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Activity 002: Power and Speed Settings Demonstration

Activity ID: U3M1-ACT-002 Duration: 40 minutes Objective: Students will observe a power/speed test matrix cut on sample material and analyze how settings affect cut depth, edge quality, and engraving appearance. Group Size: Full class observation + 2-3 per analysis station Materials Cost: ~$3-5 (scrap wood or acrylic for test cuts)

Overview

The instructor demonstrates a power/speed matrix test on a sample material (3mm plywood or acrylic). The matrix produces a grid of cuts and engravings at varying power and speed combinations. Students then examine the results, measure cut quality metrics, and determine the optimal settings for that material.

Materials & Equipment Needed

  • CO2 laser cutter (instructor-operated only for this activity)
  • Test material: 3mm birch plywood or 3mm cast acrylic (approximately 200mm × 150mm)
  • Pre-designed power/speed test matrix file (grid of cuts and engraving squares at 5 power levels × 5 speed levels)
  • Digital calipers (one per analysis group)
  • Magnifying glass (one per group)
  • Ruler
  • Analysis worksheet
  • Safety glasses (laser-appropriate for the enclosure type)

Instructions & Procedure

Phase 1: Instructor Demonstration (15 min) 1. Instructor explains the test matrix design: - 5 rows at different power levels (20%, 40%, 60%, 80%, 100%) - 5 columns at different speeds (5, 10, 15, 20, 30 mm/s for cuts; 100, 200, 300, 400, 500 mm/s for engravings) - Each cell contains: a 10mm line (for cut testing) and a 10mm × 10mm square (for engrave testing) 2. Instructor reviews safety: lid closed, exhaust running, air assist on, all students behind the safety line 3. Instructor loads the test file, sets the focus, and runs the job 4. Students observe through the laser's viewing window (if equipped) or on the control screen 5. After completion, instructor opens the lid and removes the test piece (with exhaust still running for 30 seconds)

Phase 2: Cut Analysis (15 min) 6. Each group receives the test piece (or a section of it) at their analysis station 7. For each CUT cell in the matrix, evaluate and record: - Did the laser cut completely through? (Yes/No) - Kerf width: measure with calipers at the top and bottom of the cut - Edge quality: rate 1-5 (1=heavy charring/melting, 5=clean, minimal discoloration) - Taper: is the cut wider at the top than the bottom? Estimate the difference 8. For each ENGRAVE cell, evaluate and record: - Depth: measure with calipers or estimate visually - Surface quality: rate 1-5 (1=rough/burnt, 5=clean/uniform) - Color contrast: rate 1-5 (1=barely visible, 5=strong contrast) 9. Fill in the matrix table on your worksheet with ratings for each cell

Phase 3: Optimal Settings Analysis (10 min) 10. Based on your data, identify: - The MINIMUM power and speed combination that cuts completely through the material - The OPTIMAL cut settings: complete cut with the cleanest edge quality - The OPTIMAL engrave settings: maximum contrast with clean surface - The settings that produce UNACCEPTABLE results (incomplete cuts, excessive burning) 11. Create a simple graph or table showing the "cut boundary" — the line between settings that cut through and those that don't 12. Calculate: if the optimal cut speed is 10 mm/s and a part perimeter is 400mm, how long will the cutting take? (Answer: 40 seconds for cutting alone, plus acceleration and travel time)

Discussion Points

  • Why does the same power setting produce different results at different speeds?
  • Why is the kerf wider at the top of the cut than the bottom?
  • For a production job (many identical parts), would you choose settings at the edge of the cut boundary or well within it? Why?
  • How would these optimal settings change if the material were 6mm thick instead of 3mm?

Expected Outcomes

  • Students should observe a clear relationship between power, speed, and cut/engrave quality
  • The cut boundary should show that doubling the thickness approximately requires halving the speed or doubling the power
  • High power + low speed should show excessive charring; low power + high speed should show incomplete cuts
  • Optimal settings should be in the middle of the range, not at extremes

Assessment Rubric

Criterion Excellent (5) Proficient (3) Needs Improvement (1)
Measurement Accuracy Kerf and depth measurements precise with consistent methodology Measurements present but some inconsistency Missing measurements or significant errors
Matrix Completion All cells evaluated with ratings and observations Most cells evaluated Many cells incomplete
Optimal Settings ID Correctly identified optimal cut and engrave settings with rationale Settings identified but rationale incomplete Could not identify optimal settings
Analysis Quality Insightful observations about power/speed relationships with graph/table Basic observations present No meaningful analysis

Safety Considerations

  • ONLY the instructor operates the laser cutter during this activity
  • All students remain behind the designated safety line during laser operation
  • The exhaust system must be running before, during, and for 30 seconds after laser operation
  • The test material must be a SAFE material (wood, acrylic) — never PVC, polycarbonate, or unknown materials
  • Allow the test piece to cool for 1 minute after removal before handling
  • Wear safety glasses appropriate for the laser enclosure classification

Last Updated: 2026-03-19