Slide 001: How SLA Printing Works¶
Slide Visual¶
Slide Overview¶
This slide introduces the fundamental operating principle of SLA 3D printing, focusing on the inverted MSLA architecture used by most modern desktop resin printers. Students will understand the light path from LED to cured layer, the role of each major component, and how SLA differs fundamentally from FDM extrusion-based printing.
Instruction Notes¶
The SLA Process — Step by Step¶
In an inverted (bottom-up) MSLA printer, each layer is formed through this sequence: 1. The build platform descends into the resin vat until it is one layer height above the FEP film (typically 0.050mm / 50 microns) 2. The UV LED array (405nm wavelength, 30-60W power) illuminates the LCD masking screen from below 3. The LCD displays the cross-section image for the current layer — white pixels transmit UV light, black pixels block it 4. UV light passes through the transparent FEP (fluorinated ethylene propylene) film at the bottom of the vat and strikes the liquid resin 5. Exposed resin photopolymerizes in 1-3 seconds (monochrome LCD) or 6-12 seconds (RGB LCD), bonding to the build platform or the previous layer 6. The build platform lifts 5-10mm to peel the cured layer off the FEP film (the "peel" step) 7. The platform lowers back down, leaving a gap of exactly one layer height, and the cycle repeats
Key Components¶
| Component | Function | Typical Specification |
|---|---|---|
| UV LED Array | Light source for curing | 405nm wavelength, 30-60W, uniform illumination |
| LCD Screen | Photomask — selectively transmits UV | 4K-12K resolution, monochrome preferred |
| FEP Film | Transparent vat floor, non-stick release surface | 0.1-0.15mm thick, replaced every 20-50 prints |
| Resin Vat | Contains liquid photopolymer resin | Aluminum frame, 200-500mL capacity |
| Build Platform | Part adhesion surface, precision Z movement | Aluminum, textured surface for grip |
| Z-axis Linear Rail | Vertical movement with micron precision | Ball-screw or lead-screw, 1-10 micron resolution |
SLA vs. FDM — Fundamental Differences¶
SLA is a photochemical process (light-driven chemical reaction), while FDM is a thermomechanical process (heat-driven material deposition). This means SLA produces parts with: - Isotropic mechanical properties (equal strength in all directions, unlike FDM's layer-dependent strength) - Significantly higher surface resolution (50 microns XY vs. 400 microns for FDM) - Thermoset chemistry — SLA parts cannot be re-melted or recycled like FDM thermoplastics
Key Talking Points¶
- SLA is a photochemical process, not thermal — UV light triggers a permanent chemical reaction
- The LCD acts as a digital photomask, curing an entire layer simultaneously regardless of complexity
- The FEP film must release cleanly from each cured layer — this peel force is the primary mechanical challenge in bottom-up SLA
Learning Objectives (Concept Check)¶
- [ ] Students can describe the layer-by-layer SLA printing process in correct sequence
- [ ] Students can identify the function of each major SLA printer component
- [ ] Students can explain at least two fundamental differences between SLA and FDM printing
Last Updated: 2026-03-19