DFM for 3D Printing: A Practical Design Guide
Wall thickness, tolerances, supports, and hole sizing rules for printable parts.
Read the ArticleFlame Retardant 3D Printing Material
Stereolithography (SLA) · Specialty Resins
UL 94 V-0 certified, halogen-free resin for self-extinguishing electrical and transit parts.
What Is Flame Retardant?
Flame Retardant resin is a UL 94 V-0 certified, halogen-free SLA material designed for electrical enclosures, transit components, and any part that must self-extinguish. At 56 MPa tensile and 2,900 MPa flex modulus with 111 °C HDT, it combines genuine structural capability with fire safety compliance.
Formlabs Flame Retardant Resin, printed with Stereolithography (SLA). Every order is reviewed by our engineering team - no minimum order quantity.
When to choose Flame Retardant
Choose Flame Retardant resin when your part must meet UL 94 V-0 fire-safety requirements at SLA precision. It is the only desktop-SLA resin in our catalog with certified flame retardancy, and its halogen-free formulation satisfies transit and marine fire codes that prohibit halogenated flame retardants.
At 56 MPa tensile, 2,900 MPa flex modulus, and 111 °C HDT, this is not just a fire-rated visual model - it is a structurally capable part. Use it for prototype electrical enclosures, battery-compartment housings, and connector housings where fire safety and mechanical performance are both required.
For larger flame-rated parts, FDM PC-FR offers UL 94 V-0 in a 245 mm build volume with better impact toughness (60 MPa tensile, 5–8% elongation). For aerospace FST certification, ULTEM 9085 is the required step up. Flame Retardant resin fills the niche where SLA precision matters and the part fits within the Form 4 build envelope.
Material Properties
Representative values - process- and orientation-dependent. Full technical datasheet available on request.
Process
Stereolithography (SLA)
Tensile strength
56 MPa
Elongation at break
5%
Flexural strength
75 MPa
Flexural modulus
2,900 MPa
Heat deflection (HDT)
111 °C @ 0.45 MPa
Density
1.30 g/cm³
Max build size
200 × 125 × 210 mm (Form 4)
Min wall thickness
0.5 mm
Resolution / layer
50–100 µm
Relative cost
$$$$ (1 = lowest, 4 = highest)
Design Guidelines
Plan features to print reliably and assemble cleanly in Flame Retardant. Need DFM help?
Min wall
0.5 mm - 0.8 mm+ for UL compliance
Min feature
0.3 mm - at 50 µm layer height
Clearance
0.2–0.3 mm - for mating parts
Max size
200 × 125 × 210 mm - Form 4 build volume
Dimensional tolerances
Typical tolerance on the Form 4 is ±0.1 mm or ±0.1%. The filled formulation holds dimensions well during post-cure. For UL 94 compliance, minimum wall thickness requirements apply - discuss with us at DFM review to ensure test-bar compliance.
Printing notes
Flame Retardant resin prints on the Form 4 at 50–100 µm layer height. Wash in IPA for 10–15 minutes after printing. Post-cure at 80 °C for 60 minutes under 405 nm UV light - extended cure is needed to reach full mechanical and fire-performance properties. The black pigment produces a uniform matte finish. Supports remove cleanly but the material is brittle - use flush cutters rather than twisting. Orient parts to minimize support contact on UL-critical wall sections.
How Flame Retardant Compares
Flame Retardant alongside related materials.
| Flame Retardant | PC-FR | Rigid 10K | Grey V5 | |
|---|---|---|---|---|
| Tensile strength | 56 MPa | 60 ± 4 MPa | 88 MPa | 62 MPa |
| Heat deflection (HDT) | 111 °C @ 0.45 MPa | 113 °C @ 0.45 MPa | 238 °C @ 0.45 MPa | 71 °C @ 0.45 MPa |
| Flexural modulus | 2,900 MPa | 1,890 ± 70 MPa | - | 2,750 MPa |
| Elongation | 5% | 5–8% | 1.7% | 13% |
| Density | 1.30 g/cm³ | 1.20 g/cm³ | 1.45 g/cm³ | 1.18 g/cm³ |
| Relative cost | $$$$ | $$ | $$$$ | $$ |
When to Use Flame Retardant
Where Flame Retardant fits, where it doesn't, and what to use instead.
