• CNC Assembly:• 3 axis rigid PVC structure• NEMA 17 Motors and lead
screws• Off the shelf Router and
Specialty collet• Vacuum Table to hold down work
piece• Registration system to align
board• Web Cam to view work on
monitor display• Limit and Homing sensors to
detect position
• Debris Management:• Shop Vacuum and hose
attachment at point of router contact
• Safety Systems:• Emergency Stop Button• Interlock System
• Electronics:
• Motion Control board• Motor Driver boards (3) • Input/Output board• 5, 12, 24V power supplies• Router and Vacuum Relay
• Mach3 Software • Open source CNC control
program
Implemented Features
P14311: PCB Isolation Routing SystemCustomer:The Center for Electronics Manufacturing & Assembly (CEMA)Jeff Lonneville, Lab Technician
Sponsor:Scott Systems Robert Scott, Owner
Team Members: Joseph Post (EE), Sarah Duman (IE), Richard Kalb (EE), Zoё Rabinowitz (ME), Kevin Richard (EE), Marley Collier Sears (ME), Matthew Clark (ME) (photo, from left to right)Guide: Vincent Burolla2013 - 2014
Develop an in-house prototyping system to create wiring patterns and component holes on printed circuit boards (PCBs).
Problem Statement
• Handle boards up to 5” x 5”• Reliably and accurately drill and mill patterns with ± .001” tolerance• Easy and safe to use
Objectives
• Implement automatic (no operator involvement) homing functions in all three axes• Create macros in Mach3 to improve system flow• Optimize tool path to minimize machining time• Machine vacuum table sacrificial layer from nylon to ensure a level workspace• Develop visual alert system through enclosure lighting to notify the operator about emergency situations
Suggestions for Improvements
PCB Prototyping Process
PCB milling in progress
Finished PCB
Power on the PCB Isolation Routing System
Convert PCB design files to CNC G-code
Import G-code into Mach3
Home (or “Zero”) the machine to origin of the
design
Insert 1/8” drill bits and drill registration pin holes
Re-home the machine over the origin registration pin
Insert additional drill bit(s) to drill any through hole
features
Insert the milling bit to mill board traces and features
Remove the completed PCB from the system
Remove and clean the workspace of any remaining
debris
Power down the system
Testing and Analysis
Specification (Metric) Unit of Measure
Marginal Value
IdealValue
Concluded Condition
Physical Footprint ft^3 40 8 PassWeight of Machine lbs 600 300 Pass
Eliminate potential for injuries Binary Pass Pass PassNoise Generation dBA <100 <75 Marginal Pass
Minimum Width Between Traces Supported inches 0.020 0.016 Marginal Pass
Manufacturing Cost $ 2800 2000 Fail ($3450)Minimum Tolerance to locating
positions on board inches 0.005 0.001 Marginal Pass
Feed Rate in/minute 10 100 Marginal PassDepth of Material to be removed inch 0.00137 0.125 PassRequired Voltage for Operation Volts 120 120 Pass
Maximum Tool Bit Size inches 0.125 0.25 PassMinimum Tool Bit Size inches 0.016 0.006 Pass
Router Speed rpm 15000 30000 Marginal PassDebris Removal (Copper and
Substrate) mg 11.7 1.7 Marginal Pass
TIR (Total Indicated Run out) inches <0.0006 <0.0004 Marginal Pass Vacuum Table Force lbs force 10 20 Marginal Pass