VisiJet RBK-EBK-A70 is a multi-material build configuration for 3D Systems ProJet MJP 2500 and 3000 series machines, combining VisiJet CR-BK rigid black photopolymer and VisiJet CE-BK elastomeric black photopolymer in a single jetting cycle. The composite designation refers to a build mode rather than a physical melt blend: CR-BK and CE-BK are delivered from separate printhead channels and are polymerized as discrete voxel populations. The CE-BK phase carries a nominal Shore A 70 durometer. The material set is intended for functional prototypes that require rigid structural members joined to elastomeric sealing, cushioning, or gripping surfaces without secondary insert molding. The support material is a wax formulation removed at 35–40 °C; post-rinsing uses approved mineral-oil detergent or EZ Rinse chemistry under ultrasonic agitation. Build preparation in 3D Sprint software divides CAD volumes into CR-BK and CE-BK regions. The boundary between rigid and elastomeric phases is generated as a co-jet transition, and the mechanical performance of that transition zone is sensitive to residual wax, oxygen inhibition at the elastomeric skin, and storage conditions after cleaning. The following application scenarios describe downstream sectors in which this material set is currently used for prototype and short-run functional evaluation.

Handheld Consumer Electronics Assemblies with Co-Jetted Elastomeric Sealing Ribs

Design intent for handheld consumer shells is to replace a two-shot injection mold with a single build in which CR-BK forms the front case, lens frame, battery retention rail, and snap-fit struts while CE-BK forms side-key compression pads, connector dust plugs, lens-bed compression rings, and acoustic sealing beads. The material addition strategy in the build file is voxel assignment, not physical mixing: gasket and seal volumes are set to 100 vol% CE-BK, structural volumes are set to 100 vol% CR-BK, and total CE-BK consumption in a full handset shell typically falls between 20 vol% and 35 vol% depending on the number of sealing ribs and I/O aperture seals. The exact voxel occupancy is read from 3D Sprint slice statistics and must be included in job travellers for export documentation. Print quality is maintained at 32 µm layer thickness to preserve sidewall straightness on gasket ribs and prevent stair-step flash on compression faces. The ProJet MJP platform uses a heated jetting array; ambient relative humidity above 60 % in the build chamber can promote CE-BK jet dropout and lane-to-lane durometer drift, so production scheduling should place high-seal-density consumer jobs in air-conditioned rooms or delay printing until humidity falls within the manufacturer’s recommended band. After printing, wax support is melted at 35–40 °C; ultrasonic washing is carried out at 20–30 °C with approved detergent, and the parts are dried and conditioned at 23 ± 2 °C and 50 ± 5 % RH for 24 h before durometer audit. The co-jet interface is sensitive to wax residue trapped in the narrow gap between the rigid shell and the elastomeric bead; incomplete rinse leaves a slick interfacial layer that can reduce tear resistance under peel loading. For export of functional prototypes into consumer supply chains, the resin system should be documented against RoHS Directive 2011/65/EU and REACH Regulation 1907/2006; flammability evaluation of the rigid CR-BK phase and the co-jetted interface should follow UL 94 HB or IEC 60695-11-10. Terminal part types fabricated under this scenario are smartphone drop-test mock-ups, wearable continuous glucose monitor enclosures, wireless earbud shells with integrated charging-contact seals, and virtual-reality headset face-gasket frames that combine rigid eye-box retention with a compressible facial seal of Shore A 70.

