SLA 3D Printing: High-Resolution Resin Parts
Stereolithography 3D printing with layer resolution down to 0.025mm and surface finish Ra 0.4 μm. Six resin types: standard, tough, flexible, transparent, castable, and high-temp. Tolerance ±0.1mm, parts up to 500×500×500mm, 3–5 day turnaround.
SLA 3D Printing: High-Resolution Resin Parts
Stereolithography (SLA) is the gold standard for high-resolution 3D printing. A UV laser cures liquid photopolymer resin layer by layer, producing parts with layer heights as fine as 0.025mm and surface finishes of Ra 0.4 μm — smooth enough to eliminate visible layer lines entirely. SLA excels at fine details, thin walls, and complex geometry that other technologies cannot achieve.
At FIRMFG, our SLA service offers six resin types: standard for concept models, tough for functional prototypes, flexible for elastomeric parts, transparent for optical components, castable for investment casting, and high-temp for moulds and thermal applications. Parts are printed with tolerances of ±0.1mm and a maximum build volume of 500 × 500 × 500mm.
This guide covers SLA technology, resin selection, design guidelines, comparison with FDM and SLS, post-processing, and cost factors. Or, skip ahead and request a quote for an immediate price and lead time.
SLA Quick Specifications
Key capabilities and specifications of SLA 3D printing at FIRMFG.
Layer Height
0.025 – 0.1 mm
Dimensional Tolerance
±0.1 mm (±0.004")
Maximum Part Size
500 × 500 × 500 mm
Surface Finish (Ra)
0.4 μm (smooth, no layer lines)
Lead Time
3 – 5 business days
Available Resins
Standard, Tough, Flexible, Transparent, Castable, High-Temp
How SLA 3D Printing Works
SLA uses a UV laser to cure liquid photopolymer resin layer by layer. The process produces the smoothest surface finish and finest detail of any 3D printing technology.
Step 1: CAD Model Preparation
Your 3D CAD file is imported into SLA preparation software. The model is oriented to minimise support contact on cosmetic surfaces and optimise cross-sectional area for peel forces. Support structures are generated as thin, breakaway points. The model is then sliced into layers as thin as 0.025mm.
Typical use: STL/STEP files, 0.025–0.1mm layer height, auto-generated supports
Step 2: UV Laser Photopolymerisation
A UV laser (355nm or 405nm) traces each layer cross-section on the surface of a liquid photopolymer resin vat. The laser cures the resin through photopolymerisation, solidifying a precise 2D cross-section. The cured layer adheres to the build platform or previous layer.
Typical use: UV laser 355–405nm, 25–100 micron spot size, bottom-up or top-down
Step 3: Layer-by-Layer Build
In bottom-up (inverted) systems, the build platform lifts out of the resin vat after each layer, and the vat recoats with fresh resin. In top-down systems, the platform descends into the vat. Each layer takes 5–30 seconds to cure depending on area and resin type. Build continues until the full part is complete.
Typical use: Bottom-up (inverted) or top-down configurations, 5–30 sec/layer
Step 4: Washing & Cleaning
The printed part is removed from the build platform and washed in isopropyl alcohol (IPA) or TPM solvent to remove uncured liquid resin from surfaces and internal channels. The part is then air-dried. Thorough cleaning is critical — any residual uncured resin will cure during post-curing and cause surface defects.
Typical use: IPA or TPM wash, 10–15 min, ultrasonic for complex geometry
Step 5: UV Post-Curing
The cleaned part is placed in a UV post-curing chamber (405nm UV light, 60°C) for 15–60 minutes. Post-curing fully polymerises the resin, achieving final mechanical properties including tensile strength, hardness, and temperature resistance. Without post-curing, parts remain brittle and under-cured.
Typical use: UV chamber 405nm, 60°C, 15–60 min depending on resin and geometry
Step 6: Support Removal & Finishing
Breakaway supports are carefully removed with flush cutters and the contact points sanded smooth. Optional post-processing includes sanding, priming, painting, or clear-coating. Transparent resins can be polished to optical clarity. Parts are inspected for dimensional accuracy and surface quality.
Typical use: Support removal, sanding, polishing, painting for transparent parts
SLA Resin Types
Standard Resin
General-purpose resin for visual prototypes, concept models, and display parts. High detail reproduction, smooth surface, available in grey, white, and black.
Best for: Concept models, visual prototypes, display parts
Tough Resin
ABS-like and PC-like resin with impact resistance and mechanical strength. Suitable for functional prototypes, snap-fits, and assemblies requiring durability.
Best for: Functional prototypes, snap-fits, enclosures, assemblies
Flexible Resin
Shore 50A–80A elastomeric resin simulating TPU and rubber. Flexible, tear-resistant, and suitable for gaskets, seals, grips, and wearable devices.
