The material supplied as 3D Systems Figure 4™ JCAST-GRN 10 Plastic is a green-pigmented, filled photopolymer resin cartridge intended for the Figure 4 digital light processing platform. The imaging system projects a 405 nm LED charge through a UV-transparent membrane and polymerises the resin layer by layer. The product is not a structural end-use plastic; it is a sacrificial pattern material for investment casting of jewellery and precision metal parts. The “GRN” designation identifies the green colourant package, which supports visual inspection during washing and tree assembly. Qualification for foundry use centres on viscosity, green-state dimensional stability, and combustion residue after burnout; the manufacturer’s technical data sheet is the controlling document for lot-specific values.

The Figure 4 Standalone, Modular, and Production configurations share the same fundamental imaging architecture but differ in automation and throughput. The published build volume for the Standalone platform is 124.8 mm × 70.2 mm × 196 mm, and the user must reserve space inside that envelope for supports, sprue bases, and ventilation clearance. The material is supplied in an RFID-tagged cartridge that allows the printer to verify the resin type and expiration. The cartridge contains a proprietary photopolymer with a green pigment dispersion; it is not an unfilled methacrylate, because the filler system modifies rheology and green-state fracture behaviour. Liquid viscosity is measured by rotational viscometer methods based on ISO 2884-2, and cured green-state mechanical properties are tested under ASTM D638-14 or equivalent methods where applicable. A combustion residue value is determined by thermogravimetric analysis and reported on the material datasheet; that value should not be treated as a substitute for full-flask burnout validation.

In service bureaus running multiple Figure 4 materials on the same machine, cross-contamination is controlled through dedicated resin trays, build platforms, and wash containers. The green pigment is a deliberate process marker: any transfer of this material into clear or amber resins is visible under normal inspection. The resin should be stored in a dark, sealed cabinet within the temperature range stated on the safety data sheet. Exposure to office lighting or sunlight before printing can initiate premature polymerisation. Unlike traditional pattern wax, the uncured resin is not re-meltable after polymerisation; rejected prints are waste, not feedstock.

The filler system also influences the resin’s settling behaviour. Before a production run, the tray should be checked for pigment separation or sediment; if a visible density gradient is present, the material should be conditioned according to the manufacturer’s instruction. The printer’s software uses the cartridge RFID to set native build parameters, including layer height and exposure time. Users should not override these parameters, because underexposure weakens green state and overexposure increases the pattern’s thermal expansion and can elevate the residue load. The system builds at the specified layer height; when fine feature retention is required, a mode with a smaller Z-step is used, but total build time increases. Detailed stone-setting structures, such as undercuts and bearer tracks, require support strategies that leave minimal witness marks on the casting surface. Support contact points are removed before investment; if the pattern is sanded or scraped, the debris must be removed because loose green dust can settle in the working area.

How Does the Resin Transfer From Photopolymer to Ceramic Shell Without Pattern Collapse?

The sacrificial pattern is attached to a runner tree using a compatible adhesive and then invested in a gypsum-bonded or phosphate-bonded refractory. During setting, the investment releases heat through hydration. If the exotherm exceeds the green-state heat deflection limit, thin sections such as filigree rails or gallery walls may distort. The investment powder is blended at the water-to-powder ratio stated by the investment supplier; for gypsum-bonded jewellery formulations, this commonly lies between 38:100 and 40:100 by mass. Additional water must be avoided because it reduces mould strength and increases steam pressure during burnout. Vacuum mixing and de-airing at a suction level that prevents boiling at ambient temperature are standard; production cells commonly use units rated to -0.08 MPa gauge or better.

The invested flask must not be disturbed before the investment reaches its release strength. In the burnout furnace, the pattern undergoes thermal expansion, network scission, and oxidative carbon removal. A staged ramp is used: a low-temperature plateau removes residual alcohol and water; an intermediate ramp decomposes the cured organic network; a final oxidative soak burns carbon residue. The final soak temperature is selected from the investment supplier’s datasheet, often in the range of 600 °C to 750 °C, but it is not solely resin-dependent. A thermocouple placed at the centre of the load is preferable to furnace air temperature because the flask interior lags the chamber by several minutes. If the ramp is too fast, decomposition gases cannot escape through the shell permeability and shell cracking or trapped carbon may result. In high-karat gold alloys, trapped carbon can generate gas porosity; therefore, the shell interior should be clean and grey-white before casting. The manufacturer’s ash value is measured on clean cured specimens under a controlled TGA protocol, not on a full tree with adhesive and sprue wax; mixed-material trees should be validated as a system.

