| HS Code | 290151 |
| Material Type | Polystyrene |
| Color | White |
| Density | 0.9 g/cm³ |
| Tensile Strength | 2.4 MPa |
| Tensile Modulus | 1500 MPa |
| Elongation At Break | 15% |
| Flexural Modulus | 1400 MPa |
| Heat Deflection Temperature | 70 °C at 0.45 MPa |
| Melting Point | 100 °C |
| Ash Content | <0.02% |
| Particle Size | 50-100 µm |
| Layer Thickness | 0.10 mm |
As an accredited 3D Systems CastForm™ PS Plastic for SLS Systems factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
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For short-run stainless steel valve bodies and pump casing prototypes conforming to ASTM A743/A743M, the substitution of milled wax-injection dies with selective laser-sintered CastForm PS patterns removes pattern-tool validation from the pre-production schedule. The pattern is produced on a CO₂-laser SLS platform operating at a layer thickness of 0.10 mm; the powder bed is heated to a point below coalescence onset, and part growth is managed by modulating laser energy density rather than by blending additives into the polymer. The relevant addition ratio is the mass fraction of virgin powder used to replenish the recovered powder bed, set initially at 50 wt% virgin material and raised when laser-diffraction particle size analysis shows a fines population above the qualified envelope after tall builds. This ratio is held constant only within a qualified lot; batch-to-batch adjustments are made using bulk density measurement per ASTM D1895 Method A and ash content per ISO 3451-1. The pattern is depowdered with compressed air and inspected under collimated low-angle light because thin impeller vanes and casing bosses are prone to frosting when the reclaimed fraction exceeds the fill ratio.
After the SLS pattern is removed and depowdered, the surface is sealed with a microcrystalline wax or acrylic lacquer compatible with low-ash burnout before shelling. The ceramic shell system for CF8M valve bodies consists of a colloidal silica front coat with 325 mesh zircon stucco, followed by 6–8 fused-silica or aluminosilicate backup coats dried under a controlled high-humidity cabinet. Waxless burnout is performed in a gas-fired car-bottom furnace with programmable ramping. The shell is ramped at 1–2 °C/min to 300 °C to volatilize the bulk of polystyrene, held for a period determined by flask mass, then raised at 3–5 °C/min to 750 °C to oxidize carbon residue. A burnout cycle that accelerates the 250–500 °C interval exceeds the shell permeability of thick sections and has been associated with shell cracking in impeller cores. The pattern is not autoclaved with high-pressure steam; steam would introduce moisture into the primary coat before the backup layers reach green strength.
Melting and pouring is performed under an argon cover with a superheat of 100–150 °C above liquidus for CF8M. Terminal components include pump casings, impellers, and valve bodies for chemical and marine service, each tested hydrostatically according to EN 12266-1 or MSS SP-61 where the valve class requires closure verification.
Aluminium gravity pouring differs from ferrous shell practice because A356.0 and A357.0 are processed at 700–760 °C, below the temperature at which residual pattern carbon is fully oxidized on the shell wall unless an extended oxidizing hold is inserted. The CastForm PS pattern is therefore burned out under a two-stage schedule that delays high-temperature ramping until the shell face coat has reached uniform color, reducing gas porosity at the metal-shell interface. Dimensional conformance for prototype gearbox covers and inverter housings is evaluated against ISO 8062-3 and the material specification ASTM B618/B618M. The material proportion relevant to this route is the virgin/reclaimed powder ratio in the SLS feed bed. For aluminium foundry prototypes, reclaimed powder is reintroduced up to 60 wt% after sieving at 150 µm and blending in a tumble mixer for 15–20 min; trial builds with 40–60 wt% recovered material are accepted only when ash content per ISO 3451-1 remains below the threshold established by the foundry’s casting scrap data.
The shelling sequence for aluminium prototypes uses a primary colloidal silica slurry with a viscosity of 12–16 s on a Zahn cup #4, followed by three to four backup coats with increasing stucco particle size. After drying to 40–60% relative humidity, the shell is flash-fired in a forced-air burnout furnace; the critical control window is the 250–500 °C ramp, where the polystyrene expands faster than the shell face coat can accommodate if the pattern wall exceeds 3.0 mm. Published data for this specific configuration are limited, but foundry trials consistently avoid ramp rates above 2 °C/min in this interval for patterns with internal ribs. The shell is then preheated to 180–250 °C before gravity pouring; a transfer delay beyond 20–30 s between removal from the preheat furnace and metal entry has been observed to produce misruns in thin wall sections.
