3D Systems VisiJet RBK-ENT-A60 Multi-Material Composite (VisiJet CR-BK + VisiJet CE-NT) is a jetted photopolymer digital material produced on the ProJet MJP 5600 MultiJet Printing platform. The product designation indicates a target Shore A 60 durometer response under ASTM D2240-15; the RBK portion is derived from the rigid black VisiJet CR-BK feedstock, and the ENT portion is derived from the elastomeric natural VisiJet CE-NT feedstock. RBK-ENT-A60 is not a pre-mixed resin. The printer deposits CR-BK and CE-NT at controlled voxel ratios and cures each 32 μm layer by ultraviolet irradiation at 1200 × 1200 × 1600 dpi resolution. Supplier-published typical values include tensile strength 2.4 MPa tested to ASTM D638-14, tensile modulus 1.9 MPa, elongation at break 165%, tear strength 10.2 kN/m tested to ASTM D624-00(2020), and density 1.06 g/cm³ tested to ASTM D792-20. VisiJet CE-NT is specified at Shore A 27 with lower tear strength, while VisiJet CR-BK is specified at Shore D 82 with tensile modulus near 1,950 MPa. The composite closes a property gap between rigid black and ultra-soft natural elastomer within a single MultiJet Printing build.

Primary use is in non-implantable anatomical models for ear, nose, and throat surgical planning and education, particularly where dark rubber-like soft tissue, nasal alae, epiglottis, airway rings, or compliant peripheral structures must be represented without separate silicone overmolding. The material also appears in functional prototyping of flexible gaskets, grommets, grips, and seals. The product is not a direct replacement for high-consistency silicone in long-term dynamic seals because published data for compression set, fatigue, and abrasion are limited. Application-specific validation under ASTM D395-18, ASTM D4060-19, and ASTM D4482-21 is required where relevant. No permanent implantation or long-term mucosal contact should be assumed without finished-device biocompatibility evidence.

What Processing Parameters Govern the Shore A 60 Transition in MultiJet Printing?

The RBK-ENT-A60 hardness is not user-variable on current ProJet MJP 5600 firmware. The printer controls the CR-BK/CE-NT volumetric ratio, jetting waveform, and ultraviolet dose for the specified Shore A 60 output. The base resins are maintained at controlled jetting temperatures to keep their viscosities within the printhead jetting window. The supplier does not publish complete rheology curves for RBK-ENT-A60 in the public datasheet, but process stability depends on printhead purge intervals, ambient humidity, and the absence of partially polymerized material in the recirculation loop. On production-scale machines, degraded printhead alignment or spent cap wiper assemblies can cause black-to-natural phase bleed at the voxel transition, which alters local hardness and surface coloration without changing the overall build ratio.

Layer-wise photopolymerization produces anisotropic mechanical response. Tensile properties from ASTM D638-14 specimens built in the Z orientation are generally lower in elongation than those built in the XY plane due to interlayer conversion gradients. Users should validate all build orientations when RBK-ENT-A60 is used as a rubber hinge or snap feature. The cured part is not subjected to a thermal post-cure cycle in the standard workflow; support removal and cleaning are the main post-process variables that affect surface tack, residual monomer, and durometer. Prolonged solvent immersion in isopropanol or ketone-bearing cleaners can swell the CE-NT-rich phase and lower the Shore A reading. A production line should therefore qualify the cleaning solvent, temperature, and drying time before mechanical testing.

The ProJet MJP 5600 uses a multi-jet head array with separate channels for support material and build materials. Support material occupies overhang regions and thin sinus channels, then is removed by oven heating and ultrasonic cleaning. Incomplete support removal is a known production bottleneck for RBK-ENT-A60 because trapped wax residue in blind cavities increases flexural stiffness and produces a non-uniform Shore A measurement. Small airway models below 2 mm internal diameter should be validated for support cleanout by cross-sectioning or micro-CT before lot release. The supplier’s recommended cleaning chemistry for CE-NT and RBK-ENT-A60 is not universally interchangeable with aggressive solvent baths; operators should obtain the material-specific post-processing bulletin for the production machine.

