Machine Guards

Machine guarding does more then protect employees from physical harm; it also controls traffic, keeps vehicles out of certain areas and contains flying debris. Because of the vast dangers of certain machinery, machine guards are regulated by OSHA standards, to ensure that every worker is protected by a product sound and strong. Machine guards are mostly used in factories, manufacturing facilities, warehouses and plants and come in many different sizes and configurations. Some are specifically meant to encase certain types of machinery, like lathe guards and chuck guards, which protect machinists from flying tool bits and shards of excess material. A wire guard, which is one example of a safety barrier, usually forms a partition around a machinery area and acts as machine guard fencing. Other safety guards, like drill press guards and milling machine guards, are designed to fit around machines that require workers in close contact with potentially dangerous components, like blades or powerful presses. Some machine guards, rather than form a physical barrier, are invisible and shut down a machinery system when a certain partition has been breached. These are called safety light curtains, and they use infrared lights to form a barrier around dangerous machinery. Brake monitors are also non-physical guards, and signal workers or shut down systems when a brake system is failing or in need of repairs.

There are four different types of machine guards, as defined by OSHA. The first are called fixed machine guards, and are an integral part of the machinery. They are permanent components made from sheet metal, wire mesh, bars or plastic panels. Interlocked machine guards are electronically connected to the machinery. When a breach occurs, the machinery is automatically shut down immediately. Adjustable machine guards allow workers to move them around, and self adjusting features automatically alter their positions. All machine guards, regardless of application, must adhere to five OSHA requirements. First, they must prevent all contact with the dangerous components of the machinery. They must always be secured. If the machine guard is not secured to the machine itself, then it must be secured to the walls or ground. All guards must have high impact strength to stay in place at all times. They must all protect workers from falling and flying objects and create no new hazards. Machine guards must not create an interference that could slow down the manufacturing or fabrication process, or create difficulty for any workers. Finally, since many machines must be regularly lubricated to work properly, machine guards cannot inhibit, but should rather allow plenty of room for a machine to be safely and easily lubricated.

Manufacturers produce machine guards that are made of several different materials. However, metal is usually the top choice. They can come in different forms, such as pipe, bar, panel, wire mesh or sheet metal. In situations where visibility is an important necessity, a strong plastic material called polycarbonate is used to fabricate transparent panels that are shatter proof, can withstand continuous high impact and are stronger than glass. Wood is only used in applications where temperatures aren't extreme and corrosive chemicals are not present. In place of these basic machine guards, different aids can also be used. Awareness barriers like safety light curtains call attention to the danger zone, but do not physically prevent the operator from entering it. However, if the worker does walk through the barrier, the system automatically and immediately shuts down. The mechanics involve a transmitter that emits infrared lights surrounding the object or machine that is dangerous, which are connected by the receiver that comes in the form of many photoelectric cells. When any of the connections between the transmitter and the receivers are broken, that is when the system is shut off.

Almost all machines need safety guards. Any type of machine that shears or impacts, has meshing gears, rotating parts, reciprocating arms, cutting teeth or moving belts has the potential to be hazardous and must have a safety barrier of some kind. Presses, milling machines, automated assembly line machinery, robotics, saws and feeders, among others, have potentially dangerous components that require a machine guard to operate safely. They are crucial to these types of machines in order to prevent crushed fingers or hands, loss of limbs, burning, blindness, or death. More and more often, machines are manufactured with integral machine guards, but some need to be analyzed before the proper user-built guard can be installed on the point of operation. Robots also need proper machine guarding. Recently, more attention is being paid to the ergonomic factor of machine guards. Effectively integrated safety guards can help to prevent worker stress and fatigue. Another new idea is to integrate the safety of a machine into the control system so that both become one single unit. This helps to save on costs in three areas: installation, materials needed and design.
 

Machine Guards and Machine Guard Manufacturers Images Provided by Gordon Engineering Corp.

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Machine Guard Types

• Adjustable guards are able to work with many different applications, and can fit with almost any size of stock.
  
