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• 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 System Customer: 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 Burolla 2013 - 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 Ideal Value Concluded Condition Physical Footprint ft^3 40 8 Pass Weight of Machine lbs 600 300 Pass Eliminate potential for injuries Binary Pass Pass Pass Noise 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 Pass Depth of Material to be removed inch 0.00137 0.125 Pass Required Voltage for Operation Volts 120 120 Pass Maximum Tool Bit Size inches 0.125 0.25 Pass Minimum Tool Bit Size inches 0.016 0.006 Pass Router Speed rpm 15000 30000 Marginal Pass Debris 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
