P14311: PCB Isolation Routing System Subsystems Review

Agenda 1.Review of Systems Level Design 2.Determination of Subsystems 3.Critical Subsystems Review a. Vacuum Table Assembly b. Transverse Feed Assembly c. Vertical Spindle Feed Assembly d. Electrical Architecture 4.Risk Management Update 5.Schedule Update

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 o Long lead times o Expensive o Limits circuit refinement o Students not involved in process

Selected Concept

Subsystems Definition Priority LevelSubsystem #Subsystems NameDescription 3 1 Debris Management SystemRemoves, isolates, and contains copper/substrate debris 1.1 Pressurized Air SystemDelivers pressurized air to the system 9 2 Vacuum Clamp Assembly Uses vacuum force to secure/align PCB copper bare board to mill base plate 2.1 Registration Subsystem Makes sure board is aligned with a zero zero reference point in place 9 3 Transverse Feed Assembly Energizes and Controls motion in the X-Y axis in defined increments 9 4 Vertical Spindle Feed Assembly Energizes and Controls motion in the Z axis in defined increments

Priority LevelSubsystem #Subsystems NameDescription 3 5 Enclosure Assembly Creates a physical barrier between the operator and the milling/debris subsystems Safety System Interlock circuitry to shut off machine if physical barrier is disrupted (the saftey electrical circuit becomes open) 9 6 Control System/Controller System Takes commands from the computer and output signals to control the various motors. 6.1 Feedback Sensor SystemMonitors key elements of the process and provides feedback to the user 6.2 Control Display SystemDisplays feedback and information to operator 3 7 Support AssemblyFoundation for entire machine consisting of base, column, and headstock 3 8 Milling Head or Spindle AssemblySpindle, Mounts, Collets, Bits, etc 9 9 Power SystemConditioning and distributing across assemblies 3 10 Software Interface systemMach3, G code, optimization code\ Optimization

Critical Subsystems Priority LevelSubsystem #Subsystems NameDescription 92 Vacuum Clamp Assembly Uses vacuum force to secure/align PCB copper bare board to mill base plate 93 Transverse Feed Assembly Energizes and Controls motion in the X-Y axis in defined increments 94 Vertical Spindle Feed Assembly Energizes and Controls motion in the Z axis in defined increments 96 Control System/Controller System Takes commands from the computer and output signals to control the various motors. 99Power System Conditioning and distributing across assemblies

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

Vacuum Clamp- Shopvac vs 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 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

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.

Shop Vac Vacuum Clamp Demo

Registration System on Vacuum Clamp Assembly 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 ●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

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

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 o Technical suggestions for our project from a Engineer Support Representative o Gave a cost estimate for their system

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.

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

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

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

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

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

Spindle Motor Considerations Feasibility o Air motors - Infrastructure (air dryer, supply regulator, etc.) - Rare and Expensive (All supplier quotes over budget) + Easily reach speeds of 100,000+ RPM o DC motors + Simple implementation (voltage or PWM speed control) - Low speed (12,000 RPM unless specialty and over budget) o 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)

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 < ” + Can control speed with PWM or built in dial Bosch PR20EVSNK Colt and aftermarket collet from precisebits.com

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 24,000 to 60,000 RPM For a 0.625”/1.6mm mill bit on.5 to 1 oz Copper: 60 24,000 to 40,000 RPM

Control Software and Breakout Board Selection ●Considered Software Options ●Software Breakdown ●Hardware Breakdown ●Concept Scoring ●FInal Selection

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

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

Concept Scoring

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 Controller MK2/4CNC USB Software

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

System Architecture - Controls Breakout Board Main Logic Board Computer X Motor Driver Y Motor Driver Z Motor Driver Router Motor Driver USB Vacuum System Interlock System Breakout Board - Processes design file, converts file to motor control signals 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 Main logic Board - Monitors all systems (ie halts operation if vacuum table is off, interlock open)

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: o Modifying router circuitry o Microcontroller: Using a microcontroller with PWM channel and H-bridge configuration.

Spindle Motor Control Cost MethodProsConsPicture VFD ● Easy to implement (off-the- shelf) ● Can interface to main logic board ● Available in single or three- phase I/O ● Adds additional stand- alone “box” to design ● Can be bulky Triac Phase Control Microcontrolle r and H- Bridge

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

Updated DMC Estimate

Risk Analysis Update

Schedule Update

Next Steps