DruckWege TYPE D FLEX BLACK Basic Model UV Resin is a flexibilized photopolymer formulated for bottom-up masked stereolithography and digital light processing platforms operating at 385–405 nm. The material belongs to the black-pigmented flexible resin class, in which the radiation-absorbing filler lowers working curve depth and narrows the exposure latitude relative to clear or lightly coloured resins. Production users should therefore treat build parameters as machine-specific and not transfer exposure times from other resins or other printers without recalibration.

The flexibilized matrix is typically an acrylate/urethane acrylate hybrid. Urethane acrylate oligomers contribute toughness and lower Shore hardness, while acrylic monomers control viscosity and reaction rate. The black pigment is commonly a surface-treated carbon black or a black oxide dispersion. Surface treatment affects storage stability because untreated carbon black can adsorb moisture and stabilizer components from the liquid resin, changing viscosity and promoting particle agglomeration. Incoming lots should therefore be checked for pigment dispersion stability by ISO 18314-1:2015 colorimetric procedures or by controlled drawdown. The Basic Model designation should not be assumed to contain the same pigment system as other flexible resins in the DruckWege Type D range; exact pigment chemistry and particle size distribution must be obtained from the current supplier documentation.

Uncured viscosity is among the first variables to review because it affects recoating speed, bubble release, and resin level sensing. For heavily pigmented flexible photopolymers of this general composition, cone-and-plate measurements at 25 °C frequently fall between 250 and 1200 mPa·s; the exact value for the Basic Model must be read from the current DruckWege technical data sheet, because batch-to-batch variation in pigment dispersion can shift viscosity by 10–20 %. Low-viscosity behavior may require longer idle settling time before printing, while higher viscosity can increase the risk of resin starvation in tall or solid builds.

Mechanical property measurement after post-cure does not follow a single standard.

Specimen geometry and test speed materially influence reported tensile values for flexible UV resins. Tensile strength and elongation at break should be reported according to ISO 37:2017 or ASTM D638-14, but the two standards use different jaw separation rates and dumbbell proportions, so values cannot be interchanged. Shore hardness is evaluated under ISO 7619-1:2010 or ASTM D2240-15; elastomeric black formulations are typically measured on the Shore A scale, but the presence of high crosslink density can push the response into the Shore D range. Tear strength is relevant for gaskets, bellows, and snap features and is commonly tested under ISO 34-1:2022. The black pigmentation introduces a vertical cure gradient: if layer thickness is too high or post-cure dose is insufficient, the surface layer may be harder and less elastic than the interior, producing misleading hardness readings and premature tear initiation.

Post-cure scheduling for black flexible resins is not interchangeable with schedules used for rigid black photopolymers. Class-typical processing for similar flexibilized 405 nm resins uses LED post-cure chambers at 30–40 °C for 30–45 min, but black formulations may require longer exposure because the pigment competes for UV during the initial photopolymerization. Over-cure in air can cause surface oxidation and embrittlement; under-cure leaves residual monomer and lower tensile modulus. Thin walls, living hinges, and snap features should be supported during post-cure to avoid thermal distortion. The manufacturer’s written post-cure settings for TYPE D FLEX BLACK Basic Model should supersede class-wide values.

Anisotropy influences flexible black prints more than rigid ones because elongation and tear strength are reduced in the build direction if interlayer conversion is incomplete. A plate or tensile specimen printed in vertical, horizontal, and 45° orientations reveals the degree of anisotropy. For quality assurance, tensile specimens should be printed in the same orientation as the production part. A vertically printed tensile specimen may show 20–50 % lower elongation at break than a horizontally printed specimen in many UV resin systems; the exact loss for TYPE D FLEX BLACK Basic Model requires internal evaluation because published data for this specific configuration is limited.

What Distinguishes the Basic Model from Rigid and High-Elongation Black Resins?

Relative to a rigid black photopolymer, TYPE D FLEX BLACK Basic Model trades flexural modulus and compressive stiffness for higher elongation, lower Shore hardness, and improved resistance to impact-induced fracture. The trade is not universal: elastic recovery and long-term dimensional stability under continuous load may be inferior to a rigid high-crosslink formula. Compared with a clear high-elongation flexible resin, the black pigment in the Basic Model reduces working curve depth and therefore requires higher exposure energy or slower print speeds to achieve the same layer thickness. Unlike water-washable flexible resins, the Basic Model is expected to require an organic solvent or detergent-based wash sequence unless the current DruckWege instructions state otherwise. The Basic Model should be treated as a general-purpose elastomeric prototyping material; it is not a certified high-tear silicone substitute, nor a medical-grade photopolymer unless current regulatory documentation explicitly demonstrates compliance.

Wash compatibility is part of the material selection decision. Flexible black photopolymers have a lower crosslink density than rigid grades, so prolonged exposure to aggressive solvents can extract unreacted monomers and plasticizers, leading to mass loss and hardening. Isopropanol or ethanol-based wash solvents may be suitable for short post-print cleaning, but parts should not be soaked beyond the time recommended by DruckWege. Ultrasonic cleaning may accelerate extraction and should be used only if the manufacturer’s technical bulletin permits. The effect of wash solvent on Shore A hardness and tear strength can be assessed before production by immersion testing under ISO 175:2010 or an internal soak method.

