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Slide 001: Cutting Operations β€” Materials & Tool Selection

Slide Visual

Cutting Operations β€” Materials & Tool Selection

Slide Overview

This slide covers the practical aspects of CNC cutting operations, focusing on material-specific considerations and tool selection for optimal results. Students will learn to match the right tool to each material and cutting operation.

Instruction Notes

Material Categories for CNC Routing

Wood & Wood Products - Softwoods (pine, cedar, poplar): Easy to cut, lower cutting forces, tend to produce fuzzy edges. Use sharp tools and adequate feed rates to prevent burning. - Hardwoods (oak, maple, walnut): Higher cutting forces, better edge quality. Require slower feed rates and moderate spindle speeds. Figured grain (curly maple, burls) requires downcut or compression bits. - Plywood: Cross-laminated layers resist tearout in one direction but are prone in the other. Compression bits provide clean edges on both faces. Watch for glue lines dulling tools faster. - MDF: Highly abrasive (resin binder wears tool edges quickly). Produces fine dust β€” excellent dust collection is essential. Very consistent and flat β€” ideal for jigs and templates.

Plastics - Cast acrylic: Machines well with sharp single-flute tools. Chip clearance is critical β€” chips that don't evacuate will re-melt and weld to the tool. Use moderate RPM (12,000-16,000). - Extruded acrylic: Lower melting point than cast β€” more prone to gumming. Reduce RPM further and use aggressive chip load. - HDPE/Delrin: Flexible chips, high chip load OK. Single-flute O-flute preferred. Very forgiving material for beginners.

Metals (on CNC Routers) - Aluminum 6061-T6: Machinable on CNC routers with appropriate parameters. Single-flute, polished O-flute bits required. Cutting fluid mandatory. Maximum stepdown: 0.04"–0.06" per pass. Feed rate: 30-60 IPM at 10,000-16,000 RPM. - Brass: Similar to aluminum but more forgiving. Use 0-flute or single-flute bits. - Steel: NOT suitable for CNC routers β€” requires CNC mill rigidity and low spindle speeds.

Tool Selection Matrix

Operation + Material Recommended Tool
Profile cut, plywood ΒΌ" compression spiral
Pocket, hardwood ΒΌ" 2-flute upcut spiral
Through-cut, acrylic ΒΌ" single-flute O-flute
V-carve, any wood 60Β° or 90Β° V-bit
3D contour, finishing ΒΌ" ball-nose end mill
Slotting, aluminum β…›" single-flute O-flute
Engraving 30Β° or 15Β° engraving bit
Spoilboard surfacing 1"–2" flattening/fly cutter

Recognizing Good vs. Bad Cuts

Train your eyes and ears: - Good cut: Consistent chip formation, clean edges, no burning, steady cutting sound - Rubbing: Fine dust instead of chips, burning smell, high-pitched noise - Overloaded: Rough edges, chatter marks, tool deflection visible, motor straining

Key Talking Points

  1. Material selection drives tool selection β€” never use the wrong tool for the material
  2. Plastics require special attention to chip evacuation and heat management
  3. Aluminum CAN be cut on a CNC router but requires significant parameter reduction
  4. Learning to read chip formation is the most important diagnostic skill
  5. MDF is the most abrasive common material β€” expect faster tool wear

Learning Objectives (Concept Check)

  • [ ] Select the appropriate cutting tool for 5 different material/operation combinations
  • [ ] Describe material-specific challenges for wood, plastic, and aluminum
  • [ ] Identify good vs. bad cutting conditions by visual and auditory cues

Last Updated: 2026-03-19