• Brake monitors are devices that monitor the stopping time of a brake system running in or with a potentially dangerous machine. A warning system is also installed in a brake monitor.
• Chuck guards are attached to piece of possibly dangerous machinery to guard the operator from flying debris while the system is in use.
• Drill press guards are machine guards that protect the hands and eyes of operators from cutting tools and hot liquids that may splash.
• Electromechanical sensors have a probe or contact bar that moves a predetermined distance as the operator starts the machine, and if there is something blocking the bar, the machine will not begin.
  
• Fixed guards permanently attach to the machines, and they do not depend on moving parts to function. Fixed machine guards can be made out of plastic, bars, sheet metal, screen or wire cloth.
  
• Gate barriers are used to protect the operator at the point of operation. If the gate is not in place, the machine will not begin its cycle.
  
• Interlocked guards automatically stop the parts of the machine that are moving when they are removed, not allowing workers to enter the problem area. Interlocked safety guards provide maximum protection.
  
• Lathe guards are shielding devices designed specifically to protect the operators of lathes, by keeping debris from flying out as well as fingers getting to close to the blade.
• Machine guard fencing is a machine enclosure that acts as a physical barrier between the operator and potentially dangerous machinery.
• Machine guarding protects workers from preventable injuries caused by moving parts in industrial settings.
• Milling machine guards are enclosures with two or three walls that surround milling machines, keeping workers safe as well as keeping the area significantly cleaner.
• OSHA machine guarding regulations are put in place by a safety standards organization called the Occupational Safety and Health Administration in industrial applications, making sure proper machine guards are built and used so that workers are safe.
• Photoelectric sensing devices use light fields to stop a machine's activity if the field is disrupted.
  
• Press safety refers to the area of manufacturing that deals with protecting workers from bodily damage caused by industrial presses.
• Radiofrequency devices use radio beams to interrupt or prevent the machine from starting.
  
• Safety barriers are physical blockades that keep workers in industrial settings away from dangerous machinery, ensuring fewer accidents. These barriers include fencing, gates, safety cones and railings.
• Safety guards are protective barriers that keep industrial workers from harm in regards to the machines they run. These guards are often specially made to fit certain machines.
• Safety light curtains are a type of photoelectric device that will continue to stop the machine's cycle if a component of the device itself is not working.
• Self-adjusting guards only allow a particular size of stock to go into the machine before they come back into place to separate the operator from the danger zone.
  
• Two-hand control guards require the operator's hands to be safely located on the controls while the machine is running. Once the pressure from the hands is released, the machine will stop.
  
• User-built guards are made by the user of the machine and are necessary because not all machines come with machine guards already attached.
• Wire guards are metal wire barriers built to protect people from the dangers of certain machinery, mostly in industrial contexts.

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Machine Guard Terms

Belts - Moving parts of machine such as transmission belts, flat belts, V-belts or round belts.

Brake - Stops and holds the crankshaft on a mechanical press when the clutch is disengaged.

Danger Zone - The part of machine where action is taking place that could potentially injure the operator.

Device - An attachment to a press that can either stop the press from operating if the worker's hands are near the point of operation, or prevent the operator of the machine from reaching into the point of operation.

Enclosures - Mounted barriers preventing access to machine parts or equipment that is in motion.

Guard - Barrier that restricts entry of any body part or object into the point of operation.

Hand Feeding Tool - Hand held tool used to place or remove material being processed within or from the point of operation.

Mill - Machine with two metal, horizontal rolls revolving in opposite directions.

Nip Points - Caused by rotating parts that are either touching or close to each other. Nip points may cause injury if something is caught in them and the machine does not stop.

Point of Operation - The area where work is performed on a machine.

Power Transmission Apparatus - Mechanical system parts transmitting energy to the section of the machine performing work.
Components may include cams, gears, pulleys, connecting rods, coupling belts, flywheels, chains, cranks and spindles.

Press - Mechanically powered machine built to shear, punch, form or assemble material by means of shaping, cutting or using various dies attached to slides.

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