Tear resistance, Shore hardness, and long-term dimensional stability

Tear propagation resistance in low-Shore flexible resins depends on print orientation and layer interface integrity. Black pigments can reduce polymerization conversion in the interlayer region, leaving a weak boundary that fails under peel or fatigue loading. For sealing or snap-fit parts, tear testing under ISO 34-1:2022 should be performed on specimens printed in the direction of service loading. Shore hardness measurements should be taken after full post-cure and after temperature conditioning, because elastomeric photopolymers soften at elevated temperatures and harden below their glass transition. Long-term dimensional stability should not be assumed from short-term tensile data; creep and compression set testing under continuous strain are required for functional prototypes. Comparative batches should be measured under ISO 815-1:2019 compression set or an internal production specification to detect lot drift.

When the black pigment absorbs UV and suppresses through-cure in low-power projectors

Calibration in low-power digital light processing hardware requires attention to irradiance, layer thickness, and exposure time. A black resin with high pigment loading can show a disproportionate loss of cure depth when projector intensity drops from 10 mW/cm² to 3 mW/cm², because the pigment consumes a portion of the dose that would otherwise penetrate the layer. Production-scale print lines should therefore monitor light engine output with a calibrated radiometer at the build plane, not rely on manufacturer default settings. For layer thicknesses between 25 µm and 100 µm, exposure times may require a 20–40 % increase relative to clear resins of similar viscosity. The Basic Model may also exhibit an induction period before gelation at low intensity; prematurely starting peel can leave a soft layer that adheres to the release film. Published data for this specific configuration is limited, so process engineers should generate a working curve for each lot of resin and for each printer light source.

Working curve plotting of measured cure thickness against the logarithm of exposure dose identifies the minimum dose needed for a given layer thickness. For black-pigmented formulations, the slope and critical energy values differ from clear formulations, and the curve may flatten at low dose. A thickness gauge should be used after cleaning to measure the resulting cured layer. The collected data show whether the light engine is operating below critical exposure and whether the process window is wide enough for production without frequent failure. The constants are specific to the light source spectrum, pigment dispersion, and release film transmittance.

In production-scale vats, black-pigmented flexible resins can sediment after idle periods. Carbon black, mineral fillers, and oligomer phase separation may produce a concentration gradient after 8–24 h without stirring. The first layers printed after idle can then show low hardness or delamination because the resin at the build surface is depleted or enriched. Bottom-up systems using fluorinated ethylene propylene or polyimide release films are sensitive to particle loading; settled pigment increases separation force and may reduce release film life. Operators should recirculate or mix the vat before start-up and should verify viscosity or pigment dispersion from the center and edges of the vat. This is not a one-time calibration; batch changes and ambient temperature shifts require rechecking.

A batch acceptance protocol for production use should include viscosity, Shore hardness, tensile elongation, and tear strength on every incoming lot. Without these checks, drift in pigment dispersion or oligomer ratio can pass unnoticed until functional parts fail. The frequency of testing can be tied to part criticality; prototypes with low risk may use reduced inspection. For production quantities, a certificate of analysis should accompany each batch and state whether the resin was manufactured under an ISO 9001 quality management system. The absence of such a certificate may limit traceability and should be treated as a supply-chain risk.

The black pigment gives the cured material low light transmission. For black rubber-like parts, transmittance across the 400–700 nm range is typically below 5 % at 2 mm thickness, but published data for this precise grade is limited. Low transmission is useful for light-exclusion prototypes, but it also means that laser or structured-light scanning for dimensional inspection may require powder coating or white contrast spray because the black surface absorbs light and reduces scan resolution. The user should include this inspection constraint when selecting black resin for parts that will be digitally verified.

The cured Basic Model will exhibit temperature-dependent stiffness. The polymer may soften above a service temperature related to its glass transition or soft segment relaxation. Differential scanning calorimetry under ISO 11357-2:2020 can be used to measure the main glass transition of the cured material, but flexible UV resins often display broad transitions rather than a single sharp peak. If parts will be used under repeated compression or high ambient temperature, the appropriate upper service temperature should be determined by dynamic mechanical analysis rather than by Shore hardness alone. Creep and stress relaxation are accelerated in the black material because the pigment increases heat absorption; dark parts exposed to direct sunlight can reach surface temperatures above the surrounding air, softening thin sections and reducing dimensional accuracy. This operational boundary should be considered for outdoor or high-UV service prototypes.

The uncured resin is a sensitizing acrylate mixture. Handling should occur with nitrile gloves under local exhaust or equivalent ventilation. The safety data sheet should be checked for specific ignition, skin irritation, and disposal classifications. Black pigments may contain residual polycyclic aromatic hydrocarbons depending on the carbon black source; therefore REACH Article 31 safety data sheet documentation and any relevant RoHS exemptions must be current before production deployment. The Basic Model is not automatically rated for food-contact or medical use under FDA 21 CFR or ISO 10993; such claims require supplier certification for the exact lot and final post-cure condition. Do not blend the resin with amine-catalyzed or moisture-cure compounds, because residual amines can promote premature dark polymerization or alter storage stability. Containers should be stored at 5–30 °C in opaque packaging and should be filtered after contamination or gel formation.