Robotics in the Workplace

Robots are machines that load and unload stock, assemble parts, transfer objects, or perform other tasks.
Add a note hereRobots are used for replacing humans who were performing unsafe, hazardous, highly repetitive, and unpleasant tasks. They are utilized to accomplish many different types of application functions such as material handling, assembly, arc welding, resistance welding, machine tool load/unload functions, painting/spraying, etc.

Add a note hereStudies in Sweden and Japan indicate that many robot accidents have not occurred under normal operating conditions but rather during programming, program touch-up, maintenance, repair, testing, setup, or adjustment. During many of these operations, the operator, programmer or corrective maintenance worker may temporarily be within the robot’s working envelope where unintended operations could result in injuries.

Add a note hereAll industrial robots are either servo or non-servo controlled. Servo robots are controlled through the use of sensors which are employed to continually monitor the robot’s axes for positional and velocity feedback information. This feedback information is compared on an on-going basis to pre-taught information which has been programmed and stored in the robot’s memory.

Add a note hereNon-servo robots do not have the feedback capability of monitoring the robot’s axes and velocity and comparing with a pre-taught program. Their axes are controlled through a system of mechanical stops and limit switches to control the robot’s movement.

Type of potential hazards

Add a note hereThe use of robotics in the workplace also can pose potential mechanical and human hazards.
Mechanical hazards
Add a note hereMechanical hazards might include workers colliding with equipment, being crushed, trapped by equipment, or being injured by falling equipment components. For example, a worker could collide with the robot’s arm or peripheral equipment as a result of unpredicted movements, component malfunctions, or unpredicted program changes.

Add a note hereA worker could be injured by being trapped between the robot’s arm and other peripheral equipment or being crushed by peripheral equipment as a result of being impacted by the robot into this equipment.
Add a note hereMechanical hazards also can result from the mechanical failure of components associated with the robot or its power source, drive components, tooling or end-effector, and/or peripheral equipment. The failure of gripper mechanisms with resultant release of parts, or the failure of end-effector power tools such as grinding wheels, buffing wheels, deburring tools, power screwdrivers, and nut runners are such hazards.
Human errors
Add a note hereHuman errors can result in hazards both to personnel and equipment. Errors in programming, interfacing peripheral equipment, connecting input/output sensors, can all result in unpredicted movement or action by the robot which can result in personnel injury or equipment breakage.

Add a note hereHuman errors in judgment result frequently from incorrectly activating the teach pendant or control panel. The greatest human judgment error results from becoming so familiar with the robot’s redundant motions that personnel are too trusting in assuming the nature of these motions and place themselves in hazardous positions while programming or performing maintenance within the robot’s work envelope.
Add a note hereRobots in the workplace are generally associated with the machine tools or process equipment. Robots are machines, and as such must be safeguarded in ways similar to those presented for any hazardous remotely controlled machine.

Add a note hereVarious techniques are available to prevent employee exposure to the hazards which can be imposed by robots. The most common technique is through the installation of perimeter guarding with interlocked gates. A critical parameter relates to the manner in which the interlocks function. Of major concern is whether the computer program, control circuit, or the primary power circuit, is interrupted when an interlock is activated. The various industry standards should be investigated for guidance; however, it is generally accepted that the primary motive power to the robot should be interrupted by the interlock.

Add a note hereThe ANSI safety standard for industrial robots, ANSI/RIA R15.06, is very informative and presents certain basic requirements for protecting the worker. However, when a robot is to be used in a workplace, the employer should accomplish a comprehensive operational safety/health hazard analysis and then devise and implement an effective safeguarding system which is fully responsive to the situation. (Various effective safeguarding techniques are described in ANSI B11.19.)

Add a note hereEssentially, robots perform work that would otherwise have to be done by an operator. They are best used in high-production processes requiring repeated routines where they prevent other hazards to employees. However, they may create hazards themselves, and if they do, appropriate guards must be used.
Add a note hereThe following figures show a type of robot in operation, the danger areas it can create, and an example of the kind of task (feeding a press) it can perform.

Figure 1: Robot movement capability


Figure 2: Potential danger areas in robot envelope


Figure 3: Using barrier guards to protect robot envelope 



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Slitters | Safeguarding for Specific Types of Machinery

