Contact : Stephen Gass Advisor :Faryar Etesami Team Members : James Boag Jerry Boyum Cory Nardin Roger Smith

Presentation Topics Final 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

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

Quick Review of PDS Stopping Time: < sec Target sec Compatible With Other Safety Features Reliability: > 98% Target > 99% Does Not Change Ergonomics Or Obstruct View Lightweight: < 2 lbs Target < 1 lb Cost: < $20 Target < $15 Maintenance Free Durability: (Withstand a drop from 6 ft 3 times) Working Life: > 10 years Target > 40 years

Method Of Refining Choices Brainstorming and refining Voting and intuition (reduced choices to 4) Scoring Matrix

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

Methods of Stopping Saw Blade Electric Stop Simple Block Gear Stop Housing Stop Winner!!! Simple Block Why?

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

Types Of Actuation Explosives or Gas Linear Spring Torsion Spring Electrical Actuation

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.

Placement Of Stopping Device Front of Housing Side of Housing Top of Housing Back of Housing Which Place ???

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.

Materials Metals (such as aluminum) Carbon fibers Kevlar Plastics

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.

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.