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Student Material 001: CNC Routing Troubleshooting Guide & Material Reference

Material ID: U4M4-MAT-001 Purpose: Quick reference for diagnosing CNC routing problems and material-specific cutting parameters Updated: 2026-03-19

Troubleshooting Flowchart

PROBLEM OBSERVED
β”‚
β”œβ”€β”€ Visual Defect on Cut Surface?
β”‚   β”œβ”€β”€ Burn marks β†’ Feed too slow OR dull tool
β”‚   β”‚   Fix: Increase feed 25-50%, check/replace tool
β”‚   β”œβ”€β”€ Chatter marks (even ridges) β†’ Vibration/resonance
β”‚   β”‚   Fix: Change RPM Β±15%, reduce stepdown, shorten stick-out
β”‚   β”œβ”€β”€ Fuzzy/torn edges β†’ Wrong bit geometry OR dull tool
β”‚   β”‚   Fix: Use downcut/compression bit, replace dull tool
β”‚   β”œβ”€β”€ Rough/splintered β†’ Dull tool OR excessive chip load
β”‚   β”‚   Fix: Replace tool, reduce feed rate
β”‚   └── Melted/welded (plastics) β†’ RPM too high, feed too slow
β”‚       Fix: Reduce RPM, increase feed, use single-flute
β”‚
β”œβ”€β”€ Dimensional Error?
β”‚   β”œβ”€β”€ Consistently oversized β†’ Tool deflection
β”‚   β”‚   Fix: Reduce stepdown, reduce feed, shorten stick-out
β”‚   β”œβ”€β”€ Consistently undersized β†’ Tool diameter wrong in CAM
β”‚   β”‚   Fix: Verify tool diameter setting, measure actual tool
β”‚   β”œβ”€β”€ Off by percentage β†’ Steps/mm calibration error
β”‚   β”‚   Fix: Recalibrate axis in controller settings
β”‚   └── Varies across bed β†’ Spoilboard not flat
β”‚       Fix: Resurface spoilboard with flattening bit
β”‚
β”œβ”€β”€ Abnormal Sound?
β”‚   β”œβ”€β”€ High-pitched squeal β†’ Rubbing (chip load too low)
β”‚   β”‚   Fix: Increase feed rate OR decrease RPM
β”‚   β”œβ”€β”€ Chattering/vibration β†’ Resonance
β”‚   β”‚   Fix: Change RPM, reduce depth, improve workholding
β”‚   β”œβ”€β”€ Grinding/clicking β†’ Mechanical issue
β”‚   β”‚   Fix: STOP β€” check bearings, lead screws, couplers
β”‚   └── Motor straining β†’ Overloaded
β”‚       Fix: Reduce feed rate and/or stepdown
β”‚
└── Machine/Safety Issue?
    β”œβ”€β”€ Material shifted β†’ Workholding failure
    β”‚   Fix: E-STOP, re-secure, add hold, reduce forces
    β”œβ”€β”€ Tool broke β†’ Overload, collision, or fatigue
    β”‚   Fix: E-STOP, inspect, determine cause before resuming
    β”œβ”€β”€ Smoke/fire β†’ Friction, dust ignition
    β”‚   Fix: E-STOP, extinguisher if needed, ventilate
    └── Lost position/steps β†’ Motor stall or missed steps
        Fix: Re-home, check motor current, reduce rapid speed

Material Quick Reference Cards

Wood (Softwood & Hardwood)

Parameter Softwood (Pine) Hardwood (Oak/Maple)
Tool ΒΌ" 2-flute upcut ΒΌ" 2-flute upcut
RPM 16,000–20,000 16,000–18,000
Feed (IPM) 120–180 100–150
Chip Load 0.003–0.005 0.003–0.005
Stepdown 0.1875"–0.25" 0.125"–0.1875"
Key Issue Burning, fuzzy edges Tool wear, burning
Pro Tip Increase feed if burning Use sharp tools, reduce RPM for figured grain

Plywood & MDF

Parameter Plywood MDF
Tool ΒΌ" compression (through-cut), upcut (pocket) ΒΌ" 2-flute upcut
RPM 16,000–18,000 16,000–18,000
Feed (IPM) 100–150 100–150
Chip Load 0.003–0.005 0.003–0.005
Stepdown 0.125"–0.25" 0.125"–0.25"
Key Issue Veneer tearout Dust (health hazard), tool wear
Pro Tip Compression bit for clean both faces P100 respirator mandatory, expect faster tool dulling

Plastics

Parameter Cast Acrylic HDPE/Delrin
Tool ΒΌ" single-flute O-flute ΒΌ" single-flute O-flute
RPM 10,000–16,000 10,000–14,000
Feed (IPM) 60–120 80–140
Chip Load 0.003–0.006 0.004–0.007
Stepdown 0.10"–0.1875" 0.1875"–0.25"
Key Issue Melting, chip re-welding Stringy chips, gumming
Pro Tip Lower RPM, aggressive feed, leave protective film on Very forgiving β€” great learning material

Aluminum (6061-T6)

Parameter Value
Tool ΒΌ" single-flute O-flute (polished)
RPM 10,000–16,000
Feed (IPM) 30–60
Chip Load 0.001–0.003
Stepdown 0.04"–0.06"
Stepover 25–40% of tool diameter
Cutting Fluid Required β€” WD-40, IPA, or aluminum cutting fluid
Key Issue Chip welding, heat, tool breakage
Pro Tip Light passes, good lubrication, clear chips frequently

Tool Life Indicators

Indicator New/Sharp Tool Worn Tool Replace Immediately
Cutting edge appearance Matte, clean edge Slightly shiny/rounded Bright, reflective edge
Cutting sound Smooth, consistent Slightly louder Squealing, straining
Chip formation Clean, consistent curls Smaller, dustier chips Powder/dust only
Surface finish Smooth, clean Slightly rough Rough, burned
Dimensional accuracy Within Β±0.005" Drifting oversized >0.015" error
Approximate life (wood) 0–2 hours 2–4 hours 4+ hours
Approximate life (MDF) 0–1 hour 1–2 hours 2+ hours
Approximate life (aluminum) 0–30 min 30–60 min 60+ min

Post-Cut Quality Checklist

Dimensional Verification:
[ ] Overall X dimension measured: ___" (target: ___")
[ ] Overall Y dimension measured: ___" (target: ___")
[ ] Pocket depth measured: ___" (target: ___")
[ ] Hole diameter measured: ___" (target: ___")
[ ] Corner radius verified: ___" (target: β‰₯ tool radius)

Surface Quality:
[ ] No burn marks
[ ] No chatter marks
[ ] No tearout or fuzzy edges
[ ] Consistent finish across entire cut
[ ] All tabs present and intact

Documentation:
[ ] Material type recorded
[ ] Tool type and diameter recorded
[ ] RPM and feed rate recorded
[ ] Any issues noted with corrective action taken
[ ] Photos taken of finished part

Last Updated: 2026-03-19