Materials and stress simulation¶

Materials¶

An assigned material determines a part's mass and viewport appearance. It also provides inputs for simulation and the filament settings used for printing. N3XD uses one material library for all of these features.

• The built-in catalog includes common plastics (PLA, PETG and TPU) and metals (aluminium 6061, mild steel and brass).
• You can derive a custom material from a built-in material, then assign it to a part.
• When you are signed in, the Materials tab on the Library page gives you a library shared across your projects. Select Duplicate on a material to open a prefilled copy that you can edit and save. Assigning a library material copies it into the project, so the project file stays self-contained. Select Save to library to copy a project material back into your library.
• Each material includes a density and the mechanical properties that simulation needs, such as Young's modulus, Poisson ratio and yield strength.
• Materials give parts a physically based viewport appearance and a base colour in 3MF exports. N3XD calculates mass 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 estimates the properties of a mixture of two materials. Select both materials and set their mass fraction. The panel then reports density, stiffness, strength, glass-transition and print temperatures, as well as whether the materials are compatible.

The compatibility verdict matters as much as the numbers. Immiscible does not mean the blend has failed: for example, dispersed TPU can toughen PLA even though the phases remain immiscible. However, a weak interface between the phases reduces strength, and the prediction estimates that reduction. Warnings also identify incompatible processing conditions. For example, a 50/50 PLA/PETG blend needs 255 °C to melt, while PLA starts degrading at 240 °C.

Account for compounding estimates how melt processing affects the polymers on their way to filament. Enter the melt temperature, time per pass and number of passes (for compounding, filament drawing and printing). The model then accounts for chain scission in each component before mixing the blend. The report shows which component is degrading, how much chain length remains, and how that affects strength and melt viscosity. This can reveal problems that are not obvious from the initial blend prediction: for example, PETG needs 250 °C, but PLA cannot withstand five minutes at that temperature.

The model deliberately leaves out two effects. First, it estimates thermal degradation only and does not model moisture. Undried polyester pellets can hydrolyse several times faster, so the report recommends drying them. Second, it does not model shear. Published extrusion studies found that, at normal temperatures, residence time affects degradation more than screw speed.

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

These engineering estimates use published correlations to help you screen candidates before compounding pellets and printing test specimens. They are not measured data and cannot replace testing a printed part. Each prediction names its model, identifies missing data and explains where the estimate is deliberately conservative. Blending depends on thermal and chemical properties; if those properties are missing, the panel reports only mixing-rule estimates and marks compatibility as unknown.

Printing properties¶

Turn on Printable to make a material available to the slicer and fill in the defaults for its filament family (PLA, PETG or TPU). You can then edit the temperatures, cooling and flow settings for that material. Edit these settings in this panel or in the library; the slice panel only shows which material a part will use. See Slicing and printing.

The built-in plastics are printable, while the metals are not. You can still slice a part designed in metal by choosing a printable stand-in in the slice panel, such as PLA for a steel bracket prototype. If you do not choose one, N3XD uses generic PLA and tells you.

Stress simulation (linear-static FEA)¶

1. Select the body and start the Stress operation. It appears in the toolbar when the body is selected, but not when a face or edge is selected. You can also find it in the F1 palette regardless of your selection.
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, then choose its direction. A study with only self-weight does not need another 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¶

Printing also changes a part before it carries any load. Molten plastic cannot hold stress until it cools past its glass transition. By then, however, the layers below have set and prevent it from shrinking freely. As each layer pulls on the layers beneath it, the finished part moves until those forces balance. This is why the corners of a wide, flat part can lift from the bed.

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.

Use warpage results to compare designs and print settings. For example, solve the same part printed flat and on edge, then compare the results. You can also raise the bed temperature or change the material. A setup with less predicted movement should also move less in practice.