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Assemblies and mates

A project is always an assembly. You build multi-part assemblies by instancing parts and positioning them, by hand or by solving mates.

Instancing and placement

  • Reuse a part as an instance in the assembly.
  • Position it with an Euler-angle placement (translation plus rotation), or with the 3D manipulator in the viewport.
  • The manipulator snaps or moves freely depending on where the cursor is, so neither needs a modifier key. A rotation ring turns with the cursor and snaps to 45° steps while the cursor stays near it; drag well outside the ring to rotate freely, back in to snap again. A translation arrow follows the cursor exactly along its axis; pull sideways off the arrow and the movement snaps to the grid spacing shown in the viewport, which adapts to the zoom level. A snapping handle turns white: arrows become dashed, rings show ticks.
  • The placement editor shows coordinates relative to the parent assembly. Switch Rel / Abs to read and edit the same fields in world coordinates; the value is converted back to the stored relative placement on Apply. Absolute mode takes literal numbers only, no expressions. The toggle is hidden for the top-level assembly, whose placement is already absolute.
  • Reset to origin (circular-arrow icon) zeroes a part's placement.

Mates

Mates are constraints between parts. Pick faces, edges or origin planes and axes in the viewport and the solver positions the parts. The types are coincident (faces, edges, planes, axes), concentric (cylindrical faces, axes, circles), distance, angle and fixed.

While a reference slot is armed, each part shows the axes of its cylindrical faces as dashed lines. Clicking one references that axis, which is usually easier than finding the right face: on a threaded shaft or a tapped hole there is no smooth cylinder left to click, only the helical crest and the groove flanks. Mating a bolt to a nut is then two clicks and Concentric.

Mate references are topologically anchored, so they survive rebuilds, and offsets can be bound to parameters and expressions. The solver runs a 6-DOF Gauss-Newton / Levenberg-Marquardt solve. Mates work across the whole assembly tree: selecting a part inside a sub-assembly mates it against everything else the model places, and the mate is stored on the deepest assembly that owns both references.

Checking for interference

Boolean → Interference answers whether parts actually fit. Press Check interference and every pair of bodies is tested where the assembly puts them, so a part used several times is checked at each position, including against its own copies.

Each pair comes back as one of:

  • Overlap: the bodies occupy the same space, with the overlap volume. The shared volume is drawn in red, visible through the bodies containing it, and hovering a row brings its volume forward.
  • Touching: surfaces in contact without penetrating. Mated faces resting against each other land here, so this is normally what you want to see.
  • Clear: separated, with the gap. Pairs far apart are only counted in the summary.
  • Unresolved: the kernel could not decide that pair. The rest still stands.

Select two or more bodies first to check just those; with nothing selected the whole assembly is checked. Dismissing a row hides it until the next check. The results clear when you edit the model, since they describe where things were.

The AI assistant can run the same check and read the numbers back, so you can ask it whether a design fits and have it fix what does not.

Combining bodies

Boolean → Combine merges bodies into one. Select two or more, choose an operation and apply:

  • Union merges everything into one body.
  • Cut subtracts the rest from the first. Make target on a row picks which body is cut.
  • Intersect keeps only the volume they share.

Bodies are combined where the assembly places them, not at their model origins. The result is a new part; the originals are kept and hidden, so you can show them again or undo without losing anything. Leave Update when the sources change on and the result rebuilds whenever an original is edited; turn it off to freeze it.

Checking a mechanism for collisions

A mechanism can fit at rest and still bind partway through its travel. In the Motion panel, tick Check for collisions before Compute motion and every position in the sweep is tested. Positions where bodies overlap get a red tick under the scrubber, and scrubbing onto one shows an Overlap marker, so you can find exactly where it jams.

Simplified display for large assemblies

Fine detail is expensive to draw and invisible at assembly scale: a modeled thread on an M8 screw is smaller than a pixel in a 10 m structure and still costs a full helical mesh. View → Simplified draws every part with its detail features hidden, which keeps large assemblies responsive.

Hidden are modeled threads, embossed text, surface patterns, and fillets or chamfers at or below the size shown under the toggle (2 mm by default).

This only changes what you see. Exports, measure, mass properties, simulation and mates always use the full geometry. A Simplified badge sits in the viewport while it is on, and clicking it returns to full detail. Opening a large assembly turns it on automatically and says so.

The part you are editing always shows full detail, so picking faces and edges works normally. For full detail on a specific feature regardless of the rule, open it and set Simplified display to Keep (or Hide to always drop it), see Modeling features.

Shared and multi-device viewing

A project can be open on several devices at once with read-only sync over WebSocket, including presence (avatars, per-user colors) and shared-camera following.