For procedure-specific anatomical replicas in medical education programmes, the RBK-EBK-A70 configuration is used to produce cortical bone analogues from CR-BK and soft-tissue analogues from CE-BK within the same build. The build process begins with DICOM segmentation in Mimics or 3D Slicer; cortical shells, pedicle channels, and calcified structures are exported as rigid volumes, while intervertebral discs, meniscal rims, labral structures, vascular sheaths, or parenchymal tissues are assigned CE-BK. The composition in the material train remains separate; bone-analog regions are printed at 100 vol% CR-BK, soft-tissue analogue volumes at 100 vol% CE-BK, and intermediate digital blends are generally avoided because they compromise the intended Shore A 70 response. Part orientation is selected to keep thin meniscal edges and tubular vessel analogues in low-peel orientations during wax removal; unsupported elastomer overhangs more than 5 mm often require breakaway anchor tabs that are removed after the rinse cycle. Post-cure UV exposure is limited to the manufacturer-specified dose for the rigid phase because overtreatment of CE-BK raises crosslink density and can alter compression set and puncture resistance. Laboratory evaluation for patient-contact training devices requires biocompatibility screening on leachates from the co-jetted interface according to ISO 10993-5:2009 for cytotoxicity, ISO 10993-10:2021 for sensitization, and ISO 10993-23:2021 for irritation; published data for this specific configuration is limited, so procurement specifications should require batch-specific test reports. These models are not implant devices, and medical-grade certification must be obtained for any use beyond bench-top or synthetic-tissue skills training. Terminal product types include lumbar discectomy simulators, shoulder arthroscopy models, transnasal sinus surgery trainers, and atrial access task trainers in which the septal analogue must exhibit puncture resistance and self-sealing behaviour under repeated needle entry.

What Limits Compression Set Readings in Automotive Wiring Harness Grommet and Connector Interlock Prototypes?

Automotive pre-production teams evaluate cable entry grommets, inline connector seals, and ECU isolator bodies in RBK-EBK-A70 when the part must consolidate a rigid retention clip and an elastomeric bellows without a moulded gasket assembly. In the sliced file, the bellows section is printed at 100 vol% CE-BK; the interlock collar and clip teeth are printed at 100 vol% CR-BK. For a firewall grommet where the bellows dominates the part volume, total CE-BK consumption may exceed 50 vol%; for small connector seals, the elastomer volume fraction can fall below 15 vol%. The critical process conflict is thermal: wax support removal must occur at 35–40 °C, but thin CE-BK bellows walls sag when exposed to the upper end of that range for more than 45 min. Ramping the wax melt-out oven at 35–38 °C and supporting parts on PTFE-mesh racks preserves conic section geometry. After cleaning, compression set is tested according to ISO 815-1:2019 at 25 % deflection for 22 h at 70 °C; published data for this specific co-jetted configuration is limited, so acceptance limits should be benchmarked against injection-moulded thermoplastic elastomer control specimens rather than generic photopolymer datasheets. For underhood or cabin applications, environmental stress screening follows the vibration and thermal shock provisions of SAE J1455; interior flammability screening is conducted under FMVSS 302 burn-rate procedures. The co-jet boundary at the bellows-to-collar transition is the most common failure initiation site under repeated flexural loading; design reviews should include a radius not less than 1.0 mm at the transition and a witness groove for post-test tear inspection. Terminal part types include engine-bay pass-through grommets, door-harness conduit seals, onboard charger connector strain-relief boots, and ECU bracket isolators where a rigid mount face must be damped at the bolt contact.

In collaborative robot end-of-arm tooling, the dual-material build is used to produce a CR-BK structural backer with integral CE-BK contact pads whose target hardness is Shore A 70. The material assignment strategy uses 100 vol% CE-BK on the contact face and 100 vol% CR-BK in the mounting plate; the physical transition is created as a castellated interlock zone between 0.8 mm and 1.2 mm in depth, generated in 3D Sprint. The build is oriented with the contact face away from the support plane so that wax does not accumulate in the pad texture; a rhombic surface texture with 0.5 mm feature size is used for low-slip contact. Post-processing follows the standard MJP sequence: support wax melt-out at 35–40 °C, warm mineral-oil ultrasonic cleaning at 20–30 °C, forced-air drying, and a 24 h rest period at 23 ± 2 °C. Batch-to-batch durometer variance of ± 3 Shore A points across large production trays can often be traced to capping station maintenance or recirculation interruptions rather than CE-BK resin lot variability; the 3D Systems MJP service schedule should be advanced in high-humidity environments. Mechanical verification uses ASTM D2240-15 for durometer, ASTM D412-16 for tensile and elongation with a Type C die, and ASTM D624-20 for tear strength; slip-resistance screening may use ASTM D1894-21 with the caveat that the film-friction fixture is not fully representative of curved gripper pads. Collaborative robot applications also require contact pressure assessment against the body-region limits in ISO/TS 15066. Terminal finished part types include vacuum-cup adapter lips, battery-cell radial gripper jaws, vial pick-and-place fingers for packaging lines, and depalletizer edge clamps where rigid mounting and low-marking contact are required in a single part.

