The enduring use of pneumatic grippers

In two previous articles, we detailed example integrations of motion control and robotics as well as peripheral motion systems that complement robotics.  In fact, end effectors are another motion design for robotic workcells. The Design World library has more information on end-of-arm tooling (EOAT) such as process tools (for welding, for example) and inspection sensors that aren’t grippers. Here, we’re just going to talk about grippers.

PHD Inc. supplies gripping, clamping, and work-holding end effectors. The rod feeder shown above is a custom solution for machine tending.

Mechanical jaw grippers driven pneumatically or electrically are indispensable and ubiquitous. These include parallel grippers, three-finger grippers, and angled-finger grippers. Permanent-magnet and electromagnet-based end effectors handle ferrous parts for the machine-tool industry. Stampings and castings are often best handled with magnetic grippers, especially if they have an odd shape or going to be oily. Other grippers are needle, Bernoulli air levitation, and internal-diameter expanding-donut grippers for niche applications in textiles, porous materials, fragile surfaces, or bore handling.

From sister brand pneumatictips.com: Pneumatic grippers news
From The Robot Report archives: End effectors and industrial grippers
Design World robotics and end-effectors news

Finally, robotic tool changers as well as rotating multi-tool end effectors are useful where arms serve multiple functions. For the latter, end effectors rigidly mount to the arm at different offsets from center. Rotating between them lets the arm perform different functions — sometimes with only slight compromise in overall reach.

So-called adaptive grippers include parallel grippers with proprietary variations (as the one above from Robotiq) serving multiple functions and handling multiple SKUs:

“Adaptive” can also imply some kind of software with machine learning … or that the gripper hardware itself is compliant as shown in the example below from Festo.

In fact, fluid power is featured in many cutting-edge soft robotic grippers. Some of these have adaptive elastomer fingers that are pneumatically actuated to carefully conform to irregularly shaped consumer goods, easily bruised food items, and delicate life-science components without any especially complex programming.

We at Design World often discuss with our Fluid Power World colleagues the choice between electric and pneumatic solutions. Bottom line? Some fluid-power technologies will never be displaced. According to current market research on industrial robot grippers, those that are pneumatically driven constitute 16% of all units procured annually. Other sources report pneumatics are about 37% of the robot-gripper market by revenue. These numbers illustrate just how much the low upfront cost and dead-simple operation of pneumatics keep them extremely relevant.

Other fluid-power end effectors include vacuum grippers featuring suction cups or foam pads to grip workpieces. These dominate packaging, palletizing, food handling, and sheet-material handling. That’s because they’re mechanically simple, tolerate workpiece variations, and are fast. Of course, the workpieces need to be solid and rigid to allow for the formation of suction.

Some advancements for pneumatic grippers aim to boost efficiency (and address the most common knock against fluid power) or improve supply arrangements. For example:

• The servo-actuated ERVG vacuum generator we see here from PHD Inc. electrically generates on-demand vacuum for suction cups and vacuum pickups. Servo-driven pistons extend and retract to rarefy the connected air volume. That yields efficiency better than that of pneumatically powered Venturi vacuum generators.

• ERPP pneumatic pumps are point-of-use compressed air sources with servo-driven pistons that fill an accumulator to automatically maintain air.

• The servo-actuated ERDP remote drive we see here electrifies pneumatic actuators in a closed-loop system via standard air lines to one or more actuators. The power system installs near the point of use and imparts significant energy savings over other compressed-air systems.