Contact: Stephen Gass Advisor:Faryar Etesami

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Contact Stephen Gass AdvisorFaryar Etesami

• Team Members James Boag
• Jerry Boyum
• Cory Nardin
• Roger Smith

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Presentation TopicsFinal Evaluation and
Selection

• Objective / PDS Review
• Most Important Features
• Method Of Refining Choices
• Methods Of Stopping Saw Blade
• Types Of Actuation
• Placement
• Materials
• Final Selection / Conclusion

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OBJECTIVE

• To design a device to stop the blade of a hand
  held circular saw

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Quick Review of PDS

• Stopping Time lt 0.005 sec Target 0.003 sec
• Compatible With Other Safety Features
• Reliability gt 98 Target gt 99
• Does Not Change Ergonomics Or Obstruct View
• Lightweight lt 2 lbs Target lt 1 lb
• Cost lt 20 Target lt 15
• Maintenance Free
• Durability (Withstand a drop from 6 ft 3 times)
• Working Life gt 10 years Target gt 40 years

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Method Of Refining Choices

• Brainstorming and refining
• Voting and intuition (reduced choices to 4)
• Scoring Matrix

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(No Transcript)
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Results of scoring matrix
Category 1 Stopping method Simple block
Category 2 Actuation Method Linear Spring and
Torsion Spring
Category 3 Placement Front and Top
Category 4 Material Plastic
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Methods of Stopping Saw Blade
Winner!!!

• Electric Stop
• Simple Block
• Gear Stop
• Housing Stop

Simple Block Why?
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• Electric Stop Method to slow for our purposes.
• Gear Stop Blade could come lose and continue to
  spin or even come off.
• Housing Stop Wrong angle to stop the blade.
• Simple Block Has ability to stop blade quickly,
  less expensive and easier to replace

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Types Of Actuation

• Explosives or Gas
• Linear Spring
• Torsion Spring
• Electrical Actuation

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The Choice is? Springs

• Explosive or Gas Actuation This method would be
  more expensive and less reliable than springs.
• Electrical Actuation The block needs to be held
  into the blade, which would be more complicated
  and possibly less reliable than springs.
• Linear Springs Lower cost, scored the same as
  torsion springs on matrix for two team members
• Torsion Spring Lower cost, members choice on
  scoring matrix.

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Placement Of Stopping Device

• Front of Housing
• Side of Housing
• Top of Housing
• Back of Housing

Which Place ???
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Where to place it?

• Back The blade guard retracts under the
  housing, which means the guard would get in the
  way of the stopping device.
• Side Difficult to get to the blade teeth from
  the side. Makes for a more complex and less
  reliable device.
• Top Good for getting to the blade teeth, but
  may interfere with the blade guard.
• Front Does not interfere with the blade guard,
  but the mounting is more difficult.
• A top and front combination will work.

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Materials

• Metals (such as aluminum)
• Carbon fibers
• Kevlar
• Plastics

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What Material ?

• Metals They are durable and work well, but
  they, require machining and are more expensive
  than plastics.
• Carbon Fiber May be to hard and is expensive.
• Kevlar Also expensive. Needs to be tested.
• Plastics Testing is in progress.
• Materials being tested are Polycarbonate,
  Urethane and ABS plastics.

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Final Selection and Conclusion

• The final selection incorporates a plastic block
  mounted on the top front of the housing using a
  spring (linear or torsion) to actuate the block
  and hold it in position.