Slitters use rotary knives to slit flat rolled metal, plastic film, paper, plastic, foam, and rubber as well as other coiled or sheet fed materials. Slitters range from small hand-fed paper slitters to large-scale automated metal slitters, complete with metal processing and handling units such as unwinders and rewinders. Both light and heavy gage slitters are available.
Slitter hazards
Add a note hereAmputations often occur when clothing or body parts come in contact with slitter blades or get caught in the movement of coils and rolls. Here are some example:
§  Add a note hereWorkers can inadvertently get their fingers and hands caught in the in-going nip points of the slitter or associated machinery such as rewinders.
§  Add a note hereGloves, jewelry, and loose clothing can get entangled in in-going nip points or in the rotary knives of the slitter.
§  Add a note hereWorkers can suffer an amputation when clearing, adjusting, cleaning, or servicing the slitter while it is either still operating, or shut off but still plugged in (energized).
Case History 
Add a note hereAn employee was feeding cardboard strips onto slit steel as it was being coiled on a slitter machine. While the machine was operating, the employee was placing the cardboard strips on the coils. After reaching over the steel strips, the coiled steel on the mandrel pulled his right arm into the machine and amputated it.
Add a note hereSource: OSHA IMIS Accident Investigation Database
Slitter machine safeguards
Add a note hereYou can use guards and other engineering controls such as the following:
§  Add a note hereInstall a fixed or adjustable point of operation guard at the in-feed and out-feed section of the machine.
§  Add a note hereInstall a fixed point of operation guard to cover the sides of the unwinder/rewinder to prevent an employee’s hands or clothing from entering into the rollers.
§  Add a note hereInstall fixed or interlocked guards to cover other moving parts of the machine such as the power transmission apparatus.
§  Add a note hereUse an awareness barrier guard with an interlocking gate around the perimeter of the machine to prevent unauthorized entry.
§  Add a note hereProvide guards for operator control stations to prevent inadvertent activation.
Work practice and administrative controls
Add a note hereYou can also implement work practices and administrative controls to help do the following:
§  Add a note hereDevelop and implement safe work procedures for machine operators and conduct periodic inspections to ensure compliance.
§  Add a note hereEnsure that all operators receive appropriate on-the-job training and supervision until they can work safely on their own.
§  Add a note hereInstruct employees to perform servicing and maintenance activities under an energy control program in §1910.147.

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Grinding machines | Safeguarding for Specific Types of Machinery

Grinding machines primarily alter the size, shape, and surface finish of metal by placing a workpiece against a rotating abrasive surface or wheel. Grinding machines may also be used for grinding glass, ceramics, plastics, and rubber. Examples of grinding machines include abrasive belt machines, abrasive cutoff machines, cylindrical grinders, centerless grinders, gear grinders, internal grinders, lapping machines, offhand grinders, surface grinders, swing frame grinders, and thread grinders.
Grinding machine hazards
Add a note hereAmputation injuries occur when the operator’s hands enter the point of operation during the following activities:
§  Add a note hereGrinding on the side of the wheel not designed for grinding.
§  Add a note hereUsing an inadequately guarded grinding wheel.
§  Add a note hereUsing an incorrectly adjusted or missing work rest or a poorly maintained or unbalanced abrasive wheel.
§  Add a note hereWedging a tool between the work rest and the abrasive wheel, causing the wheel to break into flying particles.
§  Add a note hereAdjusting the work rest, balancing the wheel, cleaning the area around the abrasive wheel, attempting to stop a rotating abrasive wheel by hand, and loading and unloading parts or measuring parts while the abrasive wheel is still rotating.
Case History 
Add a note hereAfter grinding a piece of steel on an offhand grinder, an employee turned off the machine and tried to stop the wheel with a piece of scrap steel. His hand slipped and hit the rotating abrasive wheel, amputating the tip of his left middle finger.
Grinding machines safeguards
Add a note hereYou can help prevent worker accidents and injuries by using guards and other engineering controls. Here are some examples:
§  Add a note hereInstall safety guards that cover the spindle end, nut, and flange projections or otherwise ensure adequate operator protection.
§  Add a note hereInstall adjustable and rigid work rests on offhand grinding machines.
§  Add a note hereInstall guards on foot-operated controls to prevent accidental activation.
§  Add a note hereInstruct operators to use hand tools to maintain a safe distance between the operator and the point of operation when needed.
Work practice and administrative controls
Add a note hereWork practices and administrative controls also are important. Here are some recommended ways to safeguard grinding machines by using the following controls:
§  Add a note hereDevelop and implement safe work practices for grinding machine operations and conduct periodic inspections to ensure compliance.
§  Add a note hereEnsure that all operators receive appropriate on-the-job training and supervision until they can work safely on their own.
§  Add a note hereInstruct operators to inspect the grinding wheel to ensure that it is not defective, unbalanced, loose, or too small.
§  Add a note hereInstruct operators to inspect the point of operation guard and to adjust it if necessary prior to each use.
§  Add a note hereInstruct operators to adjust the work rest to within 1/8 inch from the wheel.
§  Add a note hereInstruct employees not to wear gloves, jewelry, or loose-fitting clothing while operating grinding machines and to secure long hair in a net or cap.
§  Add a note hereInstruct employees to keep their hands as far away as possible from the point of operation while feeding work into an offhand grinder.
§  Add a note hereInstruct employees not to adjust the guard or clean the grinding machine while the abrasive wheel is still rotating.
§  Add a note hereInstruct employees to perform servicing and maintenance activities under an energy control program in §1910.147.

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