P14311: PCB Isolation Routing System

1. P14311: PCB Isolation Routing System Subsystems Review

2. Agenda • Review of Systems Level Design • Determination of Subsystems • Critical Subsystems Review • Vacuum Table Assembly • Transverse Feed Assembly • Vertical Spindle Feed Assembly • Electrical Architecture • Risk Management Update • Schedule Update

3. Problem Statement • RIT students need rapid prototyping for creation of unique circuit boards • Requires multiple revisions to perfect each circuit board • Currently each iteration must be created off campus • Long lead times • Expensive • Limits circuit refinement • Students not involved in process

4. Selected Concept

5. Selected Concept

6. Subsystems Definition

8. Critical Subsystems

9. Vacuum Clamp Assembly • A system that creates negative pressure to hold down work pieces during machining • Will allow for easy set up by user • Work pieces will be held down after being cut • Collect debris being cut from board • Corrects for board warpage

10. Vacuum Clamp- Shopvac vs Pump Vacuum Pump + Quieter than shopvac - Can be expensive - Very low flow rate(~10 cfm) - Could not have any leaks in system - Could not allow debris to reach vacuum pump Shopvac + More affordable + Very high flow rate(150+ cfm) + Could share vacuum with debris management system. + Allows for leaks in system + Also acts as a debris management system - High noise level

11. Vacuum clamp calculations About 2.5 lbf is supplied from each hole. In a feasibility test, our prototype had 16 holes. A total of 40 lbf was applied to the PCB.

12. Shop Vac Vacuum Clamp Demo

13. Registration System on Vacuum Clamp Assembly • Particularly important for zeroing a double sided PCB board • Ability to hold the board more securely and flip the board halfway through • Pins help restrict translational degrees of freedom and z-axis rotation and allow for realignment when flipping the board over • Pin holes can be incorporated into the PCB design • At least 2 pins needed, possibly up to 4 Process 1.PCB is secured to vacuum table 2.A number 57 bit (42 mil) is inserted into the mill and can drill holes the size of a push pin 3.Drill alignment holes for reference pins 4.Stop the mill and insert pins through holes into sacrificial layer 5.Mill one side, flip the board over, and re-pin

14. Transverse Feed Assembly Motion in the X and Y direction was initially planned to occur exclusively in the base plate of the mill • Mount the vacuum table on two linear slides perpendicular to each other • Wire Management will be more manageable than with a gantry system • With less movement of the spindle head, likely to be more accurate

15. Analysis of XY Base Plate motion • Initial Vacuum Table Weight Estimate- 40 lbs max • Contacted Isel USA, a linear slide company to get more information about their rail and table systems • Technical suggestions for our project from a Engineer Support Representative • Gave a cost estimate for their system

16. Transverse Feed Cost Estimates • Isel USA systems cost upwards of $3000- way over our budget • Other sources- these types of systems are more expensive than expected- $350 for just the slides, around $700 for entire structure.

17. Mobile Bed vs. Mobile Gantry Mobile Bed Design +Typically found on smaller CNCs (PCB, engraving, etc.) +Sturdy, will not flex under load +Better wire management - Requires a larger footprint - Must Consider moving the weight of the table - Hard to support router/spindle

18. Mobile Bed vs. Mobile Gantry Mobile Gantry Design +Can be designed to be as sturdy as a fixed gantry +Most popular for DIY CNC routers +Can be arbitrarily large- Must consider weight and size of the gantry - Must account for deflection and vibration

19. Gantry System Cost Estimates • DIY CNC Gantry Kits for as low as $350 • This handles motion in the X and Y while also including the structural support for Z motion and Spindle.

20. Zen Toolworks CNC DIY Kit • Gantry supports are manufactured from PVC • Modulus of Elasticity 370 – 409 ksi • Easily replaced with Aluminum plate • Modulus of Elasticity 10,000 ksi • Refine gantry height

21. Stepper Motor Calculations Equations from Shigley’s Mechanical Engineering Design (8-1) and (8-2)

22. Spindle Motor Considerations • Feasibility • Air motors - Infrastructure (air dryer, supply regulator, etc.) - Rare and Expensive (All supplier quotes over budget) + Easily reach speeds of 100,000+ RPM • DC motors + Simple implementation (voltage or PWM speed control) - Low speed (12,000 RPM unless specialty and over budget) • AC motors +/- Inexpensive and common (many vendors, but little documentation, no warranty) - High complexity (VFD speed control, could be purchased) + Acceptable speeds (24,000 to 48,000 RPM)

23. Reconsideration of Commercial Routers + Affordable at around $200 + Available at any home improvement store + Speed of 16,000 to 35,000 RPM + Mounting documentation available from gantry manufacturer + Aftermarket collets with published TIR < 0.0004” + Can control speed with PWM or built in dial Bosch PR20EVSNK Colt and aftermarket collet from precisebits.com

24. Spindle Speed and Feed Rate • Low Feed Rate and High Spindle Speed for small mill bits (< ~0.020”/0.5mm) • High Feed Rate and Lower Spindle Speed for larger mill bits ( up to 0.125”/3.175mm) • For a 0.015”/0.38mm mill bit on .5 to 1 oz Copper: 10 to 40 in/min @ 24,000 to 60,000 RPM • For a 0.625”/1.6mm mill bit on .5 to 1 oz Copper: 60 in/min @ 24,000 to 40,000 RPM

25. Control Software and Breakout Board Selection • Considered Software Options • Software Breakdown • Hardware Breakdown • Concept Scoring • FInal Selection

29. Software Breakdown (Top Three) * Software and Hardware included in one price

30. Hardware Breakdown (Top Three) * Software and Hardware included in one price

31. Concept Scoring

32. Final Selection It was a difficult and arduous process, but with aid from the Concept Scoring exercise, we ultimately chose to go with the CNC USB Controller Package CNC USB Software CNC USB Controller MK2/4

33. System Architecture - Power Distribution Wall Outlet DC Power Supply 12-36V, DC 120V,60 Hz X Motor Driver Y Motor Driver Z Motor Driver Wall Outlet Main Logic Board 120V,60 Hz Breakout Board 6V Palm Router

34. System Architecture - Controls Breakout Board - Processes design file, converts file to motor control signals Main logic Board - Monitors all systems (ie halts operation if vacuum table is off, interlock open) Vacuum System Main Logic Board Computer USB Breakout Board Interlock System Motor Drivers - Takes motor control signals and amplifies to usable form to drive motors Router Motor Driver - Takes signal and modifies it for variable speed Router Motor Driver X Motor Driver Y Motor Driver Z Motor Driver

35. Router Speed Control • Radial motion in our machine will accomplished using a palm router. Different speeds are required for drilling and milling. Here are some options being considered: • Modifying router circuitry • Microcontroller: Using a microcontroller with PWM channel and H-bridge configuration.

36. Preliminary Family Tree Diagram PCB Isolation Routing System PC Shop Vacuum Milling Machine Assembly Supply / Interconnect System Zen ToolworksCNC DIY Kit USB / Serial Cable Router Assembly Safety Enclosure Control Architecture Pressurized Air Line 120 VAC Power Vacuum Piping

37. Updated DMC Estimate

39. Risk Analysis Update

40. Schedule Update

41. Next Steps