The aluminium is poured from a resistance-heated holding furnace at 720–740 °C with a pour time not exceeding 10 s for a 20 kg flask; the shell is returned to a controlled cooling zone to prevent localized shrinkage in isolated heavy sections. Terminal castings include A356.0 intake manifold prototypes, oil pan sumps, and electric vehicle inverter housings, each subjected to fluorescent penetrant inspection per ASTM E1417/E1417M before machining.
Cobalt-chromium orthopaedic investment castings impose a tighter feedstock-control protocol than visible industrial castings because the terminal device is evaluated against ISO 5832-4 and ASTM F75. For as-cast Co-Cr-Mo femoral knee trial components and acetabular cup bodies, the SLS pattern is built with a deliberate surface offset to compensate for ceramic shell expansion and alloy solidification contraction; the CAD file is scaled per the foundry’s shrinkage model, not by a universal factor. In the SLS feed system, medical-grade CastForm PS is handled as a closed-lot material; the reclaimed fraction is either excluded entirely or held below 30 wt% and supported by lot-specific ash testing per ISO 3451-1 plus heavy-metal screening of burnout residue. The ratio is not a fixed additive formula; it functions as a traceability boundary that reduces variation in pattern density and preserves reproducibility of the shell face coat from multi-cavity trees.
The shell is produced with a primary zircon face coat and a backup system selected for thermal expansion compatible with Co-Cr-Mo. The shell is preheated to 900–1100 °C before vacuum induction melting; the alloy is melted under partial argon and poured at 1450–1500 °C to ensure complete filling of thin protrusions and deep retention features. Shells for CoCr cannot be held above 1000 °C for longer than 4 h during preheat because the zircon face coat begins to densify and reduce permeability, which increases gas entrapment in the liquid metal. After solidification, the shell is removed by mechanical knockout and the castings are cut from the tree, hot isostatically pressed, and machined. Terminal components include cast Co-Cr-Mo femoral knee trial components, acetabular cup bodies, and resurfacing system frames finished to the dimensional acceptance criteria of the implant quality system.
When titanium alloys are poured against ceramic shells, the pattern burnout schedule is governed by the oxygen and chloride sensitivity of Ti-6Al-4V rather than by the polymer’s melting behavior. The terminal casting standards ASTM B367-22 and AMS 4991 require a stable alpha-case depth and low interstitial contamination, so pattern ash and chlorine are handled as process hazards. The shell face coat uses yttria or yttria-stabilized zirconia, and the burnout cycle includes a final oxidizing hold at 850 °C before the shell is transferred to the melting chamber; any residual carbon from incomplete polymer removal contributes to alpha-case formation during vacuum arc remelting and pouring. The relevant blend ratio in this route is the virgin-to-reclaimed powder ratio in the SLS bed; titanium foundries typically do not reintroduce reclaimed powder unless it passes ISO 3451-1 ash testing and chloride analysis by combustion ion chromatography below a foundry-defined limit. Production builds therefore commonly run 70–100 wt% virgin CastForm PS, not as a formulation additive but as a contamination control.
Melting is performed in a water-cooled copper crucible by vacuum arc remelting or induction skull melting; the preheated shell is placed in the casting chamber under vacuum or argon backfill; the titanium alloy is poured by centrifugal or gravity tilt. Shell preheat for Ti-6Al-4V is typically 650–950 °C depending on wall thickness and face coat reactivity. Autoclave dewax using high-pressure steam is incompatible with this pattern material; steam at 150–170 °C can soften the pattern before the shell has developed sufficient green strength, causing shell collapse at the pattern-shell interface. The terminal parts include cast Ti-6Al-4V airframe brackets, engine mount lugs, and corrosion-resistant valve bodies for marine applications, each subjected to radiographic inspection per ASTM E1320 when specified by the casting class.
