Team Members Industry Contact Academic Advisor Dr. Faryar Etesami

1. Team Members • IndustryContact • AcademicAdvisor • Dr. Faryar Etesami

2. Overview • Introduction / motivation • Scope • Mission statement • PDS review • Beginning design • Initial design and parts • Initial testing • Refining • Prototype / final testing • Conclusion

3. Introduction / Motivation • According to the Consumer Product Safety Commission, injuries suffered from the use of hand held portable circular saws is second only to power drills. The reason for this is due to the inherent danger involved with the saw and its availability to a large cross section of the general population.

4. Scope This project involves the following. Isolating the blade and electronics Stopping the blade Adaptation to current circular saws

5. Mission Statement “To design a blade-arresting device for a hand held portable circular saw that will reliably and effectively stop a moving blade upon contact with human tissue. The device must be readily adaptable for mass production by either existing circular saw manufacturers or by the client company, SawStop LLC.”

6. PDS Review Stopping Time: < 0.005 Sec Target 0.003 Sec Compatible With Other Safety Features Reliability: > 98% Target > 99% Does Not Change Ergonomics Or Obstruct View Lightweight: < 2 Lbs Target < 1 Lb Cost: < $8 Target < $5 Maintenance Free Durability: (Withstand a Drop From 6 Ft) Working Life: > 10 Years Target > 40 Years

7. Beginning Design • Forces • Methods of Stopping Saw Blade • Placement on the Saw

8. Force Force On Stopping Block I=moment of inertiaw=angular momentum=3500rpma=angular accelerationk=radius of gyrationm=mass=0.678 lbmd=diam=7.25inT=torqueF=force Design Time of .002sec <__Known Parameters

9. Methods of Stopping BladePrevious Design Ideas • Motor Braking • DC current injection. Not Fast Enough • Friction Braking • Similar to car brakes. More bulky and complex, less reliable than others and more weight. • Gear Braking • Pawl in gears. Possible gear damage, blade will still move • Impact Braking • More to follow

10. Placement Due to the above restrictions the front of the housing was selected as the best placement. Must Be Compatible With Current Safety Features Must not obstruct view Must not create a hazard

11. Initial Design and Parts • Spring to actuate block. Most reliable • Block • Housing • Pivot • Wire

12. Concept Block

15. Initial Testing

16. Testing Materials and Shape

17. Refining Testing refinement Redesigned Test Apparatus – Uses Spring Actuation to Force the Block into the Blade

18. Test blocks from second test. Polycarbonate blocks are on the left, and aluminum blocks are on the right.

19. Test Block Results

20. Springs

21. Spring Force

22. Spring refinement

23. Restraining

25. Prototype

26. Seal / Insulator

27. Housing

29. Final Testing Setup Testing apparatus Electrical testing setup

30. Testing Circuit Schematic

31. Prototype Test Setup

32. Prototype Parts

33. Testing Results Housing fracture

34. Testing Results Blade Stopped in one tooth and simply manufactured block fractured

35. Final Design

36. Refinement and changes to be made • Strengthened housing. Depends on manufacturer • Better manufactured block • Cover for housing. Will depend on manufacturer. Main components including spring, insulator, wire attachment, block and housing performed as expected.

37. Conclusion The final design is a stopping device that is reliable, light (less then ½ pound), fast (one tooth of blade), Compatible with other safety features, inexpensive (approx. 1.70$), maintenance free and does not change the ergonomics of the saw.