VisiJet RWT-EBK-A70 is a two-base-material digital composite produced in the 3D Systems MultiJet Printing (MJP) portfolio. It is not supplied as a premixed resin or as a single filament; the final part is generated by simultaneous high-temperature jetting of VisiJet CR-WT 200 rigid white ink and VisiJet CE-BK black elastomer ink through separate printhead channels, followed by UV crosslinking after each layer. The A70 suffix designates a nominal Shore A hardness of 70 when measured according to ASTM D2240-15. The product is used for single-build components that require rigid structural sections combined with elastomeric sealing lips, living hinges, gasketing, vibration-isolation tabs, or overmoulded gripping surfaces without secondary assembly or adhesive bonding.

The base inks are supplied in sealed 2 kg hot-melt cartridges and are processed on the ProJet MJP 5500X multi-material platform. The printer uses a planar multi-nozzle array with an addressable resolution of 694 × 750 × 1600 DPI and a native layer thickness of 0.016 mm. The maximum build volume is 533 × 381 × 304 mm. During printing, a heated planarizer levels both jetted inks and the wax support phase, and UV flood lamps cure the voxels before the platform indexes downward. Because the composite is formed from UV-cured thermoset polymer networks, it cannot be re-melted or welded after build; this distinguishes the product from thermoplastic elastomer feedstocks used in fused filament fabrication.

How Does Voxel-Level Mixing of the Two Inks Yield a Shore A 70 Composite?

The printer dithers the two inks at the voxel level according to a fixed digital-material recipe; the black elastomer phase forms the majority, while the rigid white phase increases hardness and tensile strength but reduces elongation. The A70 recipe produces a composite whose Shore A value lies above that of the neat black elastomer and below that of the rigid white material. Voxel dimensions of approximately 0.036 × 0.036 × 0.016 mm permit transition zones between rigid and elastomeric regions to be resolved over distances of 0.1–0.5 mm in the XY plane. In the Z direction, the transition sharpness is limited by layer height and by the planarizer, which can create a graded interlayer rather than a mathematically discrete interface.

The A70 composite therefore occupies an intermediate property envelope: it is softer and more compliant than the rigid white base but harder and more tear-resistant than the neat black elastomer. The primary technical trade-off is elongation; the rigid white phase suppresses the viscoplastic extension of the elastomer network, so elongation at break falls by roughly 50–65% relative to the neat black elastomer.

Jetting stability for both base inks is highly sensitive to idle time, room humidity, and printhead temperature. The production environment is controlled at 18–28 °C and 20–60 % RH; excursions above 60 % RH increase the risk of moisture uptake in the warm ink reservoir and produce intermittent nozzle firing or weak interlayer adhesion. The onboard thermal management preheats cartridges to the process range, typically 65–85 °C, to reduce viscosity below the thresholds required for piezoelectric jetting. Printhead idle time is limited; if a head is left inactive for more than 48 h without purging, the black elastomer ink can skin over at the nozzle plate and require purge cycles of 5–10 min before stable jetting returns. On production lines, batch-to-batch viscosity variation within the specified ±5% tolerance can shift the layer thickness and the sharpness of rigid-to-elastomer transitions, so the printer’s jet voltage and pulse width are adjusted only after a qualification coupon has been printed.

Support wax removal is the most common production bottleneck for multi-material builds with sealed channels. The RWT-EBK-A70 composite is chemically resistant to the warmed oil-based support removal bath, but the mechanical stiffness of the rigid white shell restricts thermal expansion of the enclosed elastomer phase. When an internal channel diameter falls below 2 mm, molten support wax cannot fully evacuate during oven dwell at 65–70 °C; residual wax solidifies on cooling and blocks the feature. For blind cavities, a minimum drain port diameter of 4 mm is required unless ultrasonic solvent-assisted cleaning is used. In vertical channels, support evacuation is gravity-driven; designs should include drainage openings spaced every 10 mm for complete wax removal. Heating above 75 °C accelerates wax flow but introduces dimensional creep in elastomeric sections thinner than 1 mm, causing permanent deformation that is not recoverable after cooling.

