1. Multidisciplinary Engineering Senior Design Project 06431 Project Card Guide Redesign and Manufacture Preliminary Design Review November 11, 2005 Project Sponsor: Dwayne Niewiemski Team Members: Bill Rowe Brad Good Laren Olson Team Mentor: William Scarbourgh Acknowledgements: Dr. Wayne Walter Kate Gleason College of Engineering Rochester Institute of Technology

2. Project Overview

3. Project Background Data Systems (MDS) has designed a printed circuit board (PCB) chassis Chassis is 1U high and can have up to eight PCB assemblies slid into the front of the chassis and mounted into a backplane assembly To support the PCBs, MDS is using a custom designed aluminum extrusion as a PCB card guide Having difficulties when the PCB extrusion guides are fastened onto the chassis To mount the card guides to the chassis and cover, MDS uses flat-head machine screws (21 in total to complete the assembly)

4. Project Background Cont. To keep costs down, the card guide is not tapped for each machine screw The screw forms the thread while being fastened into the aluminum extrusion The problem is when the screw is trying to “catch” into the aluminum extrusion to form the first thread The screw is walking up and down the slot of the card guide If the screw is not centered in the chassis hole, the screw head will not sit flush into the countersink

5. Major Needs of the Sponsor Reduce the total number of screws Make the chassis easier to assemble Come up with solutions to grounding issues and reduce cost Make board removal and maintenance easier Modify or get rid of the small faceplate

6. Major Needs of Sponsor Cont. Have fewer screws on the faceplates Have screws on the faceplate that do not get lost or discarded Have self taping screws to hold the aluminum extrusions in place A working prototype Tests proving the worth of the prototype

7. Project Schedule Gantt Chart – Used to keep design team on a strict schedule – To prevent time loss – To prevent team from getting side-tracked

8. Gantt Chart Events Allocated Time (weeks) 1234567891011121314151617181920 Prob. Def. & Brain Storming Spec. & Mock up Function Anal. & Research Design Concept & Scope Detail Drawing Prototype Construction Prototype Testing Feasibility Analysis Re-design & Modifications Prototype Construction Prototype Testing Feasibility Analysis Presentation & Validation

9. Order Winners Reduce the total number of screws Make the chassis easier to assemble Come up with solutions to grounding issues and reduce cost Make board removal and maintenance easier Modify or get rid of the small faceplate Have fewer screws on the faceplates

10. Order Winners Cont. Have screws on the faceplate that do not get lost or discarded Have self-taping screws to hold the aluminum extrusions in place Maintain thermodynamic efficiency and improve if possible Be reliable Be user friendly

11. Needs Assessment Concept Development Detailed I-DEAS Drawings Preliminary Budget Methods of Analysis Technical Data Report (PDR)

12. Needs Assessment Cont. A working Prototype Tests performed on the Prototype Final Report / Group Binder / Log Book

13. Concept Development and Feasibility Assessment

14. Concept Development Concept Development Process – Objective Tree – Process of Proposed Design – Brainstorming – Research

15. Objective Tree PCB Chassis QualityEfficiencyCost Effectiveness Dura.Easy to Maintain Resis. to Corrosion Easy to Produce Low Maintenance Affordable to Produce Affordable to Customer Easy to Modify Easy to Repair More Access. Fewer Screws Panel is Easier to Access Boards are Easier to Replace

16. Process of the Proposed Design

17. Concept Development Cont. Solutions for solving structural assembly issues – Using only self-threading screws no guiders – Using self-threading screws with guiders

18. Concept Development Cont. Self-threading screws no guiders – Problem: The machine screws that secured the sheet metal into place do not sit well in the extrusions Machine screws ride up and down on the extrusion and give operators a lot of problems during the manufacturing process

19. Concept Development Cont. – Solution: To have machine screws replaced by self-threading screws

20. Concept Development Cont. Using self-threading screws with guiders – Problem: Too many screws on the chassis Cost Same as the last concept

