Activity 001: Resin Properties Comparison Lab¶

Activity ID: U2M1-ACT-001 Duration: 40 minutes Objective: Students will compare the mechanical properties, surface quality, and handling characteristics of three different resin types by examining pre-printed test specimens. Group Size: 2-3 students per station Materials Cost: ~$10-15 (pre-printed test specimens, reusable)

Overview¶

Students examine sets of pre-printed and fully post-cured test specimens (dog-bone tensile bars and detail test prints) made from standard, tough, and flexible resin. They perform qualitative mechanical tests, measure dimensional accuracy, and evaluate surface quality to understand how resin chemistry translates into real-world part properties.

Materials & Equipment Needed¶

Pre-printed test specimen sets (prepared by instructor, fully washed and cured):
3x dog-bone tensile bars (ASTM D638 Type V): standard, tough, flexible resin
3x detail test prints (miniature with fine features): standard, tough, flexible resin
Digital calipers (0.01mm resolution)
Magnifying glass or digital microscope
Spring scale or fish scale (0-5kg range)
Safety glasses
Nitrile gloves (specimens are fully cured but good practice)
Comparison worksheet
Reference photos of each resin type's data sheet properties

Instructions & Procedure¶

Phase 1: Visual and Tactile Examination (10 min) 1. Put on nitrile gloves and safety glasses 2. Examine each dog-bone specimen visually and record: - Color and transparency (opaque, translucent, transparent) - Surface finish (glossy, matte, textured) - Presence of layer lines (visible, faint, invisible) 3. Gently flex each specimen between your fingers (do NOT attempt to break): - Standard resin: should feel rigid and glassy, minimal flex - Tough resin: should flex slightly before springing back - Flexible resin: should bend easily and return to shape 4. Rate the flexibility of each on a 1-5 scale (1=rigid, 5=rubber-like) 5. Examine the detail test prints under magnification and rate feature clarity 1-5

Phase 2: Dimensional Accuracy Measurement (10 min) 6. Using digital calipers, measure the width and thickness of each dog-bone specimen at 3 points along the narrow section 7. Record all measurements on your worksheet 8. Compare measured dimensions to the designed dimensions (provided on worksheet): - Design width: 3.18mm ± 0.05mm - Design thickness: 3.00mm ± 0.05mm 9. Calculate the dimensional error for each resin type 10. On the detail test prints, measure the smallest successfully printed feature (hole, pin, or wall)

Phase 3: Qualitative Mechanical Comparison (15 min) 11. Scratch test: Using your fingernail, attempt to scratch the surface of each dog-bone specimen. Rate scratch resistance 1-5. 12. Impact test: Hold each specimen 30cm above a hard surface and drop it. Observe and record: - Standard resin: may chip or crack - Tough resin: should bounce with no damage - Flexible resin: should bounce and deform momentarily 13. Flex test with spring scale: Clamp one end of each dog-bone in a vise (provided). Hook the spring scale to the other end and pull perpendicular to the specimen until it deflects 5mm. Record the force required: - Standard resin: high force, sudden break likely if pushed further - Tough resin: moderate force, gradual deformation - Flexible resin: low force, large elastic deformation 14. Record all force values and observations

Phase 4: Application Matching (5 min) 15. Based on your observations, match each resin type to its best application scenario: - Scenario 1: A detailed architectural scale model for a client presentation - Scenario 2: A replacement clip for a laptop hinge that must snap on and off - Scenario 3: A custom phone case that needs drop protection and grip

Discussion Points¶

Why does standard resin produce the finest detail but break most easily?
How does the cross-link density of a resin affect both its hardness and its brittleness?
Would you ever mix resin types? Why or why not? (Answer: generally no — different chemistries can be incompatible)
How would you verify resin properties for a critical application (e.g., medical device)?

Expected Outcomes¶

Standard resin should show the highest dimensional accuracy and surface detail but lowest impact resistance
Tough resin should show moderate detail with significantly higher impact resistance
Flexible resin should show lowest detail and accuracy but highest elongation and impact absorption
Students should correctly match resins to application scenarios

Assessment Rubric¶

Criterion	Excellent (5)	Proficient (3)	Needs Improvement (1)
Measurement Accuracy	All dimensions measured correctly within 0.02mm; error calculations accurate	Most measurements correct; minor calculation errors	Missing measurements or significant errors
Observation Quality	Detailed, specific observations with numerical ratings for all properties	Observations present but lacking specificity	Generic or missing observations
Mechanical Testing	All tests performed correctly with recorded values; insightful comparisons	Tests performed with some missing data	Tests incomplete or incorrectly performed
Application Matching	All scenarios correctly matched with detailed technical justification	Correct matches with basic reasoning	Incorrect matches or no justification

Safety Considerations¶

Wear nitrile gloves when handling all resin specimens (even fully cured parts may have residual surface chemistry)
Wear safety glasses during the drop and flex tests — brittle resin specimens may shatter and produce sharp fragments
Do not attempt to break specimens intentionally — they are reused across class sections
If a specimen does break, do not handle sharp edges with bare hands; sweep fragments into waste bin

Last Updated: 2026-03-19