Proto3000 Objet Digital Materials™ DM_8505Gray20 Rigid Opaque Prototyping Polymer is a UV-curable PolyJet resin supplied in sealed cartridges for multi-jetting systems that support digital material blending. The designation separates the product from single-cartridge rigid resins: the DM prefix indicates a digital material, the 8505 segment is consistent with a nominal Shore D 85 hardness class, and the Gray20 suffix identifies a 20 % gray pigment loading in the manufacturer’s color formulation. The material is jetted through multi-nozzle inkjet arrays and cured in the same pass by narrow-spectrum UV lamps, producing an opaque thermoset solid. Typical High Quality and Digital Material print modes on Objet Connex-class platforms operate at 16 µm and 30 µm layer thicknesses, respectively; the appropriate mode for DM_8505Gray20 must be selected from the system’s validated material menu because not all modes are available for every digital material.

Published certified values for this specific DM_8505Gray20 configuration are limited in publicly available technical bulletins. Engineering groups should therefore treat the product as a rigid opaque prototyping material with Shore D 85 class hardness and gray opacity, and should generate internal design allowables before load-bearing service. The material is intended for form-and-fit models, master patterns, short-run inspection fixtures, and static functional prototypes; it is not a direct substitute for production engineering thermoplastics such as polycarbonate or glass-filled nylon. Its principal difference from general-purpose clear or translucent PolyJet resins is the opaque gray pigmentation, which provides contrast for dimensional scanning and photographic documentation, but which also reduces the effective UV penetration depth compared with clear resins.

What processing constraints define the safe envelope for DM_8505Gray20?

The build envelope is bounded by the same environmental variables that affect all PolyJet resins. Manufacturer installation guidance for Objet Connex-class systems commonly specifies an ambient temperature of 18 °C to 25 °C and relative humidity of 30 % to 70 %; excursion beyond this band can shift inkjet viscosity and reduce droplet placement accuracy, which in turn alters edge definition on fine features. The cartridge should be conditioned at the build temperature for at least 12 h before loading, and partially used cartridges should be sealed against ambient humidity. Because DM_8505Gray20 is opaque, UV cure is dominated by surface-near absorption; thick sections require the system’s standard lamp dose and cannot be accelerated by increasing layer thickness alone. The standard printhead cleaning cycle should follow the platform manufacturer’s schedule, with increased frequency when the ambient particulate count exceeds the manufacturer’s threshold.

Support removal is the primary manufacturing bottleneck in the post-processing flow. The support material in PolyJet builds is removed by water-jet or immersion cleaning. Blind holes smaller than 2 mm and internal channels with length-to-diameter ratios above 5:1 can retain support residue even after automated cleaning. A programmable water-jet station operating at 1 500 psi to 2 000 psi is common for this material class, but jet pressure above the system-specific limit can erode sharp edges and thin partitions. Features with wall thickness below 0.8 mm should be protected or cleaned at reduced pressure, and destructive sectioning of one part per batch is recommended to confirm support removal in internal passageways. If downstream bonding is planned, residual support films can reduce adhesive wetting; a water-break test following cleaning is a simple in-process check for support-free surfaces.

Surface finishing is influenced by the layered nature of the build. Up-facing surfaces are smoother than down-facing surfaces; when the application requires low friction or consistent reflection, wet sanding with 400 to 600 grit abrasive is typically used. Chemical vapor polishing may be attempted, but the crosslinked network can absorb low-molecular-weight solvent and exhibit transient dimensional change. The engineering group should screen any solvent polish under ASTM D543-20 before release, because the published data for DM_8505Gray20 is too limited to support a generic approval. Coating adhesion to the opaque surface is generally improved by mechanical abrasion or plasma treatment, but coating compatibility must be confirmed by cross-cut adhesion testing under ASTM D3359-17 and, for interior surfaces, by a thermal-humidity cycle representative of the intended service.

