Seen at IMTS: Universal Gripper Simplifies Robotic Part Removal

Robotic automation is becoming essential to machining operations for the benefits it provides in productivity, quality, and economy. At last week's International Manufacturing Technology Show (IMTS) robots were everywhere - not only in the booths of automation suppliers but on display alongside machining systems and other production equipment. They were certainly more numerous than at the last IMTS in 2012.

One point to emerge from IMTS is that shop owners don't need to make major investments to acquire and use robots, whether they are for loading or unloading workpieces, pick-and-place operations, or other machining or work cell functions. As noted before, some robot suppliers offer cost-effective, easy-to-program systems that reportedly provide fast payback.

The Versaball robot gripper can lift any object shape. Credit: Empire Robotics The Versaball robot gripper can lift any object shape. Credit: Empire Robotics

The latest enhancement for these low-cost robots (and even high-end versions) is a cost-effective universal gripping system from Empire Robotics, based in Boston. The two-year-old company licensed gripping technology from developers at two universities, Cornell University and the University of Chicago, and commercialized it in a product called Versaball. The U.S. Defense Advanced Research Projects Agency and iRobot Corp. also contributed to research and development.

Versaball looks unlike any robot gripper on the market. Its operation is simple and easy to grasp. The device consists of a balloon-like polyurethane (PUR) head loaded with sub-millimeter granular particles, says John Amend, chief technology officer, who helped develop the system while in a doctoral program at Cornell University.

The gripper uses "jamming phase transition of granular materials" to lift objects. Here is how it works. Air is injected into the granulate-loaded PUR head to soften it. The gripper, attached to a robot arm, is then pressed against an object to be moved. The softened external surface wraps around the object at the point of contact. When this happens a vacuum is automatically pulled, causing the granular material to become dense - the jamming phase transition - and exert a "distributed pinch force," as Amend describes it, along the object to hold it in place.

The robot can then move the object. The process is fast, repeatable, and can be used with different-shaped objects - all the gripper has to do is make contact with an object, form around its shape, and pull a vacuum and lift it. To release an object, the PUR head reinflates, which loosens the grip of the granular material. (A video of the gripper in operation can be seen at www.empirerobotics.com.)

Importantly, the gripper has infinite degrees of freedom, and unlike multi-fingered grippers on conventional robots, it does not need tactile sensing, computer vision, and other advanced controls for accurate, repeatable operation.

The PUR head mounts to a pneumatic base plate, which in turn connects to an adapter. The adapter attaches to the robot arm and is compatible with almost any robot. Shop air for inflation is supplied through the base plate. A solenoid valve controls the inflation and vacuum sequences. The gripper lifts and moves objects weighing 20 lb, Amend says.

Three versions are available. The initial offering, called the Research Kit, contains a 6.5- and 3.5-in-dia Versaball head, along with a pneumatic base and adapter plate, for testing and evaluation. The Commercial Installation version comes with pre-installation testing and grip-optimization services and other support from the company. The Custom Application version features heads and components that can be tailored for special needs.

Amend says the Research Kit costs around $3,950, while the Commercial Installation model is in the $4,000 to $5,000 range including setup. Head replacements average $100 to $200 apiece. Each inflatable head is good for about 60,000 grips, he adds, though that depends on the objects being moved and the amount of system tailoring done.

At IMTS, the gripper was demonstrated on a UR5 six-axis robot from Universal Robots.

Information on the technology first appeared in a technical paper four years ago in the Proceedings of the National Academy of Sciences of the United States of America (Nov. 2, 2010). The eight authors, including Amend, described work with the gripper using ground coffee as the granular material. (Amend declines to identify the current material.)

In the paper the researchers report that a vacuum-induced volume change of less than 0.5 percent is enough "to grip objects reliably and hold them with forces exceeding many times their weight."

The work was focused on gripping objects rather than manipulating them, and sought to "offload system complexities" with the design.

 

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