Best for: Gaskets, seals, grips, wearables, overmould simulation
Transparent Resin
Optically clear resin simulating polycarbonate and PMMA. Transmits 90%+ visible light. Can be polished to optical clarity for lenses, light pipes, and housings.
Best for: Lenses, light pipes, transparent housings, optical parts
Castable Resin
Burnout resin for investment casting. Leaves zero ash residue, captures fine detail for jewellery, dental, and small metal parts. Cast directly into gold, silver, or bronze.
Best for: Jewellery prototypes, dental casting, small metal parts
High-Temp Resin
Heat-deflection temperature 230–280°C. Suitable for moulds, inserts, and parts exposed to elevated temperatures. Compatible with injection moulding tools for short runs.
Best for: Injection mould inserts, heat fixtures, thermal testing
SLA Design Guidelines
Follow these DFM rules to optimise parts for SLA printing. Proper design ensures successful builds, minimal supports, and optimal surface finish.
| Design Feature | Recommended | Minimum |
|---|---|---|
| Minimum Wall Thickness | 0.8 mm (0.031") | 0.6 mm (0.024") |
| Minimum Feature Size | 0.3 mm (0.012") | 0.2 mm (0.008") |
| Minimum Hole Diameter | 0.5 mm (0.020") | 0.3 mm (0.012") |
| Clearance for Assemblies | 0.3 mm gap | 0.15 mm gap |
| Support Placement | On non-cosmetic surfaces | Minimal contact points |
| Hollow Parts (Drain Holes) | 2 mm drain holes | 1.5 mm drain holes |
| Tolerance | ±0.1 mm | ±0.05 mm (small features) |
| Post-Cure Shrinkage | 0.5 – 1.0% | Accounted for in design |
DFM Tips for SLA Printing
- Orient parts to minimise support contact on cosmetic surfaces. The bottom face in contact with supports will require sanding.
- Hollow large parts to reduce resin cost and peeling forces during printing. Add drain holes of at least 2mm for uncured resin to escape.
- Maintain a minimum clearance of 0.3mm between mating parts to account for resin shrinkage during UV post-curing.
- Avoid large flat surfaces facing the resin vat. These can cause suction forces during peeling. Angle large faces by 10 to 20 degrees.
- Account for post-cure shrinkage of 0.5 to 1.0% in critical dimensions. The design can be pre-scaled to compensate.
- Design escape holes for internal channels to allow uncured resin and wash solvent to flow freely during cleaning.
SLA vs FDM vs SLS Comparison
Compare SLA against FDM (fused deposition modeling) and SLS (selective laser sintering) to choose the right 3D printing technology for your application.
| Criteria | SLA | FDM | SLS |
|---|---|---|---|
| Accuracy | ±0.1 mm | ±0.3 mm | ±0.2 mm |
| Surface Finish | Ra 0.4 μm (smoothest) | Ra 12–50 μm (visible layers) | Ra 5–10 μm (grainy) |
| Material Strength | Low–Medium (resin) | High (thermoplastics) | High (nylon) |
| Material Variety | 6 resin types | 7 thermoplastics | Nylon only |
| Post-Cure Required | Yes (UV post-cure) | No | No |
| Support Material | Yes (breakaway) | Yes (soluble/breakaway) | No (self-supporting powder) |
| Best For | Smooth, detailed, precise parts | Functional, large parts | Complex geometry, no supports |
SLA is the optimal choice for smooth surfaces, fine details, and high accuracy. Choose FDM for functional strength and large parts, or SLS for complex geometries without support material.
Choose SLA When
You need the smoothest surface finish, finest details (0.2mm), transparent parts, or master patterns. Best for appearance and precision.
Choose FDM When
You need functional prototypes in production thermoplastics, large parts over 300mm, or low-volume end-use parts. Best for strength and cost.
Choose SLS When
You need complex geometries with internal channels, no support material, or batch production of nylon parts. Best for design freedom.
SLA Post-Processing Options
SLA parts require post-processing to achieve final mechanical properties and surface quality. All parts are washed, UV post-cured, and have supports removed before optional finishing.
Solvent Washing
Parts are washed in IPA or TPM to remove uncured resin. Ultrasonic cleaning is used for complex internal geometry. Critical for achieving defect-free surfaces.
UV Post-Curing
UV chamber curing at 405nm and 60°C for 15–60 minutes. Achieves final mechanical properties — strength, hardness, and temperature resistance. Essential for all SLA parts.
Support Removal
Breakaway supports are removed with flush cutters. Contact points are sanded smooth. Supports are placed on non-cosmetic surfaces to preserve visible finish quality.
Sanding & Polishing
Progressive sanding from 400 to 2000 grit removes support marks and micro-imperfections. Polishing compound achieves glossy finish. Transparent resins can reach optical clarity.
Painting & Priming
Primer, base coat, and clear coat for professional colour matching. Matte, satin, or gloss finishes. Pantone colour matching available for brand-specific requirements.
