Robotic cells for material handling, packaging, and automation applications all have one thing in common: the robot is only as good as its end-of-arm tooling (EOAT). Robotic EOAT can range from a simple vacuum cup tool to sophisticated assemblies with multiple actuators. An EOAT tends to be specific to an application, although not every application requires a custom EOAT. Given the wide variety of standard modular EOAT components currently on the market, some simpler applications may be handled cost-effectively by assembling an EOAT from standard parts. The question of how to decide whether to build an EOAT from standard parts or have a custom EOAT designed and built is not a simple one to answer, but can depend upon available resources and skill level.

Typical pick-and-place applications usually have straightforward EOAT assemblies made of modular EOAT components with possibly a few custom details. The robot performs all of the product/workpiece manipulation while the EOAT is basically there to secure the product or workpiece. Of course, in order to achieve the maximum flexibility and efficiency from a given robotic system, it makes sense to consider the requirements for the EOAT early in the project or application development.

Usually a custom EOAT is warranted when it needs to do more than simply secure a part. A custom EOAT can help get more out of a robot by reducing the need for a second robot and/or reduce the need for manual labor as part of secondary assembly operations. The following are examples that typically call for development of a custom EOAT:

• The product geometry does not lend itself to be secured by standard components.
• The environment or product characteristics contribute to special handling (oils, liquids, heat, texture, weight, etc.).
• Several different sizes or configurations of product must be secured by the same EOAT.
• Product spacing must be manipulated on the EOAT.
• Equipment that interfaces with the EOAT / product has envelope constraints (fixtures, machines, etc.).
• The EOAT must add some functionality to the automated process, such as assembly.

The more complex a product is, and the more functionality that is required from the EOAT, the more likely it is that a custom EOAT will be needed. The decision to use standard components or a custom EOAT should be made in the planning stages of any robotic cell. Once it has been decided that automation is necessary and justified, it will be necessary to review how to get the most from the investment. Functionality can be added to a robotic cell if warranted by a productivity analysis of the application. Examples of functionality that can be added include machining operations, part finishing, packaging, assembly, and other value added procedures. Additional fixturing, machinery, or custom EOAT can enable a robot to do more in a given cycle.

Once the specifications for a robotic system and its EOAT have been established, it is time to meet with an automation engineer. Laying out the details of the full operation is critical to helping an engineer understand how to apply available technology to the application. An automation engineer or qualified automation technician is in the best position to recommend additional operations that a given EOAT assembly may be capable of handling.

This custom EOAT assembly was designed for a high-speed palletizing application.

For example, consider a packaging application in which bottles are being picked up from a conveyer line or belt and placed into a case. For a single robot to handle this application, it must pick up six bottles during each cycle. The center-to-center spacing of the bottles must be reduced to fit the bottles inside of the case and to place them all at once. A custom EOAT assembly can adjust the center-to-center spacing of the bottles while the robot is in route to the case. This operation is a simple pick-and-place application for the robot when there is more functionality on the EOAT.

A wide variety of pneumatic actuators are available that are typically used to add motion and functionality to gripping mechanisms on custom EOAT solutions. These extra motions are used to secure, rotate, shuttle, and manipulate the product. External slides and bearing /rod assemblies are often included to make an EOAT solution more robust. Motors of various kinds can be incorporated as well to add actuation to a custom EOAT.

Palletizing Cases

Custom tools can be particularly useful on some palletizing applications. For example, for a particular application, a manufacturer specified the following requirements for palletizing cases: Secure unsealed cases containing fragile products. Secure the pallet. Palletize the cases as close to each other as possible in one robotic placement operation to minimize the cycle time. Make sure that the fragile products are not crushed. For this application, a custom EOAT was needed to meet these demanding palletizing requirements. The EOAT secures the cases with independent mechanical grippers assisted by vacuum cups. The mechanical grippers have a static side and a movable side. The static side is made of one-quarter-inch steel plates with a rubber insert to increase the friction coefficient. The profile of the static side was designed to be thin so the robot could place the cases as close as possible.

This palletizing EOAT assembly was designed to handle cases with minimal pressure and protect the palletized products from damage.

The movable side is actuated by pneumatic cylinders. The motion is controlled by bearings and rods. By employing independent grippers, the robot could palletize the cases in various configurations. Vacuum cups were integrated into the movable side of the grippers so the pressure exerted on the cases could be reduced. This protected the case and the product.

Mechanical fingers were used to secure the pallets and place them into position for loading. Pallet sensors were utilized for accurately locating the pallets for pickup. A tool for such a diverse multi-function application required significant design and testing. First, concepts were discussed and reviewed among key personnel. Then, general layouts were established for a second review. Once the general concept was approved, a three-dimensional (3D) image was prepared to ensure tolerances and clearances were within design parameters. Testing of the completed EOAT in a "production-like" environment completed the process before incorporating the machinery into the actual production cell.

In-mold labeling (IML) is a custom application for plastic injection molding where labels are placed into the mold each cycle and electro-statically held in place. The label gets molded to the plastic part so it never tears, peels, or fades. The benefits of the IML process are clear: in return for this type of automation, better looking products result, with secure labels. Automating the IML process is where cost justification comes into play. Eliminating operators who are just placing labels into injection molds is the goal of the EOAT. Labels must be precisely staged and then transferred (via a robot with the proper EOAT) into the mold in a repeatable manner.

Accurate label dispensers are critical to precise label placements inside the mold, which ensures an accurately placed label in the finished product. A well-designed label dispenser can maintain label orientation, dispense one label at a time, and hold enough labels to keep the process running for many hours without operator intervention.

A custom IML EOAT should provide a number of functions and capabilities, including:

1. Attach each label securely; 
2. Locate the label precisely in the mold; 
3. Secure the molded parts; and 
4. Perform with high repeatability.

In an IML application, additional cables must run through the robot cable tracks to transmit the charge from the charging unit to the charge applicators. If the charge applicators are located outside of the mold, then an IML EOAT must be equipped with a vacuum plate with an antistatic pad to keep the electrostatic field on the label. A low-cavitation, cost-effective IML process requires dependable EOAT and staging equipment, and preferably servo robots, along with good-quality labels.

The amount of movement that is required by a custom EOAT is also dependent on the type of robot being used. A Cartesian robot (normally a three- to four-axis system) will have more limitations than an articulating robot (normally a five- to six-axis system) with more robotic movement capability. For those instances when the robot and EOAT can be designed together, it is possible to reduce the costs of the robot by designing more movement capabilities into the custom EOAT.

A custom EOAT is a proven means for achieving greater flexibility and productivity from a robotic investment through increased efficiency and functionality. The best results for an automation project usually come from considering the type of EOAT and functionality required as early in the project's planning stages as possible.

A custom EOAT developed for insert mold labeling (IML) applications can repeatably and precisely position and secure labels to products.

Contact Information
SAS Automation, Xenia, OH
(937) 372-5255; www.sasgripper.com