Tech Briefs Magazine - April 2021 - MD-4

Pneumatic Grippers
(90% of market)

Electric Grippers
(10% of market)

High grip force

Less grip force

Faster cycle rates

Slower cycle rates

Basic control (open/close)

Flexible control (position, speed, force)

Lighter weight (end of arm)

Heavier weight (motor, etc.)

Harsher environments (machining,
welding)

Cleaner environments (medical,
electronics)

Less expensive

More expensive

Comparing pneumatic and electric grippers.

Other factors to keep in mind include
up-front, operating, and maintenance
costs as well as energy consumption.
Grippers fall into several categories and
your answers to the above questions will
help you determine which type you need
to get the job done as safely and efficiently as possible.

Mechanical Grippers: Proven
Reliability, Flexibility, and
Durability
When it comes to handling applications, pneumatic or electric mechanical
grippers are the most common. Pneumatic grippers, which make up 90 percent of the market, tend to be more
lightweight and cost-effective than their
electric counterparts. They also feature
higher grip forces, can handle faster
cycle rates, and are more suitable for
harsh environments. Electric grippers,
on the other hand, offer greater precision, affording end users with force and
travel control. At the same time, they
tend to be heavier due to the presence of
a motor and other internal components,
which also drives up their up-front costs.

Whether electric or pneumatic, mechanical grippers fall into several design
classes. Parallel grippers, for example,
incorporate fingers that pull directly
apart. Two-finger designs are the most
common, making up 85 percent of the
mechanical gripper market, while threefinger designs are suitable for handling
round objects or performing centering
functions. Other examples include radial and angular grippers that feature fingers that open at an angle. Radial grippers open to 180 degrees, making them
suitable for applications involving varying or inconsistent workpiece sizes.
Angular grippers tend to be faster than
180-degree designs and open to roughly
30 degrees.
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

Robust parts with high friction

Slippery parts with more precision

for bulky or robust parts, while encapsulated designs work best for slippery parts
requiring more precision.
Soft 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 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, soft and mechanical grippers
are less precise and operate at slower
speeds. They are also more susceptible
to dirt, oil, and other contaminants.
Oftentimes, soft and adaptive grippers
incorporate innovative, tweezer-like designs that can adapt to the contours of
various workpieces.

Reap the Benefits of
Compressed Air with Vacuum
Grippers
Another gripper technology is the vacuum gripper, which combines suction
cups and vacuum generators. Compact
and flexible, these grippers are ideal for
limited workspaces and can handle a
variety of objects at high speeds. At the
same time, however, vacuum grippers
can run up your maintenance and operating costs; suction cups are susceptible
to quick wear, while generators consume
high rates of compressed air and can
easily clog in the presence of dust and
other contaminants.
When it comes to suction cups, it's
important to consider the nature of
your workpiece when selecting a material. Buna suction cups, for example,
are ideal for oily or plain workpieces,
while silicon is suitable for food as well
as hot or cold objects. In addition,
polyurethane is a good choice for oily,

Delicate parts

Figure 2. Comparing the designs of three gripper fingers.

Motion Design, April 2021

Cov

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http://www.abpi.net/ntbpdfclicks/l.php?202104TBNAV

Tech Briefs Magazine - April 2021

Table of Contents for the Digital Edition of Tech Briefs Magazine - April 2021