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P14311: PCB Isolation Routing System Team Members: Joseph Post Customer: (EE), Sarah Duman (IE), Richard Kalb (EE), Zoё Rabinowitz (ME), Kevin Richard (EE), Marley Collier Sears (ME), Matthew Clark (ME) The Center for Electronics Manufacturing & Assembly (CEMA) Jeff Lonneville, Lab Technician (photo, from left to right) Sponsor: Guide: Vincent Burolla 2013 - 2014 Scott Systems Robert Scott, Owner PCB Prototyping Process Problem Statement Develop an in-house prototyping system to create wiring patterns and component holes on printed circuit boards (PCBs). Objectives • Handle boards up to 5” x 5” • Reliably and accurately drill and mill patterns with ± .001” tolerance • Easy and safe to use 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 PCB milling in progress Insert 1/8” drill bits and drill registration pin holes Re-home the machine over the origin registration pin Finished PCB Insert additional drill bit(s) to drill any through hole features Remove and clean the workspace of any remaining debris Insert the milling bit to mill board traces and features Implemented Features •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 Power down the 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 Remove the completed PCB from the system Testing and Analysis Specification (Metric) Physical Footprint Weight of Machine Eliminate potential for injuries Noise Generation Minimum Width Between Traces Supported Manufacturing Cost Minimum Tolerance to locating positions on board Feed Rate Depth of Material to be removed Required Voltage for Operation Maximum Tool Bit Size Minimum Tool Bit Size Router Speed Debris Removal (Copper and Substrate) TIR (Total Indicated Run out) Vacuum Table Force Suggestions for Improvements • • • • • 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 Unit of Measure Marginal Value Ideal Value Concluded Condition ft^3 lbs Binary dBA 40 600 Pass <100 8 300 Pass <75 Pass Pass Pass Marginal Pass inches 0.020 0.016 Marginal Pass $ 2800 2000 Fail ($3450) inches 0.005 0.001 Marginal Pass in/minute inch Volts inches inches rpm 10 0.00137 120 0.125 0.016 15000 100 0.125 120 0.25 0.006 30000 Marginal Pass Pass Pass Pass Pass Marginal Pass mg 11.7 1.7 Marginal Pass inches lbs force <0.0006 10 <0.0004 20 Marginal Pass Marginal Pass