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Page 1: CNC Assembly: 3 axis  r igid PVC structure   NEMA 17 Motors and lead screws

• 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

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