Activity 001: Multi-Material Cutting Test & Parameter Optimization¶
Activity ID: U4M4-ACT-001 Duration: 45 minutes Objective: Students will cut identical test patterns in three different materials, compare results, and optimize parameters for each material based on observed outcomes. Group Size: 2-3 students
Overview¶
Students will run a standardized test pattern (pocket + profile) in MDF, plywood, and acrylic (or HDPE), then evaluate surface finish, dimensional accuracy, and chip formation. This comparative approach develops the ability to adapt parameters to different materials.
Materials & Equipment Needed¶
- CNC router with ΒΌ" 2-flute upcut end mill (plus ΒΌ" single-flute O-flute for acrylic)
- 3 test blanks: ΒΎ" MDF (8"Γ8"), ΒΎ" plywood (8"Γ8"), ΒΌ" cast acrylic or HDPE (8"Γ8")
- Pre-programmed G-code: "material_test_pattern.nc" (2" Γ 2" pocket at 0.25" depth + 3" diameter circle profile cut)
- Double-sided tape for workholding
- Touch plate
- Digital calipers
- Magnifying loupe (10Γ or higher)
- Material test evaluation worksheet
- PPE: Safety glasses, hearing protection, dust mask (N95 for MDF)
Instructions & Procedure¶
Phase 1: MDF Test Cut (12 minutes) 1. Secure MDF blank with double-sided tape 2. Set X/Y/Z zero; load material_test_pattern.nc 3. Cut using baseline parameters: 18,000 RPM, 120 IPM feed, 0.125" stepdown 4. After cut completes, measure and record: - Pocket dimensions (width, length, depth) - Circle diameter - Surface finish quality (1-5 scale: 1=rough, 5=smooth) - Edge quality (burning, fuzz, clean) - Chip formation (dust, small chips, large chips) 5. Photograph the results
Phase 2: Plywood Test Cut (12 minutes) 1. Secure plywood blank; set zero; load same G-code 2. Cut with same baseline parameters (18,000 RPM, 120 IPM, 0.125" stepdown) 3. Measure and record same data points 4. Note any tearout on the top or bottom veneer layers 5. If time permits, re-run with a downcut bit and compare top surface quality
Phase 3: Acrylic/HDPE Test Cut (12 minutes) 1. Switch to single-flute O-flute end mill 2. Secure acrylic blank; set zero 3. Adjust parameters for plastic: reduce to 12,000 RPM, 80 IPM, 0.10" stepdown 4. Cut and observe chip formation closely β chips should be small curls, not dust or melted strings 5. Measure and record same data points 6. Note edge clarity (clear/frosted/rough for acrylic)
Phase 4: Comparison Analysis (9 minutes) 1. Complete the comparison table:
| Metric | MDF | Plywood | Acrylic/HDPE |
|---|---|---|---|
| Pocket width (target: 2.000") | |||
| Pocket depth (target: 0.250") | |||
| Circle diameter (target: 3.000") | |||
| Surface finish (1-5) | |||
| Edge quality | |||
| Chip type | |||
| Tool used | |||
| RPM | |||
| Feed rate (IPM) |
- Identify which material was most accurate and hypothesize why
- For each material, recommend one parameter change that would improve the result
- Present findings to the class
Discussion Points¶
- Why did the same parameters produce different results in each material?
- Which material produced the most accurate dimensions? The best surface finish?
- How would you modify the acrylic parameters if you saw melted/welded chips?
- What tool change would improve the plywood top surface quality?
Expected Outcomes¶
- Students observe firsthand how material properties affect cut quality
- Students can identify material-specific issues (MDF dust, plywood tearout, acrylic melting)
- Students develop the ability to recommend parameter adjustments based on observed results
Assessment Rubric¶
| Criteria | Excellent (4) | Proficient (3) | Developing (2) | Beginning (1) |
|---|---|---|---|---|
| Measurement Accuracy | All measurements precise and consistent | Most measurements accurate | Inconsistent measurements | Unable to use calipers properly |
| Material Analysis | Correctly identifies material-specific issues and causes | Identifies most issues | Identifies some issues | Cannot differentiate between materials |
| Parameter Optimization | Recommends specific, justified parameter changes | Recommends reasonable changes | Vague recommendations | No recommendations |
| Documentation | Complete, organized records with photos | Good records with minor gaps | Incomplete records | Missing data |
Safety Considerations¶
- Change to N95 or P100 respirator when cutting MDF (formaldehyde in binder)
- Acrylic chips can be sharp β handle cut pieces carefully
- When switching tools, power off the spindle and engage E-stop
- Ensure dust collection is running for all cuts, especially MDF
- Acrylic cutting can produce fumes β ensure adequate ventilation
Last Updated: 2026-03-19