Delta Robots Improve Highly Repetitive Tasks
What is a "Delta Robot?"
A delta robot is a parallel-link
robot in which its major mechanical axes act on the robot faceplate in parallel
rather than in series. This allows for both quick and precise movements.
History of the Delta Robot
Since its invention in the early 1980s, the delta robot
has evolved into an
innovative and high-speed solution for a wide range of assembly, picking,
and material handling applications.
With a three-axis delta robot, each axis
is connected directly to the faceplate. The movement of these three axes (either
one or a combination of all three) will move the faceplate in Cartesian coordinates.
Optionally, a fourth axis can be directly connected to the faceplate to
generate rotation. Because each axis only needs to accelerate the faceplate,
significantly higher acceleration rates occur. This can notably reduce cycle
times compared to a serial-link robot. Top speeds of 10 meters per second
are typical for most delta robots.
In addition to high speed performance,
a parallel-link robot provides improved repeatability at the tool tip. This
means that highly reiterative tasks such as in solar cell or other small part
assembly, can be completed quickly and perfectly every time.
Three- and four-axis delta robots were initially deployed in limited
picking and packaging industries. In these industries, products might be
picked at random from fixed tooling and packaged into a shipping box, carton,
or other type of container. These tasks can also be accomplished efficiently
when several delta robots are used in one large picking and packing system which can handle an overall system throughput of several hundred parts per
minute. Many different industries such as food, medical, electronics, cosmetics,
and so forth, now make use of picking and packing systems.
Delta robots are now being used extensively in assembly or other applications
in which high-speed and repetition must be achieved simultaneously. In many
cases, these processes are done manually and can cause repetitive strain injuries
or MSDs (musculoskeletal disorders). The U.S. Department of Labor, Occupational
Safety and Health Administration (OSHA) reports that, “According
to the Bureau of Labor Statistics, MSDs accounted for 28 percent of all reported
workplace injuries and illnesses requiring time away from work in 2009. (1)”
Injuries, time away from work, and workers' compensation claims can cost companies
billions. Incorporating robots into processes improves employees' quality
of life, in addition to being a cost savings for employers.
FANUC M-1iA Delta Robot
FANUC America offers two variations of delta robots: the M-1iA and the M-3iA.
The FANUC M-1iA is a lightweight and compact
parallel-link robot designed specifically for small part handling, high-speed
picking, packing, and assembly applications. Its very slim footprint and
envelope allow it to be installed next to a manual operation with minimal
FANUC M-3iA Delta Robot
The FANUC M-3iA offers the same unique
parallel-link structure and moderate footprint, and accommodates payloads
up to 6kg. In addition, it has the largest work envelope of any robot in
its class (1350mm x 500mm). Compared with most delta robots that are limited
to either three or four-axes, the FANUC M-1iA
and M-3iA are available in both four- and
Several M-3iA robots have recently
been installed in industries including automotive engine facilities, and baking
factories where they are used to score un-baked bread. The six-axis variant
allows for the completion of tasks which involve manipulating parts and/or
tooling at compound angles. By combining a three-axis wrist with the speed
and precision of a delta robot, and the integrated iRVision
offered by all FANUC robots, FANUC America is rapidly making possible the
automation of many tasks which are now either manual or done by expensive
hard automation. With food, this can mean random-oriented, uniform or non-uniform
products that may be fragile to the touch. A Senior Account Manager at FANUC
Robotics notes that “a lot of existing processes are predicated on manual
labor. It’s difficult for hard automation to mimic hand/eye coordination
in picking random product off of a conveyor, particularly if it’s fragile
and can’t be mashed into a corner or some other location where a hard-automation
device can pick it. This is where robots come in.” Some examples of
these applications are sorting cookies into containers, or pill or candy identification
M-3iA Picking and Sorting Cookies [VIDEO]
A food option is available with the M-3iA
in which food-grade grease is used. The robot features a special coating to
handle acid and alkaline disinfectants, and low-pressure rinsing. The M-3iA can work with primary (unpackaged) or secondary
(packaged) food products, and has an IP67 rating for the entire robot which
means it is waterproof and can withstand harsh environments, including dust
and oil mist. Most robots designed for the food market feature an IP67 rating
for the entire robot. IP ratings are a part of international IEC (International
Electrotechnical Commission) standards, known as “intrusion protection”
ratings. An IP rating of 67 means complete protection against any ingress
of dust (specified by the first digit) and the ability to be completely immersed
in water with no ingress of water (specified by the second digit). Food grade
robots also have smooth external surface finishes meaning that there are no
retention areas for food particles or bacteria.
Both force control and machine vision are becoming more and more prevalent
as part of intelligent industrial robot systems, especially in high-speed
assembly operations. Remote force sensing is now used to accomplish difficult
assembly applications quickly using six axis delta robots. By remote mounting
the force sensor, small six-axis delta robots are able to make use of this
In an ideal world, parts line up and fit perfectly. However, in the
real world workpieces often require a wiggle or visual adjustment, or are
randomly presented. Machine vision and force control are increasingly able
to handle these challenges and, when combined with a delta-style robot, the
cycle time of each operation falls dramatically. This reduces the number
of robots required and improves the return on investment timeline! Machine
vision is increasingly used for inspection either before a part is put into
an assembly or after the assembly process is completed, and delta robots can
make this process quicker and more cost effective. How? By mounting a moveable
camera on a delta robot, parts can be inspected very quickly and bad parts
and/or assemblies can be eliminated and kept out of the supply chain. This
keeps costs down and increases throughput. In picking applications for example,
machine vision is employed in conjunction with conveyor tracking to track
a randomly located product accurately on a moving conveyor belt at speeds
as high 1400 mm/sec (275 ft/min).
The machine vision camera will continually snap and locate product upstream
of the delta robots. When a product is identified by the camera, its location
is combined with the current position of the conveyor belt. As the product
enters a robot work area, the robot is able to move to the product precisely
and either pick it or work on it while matching the current conveyor speed.
Delta robots are the preferred style for this type of application since the
amount of time the robot deals with each product needs to be as short as possible
in order to maintain the usually very high system throughput. With assembly
applications, the same concept is applied where machine vision is used in
conjunction with a delta robot to locate and pick a specific part on a flexible
feeding conveyor and assemble it to a mating workpiece.
Sorting Cookies Using iRVision
Like all robots, delta robot deployments will continue to see strong
growth as more and more operations across all industries embrace automation
as a way to cut costs and stay competitive. When light payloads and very
fast cycle times are required (especially in small work areas), whether it
is assembly, picking, dispensing, or any number of other applications, delta
robots will continue to meet the challenge.
Delta Robot Example Applications
A FANUC M-1iA high speed parallel link robot and an LR Mate
200iC robot can be used to assemble and
disassemble solar panels. The M-1iA robot,
equipped with iRVision® Visual Tracking, can pick randomly located solar cells and form an array of solar cells on
an outbound conveyor.
Random Solar Cell Part Feeding Using iRVision
M-1iA Placing Solar Panels on an
Three M-3iA robots placed in series
and shown below, are used to pick vegetable bags from a conveyor, and place
them into cartons. Suction cups are used to pick up the product efficiently,
and without product damage.
Three M-3iAs Sorting Boxes
iRVision is used in the following
simulation to pick parts randomly placed on a conveyor, and place them on
an outbound conveyor.
M-3iA Picking Random Parts
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(1) U.S. Department of Labor, Occupational Safety & Health Administration website, http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=NEWS_RELEASES&p_id=19158, accessed 2/22/2011.