21. Concept Development Cont. Solution: – Guiders punched into the sheet metal – Self-threading screws

22. Concept Development Cont. Solutions for solving grounding and faceplate issues: – Hairpin Clips with edges on extrusions – Redesign of extrusions with edges – Redesign of extrusions with an offset from the backplane – Captive screws instead of machine screws – Rubber bumpers – Faceplate clip

23. Concept Development Cont. Hairpin clips with edges on extrusions – Problem: Customer had difficulties using the current face- plate design Customer would lose the screws that fastened the PCB to the chassis Loose screws could cause a short circuit or would allow the PCB to slide out of the chassis altogether Expensive grounding clips on the circuit board

24. Concept Development Cont. Solution: – Hairpin clips will hold the PCB into place – To dislodge the PCB from the extrusion and the chassis, all you would have to do is pinch the ends of the hairpin – Mounted in such a way that they ground the circuit board

25. Concept Development Cont. Redesign of extrusion with edges – Problem: Expensive $0.12 clip are being used on current design The PCBs need to be grounded to pass FCC regulations

26. Concept Development Cont. Solution: – Redesign the extrusions – The edge for the aluminum extrusions touches the bottom and top of the gold strips on the circuit board – This removes the need for the expensive clips

27. Concept Development Cont. Redesign extrusions with an offset from the backplane – Problem: Current grounding design is expensive.

28. Concept Development Cont. Solution: – Cause a slight amount of misalignment between the backplane and the PCB when they connect to one another – Creates an upward force on the back end of the PCB

29. Concept Development Cont. Captive screws instead of machine screws – Problem: Customer had difficulties using the current face- plate design Customer would lose the screws that fastened the PCB to the chassis Loose screws could cause a short circuit or would allow the PCB to slide out of the chassis altogether

30. Concept Development Cont. Solution: – Replace the thumb screws that hold the faceplate into place with captive screws – Captive screws by design are held to the chassis by a spring mechanism

31. Concept Development Cont. Rubber Bumpers – Problem: Expensive $0.12 clip are being used on current design The PCBs need to be grounded to pass FCC regulations

32. Concept Development Cont. Solution: – Attaching the rubber bumpers to the PCBs – The bumpers apply a vertical force on the circuit boards and in doing so ensure the boards are grounded

33. Concept Development Cont. Faceplate Clip – Problem: MDS’s circuit boards has an optional attachment Attach the two faceplates attached to one another because there is not an extrusion separating the two boards Not attractive More Screws

34. Concept Development Cont. Solution: – Use a U-shaped metal fixture to hold the two boards together – Use one screw to hold them together

35. Feasibility Assessment Feasibility Assessment Chart – Ranks the concepts – Ranks them according to important factors

36. Feasibility Assessment Chart

37. Feasibility Assessment Cont. Feasibility assessment for concepts solving structural assembly issues – Using only self-threading screws no guiders – Using self-threading screws with guiders

38. Feasibility Assessment Cont. Self-threading screws no guiders Pros – Similar to the original design – Fixes assembly issues – Screw sit well in the extrusion – Save on labor because less time to assemble Cons – Cost: Machine Screws= $0.03 Self-threading screws= $0.09 – Do not get rid of any of the screws Ranking on Feasibility Assessment Chart= 5 th

39. Feasibility Assessment Cont. Self-threading screws with guiders Pros – Uses the original design chassis with guiders – The guiders will be punched while the sheet metal is bent into its final shape – Will restrict the lateral movement of the extrusions during assembly – Will allow the assembler to spend less time screwing the screws into place – Fewer screws Cons – Untested – Self-threading screws cost more then machine screws – Punching is an added cost Ranking on Feasibility Assessment Chart= 2nd

40. Feasibility Assessment Cont. Feasibility assessment for concepts solving grounding and faceplate issues: – Hairpin Clips with edges on extrusions – Redesign of extrusions with edges – Redesign of extrusions with an offset from the backplane – Captive screws instead of machine screws – Rubber bumpers – Faceplate clip

