Proto3000 supplies the Objet Digital Materials™ DM_Dots_7513 Transparent Prototyping Polymer as a cartridge-based photopolymer system formulated for PolyJet multi-material jetting platforms. The designation places the product within the Objet Digital Materials family rather than a single-resin transparent rigid material: the final polymeric network is produced in situ by voxel-level combination of at least two base photopolymer feedstocks inside the printhead or at the build surface. Because PolyJet technology deposits droplets and immediately cures them with ultraviolet energy, the DM_Dots_7513 formulation is governed less by bulk mixing than by digital material scaling, droplet coalescence, and the local crosslink density produced by the specified model resin ratio. Published technical literature from Stratasys-derived Objet systems classifies such digital materials as composed of rigid transparent and flexible or elastomeric components; however, published data for this specific composite configuration is limited in openly accessible datasheets, so any design envelope should be verified using a qualification coupon on the intended machine before production release.

Which PolyJet platforms can run a digital material designated as DM_Dots_7513?

To run DM_Dots_7513, the platform must support multi-material jetting rather than a single model resin. Prior-generation Eden systems with only one model resin channel cannot execute the digital material pattern. The relevant machine classes include Objet Connex, Connex2, Connex3, and Stratasys J-series systems that are configured with at least two model resin cartridges and a support cartridge. The build software interprets the DM_Dots_7513 recipe as a digital material ratio; therefore the material cannot be used as a standalone upload. The layer thickness is determined by the selected print mode and is typically 16 µm or 30 µm in PolyJet systems. When the material is run on a machine with degraded printheads or missing jets, droplet-splitting at the boundary between base resins can produce a visible dot matrix that is not representative of the intended transparent surface. For this reason, nozzle-check verification and a flat-field transparency check are recommended at the start of each build batch. The relevant additive manufacturing terminology is defined in ISO/ASTM 52900:2021.

In a single-phase transparent photopolymer such as VeroClear or RGD720, the jetted material is expected to form a homogeneous network with a single glass transition. In contrast, an Objet Digital Materials formulation such as DM_Dots_7513 is a processable mixture of at least two model resins that are combined by the print system and cured voxel by voxel. The term “dots” may indicate discrete digital material islands rather than a continuous bulk mixture, and optical transmission should not be assumed to equal that of a fully miscible transparent resin. Total luminous transmittance is measured according to ASTM D1003-21; haze is measured with the same integrating-sphere procedure; yellowness index is measured according to ASTM E313-20. Published data for this specific configuration is limited in openly accessible datasheets. A design team should therefore generate optical coupons at the exact wall thickness, build orientation, and finishing sequence that will be used in production.

For optical applications, the digital dot structure can act as a diffraction or scattering feature if the dot spacing approaches the wavelength of visible light. A printed part may appear transparent at thick sections but develop a faint pointillist haze when viewed at grazing angles. This phenomenon is best evaluated with a laser scatterometer or an integrating-sphere haze meter according to ASTM D1003-21. Because the “dots” designation implies a pattern rather than a fully homogeneous blend, the orientation of the dots relative to the viewing axis should be fixed in the build file. If the dot pattern is printed with one spacing on the X-Y plane and a different spacing on the Z axis, optical performance will be anisotropic. In production development, three flat coupons of 1 mm, 3 mm, and 6 mm thickness should be built at the same orientation and post-processed identically to quantify thickness-dependent transmittance and haze. This practice prevents the common error of quoting a single transmittance value from a thin coupon to a thick-walled production part.

Oxygen inhibition at the droplet surface can reduce the degree of cure and leave a tacky surface. In PolyJet printing, the UV lamp intensity and carriage speed are machine parameters, but the digital material blend may require higher or lower exposure than a single resin. Incomplete cure is usually first visible as a gelatinous boundary at support interfaces or as a reduced Shore value on thin walls. Post-curing can complete the network but may also accelerate yellowing. Users should measure Shore hardness at the surface and core of a sectioned thick part because a gradient indicates cure-rate limitations. Differential scanning calorimetry can be used to measure residual exotherm and glass transition, but the method is most useful when comparing known good builds with suspect builds rather than as a daily production check.

Cartridge Rheology and Printhead Temperature Limits

At the printhead, a narrow viscosity window is required for stable droplet formation. Photopolymer resins used in PolyJet printing are conditioned at temperatures typically above ambient but below 80 °C; exact values are machine-specific and are set by the printer firmware. Cold cartridges below 15 °C can cause jetting starvation, while overheating can accelerate premature polymerization and plate-out on nozzle plates. Storage should follow the cartridge label; a common range is 15–25 °C in a closed, opaque container. Before loading, cartridges should be equilibrated and rotated manually to disperse any settled monomer or oligomer fraction. The use of hot-air ovens to pre-heat cartridges is not advised because it can induce localized thermal gradients and degrade the cartridge shell.

