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Activity 001: Material Identification Challenge

Activity ID: U3M2-ACT-001 Duration: 30 minutes Objective: Students will identify unknown materials using visual inspection, labeling, and reference documentation, then classify each as safe, caution, or banned for laser processing. Group Size: 2-3 students per station Materials Cost: ~$10-15 (sample material set, reusable across sections)

Overview

Students receive a set of 8-10 labeled material samples and must identify each material, classify it for laser safety, and justify their classification using material properties and safety data. This activity builds the critical skill of material identification that prevents toxic fume incidents.

Materials & Equipment Needed

  • Material sample set (8-10 samples, labeled A through J, prepared by instructor):
  • Cast acrylic sheet (clear, with protective film)
  • Polycarbonate sheet (clear, similar appearance to acrylic)
  • PVC sheet or pipe section (labeled with recycling symbol #3)
  • Birch plywood piece
  • MDF piece
  • Natural leather swatch (vegetable-tanned)
  • ABS sheet (recycling symbol #7 or labeled)
  • Cardboard piece
  • PETG sheet (recycling symbol #1)
  • Cork sheet
  • Material reference guide (laminated, showing recycling symbols, identification marks)
  • Magnifying glass
  • Identification worksheet
  • Material Safety Classification poster (on the wall or provided)

Instructions & Procedure

Phase 1: Initial Identification (15 min) 1. Examine each sample systematically: - Look for manufacturer labels, recycling symbols, or material stamps - Note the color, transparency, flexibility, and texture - Check for protective film (acrylic often has paper masking) - Look at edge characteristics (cast acrylic has smooth machined edges; extruded may show slight texture) 2. For each sample, record on your worksheet: - Sample letter (A-J) - Your material identification (what you think it is) - Evidence supporting your identification (label, symbol, properties) - Safety classification: SAFE / CAUTION / BANNED - If banned: what toxic hazard does it pose? 3. For the two clear plastic samples: describe how you would distinguish between them if there were no labels (hint: acrylic sheets often have a distinct smell when edge is scraped)

Phase 2: Verification and Discussion (10 min) 4. Instructor reveals the correct identification for each sample 5. Score your accuracy: - Correct material identification: 2 points per sample - Correct safety classification: 2 points per sample - Correct hazard identification (for banned materials): 1 point per sample 6. Discuss: which samples were most difficult to identify? Why? 7. For any misidentified samples, discuss what additional information would have helped

Phase 3: Decision Scenarios (5 min) 8. Answer the following scenario questions on your worksheet: - A student brings in a black rigid plastic panel with no labels. They want to cut a phone stand. What do you do? - You find acrylic offcuts in the scrap bin. Some have masking film with "CAST" printed on it; others have no markings. Can you use the unmarked pieces? - A student wants to cut a yoga mat. What is the most likely material, and is it safe?

Discussion Points

  • Why is it more dangerous to misidentify a banned material as safe than to misidentify a safe material as banned?
  • What recycling symbols help identify laser-safe vs. laser-unsafe plastics?
  • How would you set up a material management system in a makerspace to prevent unknown materials from reaching the laser?
  • What is the simplest rule students should follow regarding material identification?

Expected Outcomes

  • Students should correctly identify 6+ of 8-10 samples
  • Students should correctly classify all banned materials (PVC, polycarbonate, ABS) — misclassifying these is a safety failure
  • Students should articulate the "when in doubt, don't cut" principle

Assessment Rubric

Criterion Excellent (5) Proficient (3) Needs Improvement (1)
Material Identification 8+ samples correctly identified with evidence 6-7 samples correctly identified Fewer than 6 correct
Safety Classification ALL banned materials correctly classified 1 banned material misclassified Multiple banned materials misclassified (safety failure)
Evidence Quality Specific evidence cited for each identification (labels, symbols, properties) Some evidence but relying on guessing for others No evidence — pure guessing
Scenario Responses Correct, cautious responses demonstrating "when in doubt, don't cut" Mostly correct but one risky response Responses indicate willingness to cut unknown materials

Safety Considerations

  • All samples are handled at room temperature — no laser operation in this activity
  • Some plastic samples may have sharp edges from cutting — handle carefully
  • If any sample is broken during handling, do not attempt to smell or taste it for identification
  • Wash hands after handling material samples

Last Updated: 2026-03-19