support the weight of the load and the palletizer assembly. They serve as the attachment points for the beam, arm, and end effector assemblies. Movement up and down is facilitated by hydraulics, servo motors, lead screws, or chain drives, which raise or lower the connected parts.
Beams are horizontal load-bearing components that support the end effector assembly or end-of-arm tool. They feature guided rails that enable the translational movement of a trolley carrying the tool. A single beam allows movement along a single axis, while a two-beam assembly enables movement within the horizontal plane. Beams are commonly found in simpler robotic palletizers like Cartesian and gantry types. However, an exception is the gantry palletizer that utilizes a robotic arm as its end effector.
Arms are two-link mechanisms that allow the end-of-arm tool to move within two- or three-dimensional space through rotation, extension, or folding. The links are connected by joints that provide one or two degrees of freedom. The range of motion of the palletizer is determined by the length of the arms and the movement capabilities of the joints. Arms are specific to SCARA and articulated palletizer types.
Joints facilitate rotational or translational movement between the links of an arm. The number of joints in a palletizer system varies based on the level of versatility required. An arm with full, unrestricted motion generally includes six joints, each offering a single degree of freedom.
The wrist is the joint in a robotic arm that supports the end-of-arm tool. It typically allows for rotational movement to position the tool. Some designs also permit additional rotational adjustments, providing a two-degree of freedom movement for more versatile tool positioning.
Often called end effectors (EOAT), these are the most crucial components of a robotic palletizer, contributing significantly to the machine's versatility. EOATs are responsible for picking up and placing products in their correct location and orientation within the stack. They can be designed to handle not only finished products but also various other materials, including packaging materials, wrappers, slip sheets, and pallets.
The end-of-arm tool (EOAT) distinguishes robotic palletizers from conventional types. As discussed in the previous chapter, it is the key element that provides robotic palletizers with their versatility. Below are some of the most commonly used EOATs in the palletizing industry.
These EOATs lift products by clamping and gripping their sides. In this design, one part of the clamp remains stationary while the other moves. The gripping action is achieved by bringing the movable part closer to the stationary part, securely holding the product. Clamps can simultaneously handle and place multiple products with the same orientation, enabling faster throughput.
These end effectors are ideal for products that need support from underneath. By providing additional support, they can handle heavier loads without damaging the sides of the products. Their operation is similar to that of clamp types, involving a pushing action to load the products onto the fork. Like clamps, forks can also collect and place multiple products simultaneously.
Finger end effectors are mechanical tools that operate by opening and closing in two directions. They not only grip products at their sides but also provide support from underneath, offering a more advanced solution compared to clamps and forks. Fingers are particularly useful for handling delicate items or products packed in fragile materials such as paper or sheet plastic.
Vacuum end effectors utilize pneumatic systems with a venturi device to create vacuum pressure. These types use multiple suction cups to hold products from their top surface, which minimizes damage to packaging materials compared to mechanical types. They are also more reliable due to having fewer moving parts. However, vacuum end effectors have weight limitations and tend to palletize at lower speeds, as they can lose grip when accelerating the product quickly.
This type of EOAT uses magnetic devices for lifting magnetic products or products with magnetic casing or packaging. Permanent magnets can be used since they do not continuously consume power; however, they need a mechanical device for removing the collected object. Electromagnets are preferred due to their simple operation, as the object can be lifted or dropped simply by supplying or cutting power to the electromagnet. Their suitability as a palletizer EOAT is limited since only a few products are completely magnetic. The number of applications is further reduced since magnetism can damage products or cause them to be magnetic.
Custom EOATs are uniquely fabricated tools for handling odd-shaped products. They can be equipped with a combination of mechanical, pneumatic, or magnetic actuators. This further increases the flexibility of the palletizer. Custom EOATs also allow the robotic palletizer to execute secondary tasks such as dispensing and wrapping.
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