P 14311 PCB Isolation Routing System Subsystems Review

P 14311: PCB Isolation Routing System Subsystems Review

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

Selected Concept

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

Priority Level Subsystem # Subsystems Name Description 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) Control System/Controller System Takes commands from the computer and output signals to control the various motors. Feedback Sensor System Monitors key elements of the process and provides feedback to the user Control Display System Displays feedback and information to operator Support Assembly Foundation for entire machine consisting of base, column, and headstock Milling Head or Spindle Assembly Spindle, Mounts, Collets, Bits, etc Power System Conditioning and distributing across assemblies Software Interface system Mach 3, G code, optimization code 5 3 5. 1 3 6 9 6. 1 6. 2 7 3 3 9 3 1 8 9 10 10. 1 Optimization

Critical Subsystems Priority Level Subsystem # Subsystems Name 9 2 Vacuum Clamp Assembly 9 3 Transverse Feed Assembly 9 4 Description Uses vacuum force to secure/align PCB copper bare board to mill base plate Energizes and Controls motion in the X-Y axis in defined increments Vertical Spindle Feed Energizes and Controls motion in the Z Assembly axis in defined increments 9 6 Control System/Controller System 9 9 Power System Takes commands from the computer and output signals to control the various motors. 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 Vacuum Pump + More affordable + Quieter than shopvac + Very high flow rate(150+ cfm) - Can be expensive + Could share vacuum with debris management system. - Very low flow rate(~10 cfm) + Allows for leaks in system + Also acts as a debris management system - High noise level - 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 Vacuum Clamp Demo

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

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 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 + Simplementation (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 < 0. 0004” + Can control speed with PWM or built in dial Bosch PR 20 EVSNK 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. 5 mm) High Feed Rate and Lower Spindle Speed for larger mill bits ( up to 0. 125”/3. 175 mm) For a 0. 015”/0. 38 mm mill bit on. 5 to 1 oz Copper: 10 to 40 in/min @ 24, 000 to 60, 000 RPM For a 0. 625”/1. 6 mm mill bit on. 5 to 1 oz Copper: 60 in/min @ 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 Software CNC USB Controller MK 2/4

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

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

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

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

Updated DMC Estimate

Risk Analysis Update

Schedule Update

Next Steps