Gripper consisting of suction
cups, pliers or finger assemblies are some of the most common end-of-arm (EOAT)
tools used in industrial robots. Choosing the right clamp is essential to
ensure economic and practical success in automation projects. After all, this
is where rubber hits the road. This article focuses on the technical factors to
consider when choosing the right clamp for application from a process and part
perspective.
The Process:-
What happens to the robot?
Automation projects are very different from each other.
Task itself:- The task that
the robot must perform often determines the type of clamp to be used. Very fast
loading / unloading requirements favor suction cups, but slower processes
prefer tweezers or fingers for greater accuracy.
Cycle time:- The cycle time is determined by the speed required to
hold and / or open and close the clamp. The cycle time determines the
acceleration of the clamp and, therefore, the force G, and the greater the
clamp, the more tension G is applied to the robot, which causes wear on the
part. The robot's specification for maximum acceleration is calculated as the
sum of the weight of the gripper and the part, so that the greater the weight
of the gripper, the lower the weight of the part being processed. In addition
to this specification, the EOAT range and weight determine the resulting torque
of the robot base. We will try again to minimize the weight of the clamp.
That's why many modern tweezers prefer to use hollow aluminum parts.
Precision demand:- Some assembly work requires precision, ideal for
mechanical gripper
operated by electric servo motor. The process of classifying parts requires the
adaptability of the clamp, in particular to allow the classification of
different parts of different size ranges.
Environmental requirements:- Not all types of gripper are available
for all processes. In the food and pharmaceutical industries, for example,
hydraulic clamps are prohibited due to the risk of oil spills and
contamination. In many cleanroom industries, pneumatic and vacuum clamps are
not recommended because they can produce a flow of airborne particles. The
clamps used in dirty environments, such as foundries, machining and welding,
are exposed to dust and particles and must be protected. Corrosive or toxic
environments in the nuclear or chemical industry create special considerations
to protect the clamp to ensure its stability and safety of use. In most
applications, the clamp must be a safety device. Dropping bananas on the floor
does not have a big impact, but spilling chemicals or radioactive substances
can sometimes be fatal or toxic.
Part:-
The knowledge of the parts to
manipulate is important to determine the clamp to use. The main factors are:
Size: Except for the vacuum grippers, all other grippers must grip
the pieces with parallel or angular closure. That is, the larger the part, the
more the clamp fingers must reach. In all cases, the clamp must have a
sufficient range to handle the piece, but the longer the finger, the more
torque the tool and the robot will have, so it should not be exceeded.
Shape: The shape of the object determines what type of object you
can grab. Flat surfaces can be treated with a vacuum clamp or magnet type,
other shapes with chin, claw or several fingers. When using a complete or
fingertip understanding, you should consider calculating the fingertips.
Weight: To maintain the grip strength, the clamp must be strong
enough to support the weight of the piece and the acceleration time it can
withstand during the process. The designer cannot simply use the maximum
clamping force, as the pieces or gripper can be damaged.
Type of surface: The type of surface on which the grip will occur
is also an important factor in estimating friction.
The calculation of the clamping force
must take into account the weight of the piece, the maximum acceleration during
the process, the friction of the surface and the maximum tension that the piece
and the clamp can withstand.
