FDM / FFF deposition and stack build

Reuse the polymer library, stored-material substrate layup and existing thermal cycle to study deposition near the nozzle. Choose the steady local head field or a transient laminate-driven stack build. Both use the existing thermal cycle and material library.

FDM / FFF is a separate licensed module included in CDS Full. The thermal and material permissions used by the case are also required. Other packages can inspect saved setup, but cannot enable or run FDM.

Set up

1. Open a thermal case with its time-based cycle and substrate laminate. Enter actual substrate ply thicknesses and assign stored materials with density, specific heat and thermal conductivity. Elastic constants and CTE are not required.
2. In Incoming material conditions, choose FDM head → Set up. Enable the model and select the existing bead polymer record.
3. Enter bead width and height, travel speed, actual polymer exit temperature and contacting head-wall temperature. Actual exit temperature is a measured or estimated material temperature, separate from a heater-controller setpoint. Volume flow is width × height × speed.
4. Select a cycle time. Existing upper/chamber and lower/bed temperatures, film coefficients and ramp/step interpolation supply the local environment at that time.
5. Advanced settings contain head footprint and conductance, interface conductance, local window, property-reference temperature and Standard/Fine resolution.
6. Run the FDM case separately from other analysis cases. Open Thermal results to inspect the x–z field, both facing temperatures, signed heat flux and energy audit. Contact CSV and Field CSV preserve the stored precision.

Build a laminate, then anneal

1. In FDM setup choose the laminate stack build. In this mode the selected laminate is the final target, rather than an already-built substrate. Every target ply must reference the same selected neat thermoplastic polymer. Target ply thicknesses supply the deposited heights; bead height does not override the laminate.
2. Set the number of existing substrate plies. Zero prints all target layers on the build plate; a nonzero value starts those bottom plies at the case initial temperature. One deposition pass adds each remaining target ply. No layer is silently merged into its neighbor.
3. Enter the physical pass length and speed. A representative material column receives head exposure for footprint divided by speed and then evolves through the remaining pass time. Return time between passes is a real thermal pause. The schedule time is the start of the build; the shared cycle must cover the complete build.
4. For annealing, choose chamber/bed holds or non-extruding head passes. Holds use the entered duration without head heat. Head passes use the same pass length, speed and head exposure on the retained top layer, with no material added. Both retain the complete ply and interface history; head passes are local-column reheating events rather than a spatial raster prediction.
5. In Quality, link an intimate-contact model and optionally a healing/bonding model. Review the specified initial contact. Applied contact pressure is zero throughout, so the pressure-driven model cannot create new contact area. Thermal healing can mature the existing contact area; new interfaces start unhealed.
6. Run and inspect the growing stack, per-ply temperature histories and interface contact, healing and bonding. Physical pauses change these results; a playback Display pause changes only the animation. CSV exports retain the full saved histories.

The stack build is a transient through-thickness representative column with retained cells and finite interface conductance. It does not solve a full moving-head x–z toolpath, adjacent roads, reinforced or mixed-polymer deposition, bead shape or nozzle pressure. Thermal properties use constant reference values by default. In Laminate build, enable Temperature-dependent k / Cp to use linked material tables or linear/quadratic laws at each physical cell temperature. The nonlinear implicit solve conserves sensible enthalpy, keeps density fixed and rejects extrapolation. This option does not add latent heat or crystallization. The steady local head field retains its reference-property approximation. Interface quality is one-way postprocessing; the calibrated thermal conductance is independent of contact fraction. No crystallization, latent heat, porosity, warpage or mechanical strength is inferred. The selected interface laws require their own material-model permissions in addition to FDM.

Temperature-dependent properties and thermal degradation

Right-click the polymer material to configure temperature-dependent conductivity and specific heat. In FDM setup choose Laminate build, then explicitly enable Temperature-dependent k / Cp. The property-reference temperature becomes the sensible-enthalpy datum. Validity ranges must cover the initial, incoming melt and all reached material temperatures. Constants remain available for properties without a selected law.