When Orthotic Shell Stiffness Must Transition to Shore A 70 Cushioning Without a Secondary Bond Line

Custom foot orthoses and ankle-foot orthosis probe structures are built with CR-BK shell regions that hold the calcaneal cup, post plane, and strap slots, while CE-BK forms the heel cushion, metatarsal pad, and medial arch contact surface. The print file assigns 100 vol% CR-BK to bending-resistant regions and 100 vol% CE-BK to cushioning regions; the transition is designed as a 1.0–1.5 mm interlocking lattice rather than a butt joint, eliminating the need for a post-print adhesive. In a pair of full-foot insoles with a heel cushion and metatarsal pad, total CE-BK occupancy is typically between 40 vol% and 60 vol%; published material-consumption data for this exact application is limited and should be extracted from 3D Sprint job statistics before quoting. The clinical scanning and manufacturing sequence starts with a 3D scan of the patient’s foot or positive cast, followed by shell offsetting and thickness mapping; the build is oriented at 15 ° from the platform to reduce support adhesion on the plantar texture. Wax support removal is held at 35–38 °C because the thin elastomeric metatarsal pad can creep if exposed to higher wax-melt temperatures. Cleaning follows in an ultrasonic bath with approved EZ Rinse detergent at 20–25 °C, and conditioning is performed for 24 h at 23 ± 2 °C and 50 ± 5 % RH before hardness and compression checks. Elastomer phase hardness is verified under ASTM D2240-15; rebound resilience may be screened under ISO 4662:2017. Devices intended for prescription use in the European Union are subject to Regulation (EU) 2017/745 as custom-made Class I devices when supplied for an individual patient; material-level testing does not replace device-level conformity assessment. Terminal part types include diabetic foot offloading insoles, sports orthotic shells, metatarsal pad test articles, and AFO probe prototypes that require a rigid calf shell and soft anterior padding in one build.

For shell-and-liner impact protection prototypes, the RBK-EBK-A70 build mode supplies a rigid CR-BK outer shell and a Shore A 70 CE-BK energy-managing liner with corrugated collapse geometry. The liner is printed at 100 vol% CE-BK and the shell at 100 vol% CR-BK; elastomer volume fraction in a shin guard or knee pad is typically between 25 vol% and 45 vol%, depending on liner coverage and corrugation depth. Build preparation sacrifices part count per tray to maintain 32 µm layer thickness on the liner ribs, because thicker layers create stair-step stress concentrations that reduce flexural fatigue life. After support removal at 35–40 °C, the CE-BK liner is conditioned at 23 ± 2 °C for 48 h before impact screening; viscoelastic recovery is superior to rigid photopolymer liners, but published values for this specific configuration are limited. Elastomer rebound and energy-return screening may be performed under ASTM D2632-15; impact attenuation for industrial protective equipment is evaluated under EN 1621-2 for back protectors or EN 1621-3 for chest protectors, with the explicit condition that prototype photopolymer parts are not automatically certified for workplace use. Terminal part types include bicycle knee-armor test shells, goalkeeper glove finger-stall dorsal pads, climbing helmet liner probe structures, and riot-shield handle isolators where CR-BK carries the handle spine and CE-BK supplies damping at the grip face.