DSM Somos PerFORM Stereolithography Polymer, UV Postcure is a filled photoreactive stereolithography resin supplied for processing on 355 nm laser systems. The uncured material is an opaque high-viscosity suspension with a published density of approximately 1.61 g/cm³ and a viscosity near 2,500 cP at 30 °C; these properties require controlled vat temperature and periodic stirring after idle periods to maintain filler dispersion. Green parts are washed and then exposed to UV postcure before reaching the published mechanical profile. After postcure, the material develops a flexural modulus in the 9,000–10,000 MPa range and a heat deflection temperature above 250 °C at 0.46 MPa when tested in accordance with ASTM D648-18. The product is specified for high-stiffness fixtures, tooling, wind tunnel models, and dimensional master patterns.

What Processing Window Governs Recoat and Layer Formation?

The filled nature of the formulation narrows the recoating window relative to unfilled stereolithography resins. Build temperature is normally held at 28–32 °C because viscosity rises as temperature falls, increasing layer thickness variability and the risk of recoater blade chatter. At a layer thickness of 100 µm, recoater speed must be reduced until the recoat surface shows no visible fill depletion; production-scale units with a 250 mm build platform and 100 µm blade gap typically require slower recoater travel than clear or ABS-like materials. Filler settling occurs when the vat is idle for extended periods. If the machine remains idle for more than 60–90 minutes, a slow vat stir cycle is recommended before the next build start. Batch-to-batch viscosity variation of approximately ±10% may be observed, and this variation can shift the required recoat speed. Published data for this specific formulation’s settling rate is limited; operators should verify vat homogeneity by checking density or solids content after extended idling.

The filled suspension is abrasive relative to unfilled resins. Production vat systems with a 250 mm build platform and 100 µm blade gap show accelerated recoater edge wear, particularly at the vat walls where filler can accumulate. The blade should be inspected for scoring and replaced at intervals determined by build hours rather than by visual coating quality alone. Surface streaking that follows the recoater direction is an early indicator of filler accretion and can produce layer-to-layer density variation. Published wear-rate data for this specific formulation is limited; the interval should be calibrated against the build volume and idle time of each machine.

Mechanical Properties at 23 °C and 50% Relative Humidity After UV Postcure

Representative postcure property ranges are shown in Table 1. The values are compiled from supplier-published datasheet figures and test reports using the indicated methods. The material is considered rigid and low-elongation, which distinguishes it from unfilled and toughened stereolithography resins.

UV postcure is a critical step. Green parts retain only partial conversion; the property set in Table 1 requires a secondary UV exposure in the UV-A range with a peak near 365 nm. A typical production sequence places the washed and dried part in a UV postcure chamber for 60–90 minutes per exposed surface, with repositioning for complex internal channels. The required irradiance is geometry-dependent because shadowed regions and thick sections absorb or block UV energy. Published depth-dose data for this specific formulation is limited; therefore, thick sections above 10 mm should be staged to avoid excessive exotherm and warpage. After postcure, parts are held at 23 °C and 50% relative humidity for at least 24 hours before critical dimensional measurements are recorded. This sequence stabilizes the dimensional response and exposes any residual stress that may have developed during the build or postcure cycle.

Support removal should be performed before UV postcure. The green state is brittle enough that aggressive tooling can fracture thin walls; hand tools with a cutting edge rather than twisting motion are specified. Heat from high-speed rotary tools can locally soften the green resin and cause smearing that remains visible after postcure. If supports are removed after postcure, the cured material’s higher hardness increases the risk of chipping at the part surface. This operational boundary is independent of the resin’s final mechanical data and applies to all filled SLA systems.

When Impact or High Strain Is Present, What Boundary Conditions Apply?

The cured material exhibits brittle tensile behaviour. Elongation at break remains in the 1.0–1.5% range under ASTM D638-14, and notched Izod impact values fall between 14 J/m and 18 J/m under ASTM D256-10. These values place the product outside the acceptable design envelope for snap-fit arms, living hinges, or components exposed to repeated drop impact. Sharp internal corners below 0.5 mm radius create stress concentrations that can initiate fracture at loads significantly below the published tensile strength. When clamping is required, load-spreading washers or metal inserts are specified to avoid local crushing. For fatigue-sensitive applications, published data for this specific formulation’s cyclic loading response is limited; component validation should include strain-gauged prototypes tested at the maximum expected service load. The material’s high modulus reduces deflection, but the low strain at break means that stress-relieving geometry, generous fillets, and uniform wall thickness are the principal design controls.

