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Safe keeping

Considerations to provide a good foundation for tooling safety

Fanuc Image 1
Two material handling robots are manipulating tooling and the part into proper position for two arc welding robots. By having the robots manipulate the tooling and part, you can achieve greater flexibility in positioning compared to a positioner with one or two axes of rotation.

Regardless of the application, one piece of equipment that can easily be overlooked when investigating safety hazards is tooling. Typically, risk assessments look at automation as a whole, but may overlook the role of the tooling independently.

The same is true for risk assessments of manual stations. They may look at the load and unload procedures and the worker’s body position relative to the workpiece, but not at the tooling itself as a hazard.

When taking an objective look at tooling as part of a risk assessment, there are three considerations to start with that will provide a good foundation. These considerations are potential energy, kinetic energy and work area conditions.

Potential energy

Potential energy is the energy an object has due to its position or the configuration of its components. As a part increases in size, so does the possibility of increasing its potential energy.

In the welding industry, large parts are often placed into various positioners so that the part can be manipulated to utilize gravity and make it easier to perform various welds. The obvious danger here is the part falling out of the fixture. Smaller, lighter weight parts, such as a push mower, may be able to be held firmly in place with pneumatic clamping. However, a bulldozer frame requires a heavier duty clamping system and may rely on hydraulics to keep it in place. Both methods are suitable as long as the clamping pressure is adequate for the size and weight of the part.

Fanuc Image 2
Arc welding robots welding front bumpers for vehicles. Notice the orange covers over the hoses and wires to protect them from spatter, dust and fluids.

Once you have decided on a clamping medium (air or hydraulic), you have to regard the risks associated with it. First, consider a total loss of pressure. Fortunately, there are a couple of ways to combat a slow loss of pressure. One is to add an accumulator to the system to maintain a set amount of pressure. This can be done for both pneumatic and hydraulic systems. In addition, some hydraulic cylinders and clamps offer a locking mechanism that locks the device in its current position when it encounters a loss of pressure, therefore keeping a heavy part from falling out when rotated.

Another way to combat the possibility of the part coming out is to install an inline pressure monitor to monitor the pressure to verify the system’s integrity before allowing the tooling to be rotated. You may also want to install a monitoring system that checks the clamp placement prior to rotation to ensure all of the clamps reached their intended destination. Multiple manufacturers offer this type of “check” built directly into their clamping mechanisms.

Another risk associated with clamping is leaks. In a welding application, an air leak may be strong enough to disrupt the shielding gas and cause significant weld defects. With a high-pressure hydraulic leak in a welding application, there used to be a good chance of having a pretty fierce fire. But several innovations have been born out of such incidents and hydraulic fluid that is non-flammable is now available.

A cost-effective means to minimize the risk of a leak in either type of system due to sparks from welding or cutting is to buy heavy-duty welding-specific hoses or covers designed for welding and cutting to put over the wires and hoses. If you decide to use covers, you have the added benefit of being able to easily service the hoses because they will not have weld spatter, grinding dust and fluids built up on them.

Kinetic energy

Fanuc Image 3
Arc welding robots welding a stainless steel toolbox. Notice the plastic wrap protecting the vision cables and the robot weld torch power cable is enclosed in black tubing.

Kinetic energy is the energy of an object due to its motion. Again, if the tooling requires either manual or automatic manipulation, you must examine the kinetic energy of that tooling.

For instance, for a manual station that is rotated parallel to the floor, you need to make sure that tooling is balanced properly for all of the parts that will be run across it. If you balance the tool for a 50-lb. part and put in a 150-lb. part, the tool may rotate uncontrollably and possibly injure the worker.

Most manual tools have a spring-loaded plunger that is forced into one of multiple holes to help prevent freewheeling and also to lock the positioner into place to optimize the part for the process being done.

If you are working with automated tooling and have small parts, they can be manipulated rather quickly. If you have a tooling failure before or during this part manipulation, a part could be thrown out of the cell and into an area filled with people. So, in addition to the various tooling checks mentioned previously, you may have to install fencing around the cell to contain any mishaps, or hang curtains from the ceiling if your floor cannot afford the footprint.

Work area

The third consideration is the work area where the tooling will be placed. There are probably more hidden dangers in this consideration than in the other two combined.

First, investigate the accessibility of the tooling. For a very tall part, for example, you may look at adding a step stool, ladder or platform to help the worker reach the part. With any of these options, you have to think about a place to store that hardware when it is not being used.

Fanuc Image 4
In this automotive supplier robot line, multiple layers of safety are shown, from the fencing and hanging curtains to the protective hose covers and cable trays.

Questions you should ask yourself include:

Is this hardware going to be tall enough to reach the highest point on a part but still be useful for something much lower?

Will it have to be moved out of the work envelope every time you rotate the tooling so that new expensive industrial ladder doesn’t get crushed?

Is the portable step stool stable when the worker is on top and leaning over the tooling toward the center of the part?

Will you be able to clean and service your tooling where this additional hardware is stored or used?

After answering these questions, you may find it more efficient to enhance the tooling so that it can be raised and lowered as well as rotated to gain access to all those various heights.

Lighting of the work area is very important. When you mention the word factory to the general public, they envision a dark, dirty atmosphere filled with people and machines in constant motion. By having the proper lighting for the task at hand, you will improve the quality of the product because defects will be easier to identify. You also will improve the safety of the work area because hazards will be easier to identify. A bonus effect of proper lighting is a more enjoyable work area because workers will feel like they are in a cleaner, safer environment.

Investigate the floor conditions of the work area, as well. If the floor has cracks and chips and workers are required to push carts of various sizes in and out of the area, they could be injured if the cart flips over or incur back injuries from the strain of trying to overcome flooring obstacles.

A painted floor may help reflect more light to brighten the area, but it may also present a slipping hazard when liquids are spilled. Numerous coatings are available that have a textured consistency so that even when wet they still provide adequate traction. If you perform welding, grinding, carbon arc gouging or polishing, you may have a residue buildup on the floor that also makes it slippery. This can be addressed with mats, grating or something as simple as a broom and dustpan. Also, while performing these operations, consider the path trajectory of any debris to make sure it doesn’t go into walkways or adjacent work centers.

You may need to increase the frequency of preventive maintenance to ensure the buildup of this debris does not clog filters or short out electrical circuits.

Finally, examine the air quality of the work area. Multiple fume extraction devices are on the market that will improve the working conditions of the immediate work area and also improve the air quality of the surrounding areas.

Fanuc America Corp.