A calibrated material-linked thermal-degradation model reports accumulated conversion and, only with an explicit residue fraction, a residual mass estimate. The transient build follows each physical cell from its birth through returns and annealing. The local head mode follows bead material along the solved field at time equal to distance divided by speed; it excludes unknown internal nozzle residence. Degradation is one-way thermal-history postprocessing and does not infer strength, molecular weight or property feedback.

Feedstock formats and vendors

Materials → Additive feedstocks lists vendor filament, pellet and reinforced-compound specifications, with product links, available diameters and reinforcement descriptions. Materials → Polymers → Additive polymer grades contains shared neat-polymer records; these same material IDs are available to FDM, CREATE, compatible micromechanics models and laminate plies.

In FDM setup, open Feedstock · vendor & format. Select an optional compatible unfilled filament and choose Use reference polymer to put its linked material in the draft. Review its grade, property basis and missing inputs, then Apply. Selecting a supply specification alone does not change the bead polymer, temperature, head geometry or process schedule. A family association does not establish the vendor’s actual formulation.

Printed XY/Z coupon data stay separate from neat-polymer properties. Reinforced filaments and upstream pellets remain catalog references; the current FDM feedstock picker accepts compatible unfilled filament supplies. Use the linked base polymer as a constituent in a suitable composite model and provide measured fiber fractions, dimensions and properties. A product suffix such as CF15 or GF30 does not set a volume fraction. Unreported thermal or elastic inputs remain missing and must be supplied before a model that requires them can run.

Select the hardware

Equipment → FDM contains head records. Equipment → FDM → Support contains filament feeders, filament dryers and build platforms; an optional oven record describes the build chamber. Select these optional equipment references in FDM setup. The supplied exercise imports its linked hardware with the study.

The setup preview shows selected hardware as small buttons that open its equipment record. A warning marks a missing, incompatible or incomplete selection; choose a replacement or None in FDM setup. The spool, feeder, dryer, platform and chamber outline are schematic hardware context, not solved temperatures or printer controls.

Hardware selection does not silently replace thermal inputs. Saved case settings and the existing process schedule remain the numerical authority. If offered, explicitly copying head defaults copies only the displayed head-wall temperature, contact footprint and conductance; actual melt-exit temperature and bed/chamber schedule remain separate. No internal nozzle flow, dryer response or chamber-controller calculation is added by the equipment drawing.

A starting example

Exercise 03.79, FDM: head, bead and substrate thermal contact, uses the existing PEI / ULTEM library card with two 0.2 mm substrate layers. Its linked head and support hardware are editable setup references. Representative constant properties and prescribed temperatures support sensitivity studies; they are not a grade-specific printer calibration.

Exercise 03.81, FDM: laminate-driven build, pauses and annealing, prints four 0.2 mm neat PEEK layers, then holds the completed stack for annealing. It includes the shared head/support hardware, an explicit illustrative 60% initial contact fraction and independent teaching copies of the existing PEEK healing law. Its contact fraction is assumed, not predicted by capillary spreading or nozzle pressure.

Steady local head formulation and limits

A conservative finite-volume model solves steady head-frame axial advection and x–z conduction. A rectangular bead begins at deposition. Finite contact conductance retains a temperature jump: heat flux = conductance × (bead-face temperature − substrate-face temperature). Positive flux is from bead into substrate. Adjacent substrate layers have perfect thermal contact.

The model is width averaged and has no transverse side cooling. Polymer properties are read from the linked library at the saved reference temperature and held constant. Temperature-dependent tables are evaluated without extrapolation. Chamber/bed conditions are sampled and held fixed locally; oven geometry does not add a hidden temperature.

Actual melt-exit and head-wall temperatures are prescribed separately. Internal nozzle flow, melting and latent heat, crystallization, bead deformation, toolpaths, whole-build heat accumulation, molecular healing, porosity, residual stress and strength are outside the steady local model. Its case-linked quality models must be removed or run in the stack-build mode where supported. Roller, laser/IR, Darcy, void and squeeze models remain separate processes. Directional substrate cards need constant explicit axial/through-thickness conductivities and aligned 0/180 degree axes. Their scalar temperature-table assignments must be removed because the table has no directional-axis mapping; isotropic polymer tables remain supported.

Check mesh convergence and the energy residual before interpreting small changes. A converged thermal calculation is not evidence of a qualified weld or mechanical allowable.