Pick-and-place applications comprise both primary handling-putting individual pieces of product into a tray or carton-and case packing. Advances in materials of construction, controlling software and hardware, vision systems and other aspects have made robots, of various types, an increasingly viable option for pick-and-place.
The type of robot most appropriate for a given
pick-and-place application depends on the speed required, the size of the
payload and other factors. For most applications, only one type of robot will
be appropriate. But there are many borderline applications where more than one
type could be used, and the end user (or his/her system integrator) must
prioritize the factors.
One of the most significant developments in pick-and-place
robotics has been improvements in servo motor design. Today’s servo motors pack
more power into smaller sizes, maintaining or increasing output and payload
Another development is refinements to motion control
software and hardware. Motion control is the essence of robotics. It’s needed
to find objects, to guide the robot arm in picking them up and releasing them,
and to coordinate with equipment upstream and down.
In the past, operating a robot would have required
integration between the robot’s motion controller and the programmable logic
controllers (PLCs) that coordinate the robot’s actions with the rest of the
line. But the trend has been to combine those functions, as much as possible,
into common controllers. This eliminates software coding that would otherwise
have been required to coordinate the separate controllers.
Several kinds of robots can be used for upstream
• Delta-style robots that operate from overhead with three
or four long, thin arms that meet at the effector head;
• SCARA (selective compliant articulated robot arm) models,
which are fixed-base robots with three vertical-axis (horizontal-motion) rotary
• Multi-axis articulated robots, which can have up to six
axes, with joints that can rotate in any direction.
Choosing among these three kinds of robots depends largely
on speed and payload size. (The payload includes the weight of both the product
or package and the end-of-arm tooling needed to grip it.) Generally speaking,
delta-style robots go twice as fast as SCARA robots, which in turn go twice as
fast as six-axis articulated robots. Conversely, six-axis robots can handle the
heaviest payloads, followed by SCARA robots and delta-style models.
As with most aspects of packaging, end users want
pick-and-place to run as fast as possible. But some applications have practical
limitations. Fragile products like baked goods have to be handled gently, which
means slowing down.
Other applications have complex pattern requirements. When
objects are being deposited in single layers at a time, especially when they’re
relatively light, a delta robot arm can work fast. But in case packing or other
applications that require extra precision, delta robots may not have the
versatility to put the primary packages where they need to go. Articulated
robots can work better in such applications, because they can rotate what
they’re holding and also because they can pick up entire layers of primary
packages and drop them into cases.
Pick-and-place applications are fertile ground for robotic
equipment. As technology and other developments make such equipment
increasingly viable, end users who pick the right machines will find themselves
in a good place. F&BP
April 30, 2008