Materials and stress simulation¶

Materials¶

A part's material drives its mass, viewport appearance, simulation inputs and the filament it prints with. There is one library behind all of them.

• The built-in catalog covers common plastics (PLA, PETG, TPU) and metals (aluminium 6061, mild steel, brass).
• Derive custom materials from a built-in one and assign them per part.
• Signed in, you also get your own library on the Library page's Materials tab, shared across your projects. Duplicate on any material there opens a prefilled copy to edit and save. Using a library material copies it into the project so the file stays self-contained; Save to library pushes a project material back the other way.
• Each material carries density and the mechanical properties (Young's modulus, Poisson ratio, yield strength) simulation needs.
• Materials give parts a physically-based viewport appearance and a per-part base colour on 3MF export. Mass is computed from density.

The Material panel's details view has three tabs:

• Appearance: colour and the PBR channels (metalness, roughness, opacity).
• Mechanical: density and elastic constants, then thermal properties (glass transition, melting point, degradation onset, conductivity, specific heat, expansion) and chemical properties (Hansen solubility parameters, water uptake). The thermal and chemical values are optional and feed blend prediction.
• Printing: the FDM filament settings (below). Built-in materials are read-only; duplicate one on the Library page, or use Derive to edit in standalone mode.

Blending materials¶

Blend predicts what you get from mixing two materials. Pick both, set the mass fraction, and the panel reports density, stiffness, strength, glass transition and print temperatures, plus whether the two are compatible at all.

The verdict matters as much as the numbers. Immiscible is not a failed blend: PLA toughened with a dispersed TPU phase is immiscible by design. But a weak interface between the phases costs strength, and the prediction says by how much. Warnings call out what does not work, most usefully when no temperature melts both components without degrading one (a 50/50 PLA/PETG needs 255 °C while PLA starts degrading at 240 °C).

Account for compounding adds what melt processing costs the polymers on the way to filament. Give the melt temperature, the time per pass and the number of passes (compounding, drawing filament, printing), and each component is degraded by its own chain-scission kinetics before the blend is mixed. The report says which of the two the line is damaging, how much chain length is left, and what that does to strength and melt viscosity. This is where a blend that looks fine on paper falls over: PETG needs 250 °C and PLA does not survive five minutes there.

Two things it deliberately leaves out. Moisture is the bigger one, since the figure is thermal degradation only and undried polyester pellets hydrolyse several times faster than this, which is why the report tells you to dry them. Shear is the other and matters less: published extrusion work found residence time, not screw speed, drives the loss at normal temperatures.

Create material stores the prediction as a project material, so a blend can be assigned, sliced and simulated like any other.

These are engineering estimates from published correlations, for screening candidates before you compound pellets and print test specimens. They are not measured data and no substitute for pulling a printed part. Each prediction lists the model behind it, what data was missing, and where it is deliberately conservative. Blending needs the thermal and chemical properties to say much: with those blank you get mixing-rule numbers and a note that compatibility is unknown.

Printing properties¶

Turning Printable on makes a material available to the slicer and fills in its filament family's defaults (PLA, PETG or TPU); temperatures, cooling and flow are then editable per material. This panel and the library are the only places these are edited, the slice panel just shows which material a part prints with. See Slicing and printing.

Plastics ship printable, the metals do not. A part designed in a metal still slices: the slice panel lets you pick a printable stand-in (prototyping a steel bracket in PLA), and without one it falls back to generic PLA and says so.

Stress simulation (linear-static FEA)¶

1. Start the Stress operation from the toolbar or the F1 palette.
2. Pick the fixtures, faces or edges clamped in all directions. Prefer a face where one exists: a clamped edge is a line singularity, so the peak stress and factor of safety right at it depend on the mesh size (displacement does not). A single straight edge is refused because it leaves the part free to rotate about it; pick a second edge off that line, or a face.
3. Apply loads: force or pressure on faces or edges (choose Face or Edge then click the target), or radial / tangential torque.
4. Optionally enable Self-weight to add gravity as a body load and pick its direction. A self-weight-only study solves without any explicit load.
5. Set a mesh size and solve.

The part is meshed into tetrahedra and solved with quadratic elements. You get:

• Von Mises stress as a viewport colormap with a legend.
• Displacement, with an optional exaggerated deformed shape and a slider. A fresh result flexes once and settles back, to show where the part gives.
• Factor of safety (yield divided by peak stress). Below about 1.5 is marginal; thicken the part or pick a stronger material.

Solving the part as printed¶

A printed part is not the solid the model describes. It is beads laid in layers with voids between them, welded to the layer below by whatever heat survived the layer time, so it is stiffer along the beads than across the layers and usually gives way at a weld long before the plastic itself yields.

Switch As printed on and pick a print setup. The part is sliced first, the layer bonding is scored the same way the Bonding preview scores it, and each element is solved with the stiffness and strength the toolpaths at that spot actually produce.

Two things change in the result. The factor of safety now says what the part gives way at: the legend reads "Limited by the weld between layers" or "Limited by the material itself", and the Limiting mode colour scheme paints the two. And the part is more compliant and weaker across the layers, which is what makes the feature worth using: print the same part standing up and lying down, solve both, compare.

Predicting warpage¶

The other thing printing does to a part happens before any load. Plastic arrives molten and cannot hold stress until it cools past its glass transition, but by then the layers underneath have set and will not let it shrink freely. Every layer ends up pulling on the ones below, and when the part comes off the bed it moves until those pulls balance. That is why a wide flat part lifts its corners.

Switch the Stress panel from Loads to Warpage and pick a print setup. There are no fixtures and no loads: the part stands on the build plate and is driven by its own contraction. Solving prints it layer by layer, cools each stage, and lets the finished part off the plate.

• Max warpage: how far the part has moved from the shape you modelled. The viewport exaggerates it, because the real distortion is usually a fraction of a millimetre; drag Deform exaggeration down to see it at true scale.
• Max residual stress: what the part is left holding once it has settled. A part can be perfectly straight and still full of stress, which is what makes it crack later or move when you machine it.

The use is comparison. Print the same part flat and on edge and solve both; raise the bed temperature; swap the material. The one that moves less will move less in reality.