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Safety in motion: Avoiding hazards in the optical shop

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Ray Williamson, [email protected]

The first installment of this series addressed the organizational aspects of shop safety: policy statement, hazard awareness training, documentation, the safety team and its activities, coordination with outside agencies and facilities features. This installment covers hazards related to motion.

Shop machinery contains gears, belts, pinch points, electricity, and heavy or fast-moving parts that cannot be stopped easily. The first rule when operating any piece of machinery is this: Learn how and where to stop it before you start it! (The first item in driver education should be how to find the brake pedal.) A “panic button” should be prominent and accessible during normal operations.

The universal machine shop rule applies: Don’t wear rings, loose clothing or unrestrained long hair while operating machinery. This goes for badge lanyards and neckties, and the rule covers visitors, too. Anything that can catch on moving parts can prevent you from reaching the panic button in time. In addition, steel-toe shoes, hard hats and safety glasses or goggles are wise precautions for some situations.

Guard on roller “Warning and guard over idler wheel, pinch point on planetary polisher.”

Pinch points

Belts, gears and pinch points should be covered or out of reach whenever possible. Any such unguarded point that is uncovered (and can reasonably be covered) should be reported to maintenance. Nevertheless, it may not be practical to cover all pinch points. Be aware of them and avoid them.

Pinch points include:

• The drive and idler wheels that hold the conditioner and work rings on planetary machines.

• The thin gearlike “webs” or “carriers” orbiting double-sided laps.

• The space between the workpiece and the cutting wheel on edging machines and saws.

• The overarms and linkages on top of spindle lapping machines.

• The constantly changing space between adjacent blocks on spindle lapping machines.

• The reciprocating slide-ways on surface grinders.

Throwing points

Inadequately secured workpieces placed on a mill table or generator spindle can be suddenly and forcefully grabbed by the high-speed wheel and thrown hard and fast in a random direction. Never operate generators or mills without checking the security of the workpiece and then lowering the safety shield. Avoid looking over the shield into the mill more than is strictly necessary.

Because generator wheels are changed frequently, there are many opportunities to get it wrong. A generator wheel that comes loose will rattle for a fraction of a second and bind, then spray glass and metal shrapnel all around. Be sure to secure the wheel and the block beneath it properly, and always use the shield. If you hear a bad sound or see sparks from a curve generator, hit the panic button and duck.

Cutoff saws can bind and suddenly pull the workpiece through, but are usually operated with hands on the workpiece. Make sure that your hands are neither behind the workpiece nor in front of the blade. Also, avoid making shallow cuts; doing so invites the blade to grab.

Never hold onto a workpiece while using a core drill or drill press. Instead, clamp the workpiece.

On overarm machines, a spindle pin may jump off the block’s socket, leaving the block careening around the lap. When this happens, just turn off that station right away – do not attempt to catch the block.

The shop floor at Sydor Optics in Rochester, N.Y., demonstrates important safety practices such as clean floors, broad and unobstructed passageways, and use of carts.

Slipping and falling hazards

Slick or cluttered floors invite accidents. The combination of vinyl or concrete floors, sometimes wet with oily coolant and traversed by people who may be carrying trays that obscure their view of the floor directly ahead, is entirely avoidable. Add rumpled floor mats and extension cords to trip over, and you have a real problem. The solution is to approach safety from all sides: Keep floors clean and dry, keep pathways clear and broad, provide carts to carry large or heavy items, and plan your movements.

Safe movement:

• Where oily coolants are unavoidable, either apply a nonslip gritty epoxy floor surface or provide a continuous path of raised floorboards or rubber mats.

• Practice regular mopping to remove residues. This should be on a schedule, with additional spot mopping as needed.

• Use spill barriers to prevent spreading of pools and streams.

• Cover and mark floor extension cords with safety barriers or striped tape wherever they cannot be routed overhead.

• Mark walkways and keep them clear.

• Plan your route, and constantly look left and right, just as in traffic.

• When carrying items, look around them to see where you’re stepping.

• Use carts and dollies where available.

• Avoid wearing gum-soled or black rubber-soled shoes in areas using oily coolant – they can get very slippery (and will wear out fast).

• Doors and halls are special challenges; approach doorways on a course outside their swing radius.

• When holding items, walk through doorways shoulder first; do not lead with outstretched hands.

• Don’t clip corners in the hallway; go wide, and turn only when you can see down the next hallway.

• Install mirrors at critical corners, and use them where provided.

Lifting hazards

You will encounter heavy items, oversize boxes and awkwardly shaped items with movable parts. Some of these may (but shouldn’t) be on shelves above eye level. Basic lifting strategy applies, plus an awareness of special situations in the optics shop.

Lifting strategy:

• Plan your route: Before picking something up, know where you’re going to put it down.

• Place feet a shoulder’s width apart.

• Bend at the knees rather than the waist.

• Rotate hips forward while lifting.

• Avoid twisting while carrying a load.

• Get assistance if it’s too heavy or too large.

• Don’t jerk; move slowly.

• When attempting to lift a stubbornly stuck grinding tool from its spindle, you may be tempted to just yank at it repeatedly. Don’t – that’s a good way to injure your back. If it doesn’t yield immediately, tap lightly upward on its lower surface with a weight or a mallet until it is free.

Special situations

Let’s say you have to move a Nikon 5D autocollimator from one table to another. If you pick it up by its base, it can tip over because it’s top-heavy. If you grab it by the barrel, the barrel could slip and pinch your hand. Then you’ll surely drop it – and it still may not let go of your hand. Or, it could suddenly spin right out of your hands. If you grab it by the vertical post, it will tip because you aren’t at its center of gravity. So you plan ahead, wrapping one hand around the base and the other around the post, cradling it against your chest, and then move it. (Did you think far enough ahead to disconnect the light source?)

A safe and stable method for lifting an autocollimator on swivel mount.

The standard five-axis interferometer mount has spring movements that can catch you by surprise, pinching you or wriggling out of your hands.

Cabinets are more rigid and less likely to fall over when their doors are closed – and when heavy items are on lower shelves. No more than one filing-cabinet drawer should be opened at a time, lest the cabinet tip, possibly trapping someone underneath. Shelving should be secured to a permanent structure. Tanks of pressurized gases should be moved by dolly and always secured by chain or strap to a wall, structural post or table. Those in earthquake-prone areas (New York and California, among others) should ensure that items cannot move, tip to trap people, or block egress routes.

A final thought

While constant worry that bad things can happen is an anxiety disorder, it is simply ethical for the manager and prudent for the worker to visualize the worst-case scenarios in detail – and to take measures to avoid them. Once measures are taken, there is no need for worry.

Photonics Spectra
May 2013
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