firstfare 2012 tool design and safety
TRANSCRIPT
Tool Design and Safety
Faster, easier and better quality work is done by using the right tool for the right job. It also significantly reduces the amount of blood and skin needed to be cleaned off of your robot parts.
This presentation is focused on WHY tools are designed the way they are and HOW this affects safety.
Although this presentation is intended for everyone with less than 20 years of experience using tools; Safety Captains, mentors and parent volunteers supervising students, and newer team members, will especially get value from attending.
Presenter: Matt Driggers, Mechanical Engineer and mentor for team 2517, the Green Wrenches. Matt has been known to demonstrate his topic in gory, noisy or messy ways so beware.
Due to being a guest here and needing to keep the
room clean, no messy demonstrations are planned.
Noise will also be kept to a minimum. Sorry.
FIRSTFare 2012
Tool Design and Safety(among other things)
Matt DriggersHardware Development Engineer,
Hewlett Packard Companyand
Mechanical MentorGreen Wrenches, Team 2517
team2517.org [email protected]
Disclaimer
• I am not a trained expert on safety, tool design, or tool use.
• I am giving information based on my experiences, analysis, and knowledge.
• If an expert gives different advice, utilize it.– Please let me know so I can pass along better
information in the future.• Rules cannot apply to all situations!
– The world is complex.– Use good judgment to adapt to the situation.
Warning: Pictures may be graphic.
You do not need to look if you do not wish to, but this is REAL LIFE, things
like this can do HAPPEN.
Help prevent it happening at FIRST.
Images are chosen to illustrate a point. Injuries shown in images may not have been caused by tool use or related to topic.
Warning: Next slide is graphic.
I will try to warn you with something like this:
Topics to cover in Tool Design and Safety• WHY• Definition of Tool• 911• Personal Protection Equipment• Saws• Drills, Lathes, Mills: Rotating Machinery• Screwdrivers• Compressed Air• Files
WHY is an important aspect of safety.
• Rules go in one ear and out the other.• Telling your team members WHY a rule exists
or WHY a tool should or should not be used helps it stick in their minds.
• Training the WHY in advance makes it easier to get team members to be safety concious during the rush of building the robot...– They will understand how serious it can really be.
What is a tool?
• A tool is something that helps you accomplish a task. – A computer is a tool.– A newspaper is a tool.– A telephone is a tool.– A business plan is a tool.– A mnemonic is a tool.
• Mother Very Thoughtfully Made A Jelly Sandwich Under No Protest = Major features of our solar system in their order from our sun: Mercury, Venus, Terra, Mars, Asteroids, Jupiter, Saturn, Uranus, Neptune, Pluto.
• I will talk about more than “traditional” tools.– However I will focus more on tools that affect physical
safety and injuries.
Do You Know HOW to call 911?
911• Not a tool for robot building, but you need to know how this communication tool
works.– The operator needs certain critical information– Excess detail slows down the process.– Help is often dispatched BEFORE you get very far into your call.
• Clear information is needed, not confusion or panic.– PRACTICE helps.– As you are dialing, rehearse your first statement OUT LOUD.
• Calmly answering their questions is your main purpose.
• Start with the nature of the emergency, your name and location. – Keep your first statement SHORT and simple.– Let them guide you with questions for the rest. – Don’t freak if they ask you the same information again. They may be talking to responder and
responder wants info repeated…it is often faster to ask again instead of looking back in their notes. Also a chance to double check information.
– Repeating does not slow down help arriving. It ensures details are accurate.
Personal Protection EquipmentTools that reduce injury
• Safety Glasses– “The most important safety rule is to wear these,
safety glasses”. --Norm Abrams, The New Yankee Workshop
– Wrap around or side shields• Ninja shards are always trying to attack. • A good castle wall will help.
– Splash goggles are for that: Splashes• Usually not working up a sweat in chemistry class like
when working on robots.• Fogging is a major safety hazard.
Personal Protection EquipmentTools that reduce injury
• Hearing Protection– Small gaps defeat purpose. They allow loud sounds in.
• Ear plugs are supposed to conform.• Ear muffs have flexible surface.• Rub your fingers together to check.
– Most commonly overlooked damaging noise sources in robotics:
• POWER DRILLS• BAND SAWS• SPEAKER SYSTEMS (music, public address systems)
– Tinnitus is permanent. Damage can be done so slowly it is not noticed.
Personal Protection EquipmentTools that reduce injury
• Gloves– Use at appropriate times.
• Lifting robots• Handling fresh-cut metal.• When welding or helping a welder.
– Be cautious around power tools.• There are times to use and not use. THINK!
OK, you’ve been patient. We are now coming up on the gory parts.
