Within the Figure 4 projection-based photopolymerization platform, 3D Systems supplies Figure 4™ TOUGH-GRY 10 Plastic as a gray production-grade photopolymer intended for functional prototypes, manufacturing aids, and low-volume end-use parts. The material is formulated to deliver a measured balance of tensile strength, flexural stiffness, and notched Izod impact resistance; its datasheet anchors these properties to ASTM D638, ASTM D790, ASTM D256, and ASTM D648. The resin is processed on Figure 4 Standalone, Modular, and Production configurations using 405 nm UV projection, with build parameters and support structures controlled through 3D Sprint or equivalent machine software. The number 10 in the grade designation identifies the lower toughness tier within the tough-gray family, not a filler weight percentage or viscosity value. Parts printed in TOUGH-GRY 10 are supplied in a gray tone that can be machined, sanded, or painted after post-cure. Operational boundaries should be derived from heat deflection temperature under 0.455 MPa and 1.82 MPa rather than from short-term visual appearance after printing.

Mechanical property data generated under ASTM D638, D790, and D256 conditions

Manufacturer-reported typical values are generated after conditioning specimens at 23 ± 2 °C and 50 ± 5 % RH for 24 h. The tensile strength at break is reported near 42 MPa, tensile modulus near 1.8 GPa, and elongation at break near 9%. Flexural strength is approximately 59 MPa with flexural modulus near 1.75 GPa. The notched Izod impact result is approximately 28 J/m. Heat deflection temperature is approximately 54 °C at 0.455 MPa and approximately 49 °C at 1.82 MPa. Shore D hardness is approximately 80D. These values place the product in the semi-rigid engineering photopolymer class.

Build orientation introduces anisotropic mechanical response in these photocured parts. Tensile coupons built in the xy-plane typically show higher strength and modulus than those built with the tensile axis parallel to the z-axis. The difference is caused by interlayer conversion gradients and incomplete boundary crosslinking. Production lots should therefore include internal test coupons built in the same orientation and at the same layer thickness as the final parts. The notched Izod value of 28 J/m should not be compared directly with injection-molded ABS or polycarbonate without noting that ASTM D256 values are specimen-size dependent. For impact-loaded designs, edge radii and generous fillets are required because the material retains the brittle fracture behavior of acrylate-based photopolymers. The heat deflection values indicate that continuous exposure above 49–54 °C under load leads to creep and dimensional change; intermittent dry heat from machining or paint bake cycles must be kept below these thresholds.

Processing on Figure 4 systems begins with resin cartridges conditioned to 20–25 °C. Resin below this range exhibits higher viscosity that can reduce recoating uniformity and increase the frequency of first-layer adhesion defects. The liquid photopolymer is imaged at 405 nm using machine-specific layer thickness and exposure parameters supplied by 3D Systems. After printing, uncured resin is removed with an approved solvent such as isopropyl alcohol in a two-stage wash; the first bath removes the bulk liquid, and the second bath removes residual monomer from blind holes and high-surface-area support tips. Parts are then post-cured in a UV chamber using the manufacturer-specified irradiance and duration. Insufficient post-cure leaves residual acrylate groups that lower surface hardness and increase outgassing, while excessive post-cure can embrittle thin walls and support-near surfaces. Production lines should inspect blind holes and undercuts with a borescope or ultraviolet flashlight to detect uncured pools, because trapped liquid monomer continues to crosslink during storage and generates local stress concentrations. Open vat life is shorter than sealed cartridge life; resin removed from the vat should not be returned to virgin cartridges unless the facility has validated filtration and contamination control.

Resin storage follows photopolymer industry practice: sealed cartridges are kept at 5–30 °C, and partially used cartridges are blanketed with dry nitrogen if the facility has the capability. Low-temperature storage can increase viscosity and reduce first-layer uniformity; the cartridge should be acclimated to 20–25 °C for at least 4 h before printing. Shaking is avoided because entrained air produces voids in cured layers; slow rolling or gentle inversion is used instead. When resin is transferred from a vat, the operator should record the lot number and cumulative open time to track batch-to-batch variation in printed part color and mechanical properties.

Where does TOUGH-GRY 10 sit within the Figure 4 gray photopolymer portfolio?