41. Feasibility Assessment Cont. Hairpin Clips with edges on extrusions Pros: – Solves some of the grounding issues – Cost Hairpin: $0.05 Thumb screw: $0.06 – Edges on extrusions might create more contact for ground the PCB Cons: – Edges are untested – Hairpins are untested – Edges might damage PCBs Feasibility assessment chart ranking= 1st

42. Feasibility Assessment Cont. Redesign of extrusions with edges Pros: – Same cost – May solve EMI – Easy to do Cons: – Not a tested – Damage PCBs with edge – Does not solve faceplate issues Feasibility Assessment Chart Ranking= 7th

43. Feasibility Assessment Cont. Redesign of extrusions with an offset from the backplane Pros: – Same cost – Four points of solid contact which meet the grounding requirements – Simple (less=more) Cons: – Unproven – Does not solve faceplate issues Feasibility Assessment Chart Ranking= 4th

44. Feasibility Assessment Cont. Captive screws instead of machine screws Pros: – Will not come off the chassis – “user friendly” Cons: – Cost: Thumb screws: $0.06 Captive screws: $1.49 – Does not fix grounding problem Feasibility Assessment Chart Ranking= 8th

45. Feasibility Assessment Cont. Rubber Bumpers Pros: – Cost Adhesive rubber bumpers: $0.07 Grounding clips: $0.12 – PCB is grounded Cons: – Unproven – Does not solve faceplate problems Feasibility Assessment Chart Ranking= 3rd

46. Feasibility Assessment Cont. Faceplate Clip Pros: – Cheap – Fewer screws – The boards are even more secure Cons: – Untested – Not much of a change Feasibility Assessment Chat Ranking= 6th

47. Feasibility Assessment Conclusion Do not use: – Captive Screws – Edges in Extrusions Two Prototypes – Prototype A (safe) will have: Redesign of extrusion Self-threading screws No guiders Offset from the backplane – Prototype B (risk) will have: Redesign of extrusion Self-threading screws Guiders Rubber bumpers Faceplate clip Hairpin

48. Analysis and Conclusions

49. Cost Analysis Prototype Part Numbers: Prototype Costs: DesignTotal Number of Parts Current Design186 Prototype A175 Prototype B178 DesignTotal Cost Current Design$90.40 Prototype A$91.13 Prototype B$91.46

50. Assembly Efficiency The manual assembly efficiency: Current DesignPrototype APrototype B 11.625%14.588%14.500%

51. Anticipated Design Challenges/Risks Prototype A (safe design): – Redesign of extrusion – Self-threading screws – No guiders – Offset from the backplane Challenges/Risks – Cost must be kept low – Has not been Tested – Working with the Vendor to get cheap and actuate pieces

52. Anticipated Design Challenges/Risks Cont. Prototype B (risk) will have: – Redesign of extrusion – Self-threading screws – Guiders – Rubber bumpers – Faceplate clip – Hairpin Challenges/Risks: – Cost – Not tested – Hairpins may not hold PCB in place – Faceplate clip may be unnecessary

53. SD II Project Plan Follow EDGE design process – Gantt Chart Order prototype components Assemble prototypes Test and troubleshoot the prototypes Select the best design Present a final design to Sponsor and at the Final Review

54. References Boothroyd, Geoffrey, Peter Dewhurst, and Winston Knight. Product Design for Manufacture and Assembly. New York: Marcel Dekker, 1994. “Do-It-Yourself dot com.” Home Improvement, Repair, Remodeling, and Hardware Store. 30 October 2005.. “Fastenal.” Industrial and Construction Supplies. 30 October 2005.. “McMaster-Carr.” Supply Company. 30 October 2005.. “Metal-Grip.” Your Trusted Fastener Source. 30 October 2005.. “Mouser Electronics.” Electronic Component Distributor. 30 October 2005.. Rutledge, John phD. Dr. John Rutledge Blog. 7 November 2005.. “Stainless Fasteners.” Industrial Directory. 30 October 2005..

55. Questions?