Fluid Power Journal

Flexibility in Gripper Selection

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With an increasing breadth of variations in today’s applications for automation, and due to part and space constraints, it is good to have options when it comes to selecting the best gripper for an application. SCHUNK addresses this issue with flexible gripper families and different options to fit applications that don’t compromise design. The PGN-plus and PZN-plus families provide almost 180 different stroke and grip-force combinations, as well as five different sensing methods, along with several other standard options for different application environments.

Universal Gripper Families

The SCHUNK universal gripper families are available in 2-finger types: PWG-plus, JGP, PGN-plus, DPG-plus, and 3-finger concentric types: JGZ, PZN-plus, DPZ-plus. These grippers offer product advantages, such as high grip force-to-size ratio; robust guidance for high-moment loads and long finger lengths; excellent repeatability; and multiple sizes, versions, and accessories.

Even though they share many of these benefits in varying degrees, each family has its own main focus. The PWG-plus is a 2-finger angular gripper family that offers an excellent price-to-performance ratio. The 2-finger parallel JGP and 3-finger concentric JGZ families offer T-slot guidance gripper for high-moment loads and provide great performance at a reasonable cost. The PGN-plus and PZN-plus families are a step up from the JGP and JGZ, and are recognized as the most popular of the SCHUNK universal gripper families. They supply multi-toothed guidance with the most flexibility and options for accessories. The DPG-plus and DPZ-plus are sealed grippers, based on the guidance of the PGN-plus family, and provide complete protection in harsh environments. All the universal families have identical gripper mounting.

Stroke and Grip Force

In applications with restrictions on the size or weight of the tooling, the size of the gripper can be reduced by selecting an option that will increase the grip force of the end effector. This provides the advantage of using a smaller component, reducing the overall weight of the tooling. Using a universal PGN-plus or PZN-plus gripper with a spring housing (AS/IS), wedge angle (stroke 1/2), or a double piston (KVZ) could provide as many as ten different grip forces and strokes. To further increase the flexibility, any combination of these three options can be used.

Sensors

schunk1In most applications, gripper feedback is desired, such as “part-present”, “open,” “closed,” or additional feedback. The universal gripper families offer five options: magnetic sensors (MMS), inductive sensors (INW), five-position magnetic sensors (FPS), analog positioning (APS), and force sensor (FMS).

For sensing the “open”, “closed,” or “part-present” position, the magnetic and inductive sensors are perfect. If more flexibility is desired, the five-position magnetic sensor allows the ability to sense “open”, “closed,” and up to three different finger positions. This option is needed, for example, when handling different work pieces with no additional set-up. Taking it one step further, an analog sensor provides the ability to measure the position of the gripper jaws and actually gauge the gripped parts. The force sensor allows measurement and control of the grip force applied to the part.

Even more options

To further increase the flexibility of the gripper are accessories like quick-change fingers (BSWS) and finger blanks (ABR/SBR) to provide a head start on finger design and manufacturing. For applications with varying part dimensions, the quick-change fingers quickly adapt the gripper to different work pieces without changing the entire end effector. Additional standard options include Viton seals, anti-corrosive versions, dust covers (SAD), PVC protective boots (HUE), and safety devices to maintain grip force if air pressure is lost (SDV-P). The Viton seals will come into action for high-temperature environments, while the dust covers, PVC covers, and anti-corrosive versions protect against other environmental concerns that would normally reduce a gripper’s cycle life.

With the universal gripper families, there are hundreds of standard options available to fit any application requirements, such as high temperature, long stroke, and high grip forces. They are sealed for applications requiring up to IP67.

For more information: Contact SCHUNK by 800-772-4865 or visit www.schunk.com.

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