Orientation
- Critical dimensions are more stable along the build direction
- Support contacts leave marks and must avoid mating faces
- Large unsupported faces are tilted to reduce distortion
Accuracy and comparison
Accuracy is proven by repeatable numbers,
not adjectives
“Accuracy” means different things at different stages. This page breaks out what each parameter governs, along with our actual inspection methods and the factors that most often affect results.
- 22 μmXY projection pixel
- ±0.03 mmFeature tolerance (≤30 mm)
- Ra 1.6 μmSurface after finishing
- 100%Critical dimensions can be 100% inspected
Accuracy parameters
What each parameter actually governs
“Accuracy” means different things at different stages. Each parameter is broken out below so the wrong metric is not quoted against a requirement.
25 μmMinimum layer height — governs curve smoothness and layer lines
22 μmXY projection pixel — governs planar detail resolution
±0.03 mmFeature tolerance for ≤30 mm; beyond this is quoted separately
0.4 mmMinimum through-hole; yield falls below this
0.6 mmMinimum stable wall; thinner requires sample validation
Ra 1.6 μmSurface roughness after finishing; polishing goes lower
Process comparison
How DLP, laser SLA and FDM differ
All three are called 3D printing, but different forming principles give different results. The table compares them for small hearables parts.
| Item | DLP photopolymer (in-house) | Laser SLA | FDM extrusion |
|---|---|---|---|
| Forming method | Whole-layer exposure | Laser point scanning | Molten extrusion line |
| Minimum layer height | 25 μm | 25 μm | 100 μm |
| XY detail | 22 μm pixel | 80–140 μm spot | 400 μm nozzle |
| Small-batch efficiency | High — whole plate cures together | Medium — point-by-point scanning | Low — part-by-part deposition |
| Surface quality | Fine — layer lines nearly invisible | Fine | Visible layer lines |
| Best suited to | Small hearables parts, fine features, 10–500 units | Large, high-precision single parts | Large functional prototypes |
Inspection methods
How dimensions are measured and appearance judged
Inspection depth varies by order. State the application and we will define the corresponding plan instead of defaulting to a visual check.
- 01
Standard sampling
Key external dimensions measured with calipers and sampled to AQL. Suited to assembly checks and internal structural parts.
- 02
Vision-system measurement
Mating faces, tube bores and hole positions are measured on a vision system with reported actual values.
- 03
100% inspection of critical dimensions
Batch orders can specify 100% inspection of critical dimensions, with lot, material and inspection data recorded per part.
- 04
Appearance sample comparison
Once both sides approve the first-article sample, production is compared against it for colour difference, surface uniformity and support-mark placement.
Influencing factors
The same drawing can differ in these respects
Accuracy is not a single variable. These are the factors that most often affect final dimensions and appearance in real projects.
Layer height selection
- 25 μm smooths curves but nearly doubles time
- 50 μm balances most structural parts
- 100 μm suits large outlines and non-critical features
Post-processing intensity
- Sanding and polishing change dimensions — allowance required
- Over-washing affects clarity and surface of clear parts
- Over-curing makes thin walls brittle
Material shrinkage
- Shrinkage varies by grade and must be matched in slicing
- Abrupt wall-thickness changes build internal stress
- For large batches, validate shrinkage compensation on a sample first
For parts over 100 mm or cosmetic parts with extreme surface requirements, we recommend another process rather than forcing DLP.
Need a specific tolerance checked?
Send the drawing and critical dimensions; we assess the achievable range first, then set layer height and finishing tier.