Automation Canada - Automation in 2021 - 5

Robust parts with
high friction
Slippery parts with
more precision
Delicate parts
Comparing the designs of three gripper fingers.
Other important considerations when selecting your mechanical
gripper include the gripping force, the guiding strength of the jaws and
the design of the gripper itself-all of which depend on the nature of
your workpiece. In general, the longer the gripper fingers, the longer
the lever arm, which exerts more torque on the jaws. In addition, flat
finger designs provide a friction-based grip for bulky or robust parts,
while encapsulated designs work best for slippery parts requiring more
precision.
We can apply many of these principles to a recent application
example, which involved selecting a gripper for a food processing
application. The grippers had to pick up large trays with dried pasta,
rotate the trays to dump the pasta onto a conveyor belt and then return
the trays to their stack. The trays were large, roughly 4 x 2 feet. They
were also made of metal and weighed 15 pounds each. Other
important considerations included:
* Environmental. The grippers would operate at room.
temperature. The air was dry but contained some dust from the
pasta.
* Design constraints. The gripper had to be able to handle high
forces, as heavy trays had to be rotated and shaken frequently.
To meet these requirements, we recommended four heavy-duty
HGPT mechanical grippers. Thanks to their oval-shaped piston, they
provide up to 30-percent more gripping force for heavy objects. They
also include sealing air ports, preventing pasta particles from entering
the gripper jaw guide. (For more information about our HGPT, see our
sidebar.).
CANADIAN AUTOMATION
Enabling New Automation With Soſt and Adaptive Grippers
Soſt and adaptive grippers can handle workpieces of various shapes,
sizes and orientations, enabling automation in areas where it previously
didn't exist. Because they don't have any sharp edges, these types can
handle food, glass and other delicate objects without damaging or
marking the surface. They're also ideal for small work areas. Compared
to mechanical variants, however, soſt and mechanical grippers are less
precise and operate at slower speeds. They are also more susceptible
to dirt, oil and other contaminants.
Oſtentimes, soſt and adaptive grippers incorporate innovative,
that can adapt to the contours of various
tweezer-like designs
workpieces. For example, the Festo DHAS features our Fin Ray®
structure, derived from the movement of a fish tail. Two flexible bands,
which meet at the top like a triangle, are connected by ribs. Using flex
hinges, these ribs are spaced at regular intervals, creating a flexible, yet
sturdy joint connection. Available in lengths of 60, 80 and 120
millimeters, this series is ideal for pick-and-place applications involving
fragile or irregularly shaped parts. It also incorporates materials that
comply with FDA standards, making them a good fit for the food and
beverage industry.
The Parallel HGPT Mechanical Gripper
One example of a robust mechanical
gripper is the Festo HGPT. Ideal for dynamic
motion applications involving medium-size
workpieces, this series incorporates a T-slot
guiding design that resists torque. It also
incorporates a sealing air port to prevent
particles, dust and other contaminants from
entering the gripper jaws. And thanks to its
oval piston, the HGPT gripper maximizes
gripping force, providing double the force
for half the stroke length.
The Festo HGPT.
VOLUME 3, ISSUE 4
5
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