In production-scale digital material jobs, the highest yield loss occurs at the slicing and build-orientation stage rather than during resin processing. DM_8505Gray20 parts are typically orientated with critical dimensions in the X-Y plane to avoid Z-axis layer stair-stepping; however, if the part must carry load, the Z-axis is the limiting tensile direction due to interlayer fusion. A support-free orientation should not be selected at the expense of the mechanical axis. Tray packing density is constrained by the UV lamp sweep and by the need to maintain uniform jetting temperature across the build area; parts placed too close to the tray edge may experience lower lamp dose. Printhead maintenance intervals should follow the platform manufacturer’s schedule, with particular attention to orifice condition because particle or pigment settling in DM_8505Gray20 cartridges can increase printhead clogging frequency relative to clear resins. If the cartridge has been stored beyond its manufacturer-specified stirred shelf life, gentle rolling before installation is required to redisperse pigment, but published instructions for this specific product are limited and the vendor’s cartridge label remains the controlling document.

Mechanical property assessment through standardized test methods

Rigid opaque digital materials are anisotropic because the droplet-to-droplet and layer-to-layer interfaces are potential failure paths. Test coupons should be printed in flat, on-edge, and vertical orientations. Tensile properties are measured under ASTM D638-14 or ISO 527-2:2012 using Type IV or 1BA specimens at 23 °C. Flexural modulus is obtained under ASTM D790-17 with a span-to-thickness ratio of 16:1. Notched Izod impact is tested under ASTM D256-10 Method A, with notch orientation both parallel and perpendicular to the build plane. Heat deflection temperature should be recorded at both 0.455 MPa and 1.82 MPa under ASTM D648-18; for a thermoset PolyJet material, the value at 1.82 MPa is the more conservative selection for load-bearing fixtures.

Hardness is measured with a Shore D durometer under ASTM D2240-15 on a specimen at least 6.35 mm thick; readings are taken at 15 s. The product’s model designation indicates a Shore D 85 class, but production lots should be checked because pigment loading and cure variation can shift hardness by several points. Melt-flow testing under ISO 1133-1:2022 is not applicable because the material does not undergo a thermoplastic melt transition after cure. Instead, incoming resin consistency is evaluated by rotational rheometry at 25 °C or at the jetting temperature, with a 25 mm parallel plate and a shear rate of 10 s⁻¹ used as an internal reference condition. A significant increase in complex viscosity at low shear can indicate pigment agglomeration, which can then appear as printhead nozzle dropout.

When DM_8505Gray20 is selected instead of VeroGray or Digital ABS in the same build platform

The material’s role in a multi-material PolyJet cell is defined by its position between single-resin rigid opaque products and engineering digital materials. VeroGray is a monolithic rigid opaque resin with a fixed color and hardness; DM_8505Gray20 is supplied as a digital material or gray-grade resin that can be assigned to a tray with specified opacity and Shore hardness without a separate paint operation. The gray pigmentation reduces the post-printing color step for prototype housings, but it does not alter the fundamental thermoset behavior of the material. In contrast, a clear rigid resin can be dyed only on the surface and cannot deliver the same through-thickness opacity, whereas DM_8505Gray20 maintains a uniform opaque appearance when sectioned.

Digital ABS is the higher-strength comparison material for snap-fit and elevated-temperature prototypes. Digital ABS-class materials generally provide higher heat deflection temperature than rigid opaque prototyping photopolymers; therefore, DM_8505Gray20 is assigned to visual and low-rate functional parts, whereas Digital ABS is specified when the part must maintain stiffness above 60 °C or when repeated snap-fit assembly is expected. The actual transition temperature should be based on measured HDT and not on resin family. If an internal fixture must survive 60 °C continuous exposure, the design group should compare the measured HDT of DM_8505Gray20 with the safety margin established in the internal polymer test procedure. Published certified HDT data for DM_8505Gray20 is not available, so this qualification cannot be waived by a resin-family data sheet.