Thermal Expansion, Moisture Uptake, and Dimensional Stability

Heat deflection temperature at 0.46 MPa is reported between 250 °C and 270 °C under ASTM D648-18, but the higher-load HDT at 1.82 MPa falls to 110–130 °C. This difference constrains the material’s use in load-bearing tooling above 130 °C. The filled matrix restricts thermal expansion relative to unfilled stereolithography resins, but published coefficient of linear thermal expansion data for this formulation is limited and may vary with build orientation. Dimensional stability in humid service is generally improved by the filler fraction; however, no specific ASTM D570 moisture absorption value for this product is reproduced in the reviewed supplier datasheet. Users should condition parts for 48 hours at the intended service temperature and humidity before precision assembly. For spans above 150 mm, it is preferable to measure build-orientation-specific thermal expansion rather than assume an isotropic value.

Creep resistance is improved by the high modulus and filler restriction, but published creep modulus curves for this formulation are not widely available. Short-term creep at ambient temperature is typically low in stiff filled systems; however, design calculations for load-bearing fixtures should use a service factor of at least 2 on the published tensile strength if no creep data is generated. At temperatures above the 1.82 MPa HDT range, creep rate increases sharply and the part should be considered sacrificial.

Wind tunnel model programs specify the filled resin where aerodynamic loading at model scale would produce visible deflection in lower-modulus unfilled stereolithography resins. The flexural modulus of 9,000–10,000 MPa under ASTM D790-17 reduces spanwise bending, but the low elongation requires conservative support placement on thin trailing edges and probe bosses. In rapid tooling, short-run injection mold inserts and thermoforming fixtures can survive brief low-load exposure above 130 °C because of the high 0.46 MPa HDT, but the 1.82 MPa HDT range of 110–130 °C limits continuous injection pressures and clamp forces. For injection mold inserts, metal cooling lines cannot be integrated into the SLA part; thermal conductivity of the filled resin is lower than tool steel. Consequently, cycle times are longer and shot counts are limited. Dimensional master patterns, inspection fixtures, and drilling jigs use the material’s stiffness at ambient temperature to reduce measurement deflection. No independent production-case study with published statistical process capability data is available for this formulation; therefore, application-specific capability runs are necessary before committing to long production runs.

How Does This Filled Resin Differ from Unfilled and Toughened SL Products?

The primary differentiator is the filled high-modulus, high-HDT response. Compared with DSM Somos WaterShed XC 11122, which is an unfilled clear resin with a flexural modulus of approximately 2,000–2,500 MPa and a lower HDT at 0.46 MPa, PerFORM provides roughly four to five times the flexural stiffness and a substantially higher thermal deflection limit. This increase is obtained at the expense of elongation and impact resistance. Toughened stereolithography materials such as Somos NeXt or Somos Taurus are formulated for impact resistance and moderate elongation; they exhibit lower modulus and lower HDT than the filled PerFORM system, but they accommodate snap fits and rough handling that PerFORM cannot. The uncured PerFORM suspension also has higher viscosity and requires more vat management than unfilled resins. The opaque white surface limits optical transmission applications, whereas WaterShed XC 11122 is specified for clear components. For replaceable tooling surfaces, the filled product reduces elastic deflection, but its abrasive filler can accelerate recoater blade wear compared with unfilled resins.

Supplier-published values may vary by version of datasheet; users should verify against the current technical bulletin before substituting one material for another in a validated build process.

Material handling and post-processing require standard stereolithography precautions. The uncured resin is irritating to skin and eyes; suitable nitrile gloves and laboratory ventilation should be used. Consult the supplier safety data sheet for exact hazard classification, personal protective equipment, and waste disposal requirements. No food-contact, medical-device, or long-term implant claim is made for this material. The product may be included in supplier REACH and RoHS declarations, but independent certification should be confirmed against the specific lot and final postcure condition. The material should be stored in a dry, dark environment between 5 °C and 30 °C; the manufacturer-published storage range may vary by lot. Uncontrolled UV exposure can initiate polymerization in the vat and change viscosity before the build starts.