3D Systems FabPro™ Elastic BLK Elastomer is a black, UV-curable acrylate photopolymer qualified for the FabPro 1000 DLP vat photopolymerization system. The resin polymerizes at 405 nm and is supplied in pre-packaged cartridges that interface with the printer’s material handling. The material is formulated for functional elastomeric parts requiring repeated flexure, compression, or tensile recovery, rather than rigid structural housings. It is used with the FabPro 1000 build platform measuring 125 mm × 70 mm × 150 mm, with selectable layer thickness settings of 30 µm, 50 µm, and 100 µm. These layer thickness settings influence curing depth, interlayer adhesion, and support contact morphology.

Material qualification is performed after UV post-cure and conditioning at 23 ± 2 °C and 50 ± 5 % RH. Table 1 lists representative values from the manufacturer’s published datasheet. These values are batch-dependent and are not guaranteed limits. Tensile specimens are printed in the orientation specified by the manufacturer and tested according to ASTM D638-14; orientation-dependent anisotropy is present because the layer interface can act as a crack-initiating plane.

After the recommended post-cure cycle, the nominal Shore A hardness is 65 A. The effective surface hardness can be lower on undersides because of resin-rich layers that are not fully cured before support removal. Under-curing can also reduce density and increase water absorption. Batch acceptance protocols often add a control tensile bar per ASTM D638-14 and a tear specimen per ASTM D624-00(2020) because pigment dispersion and inhibitor concentration can vary between resin lots.

Rheologically, the liquid resin is formulated with a viscosity low enough for recoat at 25 °C, but it is not a Newtonian fluid at low shear. The FabPro 1000 recoat blade applies shear to the liquid film; if the material has aged or if the vat temperature is below the recommended range, the resin may not level completely before exposure and the layer thickness can vary by several micrometres. In production, recoating variation appears as horizontal banding or as localized delamination in the first 2–5 layers of the build. This failure mode is more common with elastomers than with rigid resins because the green layer’s low modulus cannot resist the peel forces during platform retraction. Operators often reduce print speed and use a longer vat stabilization period between builds when ambient conditions fluctuate.

When Shore A 65 Elastomer Replaces RTV Silicone in Low-Volume Seal Production

In fluid-sealing applications, FabPro Elastic BLK is used as a replacement for room-temperature-vulcanizing silicone when production quantity is too low for compression molding and when multi-material insert molding is not available. The primary evaluation metric for a seal is compression set, measured under ASTM D395-18 method B at 23 °C for 22 h. Published representative data place the compression set in the range of 10–20%, depending on post-cure duration and section thickness. This is higher than a post-cured platinum-cured RTV silicone system, but it is adequate for short-run dust seals, access covers, cable grommets, and low-pressure gaskets. The material is not suitable for hot-water or steam seals because the acrylate network loses stiffness above 60 °C and the water-absorption value of 0.9% after 24 h immersion can promote dimensional change.

Low-pressure seal applications include electrical enclosure gaskets, connector boots, and protective bellows. The material can be used for compression interfaces only when the applied strain is below the compression set limit. For a typical solid gasket with 30% initial compression, the retained sealing force after 22 h at 23 °C can be estimated from compression set data, but stress-relaxation data are not published. For flanges with wide gaps, a hollow or lattice geometry is preferable because it reduces the local compressive strain and keeps the elastomer within the range where recovery is more complete. A honeycomb or lattice core printed with 50 µm layers and 1.0 mm wall thickness has been used for gaskets where a solid cross-section would exceed the material’s compression set at the available preload; however, published data for this specific configuration are limited.

Vibration-isolation pads and ergonomic grips are additional uses. Damper pads printed in 50 µm layers with a 2–3° draft angle on side walls allow support removal without tearing the low-modulus surface. When printed with a solid or high-dense fill, the material provides a lower durometer contact face than rigid photopolymers, but the part should be tested under the relevant compressive load rate because the stress-strain response is viscoelastic. The manufacturer’s published data do not cover all cyclic load frequencies. For rotating equipment, a fatigue test under the intended amplitude should be performed because tear-initiated edge cracking can occur at strain concentrations. Elastomeric mounts for light-duty equipment can be produced in small batches, but the damping effectiveness is not characterized by a published loss factor. Users must perform dynamic mechanical analysis or a forced-vibration test. Without a full dynamic mechanical thermal analysis curve, applying this material at frequencies above 100 Hz or below 0 °C requires confirmation because the material may stiffen and lose elastomeric recovery.

