All layered systems can show stair-stepping in Z. Pixel-based exposure additionally samples the layer image in XY.
VAT PHOTOPOLYMERIZATION · SLA / DLP / MSLA
Vat photopolymerization: SLA, DLP and MSLA
This guide covers SLA, DLP and MSLA exposure, the bottom-up layer cycle, XY/Z resolution, orientation and supports, post-processing and results from a documented tensile-test case study.
01 · EXPOSURE METHODS
Exposure methods: SLA, DLP and MSLA
These methods differ in how light is delivered to each layer. The tabs below show the exposure system and its resolution implications.
SCANNING LASER
SLA traces the cross-section with a focused spot
Reviewed systems use typical laser spots around 50–150 μm. Exposure time grows with the path that must be scanned, while the beam can resolve smooth vector-like contours without a square pixel grid.
02 · LAYER CYCLE
Bottom-up layer cycle
In this bottom-exposure arrangement, each layer cures against a transparent vat window. The interactive cycle below shows the repeated machine sequence.
CURRENT STEP1 · Expose
Selected resin at the vat window receives enough light energy to polymerize and join the previous layer.
- Expose
- Release / lift
- Refill
- Return / set gap
03 · RESOLUTION
XY and Z resolution
Layer thickness controls Z-axis discretization. In DLP and MSLA, XY detail is also sampled by the projected or masked pixel grid; in SLA, XY detail depends on the laser spot and scan increments instead of a fixed square-pixel matrix.
Laser-spot diameter and the X/Y scan increments both influence the smallest reproducible features.
For a fixed pixel count, increasing the projected build area increases the size represented by each pixel at the vat plane.
04 · ORIENTATION + SUPPORTS
Orientation and supports
Vat-photopolymer parts are commonly printed at an angle with supports rather than directly on a large flat face. Orientation affects the cross-section exposed at each layer, the required support structure, usable build volume and the surfaces where support marks remain.
Moderate tilt breaks one large cross-section into a sequence of smaller ones, at the cost of more support contact and longer Z height.
Conceptual comparisonThis control illustrates the geometric trade-off only. Actual orientation and supports depend on the part, resin, printer and validated process settings.
05 · POST-PROCESSING
Cleaning and post-curing
Post-processing is part of the final material condition because residual resin must be removed and the curing procedure changes measured mechanical properties.
Allow excess liquid resin to leave the part and any accessible cavities.
Remove uncured surface resin using the cleaning method specified for the resin.
Support removal can leave marks or local surface defects at the contact points.
Apply the resin-specific curing procedure before treating published mechanical properties as representative of the final material state.
Published test evidence shows substantial property differences between uncured/“green” and post-cured resin data. Use the exact resin formulation and its specified cure schedule when comparing mechanical properties.
06 · MATERIALS CASE STUDY
Tensile test results: general-purpose MSLA resin
General-purpose Elegoo resin was printed on an Elegoo Saturn 4K MSLA machine in horizontal and 45° orientations. The tensile results were similar for these two orientations in this experiment; this does not establish that vat-photopolymer parts are generally isotropic.
- Printer
- Elegoo Saturn 4K MSLA
- Resin
- Elegoo general-purpose resin
- Layer / exposure
- 0.10 mm / 3 s
- Lift / retract
- 70 / 210 mm/min
- Post-cure
- 300 s
- Test standard
- ASTM D638 Type I
Source boundary: These measurements apply to the tested resin, printer, layer/exposure settings and 300 s post-cure schedule. They are not design allowables or Workpiece production qualification data.
MSLA GENERAL-PURPOSE RESINSpecific 2022 experiment
Maximum tensile stress differed by about 5%, while elastic modulus differed by about 6.7% between the two orientations.
Compare filament extrusion, layer height, raster direction and orientation effects.
ENGINEERING TERMSAnisotropy, modulus and failure behaviour →Review the mechanical terms used in this case study.
MATERIAL SELECTIONSee resin material guidance →Resin entries remain educational and are not currently orderable.