When Build Envelope Gradients Exceed 5 °C, Hardness Uniformity Is Compromised

The composite does not solidify perfectly uniformly across the 533 × 381 mm build envelope. If the ambient temperature gradient across the platform exceeds 5 °C, colder edge regions can produce slightly higher local hardness because the inks coalesce at lower temperature and the rigid white phase packs more efficiently before UV crosslinking. In production, this gradient is observed as Shore A variation of ±2–4 units between the centre and the edges of large tooling fixtures. The effect is larger for thin elastomeric sealing lips that lie parallel to the X axis near the build boundary. For critical seals, production planning often restricts multi-material jobs to a central 300 × 300 mm zone unless a heated draft shield is used; otherwise, tear resistance in the affected zone can be lower than the XY-oriented datasheet value by 10–15%. This boundary orientation effect is not a material defect but an interaction between laminar cooling, the planarizer, and the thermoset kinetics of the two inks.

Solvent Resistance Boundaries and Post-Cure Limitations in Production Handling

The A70 composite tolerates water, dilute aqueous acid, and low-molecular-weight alcohols; however, continuous immersion in ketones, esters, aromatic hydrocarbons, or chlorinated solvents causes swelling, hardness loss, and edge cracking. Cleaning with acetone, methyl ethyl ketone, or toluene is not specified because these solvents diffuse into the elastomer phase and can reduce Shore A hardness by more than 5 units within 24 h under ISO 2812-1:2017 immersion conditions. Support removal baths and rinses are therefore limited to approved isopropanol or supplier-qualified wax-dissolving fluids. Ultrasonic rinsing in isopropanol should be limited to cycles of 5 min or less to avoid solvent-induced softening of thin elastomer sections. After cleaning, parts are dried at 40 °C for 2–4 h before dimensional inspection.

The maximum continuous service temperature for loaded elastomeric regions is 60 °C. Above this, compression set increases sharply under ASTM D395-18 Method B because the crosslink density of the soft phase is not sufficient to resist high-temperature creep. Long-term direct UV exposure is also not specified; outdoor installations or repeatedly UV-sterilised medical models should be coated with a UV-blocking clear coat if annual sunlight exposure exceeds 200 h. The product is not compatible with strong oxidising acids or with amine-based post-coatings that can attack the acrylic network and induce premature surface cracking.

Rigid-to-elastomer interfaces require a transition zone of at least 1–2 mm for durable load transfer. Abrupt interfaces tend to fail by shear stress concentration because the rigid white phase has a tensile modulus roughly two orders of magnitude higher than the elastomer phase. A stepwise transition of 1 mm per Shore hardness increment is used in production to avoid tearing at the boundary under repeated flexing. The junction should be located away from areas of maximum tensile strain; otherwise, local debonding may occur after 10,000 cycles in dynamic flex testing. This failure mode is a consequence of the digital mixing process, not an inherent incompatibility of the base inks.

Unopened cartridges are stored at 15–28 °C; refrigerated storage below 10 °C can raise ink viscosity and delay thermal equilibration. Cartridges should be allowed to reach room temperature for at least 4 h before installation. Opened cartridges should be used within 90 days to prevent moisture-related jetting defects. The printer logs cartridge consumption; cross-contamination between rigid white and black elastomer is prevented by dedicated ink channels and RFID cartridge identification. A head crash or planarizer overload can force black elastomer into the white ink channel; in such cases, a full printhead purge and calibration must be performed before the next build.

Safety data sheets for the base inks should be consulted for personal protective equipment requirements. The uncured inks and support material can cause skin sensitisation; handling requires nitrile gloves and local exhaust ventilation. The cured composite is generally regarded as stable under normal handling but is not certified for food contact or long-term implantation. Published compliance data for this specific grade is limited; users requiring USP Class VI, ISO 10993, or food-contact approval must request application-specific documentation from the supplier.

Comparing the A70 Composite with Other Digital Materials and Thermoplastic Elastomers

Compared with single-material VisiJet CR-WT 200, the RWT-EBK-A70 composite trades elevated tensile modulus for integrated sealing and damping function. Compared with the neat VisiJet CE-BK elastomer, the A70 grade raises hardness and tear strength but reduces elongation and increases compression set. In the broader digital-material family, the A70 designation is selected when a Shore A 70 elastomer is required for snap-fit gaskets, living hinges, shielded cable pass-throughs, and cushioned mounting features. Softer A50 composites are used for thick acoustic isolation pads, while higher-hardness combinations are reserved for abrasion-resistant flexible grips. The primary limitation of the product is its fixed thermoset character: unlike a thermoplastic elastomer filament, RWT-EBK-A70 cannot be re-melted or welded after UV cure, and its final properties are available only on the dual-material MJP platform with both cartridges installed simultaneously.