What Limits Green-State Handling Before UV Post-Curing?

Green-state parts immediately after printing retain a liquid uncured monomer film that must be removed before the elastomer reaches handling strength. The primary processing boundary is the time between build completion and solvent cleaning. If parts remain in the printer vat or on the platform for more than 30 min in ambient air above 60% RH, the uncured acrylate surface can absorb moisture, producing a white bloom after cleaning. Dimensional drift before post-cure is observed when supports soften and allow wall movement. The printer maintains a resin temperature setpoint, but the resin tray and recoater require a controlled environment because viscosity rises below 18 °C, increasing recoating force and leading to incomplete layer wetting.

Washing is performed in two solvent baths. The first bath removes the bulk of the uncured resin; the second bath reduces residual contamination. Typical cleaning solvents are high-purity isopropyl alcohol or the manufacturer’s approved alternative. A first-stage wash of 10–15 min in an ultrasonic unit operating near 40 kHz is used for components with blind holes or undercuts; flat parts may be cleaned in 5–10 min. Aggressive agitation beyond 20 min can produce solvent uptake in the green elastomer, which swells the surface and leaves a tacky film after drying. Parts must be dried with compressed air at a pressure no greater than 2 bar before post-curing.

Post-curing is performed with a 405 nm flood source. The manufacturer’s processing guide ties the required dose to part thickness; a typical post-cure lasts 60–120 min in a calibrated chamber, with thicker sections requiring the longer duration. Undersized UV chambers that deliver less than the specified irradiance cause a lower degree of acrylate conversion, which depresses Shore A hardness and increases compression set. The effect is not linear: a partially cured sample can exhibit a Shore A drop of 2–5 points and a measurable increase in tack. Therefore, the UV chamber should be checked with a calibrated radiometer at the beginning of each shift. Building nested parts or stacking on translucent trays during post-cure reduces dose uniformity and should be avoided.

Orientation-specific anisotropy is also relevant. In a horizontally printed tensile bar, tensile strength may be higher than in a vertical tensile bar because the crack path is not aligned with the layer interfaces. The datasheet values are generally obtained from specimens printed flat on the build platform. If vertical walls are unavoidable, the cross-section should be increased or the post-cure should be extended to improve interlayer conversion. Resin lot qualification is critical because pigment dispersion and inhibitor concentration vary. A qualified lot may show a viscosity shift of ±10% from the nominal value and still produce acceptable parts, but a larger shift requires adjustment of the printer material profile. If the printer does not allow manual profile editing in production mode, incoming material should be tested by drawing a small sample through a laboratory viscometer per ASTM D2196 at 25 °C. If the viscosity is above the upper limit, the resin can be warmed gently in a sealed container, but uncontrolled heating above 35 °C can begin thermal initiation.

Tear Propagation Resistance and Compression Set in Cyclic Flexure

Tear resistance is evaluated using ASTM D624-00(2020) die C or die T specimens. The reported representative value is 15 kN/m. Tear strength is sensitive to print orientation and post-cure; vertically printed specimens often show lower values because the crack can travel along interlayer planes. For parts with living hinges or bending tabs, a tear test alone is insufficient. The elastomer should be evaluated under repeated flexure using a De Mattia flex setup or similar, because resistance to tear propagation under continuous cycling determines service life. Published datasheet values do not include a full fatigue-life curve; for safety-critical or load-bearing flexible components, internal validation is required.

Compression set and tensile properties are measured under ASTM D395-18 and ASTM D638-14. The reported elongation at break of 160% is for a fully post-cured specimen. In the green state or after only a short post-cure, elongation may be lower and failure may occur at the layer interface. The low crosslink density required for elastomeric behavior also allows creep under static load. Parts used as bumpers or spacers should be derated because creep displacement is not captured by a single tensile test. When a long-term static load is present, the manufacturer’s data do not provide a creep modulus; testing under the actual service temperature is required.

