Tips of the trade: Top EOAT tips for difficult-to-handle partsTips of the trade: Top EOAT tips for difficult-to-handle parts
The successful automated handling and manipulation of irregular or difficult-to-handle parts can significantly increase bottom line profits. By elimination of high-cost labor, operator error, and increased efficiencies, many robotic cells can produce paybacks quickly, even in six months or better. Thanks to John Westbeld, engineering manager at SAS Automation (Stand 10/F19 at the K), a leading supplier of EOAT, for offering these tips.
August 31, 2010
(Editor’s note: The K show approaches, fiscal years are closing and budgets are being prepared; as a result of all of these, plus a broad economic recovery, capital investment is on the minds of many processors. We have asked experts from some of the industry’s leading suppliers to offer their tips on what processors should consider as they buy new equipment or upgrade their current equipment. Thanks to John Westbeld, engineering manager at SAS Automation (Stand 10/F19 at the K), a leading supplier of EOAT, for offering these tips. Have your own Tips of the Trade? Willing to share them? Contact us at [email protected].)
The success of handling irregular parts depends upon the consistency of the parts to be presented to the robot in a repeatable fashion, the repeatability of the robot, and the end-of-arm tool (EOAT).
More times than not if there are going to be inconsistencies in the system, it will be with the EOAT because it is designed with the robotic limitations in mind and it interfaces with the parts. For EOAT to secure, manipulate, and deposit irregular parts effectively, consider these tips.
1. Understand the Process
To find standard grippers or vacuum systems to secure irregular parts with accuracy can be difficult. However, if you understand the process and desired outcome you can choose a part securing method that best suits your needs and helps integrate more operations into the cell. EOAT can be very versatile and can assist in cost saving assembly, deburring, machining, and packaging.
2. Know Robot Specifications & Limitations
By giving the robot company or robotic integrator thorough information on the objectives of the robot cell they can select a robot with appropriate specifications. Once the robot is chosen with the desired specifications you can begin defining the limitations of the system. From the robot specifications you can determine the repeatability, speed, work envelope, and interfaces of the robot. The repeatability will help you decide whether you need to physically locate your EOAT in the fixturing or nesting to secure the small parts within the acceptable tolerance. The given cycle time and speed of the robot lets you determine how quickly you need to secure the parts. Knowing the reach of the robot lets you determine the framework of the EOAT. The robot mechanical, electrical, and pneumatic interfaces – all affect the EOAT design.
3. Method for Securing the Parts
Securing the irregular parts with the EOAT can be difficult due to the size of the parts and the small tolerances with which the parts need to be manipulated so intricate tasks may be performed on the parts. Vacuum cups or vacuum nests can be one of the most cost effective alternatives to securing parts with reasonable accuracy. A vacuum generator will have to be incorporated into the design of the valve package to create the vacuum.
Conventional grippers can also be used to secure the small parts and usually provide excellent repeatability. Custom jaws are usually machined to interface with the parts. Grippers are usually more repeatable than vacuum systems and are typically more expensive.
An internal diameter gripper is ideal for bottles or other irregular shapes.
Other molding processes such as insert molding, overmolding and inmold labeling present difficulties in maintaining the required placement precision. The use of spring-loaded docking pins, which come in custom lengths, strokes, and diameters, provide the assurance required in complex and low tolerance applications.
4. Part Presence
The success of any robot cell is defined by the consistency with which the desired result is achieved. By knowing the status of the parts throughout the process you know that the desired operations are being performed. This can be achieved with sensors designed into the EOAT to ensure the processes are complete.
5. Compact Wiring
Small parts can also be difficult to handle and usually require small EOAT. Having a junction board that is small and multi-functional helps keep the EOAT small and compact. Junction boards that can take various types of sensors (PNP, NPN, or dry contact), put them in series, and convert the logic to the robot specifications will keep the wiring and EOAT compact.
6. Robotic Valve Package
Once the EOAT has been conceptualized, consider the valve package for the robot. Most articulating robots do not come with a standard valve package. The valve package will contain valves, vacuum generators, and junction boards that will interface the robot and EOAT. Quick disconnect plugs should be used to facilitate maintenance and troubleshooting.
7. What Types of EOAT
EOAT can basically be defined as modular or fixed. Modular EOAT can be quicker to assemble, more cost effective, adjustable, and easier to supply with spare parts. Fixed EOAT eliminates adjustability, which is desirable for relocation of spare parts. Replacement parts usually need to be machined so duplicate EOAT are often needed to eliminate costly downtime.
8. What’s in the Budget?
EOAT is usually the least expensive part of the robot cell, yet your robot is only as good as your EOAT. Even though EOAT is typically the last thing designed (and the budget has already been spent), skimping on EOAT components will hamper the costly robot’s ability to hold, manage, and manipulate your small parts.
9. Maintenance and Spare Parts
Regular maintenance and spare parts will reduce downtime. Regular maintenance of the EOAT and valve package will keep the system running smoothly especially in harsh environments. Usually this is limited to keeping dust and build-up off of the moving parts and keeping proper lubrication levels. Having spare parts of the actuating components on hand can save several days of downtime waiting for parts.
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