Unit 04: CNC Routing (ShopBot)¶

Unit Metadata¶

Microcredential ID: MCCPDL-U04-CNC-v1.0
Title: CNC Routing & Subtractive Fabrication (ShopBot Platform)
Version: 1.0
Credit Hours: 12 (3 hours per module)
Prerequisites: None; experience with CAD/CAM software helpful
Target Audience: Product designers, fabricators, woodworkers, engineers, makers transitioning to precision CNC

Unit Description¶

This unit provides comprehensive training in CNC routing using ShopBot-series machines (CNC Pro, PRT, or Buddy). Students learn CNC fundamentals (coordinate systems, axes, motion planning), CAD/CAM software workflows (VCarve/Aspire), toolpath generation and optimization, machine setup and zeroing, workholding techniques, and safe cutting operations. The unit emphasizes precision, feed/speed optimization, tool selection, and troubleshooting mechanical failures. Upon completion, students can independently design and execute CNC projects from concept through finished product.

Standards Alignment¶

ISO 13849-1:2023 - Safety of Machinery — Safety-Related Parts of Control Systems
OSHA 1910.212 - Machine Guarding General Requirements
OSHA 1910.303 - General Electrical Requirements
NFPA 79 - Electrical Standard for Industrial Machinery
ISO 1101:2023 - Geometric Dimensioning and Tolerancing (tolerances and precision)
ASA/ANSI B4.4 - Preferred Metric Limits and Fits (tolerances, fits, running clearances)
ShopBot Technical Documentation (machine-specific)

Learning Outcomes¶

Knowledge¶

Understand CNC machine coordinates (machine vs. work coordinates, homing, zeroing)
Explain spindle operation, feed rate, plunge rate, and their effects on cut quality
Identify and select appropriate cutting tools (end mill, V-groove, upcut, downcut bits)
Calculate feeds and speeds for different materials and tool diameters
Interpret toolpath visualization and detect collision risks before cutting
Recognize mechanical limitations (maximum feed, spindle speed, rigidity constraints)

Skills¶

Design toolpaths in VCarve Pro or Aspire using various bit types and cutting strategies
Home the CNC machine and establish X/Y/Z zero positions relative to workpiece
Install and verify cutting tools (measuring bit length, checking runout)
Calculate optimal feeds/speeds for wood, plastic, and non-ferrous metals
Set up workholding (clamps, vacuum, T-slots) to secure material safely
Execute cutting operations with proper spindle startup, feed control, and safety awareness
Simulate toolpaths and identify potential collisions before running on actual machine

Competency¶

Design a complete CNC project from CAD file through toolpath to finished part
Select cutting tools and feeds/speeds for optimal surface finish and tool life
Establish and maintain work-holding setups that prevent material slipping
Troubleshoot cutting errors (chat marks, tool breakage, misalignment, finish issues)
Perform preventive maintenance (dust collection, calibration, tool inspection)
Apply geometric tolerancing principles to achieve functional fit/clearance specifications

Unit Structure¶

Module	Title	Duration	Focus
M1	CNC Fundamentals & Machine Architecture	3 hours	Axes, coordinate systems, controller, spindle, gantry, machine vs. work coordinates
M2	CAD/CAM & Toolpath Generation	3 hours	VCarve/Aspire software, tool libraries, cutting strategies, feeds/speeds, simulation
M3	Machine Setup & Workholding	3 hours	Homing, zeroing, tool installation, clamps/vacuum/T-slots, spindle startup, dust collection
M4	Cutting Operations & Troubleshooting	3 hours	Running jobs, monitoring, feed rate adjustment, error diagnosis, tool breakage, finishing

Assessment Strategy¶

Formative¶

Module quizzes (10-15 questions each, emphasize safe operation)
Hands-on competency: homing/zeroing procedure, tool installation, clamp setup
Toolpath design review: students submit design + toolpath for instructor verification before cutting

Summative¶

Practical Project: Design and execute a CNC cutting project with functional tolerances (dovetail joint, press fit, snap fit)
Feed/Speed Calculation: Given material, tool, desired finish, calculate appropriate feeds/speeds and justify choices
Troubleshooting Scenario: Given a failed cut or mechanical problem, diagnose root cause and prescribe solution

Portfolio Evidence¶

Photos of 3-4 completed projects showing different materials (wood, acrylic, plastic, aluminum)
Design files demonstrating tool selection and toolpath optimization
Maintenance log (spindle inspection, dust collection cleaning, tool runout check)
Feed/speed reference sheets for materials worked with

Instructional Resources¶

Primary Resources¶

CNC Router: ShopBot CNC Pro, PRT, or Buddy series (control system: ShopBot software)
CAM Software: VCarve Pro 12+ or Aspire (primary design tools)
Cutting Tools: Upcut and downcut end mills (1/8", 1/4", 1/2"), V-groove engraving bits, multiple flute options
Workholding: Clamps, vacuum hold-down system, T-slot table, spoilboard
Dust Collection: Dust collector (1.5 hp minimum), hoses, cyclone separator (recommended)
Material Library: Plywood, MDF, hardwoods (oak, maple), acrylic, HDPE, aluminum 6061 (annealed)