Support removal and orientation are critical because the green elastomer tears more easily than rigid photopolymers. Build orientation should be arranged so that support contacts are placed on non-critical surfaces and do not cross thin flexing regions. A draft angle of 2–3° on vertical walls reduces the contact area between support tips and the part; flat undersides printed parallel to the platform increase the number of supports and raise the probability of surface scar damage. The FabPro 1000 DLP projection system has a native pixel pitch of 65 µm, but the effective resolution on a low-modulus elastomer is influenced by resin migration before photopolymerization. Shallow features below 0.5 mm may not reproduce accurately if the uncured resin film thickness on the build surface exceeds the cure depth. The minimum wall thickness for freestanding elastomeric walls is commonly larger than the equivalent rigid-resin wall; walls below 1.0 mm may distort during peeling because the part’s green modulus is too low to resist the separation force.

Surface finish is affected by layer steps and support removal. If a smooth sealing face is required, the part can be oriented so the critical face is not in contact with supports. Sanding or polishing elastomeric photopolymer is less effective than on rigid resins because abrasive particles can embed and nucleate tears. Chemical smoothing is not recommended for this material; the solvent that softens the surface may also reduce tear strength. Dimensional accuracy after post-cure is typically checked with a calibrated optical comparator or coordinate measuring machine. The manufacturer’s published tolerance is not a fixed linear value because shrinkage varies with geometry, orientation, and degree of cure; printed reference coupons should be measured before accepting a production build. Scale-up from one part to a full build tray can change the thermal history. A densely packed tray increases resin temperature during the build because the photopolymerization exotherm has less time to dissipate. That temperature rise lowers viscosity and may increase cure depth, resulting in overgrowth on undersides. Consequently, a first article from a sparse build cannot be used to qualify a high-density production tray.

How Does FabPro Elastic BLK Differ from FabPro Tough BLK?

The principal difference between FabPro Elastic BLK and FabPro Tough BLK is the crosslink density and phase structure. FabPro Tough BLK is a rigid acrylate photopolymer with high tensile strength and low elongation, whereas FabPro Elastic BLK is formulated to produce a Shore A durometer in the elastomeric range. Table 2 compares typical values from published data. The choice is based on whether the part must function as a structural housing or as a compressible seal, grip, or damper. Mixing the two resin families in the same vat is not permitted; carryover from a previous material lot can alter the crosslink density and reduce either the rigidity of Tough BLK or the elongation of Elastic BLK.

FabPro Elastic BLK is also distinct from casting resins in the FabPro portfolio. Casting resins are designed for burnout with low ash content; Elastic BLK is not designed for investment casting and will leave excessive residue if burned out. Printed elastomer parts should not be used as sacrificial patterns where thermal decomposition above 300 °C is required. The material’s typical service temperature is below 60 °C, which limits its use in engine-compartment or hot-gas applications. Exposure to acetone or methyl ethyl ketone can swell and soften the acrylate network within minutes. Even short contact with strong solvents used for cleaning the work area can create surface tack. If unavoidable, a quick wipe should be followed by drying and inspection; solvent immersion is not recommended.

Storage is part of the processing window. The resin cartridge should be stored in a dry, dark environment at 15–30 °C and allowed to reach room temperature before shaking or loading. Prolonged storage above 30 °C can accelerate inhibitor depletion and cause premature polymerization in the cartridge or vat. Before each production run, the material should be visually inspected for gel particles or pigment separation; the cartridge may require rolling or agitation according to the manufacturer’s instructions. The uncured resin contains acrylate monomers and photoinitiators. Handling requires nitrile gloves and safety glasses; ventilation should be sufficient to keep vapor exposure below the occupational exposure limits listed in the safety data sheet. The cured elastomer is not rated for food-contact applications under FDA 21 CFR 177.2600 and no compliance statement under EU 10/2011 is published. Chemical compatibility must be verified for the specific service environment; the acrylate network is generally resistant to dilute aqueous solutions but is not recommended for continuous contact with ketones, esters, chlorinated solvents, or strong alkaline cleaners. Amine-containing additives should be avoided because residual amines can react with the uncured acrylate and create a tacky, poorly cured surface.