Compared with rubber-like PolyJet materials, DM_8505Gray20 lacks the high elongation required for gaskets, seals, and living hinges. Its rigid opaque response is appropriate for static housings, brackets, and check fixtures that are not cyclically deflected. Insertion of self-tapping screws into printed pilot holes is limited by the lower pull-out resistance in the Z build direction; thread-forming operations should be qualified by torque-to-failure testing using a calibrated torque driver and the plant’s mechanical joining standard. Where the assembly requires a combination of rigid and flexible zones in a single build, the digital material capability of the platform should be used with a compatible elastomeric material instead of forcing DM_8505Gray20 into flexural service beyond its elongation limit.

Master patterns for RTV silicone tooling are a common use for opaque gray rigid photopolymers because the gray surface provides contrast against silicone and allows visual inspection of seal lines. The pattern must be sanded to the tooling finish, because PolyJet layer lines transfer to the mold surface; a sequence of 400, 600, and 800 grit wet sanding is used on seal surfaces. Dimensional verification should be performed after sanding, not before, because material removal of 0.02 mm to 0.05 mm per side is possible. For wind-tunnel models or flow-visualisation components, the internal channel surface finish is critical; the build orientation should align the flow path as closely as possible with the X-Y plane, and any remaining stair-stepping that exceeds the engineering tolerance should be removed by abrasive flow machining only after confirming that the process does not open layer interfaces.

Dimensional fixtures produced from DM_8505Gray20 are used for initial assembly trials, not for final acceptance against engineering tolerances below 0.1 mm unless the process is validated and statistically controlled. For a fixture with locating pins and bores, the printed bores are often post-machined with a reamer or a CNC tool because the as-printed bore diameter can vary with layer orientation and UV shrinkage. The post-machining allowance is typically 0.2 mm to 0.3 mm per side on holes above 5 mm diameter; smaller holes should be drilled from solid after printing to maintain location accuracy. Inspection fixtures should be stored in a dark, dry cabinet to reduce long-term color drift and moisture uptake.

Batch-to-batch variation is controlled on the production floor

Each production shift should begin with a control coupon build to isolate batch-to-batch and machine-state variation. A 10 mm cube is measured for mass, X-Y-Z dimensions, and Shore D hardness. A thickness deviation greater than ±0.1 mm from the control median is a common trigger for printhead calibration or UV lamp inspection. Because DM_8505Gray20 is an opaque pigment-loaded resin, UV penetration is lower than in clear materials; a drop in surface hardness near the build tray edges can indicate uneven lamp energy and must be corrected before serial production. The control coupon data should be plotted on an individual control chart; a single-point excursion outside ±3 s from the process mean is not necessarily a material rejection criterion but requires a machine and cartridge review.

Long-term UV exposure can reduce surface hardness and color stability. Applications placed near sunlight should be coated or kept in dark storage; weathering resistance is screened under ASTM G154-16 with periodic Shore D and color change measurements. Chemical resistance screening uses ASTM D543-20; immersion in ketones or chlorinated solvents is not recommended unless the measured mass change, dimensional change, and hardness retention meet the internal acceptance threshold. The material is not autoclavable; repeated steam exposure can crack the thermoset network. If the part must be cleaned repeatedly, a room-temperature neutral detergent wash is preferred to solvent wiping or ultrasonic cleaning with aggressive media.

Material storage, handling, and disposal must follow the safety data sheet supplied with the cartridge. PolyJet resins are not classed as thermoplastics for recycling; uncured liquid waste and cleaning water containing support residue must be disposed of according to local photopolymer waste regulations. The batch certificate for DM_8505Gray20 should be retained with the lot number and used to trace any mechanical property shift. Where regulatory compliance is claimed, the appropriate documentation is the vendor’s REACH and RoHS statement for the specific cartridge lot, not a generic resin-family declaration.