When cast Co-Cr frameworks are produced through the lost-polymer route, the investment expansion curve must match the thermal expansion of the polycrystalline metal rather than that of a wax pattern. Dental prosthetic laboratories use CastForm PS patterns for removable partial denture frameworks and implant bars under ISO 22674 and a quality system aligned with ISO 13485. The relevant material ratio inside the dental flask is the pattern volume fraction; CastForm PS patterns are sprued to occupy 10–25 vol% of the casting ring, while the phosphate-bonded investment is mixed at a water-to-powder ratio of 0.22–0.25 by mass under vacuum. When thin margins below 0.6 mm are present, the SLS feedstock is biased toward 80–100 wt% virgin powder because recycled fines reduce surface definition and contribute internal porosity in the finished framework. This proportion is adjusted per build based on ridge width, clasp depth, and the presence of metal-ceramic shoulder preparations.
The flask is bench-set for 30 min, then placed in a burnout furnace ramped at 5 °C/min to 900 °C; casting is performed in an induction centrifugal machine under argon. The terminal product is a Co-Cr removable partial denture framework or implant bar, finished by airborne-particle abrasion and electrolytic polishing to remove reaction layers formed during casting.
In precious metal production, the use of a polystyrene-based SLS pattern for gold and silver jewellery is constrained by the upper decomposition limit of gypsum-bonded investment. The terminal alloy fineness is checked against ISO 9202, while process water and disposal obligations are framed by REACH and local waste regulations. The flask recipe is defined by the investment powder-to-water ratio, typically 36–40 mL water per 100 g powder, and the CastForm PS pattern mass is limited to 1.0–5.0 g per 89 mm flask. This proportion controls both steam permeability during burnout and the pressure rise generated by polymer decomposition in the gypsum shell. Published data for the precise burnout expansion of CastForm PS inside gypsum investment is limited; flask trials are required for each new pattern geometry because hollow earring cores and micro-pavé retainer prongs react differently to localized pressure.
The tree is invested under vacuum, then saturated steam dewaxing is not used; the flask is ramped in an electrically heated burnout oven with a hold at 300 °C until the pattern has evaporated, followed by a final hold at 730 °C, below the decomposition threshold of calcium sulfate. Vacuum-assist or centrifugal casting is used for high-detail micro-pavé seats; hollow structures are gated to avoid metal stagnation at sharp curvature. The terminal products include gold and silver rings with micro-pavé retainer prongs, hollow earrings, and filigree prototypes, each finished to the required fineness and surface finish class.
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3D Systems CastForm™ PS Plastic for SLS systems is a polystyrene-based powder intended for selective laser sintering of sacrificial investment casting patterns. The material is processed in a heated powder bed under a controlled atmosphere, where a CO₂ laser selectively fuses the styrenic matrix. The resulting pattern is a low-density porous form of polystyrene; the controlled porosity permits wax infiltration after the build, an operation that seals surface voids and raises pattern stiffness before ceramic shelling. The product designation covers the powder formulation, SLS process parameters, and post-process infiltration route. The material is differentiated from general-purpose SLS polystyrene by a combined target of low post-burnout residue and reproducible dimensional stability in foundry operations. Data from production-scale SLS equipment indicate that part properties shift with build orientation, powder refresh ratio, and laser energy density; acceptance criteria should therefore be defined for each arrangement rather than transferred directly from dense-molded polystyrene data.
Porosity in CastForm™ PS parts is a direct consequence of the SLS mechanism: the laser sinters the powder only to a partially coalesced state, leaving interconnected voids. Production foundries report that the infiltration step is not cosmetic; untreated patterns can absorb ceramic slurry water, disrupt the primary coat drying front, and create shell blistering during dry cycles. Infiltration is typically performed in a vacuum or pressure vessel with a paraffin-microcrystalline wax blend heated below the distortion threshold of the sintered styrenic network. Wax bath temperatures are maintained in the range of 70 °C to 85 °C, with soak time scaled by wall thickness. Thin sections below 3 mm require shorter cycles to avoid pattern softening. The penetration depth of the wax can be checked by sectioning a sample pattern and measuring the densified shell; incomplete infiltration is visible as a porous core after polishing.