On a twin-station wash line, the first bath typically becomes loaded with dissolved monomer after 20 to 30 medium-sized patterns, depending on pattern orientation and solvent temperature. The bath life should be determined by viscosity or refractive index shift, not by elapsed time alone. After washing, parts are placed on a wire rack in a low-velocity air flow at 20 °C to 25 °C for a minimum period derived from the thickest attached cross-section. Drying time cannot be shortened by raising the air temperature above the green-state distortion limit, because thin features may warp. If the pattern is assembled onto a wax runner with a heated tool, the tool should not contact the printed resin directly; localised heat can cause surface softening and bond-line voids. Instead, the adhesive is applied to the wax side or a low-temperature cyanoacrylate is used. In shops where the pattern is weighed as a quality check, the dried part should be measured after a standardised stabilisation time, not immediately after solvent washing, because retained alcohol mass produces a false weight reading.

When Investment Mixes Contain Coarse Cristobalite or High-pH Phosphate Binders

In phosphate-bonded investments, the liquid activator is often colloidal silica or a phosphate buffer with a mixed-slurry pH that can exceed 9. The alkaline environment may attack partially cured or uncured surfaces if contact is extended. Large pattern clusters should be invested promptly after mixing, and high-pH slurry should not be allowed to stand on printed features. Coarse cristobalite or fused silica aggregates produce a rougher interior surface; where polished jewellery surfaces are specified, the investment supplier’s fine-aggregate blend should be used. The pattern surface is softer than metal tooling, so cleaning must avoid abrasive bristles. Soft camel-hair brushes or low-pressure solvent flushing are preferred. If an ultrasonic bath is used, cavitation energy can erode thin unsupported features. The standard layout for washing is a two-stage solvent station: the first contaminated bath removes gross uncured resin, and the second cleaner bath removes residual alcohol and dissolved monomer. The second bath is monitored by specific gravity or refractive index; water accumulation produces tacky surfaces after drying. A water content above 5 %v/v in the cleaner isopropanol bath is commonly treated as a rejection threshold, but this is a production heuristic rather than a published standard for the material.

Storage, Handling and Incompatibility Boundaries

Uncontrolled humidity in the printing or wash area can alter part dimensions and surface quality. Ambient relative humidity above 60 % at 25 °C is a common upper limit for handling the material before burnout; above this level, green-state absorption may increase pattern weight and produce shell defects during the water-evacuation phase. Amine residues on wetted surfaces should be avoided because amines can accelerate polymerisation in subsequent resin lots. Cleaning agents that leave a film should be validated on a test print before use on production patterns. The uncured resin has a defined pot life in the tray; after idle periods, the tray should be stirred or replaced according to the manufacturer’s current guidance. A freeze event can separate the pigment dispersion or alter viscosity; cartridges stored below the SDS minimum temperature should be quarantined rather than returned to production.

Nitrile gloves and eye protection are standard when handling uncured resin, and waste must follow the safety data sheet. The cured green pattern is not a food-contact article, and no statement is made under FDA 21 CFR or equivalent food-contact frameworks. Regulatory information is provided in the manufacturer’s SDS under REACH Regulation (EC) No 1907/2006 and, where applicable, RoHS Directive 2011/65/EU. The liquid resin’s viscosity is measured by the supplier under controlled shear rate; viscosity increases as temperature decreases. If a cartridge is taken from cold storage, it must be allowed to equilibrate to the workshop temperature before printing. The temperature window for handling is normally printed on the cartridge label. The safety data sheet provides hazard classification according to EC 1272/2008; in the uncured state the material is a skin and eye irritant. Personal protective equipment includes nitrile gloves, safety glasses, and a chemical apron when pouring waste. The cured pattern is not certified for skin contact in jewellery end-use because the pattern is burned out and not present in the final article.

In comparison with castable wax, the photopolymer does not exhibit the same plastic deformation before failure. This difference becomes significant in thin sections: a wax pattern can be bent back into shape after minor distortion, while a green photopolymer part will crack or snap. However, the photopolymer holds smaller, repeatable dimensions through the printing and washing sequence and does not shrink after injection in the same way a wax pattern can continue to relax in storage. Compared with non-castable photopolymer resins, JCAST-GRN 10 is formulated for combustion residue control and lower thermal expansion during burnout. The product should not be used as a structural connector, split pattern for vulcanised moulding, or final model because its green-state mechanical limits and residual monomer content are not specified for those applications.

For foundry validation, test flasks should be prepared with the same tree geometry as production and cast in the metal grade with the highest pouring temperature because higher superheat increases the risk of residue-metal interaction. Sectioning should examine gas porosity, inclusions, and water marks. No universal standard assigns a permissible porosity level for all jewellery alloys; acceptance criteria are developed from the foundry’s own defect board. Published data for this specific configuration is limited, so the in-house qualification record remains the controlling document.