Saws
• The Web exists, USE IT.– ehow.com
• How to choose a band saw blade
Saws• A MINIMUM OF THREE TEETH AT ALL TIMES
– Band Saws are the biggest mistake with this!• Wood blades are often used for aluminum.• Thinnest wood is ~9 mm (3/8”) thick.• Aluminum is typically thinner…sheet material or thin
walled tubing (square or round)
– Too few teeth can grab the material by taking deep bites rather than shaving.
– A deep bite might mean a tooth will break off• Creates a “ninja shard”.• Missing tooth means a big notch and an impact for the next
tooth…another ninja shard.• Risk of blade breaking…a sharp edge snake coming out at
40 feet per second!
Saws• The right number of teeth prevents tool dulling and team
member burns.– Saw teeth work by shaving off a small amount of material.
• To dig into material, must have enough pressure.• Pressure (force) and speed give rise to heat.• Ideal cuts have most of the heat carried off by the chip.
– SHARP teeth generate less heat.– Local temperature at tip of tooth is very high.
• Metal can soften and dull…meaning more heat generated meaning duller teeth.
– Dull teeth and too many teeth both increase friction thus heat.• Too many teeth can’t dig in to shave off material.
– Metal, especially aluminum, can store and conduct this heat to your hands.
• Severe burns.• May drop or fling piece.• May be distracted and get fingers into the saw blade.
Saws• Metal or plastic chip formation at the tip of a
sharp tool.
Chip Formation
• Again, USE the web!– http://thecarpentryway.blogspot.com/2012/06/chip-off-old-block-ii.html
– Video: http://www.youtube.com/watch?v=mRuSYQ5Npek
Saws• The right type of blade for the job
– Plastic is often too soft for the band saw blade types and sizes available.
– Fine pitch, low set metal blades are not appropriate.• Plastic melts rather than cuts if not cut properly.• Melted plastic jams the blade path, increasing risk.• Melted plastic grabs onto the blade pulling or throwing
the part.
– Large pitch wood blades are usually not appropriate.• Large chunks ripped out• Teeth dig in hard causing part to jerk around.
– Consult with experts, or better: use a hand saw.
Band Saw Adjustments and Guards• Cover the blade area not being used!
– Band Saws have an adjustment that can cover unused blade.– This cover is built into the blade guides and support.– Thin blades can move around giving you crooked cuts.– An unsupported blade can bind, break, and become a snake…
• The adjustable support cost the manufacturer money. Why would they include them if it costs money? – The tool works better, so customers are happier, so they spread the word
how much they like the tool, so other people will buy the tool, they make money!
– You get better quality and spend less time with a properly adjusted tool, SO USE THE ADJUSTMENTS.
– Besides spending less time filing the part to the right size, you get safety for “free”.
Saws
• Round objects must be clamped, not held!– Flat tables on band saws and table saws will
support flat items.– Miter gauge slot allows you to clamp material to
the miter gauge (short items, not just round ones).– Round items will ROLL into the saw.
• Fingers and hands holding the round item will roll into the blade when the part rolls.
• Happens FAST. Warning: Next slide is graphic.
Saws
• Graphic example of a severe injury.
Saws• Did I mention FAST?• Human reaction time is on the order of one
quarter second (250 milliseconds).– Detected by eye or nerves– Transmitted to the brain– Processed by brain– Sent to muscles– Muscle response time.
• You don’t have time to react. • Safety comes from not being in the situation.
Any Questions on the design features of saws that I mentioned?
I can only lightly gloss over the complex details of the design. Before using a tool, look at it and THINK WHY there are
safety guards and adjustments. THINK HOW the tool might be hazardous with the way you will be using it. THINK HOW
the guards can be adjusted to be in the safest positions. Continually THINK HOW you might clamp or hold the work
piece more safely.
Understanding WHY a tool is designed the way it is helps you be safe.
Safety is a SERIOUS topic. Unsafe happens VERY FAST.
Drills, Lathes, and Rotating Machinery
• Hand Drills are JUST AS DANGEROUS as mounted drills, lathes, mills, and other machinery.• Power Screwdrivers, common for Robotics, fall in this category.
• Rotating tools must deliver high torque at high speeds to get their jobs done.• Similar to saws, drill bits must have pressure to cut
• This may lead to people pushing or leaning hazardously.• Dulling occurs if tip heats from too much pressure and speed.
• Go slower and use cutting oil to cool tip of tool. • Different tool tips are needed for different hardness of materials
• Need to shave material, not dig in or gouge out material.
• Hazards include:• Pulling off rings.• Catching hair and clothing.• Throwing things – Especially chuck wrenches
Warning: Next slides are very graphic.
Loose Clothing in a Lathe
P:erson died..
Drills, Lathes, and Rotating Machinery
• Hand Drills are JUST AS DANGEROUS as mounted drills.
• Power Screwdrivers, common for Robotics, fall in this category.
• Name tags, necklaces, or keys around your neck can also be caught in drills and pull you into them.