Pressure-assisted infiltration at 0.4 MPa to 0.6 MPa is used on some production lines to reduce cycle time, but excessive pressure can close surface pores prematurely and trap air. The resulting density after infiltration is typically intermediate between the sintered density and the fully dense polystyrene value. Process control relies on measuring pattern mass before and after infiltration; a stable mass gain indicates reproducible pore volume. Because the wax is paraffinic, it must be fully removed in the subsequent burnout; leftover wax or low-molecular weight fractions can act as a temporary plasticizer and should not be present during shell firing.
Dimensional control from the SLS build is governed by thermal shrinkage in the powder bed and by the orientation of the pattern relative to the recoater. Thin foils and long unsupported features can curl when the part cake cools unevenly; production layouts often rotate the part axis at 20° to 30° from the recoater plane to reduce visible drag lines and edge distortion. The use of an inert nitrogen atmosphere is standard for styrenic powders because oxidative yellowing changes the powder recycle window and can modify the melt rheology at the laser interaction zone. Powder refresh ratios are adjusted according to machine type and part density; the manufacturer’s current SLS process notes provide the acceptable fresh-to-recycled ratio, and deviations above that ratio have been associated with increased variability in tensile elongation and surface roughness.
Compared with machined or injection-molded wax patterns, CastForm™ PS is used when the pattern geometry cannot be produced economically as a wax core or when lead time is compressed. The styrenic pattern is assembled to wax gating components; cyanoacrylate or hot-wax tacking methods are used because the styrenic surface remains sensitive to certain solvent-based wax adhesives. The assembled tree is then coated with a prime slurry based on colloidal silica and a fine refractory filler. Primary coat drying must be complete before secondary coats are applied; trapped moisture beneath the primary coat expands during the burnout ramp and can cause shell spalling.
Burnout for styrenic patterns is not identical to wax elimination. Polystyrene undergoes a glass transition near 95 °C to 105 °C; above this range the material softens and expands before decomposing. The ceramic shell must be heated on a ramp slow enough to accommodate expansion without local cracking. In foundry use, the burnout cycle is commonly staged: the initial hold below 300 °C removes wax and begins styrenic depolymerization, while the subsequent ramp to 700 °C or 750 °C burns residual carbon. Oxygen access is required for complete carbon removal; closed shell sections with blind cavities can leave carbonaceous residue if the furnace atmosphere is stagnant. Foundries use combustion air supply or extended hold at the upper end of the cycle to reduce residual carbon in such sections.
Residual ash after burnout is the principal boundary condition for the material. Standard foundry practice measures ash using ASTM D2584 or ISO 3451-1, depending on the quality system. For styrenic SLS patterns, the acceptance limit is usually specified by the caster in terms of maximum ash mass after firing; values below 0.05 wt% are common for high-integrity ferrous and nonferrous castings, but the specific value must be taken from the current material datasheet. The product is used because its styrenic matrix tends to decompose cleanly when oxidation is sufficient; carbon residue is more affected by furnace air exchange than by the original powder grade. Published data for this specific configuration is limited for low-oxygen batch furnaces, and operators report that carbon staining is more common when large solid sections exceed 12 mm thickness.
The shell permeability influences burnout more than pattern mass. A low-permeability shell envelope, created by fine flour grades and high-solids primary slurry, slows oxygen diffusion and increases the time required to oxidize styrenic carbon. The product is therefore used with shell systems designed for volatile elimination: primary silica loading is sometimes reduced, and a coarse stucco layer is applied on the secondary and tertiary coats to raise gas permeability. A production-scale rule used by foundries is to maintain a minimum shell thickness of 6 mm to 10 mm around the pattern for mechanical strength, but to avoid excessive shell thickness on heavy sections because it inhibits thermal conduction and prolongs core heat-up.