Within the Figure 4 material set, the tough-gray grades form a progression in elongation at break and impact absorption. Figure 4™ TOUGH-GRY 10 is positioned as the lower-numbered tier in this grouping. Designers requiring greater snap-fit deflection or higher notched Izod values are directed to higher-numbered tough-gray grades under the same ASTM D638 and ASTM D256 methods. Compared with Figure 4 PRO-BLK 10, a rigid production-grade photopolymer, TOUGH-GRY 10 trades tensile modulus for increased elongation at break and is therefore used when clip towers, pressed inserts, or housing snap features are present. Compared with Figure 4 FLEX-BLK 20, TOUGH-GRY 10 retains greater tensile strength and lower elongation, which limits its use in fully flexible living hinges but improves dimensional stability in structural covers and brackets. On production workstations, the gray tone provides visual contrast against black rigid components during assembly; that is an operational benefit rather than a mechanical distinction. The material is not a direct substitute for injection-molded polypropylene or ABS; its lower notched Izod and heat deflection values require redesign of sharp corners and load-bearing bosses.

When functional assemblies demand repeated snap-fit or threaded-insert performance

For connectors, sensor housings, and access covers that require repeated assembly, the resin is drilled, tapped, or fitted with threaded inserts after post-cure rather than printed with internal threads alone. Cutting threads with high-speed steel tooling at spindle speeds below 1,500 rpm avoids localized softening above the 54 °C heat deflection threshold. Press-fit inserts are acceptable when the boss wall thickness is at least 2.5 mm and the hole diameter follows the insert manufacturer’s recommendation for semi-rigid polymers. Insert pull-out values should be derated from molded-plastic tables because the layered build produces lower toughness in the boss hoop direction. In functional snap-fit designs, the 9% elongation at break allows limited undercut deflection but does not permit the reversible yield of polyamide. Repeated snap-fit cycles beyond a few hundred can initiate microcracks at the undercut root; prototypes should be evaluated under ASTM D638 conditioned samples and under actual assembly speed. When metal threaded inserts are used, the resin is compatible with post-installation torque testing to ISO 898 or equivalent internal company specifications, provided the test is stopped before the boss wall cracks.

Post-processing starts with support removal before final UV post-cure when dimensional accuracy is critical. Cured flash on support tips is removed with side cutters and sanded; wet sanding with 400–600 grit paper reduces heat and dust. The material accepts acrylic, enamel, and two-component polyurethane coatings after surface degreasing with isopropyl alcohol. Adhesion of coatings is evaluated with ASTM D3359 cross-cut tape testing; painted parts should be stored at room temperature for 24–48 h before tape pull. Dimensional stability under humid storage is governed by water absorption; unpainted parts exposed to cycling humidity can show small dimensional drift, so gauge dimensional checks should occur after a 24 h conditioning period. Machining operations—milling, drilling, reaming—are feasible with sharp carbide tooling and light depths of cut to prevent heat-induced softening near the HDT. Thread forming rather than thread cutting is not recommended in thin walls because the lower ductility compared with POM or polyamide can lead to microcracking at the thread flanks. If parts require ultrasonic welding, the process window is narrow because the photopolymer does not flow like a semicrystalline thermoplastic; published data for this specific configuration is limited.

Long-term thermal aging at 60 °C in air can shift tensile strength and color because residual photoinitiator and acrylate groups continue to react. Parts subjected to automotive interior temperatures above the heat deflection threshold should be tested under ISO 6722 thermal aging or company-specific thermal cycling. The material does not exhibit a melting point, so flow under load is the primary failure mode. Creep testing is not part of the default datasheet; if load-bearing parts are used for more than 48 h at elevated temperature, long-term creep coupons should be generated.

The resin is not recommended for continuous immersion in strong solvents, ketones, or chlorinated hydrocarbons. Short-term contact with alcohols and aliphatic hydrocarbons is generally tolerated but must be validated under final service chemicals using ASTM D543 or equivalent comparative immersion testing. Medical device prototypes should not be placed into production without a separate ISO 10993 evaluation, and the standard gray grade is not automatically food-contact certified under FDA 21 CFR. For jigs used in metalworking shops, Figure 4™ TOUGH-GRY 10 fixtures are machined to accept hardened steel bushings; bushing retention is maintained when the hole tolerance is machined after UV post-cure rather than printed to size. In electronics assembly, the resin is used for solder pallet housings and test sockets where short-cycle contact temperatures do not exceed the heat deflection threshold; long-term exposure to heated reflow fixtures is outside the material’s operational boundary. Printed components in this grade are also used for low-volume production of gripper fingers and robotic end-of-arm tooling; the gray color aids visual identification of wear particles, while the moderate notched Izod value requires blunt impact geometries.