OCTOBER 2020 HEALTH & SAFETY
Cobots are
safer than
conventional
industrial robots,
but still pose a
signifi cant risk
cobot or recovering from an
emergency stop, there must be
an intentional act to enable the
robot. For example, when an
operator activates an e-stop, the
robot shouldn’t be able to reenable
automatically, but should
fi rst need verifi cation from a
second operator.
During the design and safety
setup, hand guiding must
only be allowed if the robot
has stopped, there has been
intentional mode selection and
speed and force monitoring
are active. If hand guiding
is activated without a stop
For maximum safety in
collaborative operations,
manufacturers must validate
the safety of their cobot
applications across all
operations. There are some
guidelines they can follow when
evaluating the safety of a robot
while performing a given task
with a human operator. Some
dangers, such as drive and
power hazards, might still exist
even if the robot isn’t moving.
Operator safety
To adequately protect
operators, before starting a
Specifi c considerations for safe cobot use
1Machine tending
Experts who have completed many inspections and safety
assessments report that machine tending applications are one of the
industry’s top safety concerns. For maximum safety, manufacturers
should use a safety-rated gripper to protect operators against injury.
They should also investigate whether the product presents any
dangers (such as extreme heat or sharp edges).
2 Material handling
Material handling applications that benefi t from cobots include
picking, packing, palletising and sorting. For safety considerations,
the wide use of these applications makes them a site-specifi c
solution. Operators and other workers often move or transport
other materials around the cobot, so additional planning is needed
to avoid hazardous contact.
Safety-rated grippers are currently rare: manufacturers tend
to use pneumatic grippers, with potential safety issues relating to
impacts and the loss of power or suction. Application designers
must also investigate whether the product presents any dangers
that could cause problems if it was dropped.
3 Assembly
command or safety input, this should initiate a
safety stop and fault.
For the automatic operation of a cobot,
the operator must make an intentional mode
selection that requires all safety devices and
conditions to be validated.
For validation, a safety assessment review
should be made of the surrounding areas and
equipment, and a safety remediation service
performed if necessary. Safety service groups
should make an onsite inspection of the safety
of equipment, confi rm certifi cations, verify
safety parameter settings and fi nally document
the completion of the validation.
Conclusion
Cobots are usually considered as safe for use with
people. However, they still need risk assessments
throughout to ensure the safety of human
operators. It’s vital for manufacturers to consider
all of the potential hazards associated with handguided
teaching, as well as possible issues when
the robot is involved in an emergency stop.
Designers of automated machine tooling,
material handling and assembly applications
should look at all of the interactions between
the cobot and the human operator, along with
the risks of clamping or entrapment, and the
dangers from end-of-arm tooling due to high heat,
sharp edges or other hazards.
In summary, manufacturers who want
a successful cobot application that will
boost effi ciency and productivity must
fi rst carry out a thorough risk
assessment, and then implement
any necessary safety measures.
Assembly applications that use cobots often involve special
tooling and close collaboration with operators while also requiring
high-speed operation zones. The extensive variety of custom
end-of-arm tooling makes these applications especially complex.
If multiple robots are involved, application designers must carefully
co-ordinate the safety solutions for each one.
For all three of the above areas, it’s very important to review the
entire area for the risk of an operator being trapped by the robot
and nearby equipment, and for any heavy or hazardous products.
Other considerations for all three areas include:
Should the safety controls of other machines be linked to
prevent one from operating when another is in a safety stop
condition?
As cobots can be moved from machine to machine and from
application to application, how is their safety validated?
Are there warning zones for the operator that indicate hazards
or operation interference?
www.manufacturingmanagement.co.uk 33
/www.manufacturingmanagement.co.uk