Quality control of Shore A 60 on production parts is geometry-dependent. A hand-held durometer on a curved anatomical surface is not comparable to a flat 6 mm plaque measurement under ASTM D2240-15. The standard practice specifies specimen thickness, dwell time, and support conditions; readings taken on thin walls or void-rich regions can fall below the target even when the material is within specification. Internal batch acceptance should therefore include flat coupons printed in the same orientation and layer interval as the manufactured part, conditioned at 23 ± 2 °C and 50 ± 5% relative humidity per ASTM D618-21.

Mechanical Property Comparisons Across VisiJet CR-BK, CE-NT, and RBK-ENT-A60

The following values are drawn from supplier-published typical property sheets for the three material states. Certification batches may deviate; the table is not a specification for release testing.

The data illustrate the product’s difference from single-resin alternatives. Compared with VisiJet CE-NT, RBK-ENT-A60 raises Shore hardness from 27A to 60A and increases tear resistance from 7.2 kN/m to 10.2 kN/m without sacrificing the large-strain character needed for compliant parts. Compared with VisiJet CR-BK, RBK-ENT-A60 drops tensile modulus from 1,950 MPa to 1.9 MPa and increases elongation from 7.3% to 165%, shifting the failure mode from brittle plastic to rubber-like deformation. This three-material set allows a single ProJet MJP 5600 build to contain rigid black load-bearing features in CR-BK, soft elastomeric zones in CE-NT, and black rubber-like surfaces in RBK-ENT-A60 without mechanical assembly. The interfacial bond between these digital composites is formed by interpenetrating acrylate networks at the voxel boundary; post-print tensile tests of rigid-elastomer joints often fail in the elastomer phase rather than at the interface, although the supplier’s public datasheet does not list a lap-shear or peel value for multi-material transition zones.

In production-scale ENT workflow, the ProJet MJP 5600 build volume of 518 × 381 × 300 mm allows multiple sinus and airway models in one batch. Rigid bony and cartilaginous structures can be assigned to CR-BK, highly distensible tissue to CE-NT, and black rubber-like structures to RBK-ENT-A60. The single-body build eliminates mechanical assembly and adhesive joints, but transition-zone gradients introduce a different validation requirement: tensile adhesion between rigid and elastomeric regions is not published as a lap-shear value, so design allowables for multi-material boundaries must be generated by testing ASTM D638 specimens printed across the transition. Ceramic-like or stone-like rigid segments are not within this material system.

When ISO 10993 Skin-Contact Evidence Is Required for ENT Anatomical Models

Medical modelling groups requesting skin-contact compliance cannot rely solely on the RBK-ENT-A60 designation. The VisiJet CE-NT base material has supplier documentation for cytotoxicity and skin sensitization based on ISO 10993-5:2009 and ISO 10993-10:2010, but the combined RBK-ENT-A60 state requires finished-device testing because the CR-BK phase, post-processing fluids, and support residue can contribute to the leachable load. A conservative qualification matrix for non-implantable, short-duration mucosal or skin contact includes MEM elution cytotoxicity, guinea pig maximization sensitization, and intracutaneous reactivity under USP Class VI or ISO 10993-10. No permanent implantation or long-term mucosal contact should be assumed without additional ISO 10993-6 implantation data. The product is not supplied sterile; sterilisation by ethylene oxide, gamma irradiation, or steam may alter durometer, so the selected sterilisation method must be revalidated against ASTM D2240-15 and ASTM D638-14 after treatment.

The product is not intended for permanent implantation, bone contact, or vascular contact. No statement in the current supplier datasheet supports long-term implantation, and published data for cyclic compression set, in vivo degradation, or load-bearing fatigue in RBK-ENT-A60 is limited. Users comparing RBK-ENT-A60 with molded high-consistency silicone should recognize that ASTM D624 tear strength of printed rubber-like composites is typically below that of high-consistency silicone elastomers, and ASTM D395 compression set after 70 h at 70 °C may be higher than for medical-grade silicone. These limitations define the product’s operational boundary: it is suitable for short-contact anatomical models and functional rubber-like prototypes, not for long-term dynamic implant seals.