Repeating because it is important!
Drills, Lathes, and Rotating Machinery
• Hand Drills are JUST AS DANGEROUS as mounted drills.
• Power Screwdrivers, common for Robotics, fall in this category.
• Hazards include:• Pulling off rings.• Catching hair and clothing.• Throwing things – Especially chuck
wrenches Warning: Next slides are very graphic.
Repeating again because it is important!
Lathe Chuck left in when machine turned on.
Lathe Chuck impact with hand. Broken thumb bone visible.
Drills, Lathes, and Rotating Machinery
• Ladies, it can happen to you too!• Hair CAN get caught. • Hair CAN get caught.• Hair CAN get caught.
Warning: Next slide is graphic.
Instant New Hair Doo• Note blood all over blouse.• Will have short hair sticking straight out for next several
months so doing hair will be harder.
Actual incident did not involve power tools. Was a “tuktuk” roll-over in China.
Drills, Lathes, and Rotating Machinery
• Ladies (and some guys), it can happen to you too!
• Necklaces OFF.• Tucking necklaces in shirt is NOT good
enough…they can come out.• Jewelry such as rings and bracelets are a big
problem.• Can strip skin off of finger or arm.
• Side comment: Rings are also an issue for welding…severe burns. Warning: Next slide is graphic.
Catching Rings
Actual incident was ring getting caught on a basketball hoop.
Any Questions on the design features of drills and rotating machinery (mills, lathes)?
Tool must have high torque for cutting.
Tool is often desired to go fast to get the job done quickly, but this is often not what is needed and leads
to dulling.
Tool must shave, not spin or gouge.
Screw Drivers
• Hardened tip so it won’t bend when driving screws.
• Hard materials are usually brittle.• Ninja shards go flying if used improperly
– As a chisel (hit with a hammer)– As a pry bar – Shards travel long distances.
• Tip is sharp and can puncture hand.– Power screw drivers don’t need a sharp tip to
penetrate skin…will tear in.
Actual incident was a tiny wood chip..
Compressed Air
Warning: Next slide is graphic.
• Blowing tools (air guns) have designs to not let pressure build up against skin.– Side holes in nozzle shroud.– Cone of rim nozzle prevents sealing against skin.
• Don’t create home-made blowing tools• Don’t use damaged blowing tools.• Air can penetrate skin causing bubbles in blood
stream. – Bubbles can block blood flow…especially risky when
blocks blood to heart or brain.
High Pressure Injection Injury• Sorry…I don’t have an image of
air bubble injury that is impressive. CAT scan of a brain with an air bubble is not very graphic.
• Showing instead a high pressure oil injection injury (not air).– Small puncture wound on palm
BUT– Skin had to be peeled off up the
fingers and down the hand to get at the bubbles of fluid that were injected in.
Files• Tang on file is meant to hold
handle, not be held in hand.• Cannot directly form an
ergonomic handle in the steel, so create a mounting point for a handle.
• Drill a hole in a golf ball for a very useful handle if you don’t have easy access to file handles.– Different colors for different
file types is good.
Files
• Person cutting or drilling should immediately remove sharp edges.
• Fine tooth single cut file leaves safest surface.
• Files are hardened deeper into their metal than screw drivers– Very brittle.– Do not use as a pry bar.– Do not hit.– Large sharp edges occur when a file breaks.
Electricity
• Cars and cordless power tools are designed to be below certain voltage levels.– AC and DC levels are different.– Voltages chosen to be reasonably unlikely to generate enough
current through the heart to kill.
• Line voltages (electricity from wall) are instantly lethal. – Power strips should not point up…collect metal shavings.– Any tool with even slightly frayed or damaged cord should be
put out of service.– Grounded cord connections must NOT be bypassed…all three
prongs must be present.
Commentary
• Mentors, adult supervisors, students:– Don’t be afraid to slow robot work down by
telling anyone, even mentors, to not use a tool if you do not feel comfortable about how it is being used.
– Mentally practice calling 911.
Again,Disclaimer
• I am not a trained expert on safety, tool design, or tool use.
• I am giving information based on my experiences, analysis, and knowledge.
• If an expert gives different advice, follow it.– Please let me know so I can pass along better
information in the future.• Rules cannot apply to all situations!
– The world is complex.– Use good judgment to adapt to the situation.
Contact me if you have improvements for me.
• Matt Driggers• A mentor with FRC team 2517, the Green
Wrenches, Evergreen School District, Washington.
• Video of 2011 presentation is at– http://www.youtube.com/watch?v=s-VkYMJWqT0&feature=youtu.be
FIRSTFare 2012
Tool Design and Safety(among other things)
Matt DriggersHardware Development Engineer,
Hewlett Packard Companyand
Mechanical MentorGreen Wrenches, Team 2517
team2517.org [email protected]