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Factors for Robotic Bag Palletizing Systems

Bags are difficult for conventional palletizers - and an ergonomic nightmare for manual palletizing

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Robotic palletizer bag effector

Above: SAS Automation standardized bag-gripper

Palletizing is a standard material handling application for industrial robots, and bag palletizing is one of the most typical applications. Why? Because bag palletizing is simpler and easier than case palletizing. If your operation requires bag stacking/pallet loading – and you want to improve speed, reduce mistakes, and create a more ergonomic system, here are the things you need to know.

Robots handle bags easier than they do cartons

Because bags are generally round-shaped and bulkier than cases they require less complicated palletizing patterns than those of cases. Bags are also more malleable and have less risk of damage from collision. This means a robot can usually simply set the bag down as opposed to follow a ramping trajectory to minimize impact and collision than palletizing cases. These characteristics simplify the robot motion, the robot program, and saves cycle time for bag palletizing.

Bag pallets normally don’t usually need slip or tier sheets. This simplifies the application and cuts down cycle time. Also, bag palletizing generally is given more cycle time to meet the production rate.

Robot tools are often highly customized with claw and other types of end effectors

But bag palletizing has its own standard tools. The most commonly-used tool has a “claw of fingers” that open up, extend below the bag, wrap around it, and close to grip it. To work with the tool, the bag rests on a roller conveyor. The rollers provide even spaces for the fingers to go through and close underneath the bag. The tool can also be mechanically adjusted to accommodate a wide range of bag sizes. Top vacuum suction is an option. This tool design is universal, reliable in gripping, and capable of high-speed handling. Several tool companies provide their models of this design.

Bags are ideal loads for robotic automation, and have downsides for manual operations or conventional palletizers

Lifting a heavy bag is more difficult than more balanced, uniform loads. Since bag loads are usually bulk loads of a loose substance, they’re harder to handle and often heavier than cases. Manual bag palletizing is a terrible ergonomic burden and results in more broken bags and slower cycle times. This makes some type of automation very desirable for bag loading.

Conventional palletizers are also not ideal for bags, since they don’t handle the very round, malleable bags as well as a robotic palletizer and its end effectors built precisely for the job.

One downside of bag palletizing is that it is sometimes hard to estimate the height of the current stack since the thickness of each bag is variant. Engineers either track the current height with an additional distance sensor or simply live with this minor problem.

More information: Packaging and palletizing robots

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Scott Stone is Cisco-Eagle's Vice President of Marketing with more than thirty years of experience in material handling, warehousing and industrial operations. His work is published in multiple industry journals an websites on a variety of warehousing topics. He writes about automation, warehousing, safety, manufacturing and other areas of concern for industrial operations and those who operate them.

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