The distinction between CastForm™ PS and wax patterns is not simply material chemistry; it includes process route and dimensional error distribution. Wax patterns can be produced with smooth surfaces and are removed at low temperature, but tooling for wax injection carries fixed cost and lead time. CastForm™ PS removes the tooling requirement, but the SLS part introduces layerwise anisotropy and surface roughness that must be managed by wax infiltration and surface dressing. Compared with polyamide-based SLS patterns, the styrenic system has a lower decomposition temperature, which can shorten the burnout cycle but requires careful ramp control because polystyrene expands more than some filled polyamide grades. Polyamide patterns leave condensation residues and can require higher firing temperatures; styrenic patterns are selected when the caster wants combustion products that are largely carbon dioxide and water under proper oxidation. However, the styrenic material is more brittle in the green state than a ductile polyamide; handling damage during tree assembly is a field-observed failure mode, particularly in thin-walled sections below 1.5 mm.
| Verification target | Test method standard | Foundry use |
|---|---|---|
| Residual ash after burnout | ASTM D2584 / ISO 3451-1 | Accept/reject shell cleanliness |
| Tensile properties of sintered patterns | ASTM D638 / ISO 527-2 | Handling and assembly strength |
| Flexural modulus | ASTM D790 / ISO 178 | Rigidity of thin sections |
| Density | ASTM D792 / ISO 1183 | Infiltrant mass uptake control |
| Particle size distribution | ISO 13320 | Powder recoating and layer thickness |
| Thermal expansion | ASTM E831 / ISO 11359-2 | Shell cracking risk assessment |
| Process attribute | CastForm™ PS | Injection wax pattern | Polyamide SLS pattern |
|---|---|---|---|
| Tooling requirement | None | Metal die required | None |
| Typical removal route | Oxidative burnout at 700–750 °C | Steam or flash dewax below 200 °C | High-temperature burnout with condensation by-products |
| Green-state handling | Brittle; wax infiltration recommended | Ductile or filled-die wax grades available | Ductile |
| Carbon residue tendency | Low when sufficient oxygen is supplied | Very low | Moderate; requires controlled burnout |
| Pattern surface | Layerwise texture after SLS | Mold-smooth | Layerwise texture after SLS |
Batch-to-batch variation in SLS styrenic powders is monitored by melt flow rate and particle size. A shift in fines content below 20 µm can reduce recoater layer uniformity and create powder bed density gradients. Production-scale SLS systems with roller or blade recoating exhibit different sensitivity to fines: roller-based recoating compacts the powder and may produce stiffer cake; blade-based recoating generally gives lower green density. Powder quality control includes dry sieving at the point of loading and controlled storage at 20 °C to 25 °C and below 50 % RH. The styrenic powder is hygroscopic enough that prolonged exposure to high humidity alters flow; conditioned storage is required where ambient humidity exceeds 60 % RH.
The burnout of thick styrenic sections is limited by oxygen diffusion through the porous ceramic shell and the degrading polymer. If the furnace atmosphere remains rich in carbon monoxide or hydrocarbon fragments near the upper hold, carbon can deposit on the inner shell face as a black deposit that is visually obvious after shell removal. Production equipment with forced-air circulation and programmable ramps reduces this failure mode; batch furnaces without active airflow may require step holds at intermediate temperatures to avoid accumulation of combustion gases. Operators report that a hold at 500 °C to 550 °C improves carbon oxidation before the final excursion to 700 °C or 750 °C, especially when casting alloys with tight residual carbon specifications. The exact ramp rates must be developed for the combination of shell formulation, tree mass, and furnace volume; published data for this specific configuration is limited, so foundry trials are required.
Solvent incompatibility limits assembly operations. Styrenic patterns must be isolated from methyl ethyl ketone, toluene, xylene, and ester-based solvents because these fluids dissolve or stress-craze the sintered structure. Where solvent-bearing wax adhesives are used, they must be verified on a sintered test coupon before tree assembly. The material should not be combined with amine-based cleaners in the build area; amine residues can react with the styrenic surface and reduce local molecular weight. On SLS platforms with heated build chambers, the powder is maintained near the styrenic softening range to limit curl. The exact bed temperature set point varies with the installed CO₂ laser power and optical scan path. Excessive bed temperature causes part growth and powder cake caking, while insufficient bed temperature increases edge curl and part removal difficulty. The material is not supplied as a substitute for high-wax-content patterns in high-volume lost-wax lines where shell systems are optimized for low-temperature pattern removal without high carbon burnout.
