AS91611 Hub | Page 2: Materials Science, Slicing & CAD Optimisation

1. Filament Selection: Standard PLA vs. eSUN PLA+ vs. PETG

To reach Merit and Excellence grade boundaries in AS91611, you must justify material selection using physical testing data and mechanical properties rather than just using whatever filament is loaded into the printer.

⭐ Featured Workshop Filament: eSUN PLA+

eSUN PLA+ is an enhanced plant-based thermoplastic containing modified organic impact additives. It provides 2x to 4x greater toughness than standard PLA, features improved interlayer bonding, and significantly reduces brittleness while retaining fast print speeds and minimal warping.

Filament Type	Printing Temp / Bed Temp	Toughness & Tensile Behaviour	Limitations (Broad Context)
Standard PLA	190°C - 210°C Bed: 50°C	High stiffness, low impact strength (brittle). Snaps easily under sudden shock loads.	Softens above 55°C (e.g. inside a car on a hot day). Low UV resistance over long periods outdoors.
eSUN PLA+	210°C - 230°C Bed: 60°C - 80°C	High impact resistance & toughness. Excellent layer fusion, low stringing.	Heat deflection temperature remains around 55°C - 60°C. Not suitable for high-heat environments.
PETG	230°C - 250°C Bed: 70°C - 80°C	High impact strength, flexible elongation, excellent moisture and chemical resistance.	Prone to fine stringing, harder to finish/sand, hygroscopic (absorbs moisture from air rapidly).

2. Slicer Optimisation & Anisotropic Load Dynamics

Additive manufacturing produces anisotropic components (material strength varies depending on the direction of force relative to the layer lines):

Hotter Nozzle Temps for Layer Fusion: Printing eSUN PLA+ at 215°C to 225°C ensures the extruded polymer fuses fully with the layer below, dramatically improving Z-axis shear strength.
Perimeter Walls vs. Infill Density: Adding 1 additional perimeter wall loop adds up to 30% more flexural strength than adding 20% extra internal infill density.
Infill Geometry Selection: A Gyroid infill pattern distributes stress evenly across all three spatial axes, outperforming traditional Grid infill for structural parts.

🛠️ Slicer Trade-Off Calculator (eSUN PLA+ Optimised)

Adjust slicing parameters to evaluate impact on print time, material usage, and structural strength:

Layer Height:

Infill Pattern & Density:

Perimeter Wall Loops:

Est. Print Time: 2h 15m | Filament Used: 34g | Tensile Load Score: 85/100

3. Design for Additive Manufacturing (DFAM) Rules

📐 Overhang Angle Limit & Clearance Tolerances

FDM 3D printers can extrude over angles up to 45 degrees without requiring temporary support structures. Steeper overhangs require support material, which consumes extra filament and leaves surface marks.

For interlocking components (such as clips, hinges, or slide rails), apply a 0.2 mm to 0.3 mm clearance gap in your 3D CAD design to accommodate thermal expansion as plastic cools.

4. Module 2 Interactive Workbook & Tasks

Work through these activities during the week to complete your materials and CAD assessment evidence.

Task A: Interactive Problem-Solving (Drag & Drop)

Drag each print defect or challenge on the left into its correct engineering solution on the right:

Defects / Issues:

1. Part splits easily along layer lines under tension.

2. Interlocking pivot pin fuses tight and won't rotate.

3. Snap-fit arm snaps cleanly on first bend test.

4. Print requires massive messy support structures underneath.

Engineering Solutions: Increase nozzle temp to 220°C & re-orient print flat:

Increase CAD clearance tolerance to 0.3 mm gap:

Switch from standard brittle PLA to toughened eSUN PLA+:

Redesign angles to stay under 45 degrees in CAD:

Task B: Dynamic Multi-Choice Assessment (8 Questions)

Select a question from the drop-down menu or click 'Next Question' to complete the assessment:

Jump to Question:

Task C: Written Portfolio Scenarios & Evidence

Scenario 1: Material Justification & Hotend Optimisation

A student prints a load-bearing mounting bracket for a bicycle using standard PLA at 190°C with 15% grid infill. The bracket snaps along the layer lines on its first road test.

Explain how changing the material to eSUN PLA+, raising the hotend temperature to 220°C, and increasing perimeter wall loops will prevent this failure mode. (Target: 3-5 sentences).

Scenario 2: Design for Additive Manufacturing & Tolerance Control

You are designing a two-part sliding latch mechanism. If the CAD model is drawn with zero clearance gap (0.0 mm), the parts weld together during printing.

Explain why 3D printed parts expand slightly during extrusion, and specify the exact CAD tolerance gap you would apply for smooth mechanical operation.

Scenario 3: ⭐ Excellence Push - Partial Feature Testing Strategy

Instead of printing a full 14-hour physical outcome to verify a snap-fit clip, describe how you would design a Partial Feature Test. Calculate or estimate the savings in time, power, and filament mass, and explain how this demonstrates Excellence in resource sustainability.

Module 2 Glossary

Term	Definition in Additive Manufacturing
eSUN PLA+	A modified PLA formulation engineered with impact additives for superior toughness and high interlayer adhesion strength.
Anisotropy	Material properties varying by direction. 3D prints are strongest along extrusion paths and weaker across layer bonds.
Clearance Tolerance	The intentional dimension gap (0.2 mm - 0.3 mm) created in CAD to allow moving parts to fit together without binding.
Partial Feature Test	Printing an isolated section of a larger design (e.g. clip mechanism) to quickly test fit and function while preserving resources.