Guide-driven linear stage

Prepare the example#

Open Guide-driven linear stage in the Frame catalogue. It contains a 300 mm MGN12 rail, two MGN12H carriages, an offset demonstration tube and two rail screws. The tube demonstrates geometry following the carriages; printable mounting brackets are not included.

To build the exercise yourself, add MGN12 300 mm Linear Rail, MGN12H Linear Guide Carriage and M3×12 Socket Cap Screw to the Frame's Foreign parts palette. Create numeric parameters travel = 0 and spacing = 100, in millimetres.

Build the guide before placing hardware#

1. Create absolute nodes at (0, -150, 0) and (0, 150, 0), then a Virtual link joining them. Name it Rail construction guide.
2. Create two relative nodes on it. Set their absolute axial distance expressions to 150 + travel - spacing / 2 and 150 + travel + spacing / 2.
3. Insert the rail in On-guide mode, choosing the start node and rail guide, with Offset = 150 mm. Insert each carriage using its own node and that same guide.
4. Adjust local XYZ rotation to register the mesh with the guide: the purchased rail's Y axis runs along its length and Z points away from its mounting base. Use the finished example to inspect these settings.

Both carriages share the guide without occupying a mate site. Their pose depends on construction geometry. They are not mated to the rail instance.

Drive the moving structure#

Change travel to 30. Both carriages and the offset tube move 30 mm along the rail. Change spacing to 70: the carriages move toward one another and the tube becomes 70 mm long. Undo restores the expressions and resulting geometry.

The example's two load nodes use the same axial formulas and a 35 mm radial offset. A Physical link joins them. In a finished design, use those construction datums to locate the printable load mounts as well.

On-guide placement does not enforce travel limits, collision clearance or carriage engagement. For this 300 mm rail and 45.4 mm carriage, keeping each carriage center between -127.3 and 127.3 mm leaves its full length on the rail. Keep the two carriages clear of each other. The example starts at centers -50 and 50 mm.

Ownership and history#

Edit the construction endpoints to reposition the whole stage. Moving the rail instance alone affects its mated screws, while the carriages continue to follow their own nodes and the shared guide.

Deleting the rail removes its mated screws and leaves the carriages. Deleting the guide removes its dependent construction and guided parts. Undo restores the relationships. Cancelling a Move gesture preserves the existing placement. Detach from guide converts a selected part to Absolute at its current pose.

Keep installation mates simple#

The two rail screws use Mate mode and the rail's physical counterbore seats. A fixed mate can retain axial clocking where its interfaces are symmetric. Use construction guides for mechanism rotation, travel and shared pivots.

Older documents with sliding or spherical mates retain their exact definitions, travel formulas and owner relationships. Current catalogue parts omit those motion interfaces; moving an older mechanism to guides is an explicit redesign.

Read Foreign parts and assembly mates for placement modes and capacity, or Exporting and preparing a build to share the editable example.