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P14311: PCB Isolation Routing System. Systems Design Review. Agenda. Team Introductions. Our Senior Design Team. Problem Statement. RIT students need rapid prototyping for creation of unique circuit boards Requires multiple revisions to perfect each circuit board
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P14311: PCB Isolation Routing System Systems Design Review
Team Introductions Our Senior Design Team
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 • Long lead times • Expensive • Limits circuit refinement • Students not involved in process
Benchmarking- Scott Systems Isolation Router • Able to produce double-sided Board • Smallest bits used - .016” • Minimum width between traces - 5mm • Stepper control for Z-axis • Stepper control for X-Y movement • Alignment pins and double sided tape used to secure board • Sacrificial plastic layer • Uses an air gun to blow dust out during the drilling • PVC with shop-vac sucks up debris • Data Flow – Eagle design file G-codeFlashcut CNC Motors
Pros, Cons, Potential Improvements • Pros: • Can etch double-sided boards • Easy to switch bits • 5mm minimum trace width • Cons: • System lacks real time feedback sensors • X,Y, and Z, axis alignment is done manually. • Improvements • Improve debris management • Replace or repair Z-axis motor • Enclose system
Benchmarking- RIT Robotics Lab • Milling set-up is not used regularly because it’s a pain • Zeroing the plane is highly mechanical • Smallest tolerance is 10 mil • Floor of the mill is warped • Difficult to change drill bits • Interface software include expensive Isopro • Manual debris management • Utilizes two alignment pins • Board is secured down with tape
Pros, Cons, Potential Improvements • Pros: • Relatively Inexpensive • Cons: • Difficult to swap bits • Poor board alignment process • Z-axis solenoid • Improvements • Debris management system • Z-axis zeroing
Concept #1 X-Y axis Control of Spindle Assembly Vacuum Nest with Alignment Pins Spindle Assembly Cyclone Separator Electronic Waste Collection Upper and Lower Acrylic Guards Pressurized Air Nozzle Z axis Control of Base + Combination nozzle/vacuum with cyclone separator effectively manages debris + Straight forward design easy to understand + Vacuum nest and alignment pins ensure accuracy and repeatability - Minimal guards allow access to moving parts during operation - Difficult to relocate, much larger than Ryan’s and Rob’s systems - Large weight of gantry limits maximum accuracy - Redundant systems increase complexity
Concept #2 +Collet for holding tooling + Suction debris removal +Alignment Template system - DC motors with encoders for X,Y,Z - Horizontal Vice for mounting
Concept #6 + X- and Y-axis control using steppers and lead screws, which offers great resolution + Fully enclosed unit provides a much safer operating environment + Interlock would safely disconnect power in case of emergency/unit malfunction + Unit is overall very easy to use (assuming board is aligned) - Incineration not a feasible method of debris management - Rack and pinion Z-axis movement control would cause unnecessary backlash - Board alignment not very easily performed with electromagnets
Hybrid Solution- Selected Concept Stepper Motor with Lead Screw for Z Axis Control Vacuum Attachment Spindle Motor and Collet Assembly Vacuum Clamp Sourced From Main Vacuum Pressurized Air Nozzle X and Z Axis Wire Management Debris Management Vacuum Assembly Stepper Motor with Lead Screw for X Axis Control Vacuum Clamping w/ Replaceable Sacrificial Layer Guide Rails Stepper Motor with Lead Screw for Y Axis Control
Hybrid Solution- Selected Concept To Pressurized Air Source Acrylic Door Assembly To Vacuum Assembly with HEPA Filter Metal Casing Door Handle Emergency Kill Switch To Spindle VFD and X, Y, and Z Axis Stepper Motor Control Door Interlock
System Block Diagram Interlock Computer Debris Management System GUI USB, serial, Ethernet, etc Main Logic Board Design file G-code Motor Theta Motor X USB, serial, Ethernet, etc Power conditioning Motor Y Motor Controller Power Source Motor Z
Engineering Analysis – Vacuum Table • 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.
Engineering Analysis – Spindle vs Router • High Speed (~25,000+ RPM) but with manual control • Large run out, not published as they are typically hobbyist and woodworking • Run directly from 120 VAC line power • Heat problem, not designed to be run continuously • Low average cost (Free - $200) • Brand specific collets • Loud Commercial Routers
Engineering Analysis – Spindle vs Router • Low to Medium Speeds (usually 400 to 24,000 RPM) • Extremely low run out (typically less than 0.005mm/0.0002”) • Need an inverter (capable of producing 0-400Hz @240VAC) • Air or Water cooled options available • Higher average cost ($100 - $700) • Standardized collet sizes (ER11, ER20, R8, 3MT, etc.) • Quiet Spindle Motors
Engineering Analysis – Spindle vs Router • Higher cost of spindle motor justified by advantages • Inverter vs. speed control, ~ equal complexity (VFD) • More professional look and results from spindle • Justifies laser centering upgrade in the future
Future Engineering Analysis • Weight analysis • Can the Z motor handle the weight of spindle? • Vacuum Analysis- • Can one shop vacuum both collect debris and secure board? • Does the vacuum have enough suction to keep the board secure while milling the outline?
Potential Test Plans • PCB Trace Accuracy Analysis • Attach pen to Gantry to draw board on paper • Test movement of carriage • Check condition power