Clear Coating
UV-resistant clear coat protects transparent and coloured resins from yellowing and degradation. Improves long-term stability for parts exposed to sunlight.
Looking for professional surface finishing? Explore our surface finishing services.
SLA Cost Factors
SLA cost is driven by resin volume, machine time, and post-processing. Hollow parts reduce material cost. Bulk discounts apply for batch orders.
Standard Resin
$0.30 – $0.50 / g
General-purpose resin, most economical option
Tough / Flexible Resin
$0.40 – $0.70 / g
Engineering-grade resin for functional prototypes
Transparent Resin
$0.50 – $0.80 / g
Optically clear resin for lenses and housings
Castable Resin
$0.60 – $1.00 / g
Burnout resin for investment casting
Machine Time
$8 – $20 / hour
Based on print duration and resin volume
Post-Processing
$10 – $60 / part
Washing, UV cure, support removal, sanding
Cost Example by Resin Type
A 100 × 60 × 40mm solid part (approximately 80g resin) printed at 0.05mm layer height:
Standard Resin
$24 – $40
Tough / Transparent
$40 – $64
Castable / High-Temp
$48 – $80
Hollowing parts can reduce resin cost by 40 to 60%. Post-processing quoted separately.
SLA 3D Printing FAQ
Answers to the most common questions about SLA 3D printing at FIRMFG.
QWhat accuracy can SLA 3D printing achieve?
SLA 3D printing achieves dimensional tolerances of ±0.1 mm (±0.004") for features under 100 mm, and ±0.1% for larger dimensions. Layer heights as fine as 0.025mm produce surfaces with Ra 0.4 μm — smooth enough to eliminate visible layer lines entirely. SLA is the most accurate 3D printing technology, surpassing FDM (±0.3mm) and SLS (±0.2mm). For features requiring even tighter tolerances, post-machining of critical dimensions is available.
QCan SLA produce transparent parts?
Yes. SLA transparent resin transmits over 90% of visible light, simulating polycarbonate and PMMA (acrylic). After printing, washing, and UV post-curing, transparent parts have a translucent finish. Polishing with progressive sanding (400 to 2000 grit) and polishing compound achieves optical clarity suitable for lenses, light pipes, and transparent housings. A UV-resistant clear coat prevents yellowing over time.
QHow durable are SLA printed parts?
SLA part durability depends on the resin type. Standard resin is brittle and suited for visual prototypes only. Tough resin (ABS-like) offers impact resistance of 25–50 J/m and is suitable for functional prototypes, snap-fits, and enclosures. Flexible resin (Shore 50A–80A) provides rubber-like elasticity. However, all SLA resins are more brittle than FDM thermoplastics — for maximum mechanical strength, FDM with ABS or nylon is recommended.
QWhat is the heat resistance of SLA resins?
Heat resistance varies by resin type. Standard resin has a heat deflection temperature (HDT) of 50–70°C. Tough resin reaches 70–90°C. High-temperature resin achieves HDT of 230–280°C, suitable for moulds, inserts, and thermal testing. High-temp resin can serve as short-run injection moulding tools for 50–100 shots. For applications above 100°C, specify high-temp resin at quoting.
QWhat is the minimum feature size for SLA printing?
SLA can reproduce features as small as 0.2mm (0.008"). Minimum wall thickness is 0.6mm, minimum hole diameter is 0.3mm, and engraved details as fine as 0.1mm are achievable. This resolution far exceeds FDM (minimum 0.8mm walls) and makes SLA ideal for jewellery, dental models, microfluidic devices, and intricate decorative parts. For assembly clearance, allow a minimum 0.3mm gap between mating components.
QHow long does SLA 3D printing take?
Standard lead time is 3–5 business days. Print time ranges from 2 hours for small parts to 24 hours for large or complex geometries. Post-processing (washing, UV post-curing, support removal, finishing) adds 1–2 days. Rush service is available for 48-hour turnaround on simple geometries. Volume orders of 10+ parts are batched on multiple machines to meet delivery deadlines.
SLA 3D Printing Applications
SLA is used across industries where surface finish, detail resolution, and accuracy are critical.
Jewellery Prototypes
Master patterns for investment casting with 0.2mm detail
Dental Models
High-accuracy dental models and surgical guides
Concept Models
Presentation-quality models with smooth finish
Optical Parts
Transparent lenses, light pipes, and display housings
Complex Detail Parts
Fine features, thin walls, and intricate geometry
Master Patterns
Master patterns for vacuum casting silicone moulds
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Learn MoreStart Your SLA 3D Printing Project
Upload your CAD files and get a free SLA 3D printing quote within 24 hours. Six resin types, layer resolution down to 0.025mm, tolerance ±0.1mm. Our engineers provide DFM feedback and resin recommendations at no cost.