Software & Documentation¶

ShopBot software manual (control and communication)
VCarve/Aspire tutorials (basic to advanced)
Feeds and speeds reference charts for common materials and tools
Tool runout measurement procedure (dial indicator)
Machine calibration documentation

Safety Equipment¶

Eye protection (required; wood chips at high speed are hazardous)
Dust mask or respirator (for hardwood and MDF dust)
Hearing protection (optional; spindle is loud, ~85dB)
Proper footwear (closed-toe required; no sandals or loose clothing)
Emergency stop (E-stop) accessible and tested regularly

Accessibility Considerations¶

Visual Accessibility¶

High-contrast slide materials (16pt minimum font)
Detailed verbal descriptions of toolpath visualization and simulation
Large-format printed feeds/speeds reference charts
Screen reader compatible digital materials

Auditory Accessibility¶

CNC spindle is loud (~85dB); hearing protection available
Visual indicators for tool path simulation (color-coded cutting vs. non-cutting moves)
Written step-by-step procedures (backup to verbal instruction)
Captions on all instructional videos

Motor Accessibility¶

Pre-positioned material holders for students with limited mobility
Adaptive clamping systems (ergonomic grip alternatives)
Video demonstration of tool installation and zeroing as alternative to hands-on
Simplified setup procedure for students unable to perform certain physical tasks

Cognitive Accessibility¶

Modular structure with 15-20 minute learning segments
Flowchart for tool selection and feeds/speeds calculation
Glossary of CNC terminology (machine-specific jargon)
Step-by-step procedural guides with photos/diagrams

Neurodiversity Accommodations¶

ADHD: Timed task segments, movement breaks, color-coded tool/feed reference sheets, checklist-based setup
Autism: Consistent terminology, predictable operation sequences, advance notice of loud spindle noise
Dyslexia: Graphical guides, video demonstrations, audio descriptions, color-coded material/tool reference
Sensory Processing: Hearing protection, quiet workspace for planning/CAD work, sensory profile assessment

Unit Learning Path¶

START → M1 CNC Fundamentals (machine anatomy, coordinate systems, motion planning)
        ↓
        → M2 CAD/CAM & Toolpath (software design, tool selection, feeds/speeds, simulation)
        ↓
        → M3 Machine Setup (hands-on: homing, zeroing, tool installation, workholding)
        ↓
        → M4 Cutting Operations (supervised cutting, troubleshooting, optimization)
        ↓
        → Practical Project Design & Execution (supervised first 2-3 projects)
        ↓
        → Independent Operation (once safety/technical competency verified)
        ↓
        → Portfolio Assessment
        ↓
        END (Qualified CNC operator)

Success Criteria¶

Passing score (70%+) on knowledge assessments
Successful execution of 2+ CNC cutting projects with acceptable surface finish
Demonstration of proper homing, zeroing, and tool installation procedures
Feeds/speed calculations within 10% of instructor reference (accounting for material/tool/desired finish)
Ability to simulate toolpaths and identify collision risks before cutting
Completion of maintenance log (dust collection, tool inspection, spoilboard leveling)
Safety: zero incidents; proper PPE use; E-stop accessible and tested

Lab Setup & Safety Compliance¶

Dedicated CNC Area: Separated from other equipment; dust control system operational
Dust Collection: Continuous during cutting operations; filter checked monthly
Machine Guarding: Spindle enclosure safe; no rotating parts accessible during operation
Safety Signage: "CNC in Operation—Do Not Approach" visible; E-stop location marked
Material Storage: Organized; flammable materials (certain plastics) stored safely
Operator Supervision: First 5 projects require instructor oversight; then independent with spot checks

Regulatory Compliance Notes¶

OSHA 1910.212 requires proper machine guarding and safe operation procedures
OSHA 1910.303 mandates electrical safety compliance (machine certified per UL standards)
ShopBot machine must be operated per manufacturer documentation
Tool runout must be checked per industry standards (<0.005" acceptable for normal work)
Dust control required per OSHA standards (hazardous wood dust, MDF particle standards)
All operators must understand E-stop location and function

Integration with Other Units¶

Unit 01 & 02 (FDM/SLA): CNC can post-process 3D-printed parts or create fixtures/jigs for printing
Unit 03 (Laser): Both processes produce precision parts; laser for flat cut/engrave, CNC for 3D/subtractive
Portfolio Path: Design → 3D print (FDM/SLA) → Laser cut/engrave OR CNC rout for advanced geometry

Advanced Topics (Optional Extensions)¶

Multi-tool projects (switching bits to optimize for different features)
Advanced work-holding (vacuum tables, custom fixtures, 4th-axis jigs)
Tool optimization (feed/speed tuning for specific materials and finishes)
CAM efficiency (nesting, automatic tool changes, reducing tool path time)
3D CNC work (3D geometry, stepped toolpaths, high-Z operations)
Aluminum cutting (tool selection, coolant strategies, chip evacuation)

Career Pathway¶

Lab Technician: Supervise student CNC operations
CNC Programmer: Advanced CAM design and toolpath optimization
Production Fabricator: Small-batch manufacturing using CNC
Prototype Engineer: Design and execute rapid manufacturing projects

Last Updated: 2026-03-18 Maintained By: MCC Prototype Design Lab Curriculum Development Equipment Maintenance Schedule: Monthly inspection, quarterly calibration, annual professional service