Electrical enclosure prototypes
UL 94 V-0 self-extinguishes in <10 seconds without dripping - meets NEC and IEC requirements for prototype evaluation of junction boxes and switch housings.
EnergyTransit and rail interior components
Halogen-free formulation avoids toxic fume generation during fire events - critical for passenger-compartment compliance in transit and marine applications.
AerospaceBattery-compartment housings
111 °C HDT combined with UL 94 V-0 rating meets thermal-runaway safety margins for lithium-ion battery pack housings and charging-station enclosures.
AutomotivePCB standoffs and connector housings
56 MPa tensile and 2,900 MPa flex modulus deliver genuine structural performance for printed electronics housings that must also pass fire-safety testing.
EngineeringFlame-rated IoT and sensor enclosures
SLA precision (±0.1 mm) at UL 94 V-0 lets designers validate fire-rated enclosure geometry, wall thickness, and ventilation patterns before committing to injection tooling.
Consumer ProductsStrengths
- UL 94 V-0 certified on the Form 4 platform - the only desktop-SLA flame-retardant resin in our catalog
- Halogen-free formulation eliminates toxic halogen fumes during fire events - required by many transit and marine fire codes
- 111 °C HDT with 56 MPa tensile - real structural performance alongside fire safety, not just a fire-rated visual model
Keep in mind
- 5% elongation - brittle under impact; parts crack when dropped or subjected to sharp mechanical loads; not for assemblies that see physical abuse
- $$$$ cost tier - reserve for applications where UL 94 V-0 is a genuine regulatory requirement, not a precautionary nice-to-have
- 200 mm build volume limits part size - for larger flame-rated parts, FDM PC-FR (245 mm) or ULTEM 9085 (large-format industrial) are alternatives
Finishes & Colors
Finishing options and in-stock colors for Flame Retardant.
Standard
Washed, post-cured; matte black surface.
Best for: Electrical enclosures, fire-rated parts
In-Stock Colors
Black
Custom colors and dyeing available on request. Contact us for options.
Flame Retardant FAQ
UL 94 V-0 means the material self-extinguishes within 10 seconds and does not drip flaming particles. This is required for electrical enclosures, battery housings, and transit interior components under NEC, IEC, and various transit fire codes.
Yes. The formulation uses halogen-free flame retardants, eliminating the toxic halogen fumes that standard halogenated FR materials produce during fire events. This meets the requirements of transit authorities and marine certifiers that prohibit halogenated compounds.
Flame Retardant SLA offers ±0.1 mm precision and 2,900 MPa flex modulus in a 200 mm build volume. FDM PC-FR offers better impact toughness (60 MPa, 5–8% elongation) in a 245 mm build volume. Both are UL 94 V-0. Choose SLA for precision; PC-FR for toughness and size.
Yes. The combination of UL 94 V-0 fire rating and 111 °C HDT meets thermal-runaway safety margins for lithium-ion battery pack housings and EV charging-station enclosures. Discuss specific UL or IEC requirements at quoting.
Flame Retardant resin is structurally capable at 56 MPa tensile and 2,900 MPa flex modulus - comparable to Grey V5 in stiffness with better heat resistance (111 °C vs 71 °C HDT). However, at 5% elongation it is brittle under impact. For tough flame-rated parts, FDM PC-FR is the alternative.
The Form 4 holds ±0.1 mm or ±0.1% on Flame Retardant resin parts. The filled formulation holds dimensions well. Specify UL-critical wall thicknesses at quoting so we can verify compliance during DFM review.
At the $$$$ tier, Flame Retardant resin is primarily a prototyping and low-volume material. It is cost-effective for validating fire-rated enclosure designs (1–20 parts) before committing to injection tooling. For production volumes, injection-molded flame-retardant compounds are more economical.
Flame Retardant resin prints in matte black. The uniform black finish is standard for electrical and industrial enclosures and does not require painting for most applications.
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