Selective laser sintering · powder-bed process

SLS reuses Workbench’s material library, laser process setup and thermal chamber schedule. A top-down laser scans a powder layer on a build platform. This case has no rollers or applied compaction pressure.

Set up a study

1. Select the SLS powder-bed thermal model and open SLS powder bed → Set up.
2. Select an existing polymer material. Density, heat capacity and dense-material thermal conductivity come from its saved properties. Create a measured material card if your powder’s parent polymer is not available.
3. Choose the existing chamber and build platform equipment where applicable. Use the case’s thermal schedule for initial, chamber and lower-boundary conditions. Equipment geometry alone does not create a hidden heater temperature.
4. Enter the measured laser power, beam radius, scan speed and track length. Set powder-layer depth, initial porosity, dry powder conductivity, absorptivity and optical penetration depth.
5. Optionally enable latent heat and capillary neck growth. Supply the phase interval, latent heat, particle size, surface tension and temperature-dependent melt viscosity parameters.
6. Run the study. Compare Standard and Fine resolution, inspect the energy balance, then use the time slider to inspect temperature, liquid fraction, early-stage neck ratio and capillary mobility through the layer depth.

Default process coefficients are illustrative and are not a calibration for a commercial powder or machine. The material selector and equipment controls link existing records; they do not invent missing physical properties.

Thermal and phase model

The single-track effective two-dimensional x–z model advances heat conduction on a fixed powder grid. The laser travels along x and deposits absorbed energy downward from the powder surface. Its effective Gaussian scan profile is attenuated with depth using Beer–Lambert absorption. Reported energies and source strengths use a unit transverse model width; a three-dimensional circular spot and hatch overlap are not resolved.

The enthalpy option accounts for latent heat across the supplied solidus–liquidus interval. Local equilibrium liquid fraction is distinct from polymer crystallinity. Powder and dense-material conductivity are combined using the peak local liquid fraction as an effective conductivity proxy; this proxy retains its change after cooling. Initial porosity remains fixed, so this calculation does not predict final part density.

The case supplies the initial powder temperature. Chamber and build-platform temperatures follow the existing thermal schedule from the saved process time through scanning and cooling. Reference mode samples material properties at the saved reference temperature. The optional local-temperature mode evaluates conductivity and sensible specific heat at each cell temperature, integrates Cp analytically, and inverts enthalpy with the separate latent-heat term. The calculation must stay within the common validity range of the active thermal curves. A Cp curve containing a measured melting peak must not be combined with a separate latent-heat term for the same transition.

Optional accuracy mechanisms

In Accuracy options, enable local-temperature material properties to use the conductivity and specific-heat laws linked to the selected material. Right-click the material to add table, linear or quadratic laws. Unselected properties keep their constants. Existing studies keep reference-property mode until explicitly changed.

The Maxwell gas–particle conductivity alternative uses initial porosity, dense polymer conductivity, an explicit gas conductivity and a geometric shape factor. A factor of 3 describes ideal spherical inclusions. The gas is the continuous matrix in this closure. Compare the approximation against measured powder conductivity before treating it as a calibrated powder law. The same peak-liquid-fraction blend towards dense conductivity is retained; gas heat capacity, contact-neck transport, internal radiation and evolving porosity are not resolved.

An optional calibrated Arrhenius degradation model linked to the powder material tracks conversion in stationary powder cells on every accepted thermal step. This one-way exposure calculation does not infer strength or molecular weight and does not feed decomposition heat, mass loss or optical-property changes back into the thermal solution.

Capillary flow option

Surface tension and an Arrhenius viscosity relation provide a capillary mobility scale and an early-stage particle neck-growth estimate. The neck approximation is restricted to small necks. Mobility has velocity units, but it is not a calculated fluid-velocity field.

The model does not resolve melt-pool circulation, Marangoni flow, powder rearrangement, pore collapse, free surfaces, shrinkage, multiple layers, crystallization kinetics, mechanical strength or residual stress. Use the results to compare thermal exposure and early sintering tendencies, not to certify a finished part.

Read and export results

The thermal field uses one colour scale across all stored time snapshots. Depth z starts at the powder surface and increases downwards. Temperature history plots the bed maximum and spatial mean. Frame CSV exports every stored cell in the selected frame; History CSV exports the computed history. Numeric exports retain the stored values rather than rounded display labels.

Review absorbed, reflected, transmitted, boundary and stored energy in Model basis. A small numerical energy residual and stable mesh response are necessary checks; they do not establish powder-specific process accuracy.

Research background

• Zhang, Boutaous and Xin (2022), 3D Modeling of Polymer Selective Laser Sintering Process — equations 4–5 provide the gas–particle Maxwell effective-conductivity closure; its scattering simulation is not included here.
• Thermal modelling of laser powder-bed processing — background for absorption, enthalpy and effective thermal modelling.
• Materials 12(21), 3496 — background for early-stage viscous particle coalescence and neck-growth limits.
• Open-access laser sintering thermal and phase-transfer study — thermal and phase-change modelling context.