On a production line, batch-to-batch variation is most often detected as a shift in droplet trajectory or as feathering on the build surface, not as a bulk property change. Feathered edges reduce edge definition and can create a hazy film on vertical walls because satellite droplets are cured in place. Production-scale users typically monitor jetting quality by printing a diagnostic pattern with a flat transparent tile and measuring its minimum/maximum thickness across a predefined grid. A laser displacement probe or contact micrometer with resolution 0.01 mm can detect build nonuniformity before functional parts are started. Periodic replacement of printhead filters and wiper blades is part of stable DM_Dots_7513 operation because partially cured material accumulations at the nozzle plate alter droplet direction. If the workflow includes unattended overnight builds, the material supply should be checked for expiration date and recirculated or agitated according to the printer manufacturer’s maintenance schedule. Condensation on cold cartridges should be avoided because water contamination can destabilize droplet formation even if the model resin itself has low moisture sensitivity.

Digital material ratio control is the main process variable that does not exist for single-resin prototyping. The printer software calculates the droplet fraction of each base resin and writes it into the build file; however, the actual ratio at the part surface can deviate if one material path has lower pressure, higher viscosity, or partially blocked jets. A ratio error may not be evident from the machine display because the controller may report the commanded ratio rather than the delivered ratio. To verify delivered stoichiometry, users can print a calibration disk with known transitions and inspect it under a stereomicroscope. If the dot matrix is irregular, missing, or smeared, the build should be paused and the printhead maintenance cycle repeated. Process capability studies on production equipment should track the standard deviation of dot spacing across the tray, because the center of the tray can receive a different UV dose than the edges. These measurements are more informative than bulk mechanical tests when diagnosing intermittent transparency defects.

When build orientation and support removal dictate optical clarity

Build orientation is the primary adjustable variable for optical and dimensional outcomes. The X-Y plane is the smoothest layer plane, while the Z axis accumulates layer striations. If a prototype is intended for light-pipe evaluation or contact transparency, the inspection face should be oriented in the X-Y plane. The use of water-jet-removable or soluble support on the inspection face will leave micro-texture that reduces gloss and increases haze. Support removal by high-pressure water jetting should be followed by progressive wet sanding from 600 to 2000 grit and, if required, a clear acrylic lacquer selected for compatibility with photopolymers. Alkaline support baths should be used with controlled concentration and immersion time because prolonged exposure can induce surface whitening in transparent acrylate networks. After any aqueous process, residual moisture should be removed before mechanical or optical testing; otherwise water plasticization can artificially lower strength and increase elongation. If dimensional accuracy below 0.1 mm is required, the Z-axis should be compensated using a calibration scale bar printed in the same tray, because digital material shrinkage is not identical to that of a homogeneous resin.

After support removal, dimensional stability is evaluated by cycling parts between room temperature and the intended service temperature. Transparent photopolymer parts can exhibit secondary cure shrinkage if the UV dose during printing was incomplete; a post-cure chamber with controlled UV output may be used, but only if the part geometry can tolerate additional dimensional change. Mass and linear dimension checks before and after post-cure should be recorded. For optical parts, internal stress can be observed under a polariscope; high fringe counts near gates or support locations indicate residual stress that may cause delayed crazing or optical birefringence. These effects are not unique to DM_Dots_7513, but the digital material interface can amplify stress concentration at resin boundaries.

Mechanical data without build-specific coupons remains indicative.

Because DM_Dots_7513 is a digital blend, the ratio specified in the build file is a process parameter. Coupons should be printed in the same orientation, layer thickness, and print mode as the production parts. The table below lists minimum test designations and reporting units that are commonly applied to transparent PolyJet photopolymers. The absence of published nominal values for this specific configuration is a limitation to be managed through internal qualification rather than inferred from general PolyJet datasheets.

Chemical exposure limits for DM_Dots_7513 are similar to those of other acrylate-based PolyJet materials. Short wipe cleaning with isopropyl alcohol is generally tolerated, but prolonged immersion or ultrasonic cleaning in aggressive solvents can cause surface haze, swelling, or network plasticization. The material should not be used in continuous contact with hot water above the measured heat deflection temperature. Outdoor use in direct sunlight requires a UV-stabilized clear coat because unpigmented photopolymers can yellow or embrittle under repeated UV exposure. If the prototype will contact food, skin, or mucosal tissue, material-specific regulatory documentation under FDA 21 CFR or ISO 10993 must be obtained. Transparency and prototyping-grade classification do not establish biocompatibility or food-contact approval. Compliance with REACH and RoHS should be confirmed for the target market from the supplier’s safety data sheet and declaration letters.

Relative to single-material transparent PolyJet photopolymers such as VeroClear, the DM_Dots_7513 digital material is selected when the design needs voxel-level mechanical tuning or a combination of transparent and non-transparent digital material behavior in one build. The additional complexity is not free: digital material patterns introduce more process variables, including nozzle-to-nozzle ratio accuracy, boundary-layer mixing, and pattern scaling at the printer controller. If the application requires the highest possible optical clarity and repeatability, a homogeneous transparent resin remains the lower-risk choice. If integrated rigid-elastomeric features or local property variation are required without secondary bonding, the digital material route may reduce downstream assembly. In either case, first-article inspection should include cross-sectional optical microscopy, dimensional mapping, and mechanical testing under the exact build conditions intended for production.