Design a real mechatronic component—a NEMA-17 stepper & limit switch mounting plate—using user parameters, fully constrained geometry, heat-set insert bosses, and slotted adjustment channels.
A 3D model drawn "by eye" breaks the moment you change a screw size or motor model. In professional CAD, every geometric feature is governed by design intent: mathematical relationships, geometric constraints (coincident, concentric, tangent, symmetric), and global User Parameters.
In Fusion 360, sketches communicate their mathematical state through line colour:
• Blue lines: Under-constrained. Something is free to wiggle, stretch, or drift.
• Black lines: Fully constrained. Every vertex, length, and angle is locked by a dimension or geometric rule relative to the origin.
full_design.f3z in the shared 3D Files folder to see how finished mounting plates fit onto the robot frame.
Before drawing a single sketch line, open Modify → Change Parameters and create the global variables that will drive the bracket geometry.
| Parameter | Expression | Physical Rationale |
|---|---|---|
motor_pitch |
31.0 mm |
Standard NEMA-17 M3 hole center-to-center spacing |
boss_clearance_diam |
22.8 mm |
Motor pilot boss (22.0mm) + 0.8mm radial clearance pocket |
m3_insert_pilot |
3.2 mm |
Pilot hole diameter for M3 brass heat-set inserts |
m3_clearance |
3.4 mm |
Free through-hole for M3 motor mounting bolts |
plate_thick |
4.0 mm |
Rigid mounting plate thickness for FDM printing |
standoff_od |
6.5 mm |
Outer boss diameter for M3 insert (min 1.65mm wall strength) |
slot_travel |
6.0 mm |
Slotted adjustment distance to tension belt or index wheel |
Create a new sketch on the XY plane. Draw a Center Rectangle aligned to the origin, dimensioned to 50.0 mm × 50.0 mm. Sketch a center circle dimensioned to boss_clearance_diam (22.8mm). Verify that the rectangle and circle immediately turn solid black (fully constrained to the origin).
To allow mechanical alignment tuning, create 4 slotted holes instead of simple round holes:
motor_pitch (31.0mm).m3_clearance (3.4mm) and slot center-to-center length to slot_travel (6.0mm).A stepper motor needs a reference sensor to establish its home position. The VMA327 limit switch mounts adjacent to the motor:
standoff_od (6.5mm) spaced 9.5mm apart.m3_insert_pilot (3.2mm) for heat-set inserts.Exit the sketch and perform the solid features:
plate_thick (4.0mm) as a New Body.3.0 mm fillet to all 4 external vertical plate corners to distribute mechanical stresses and prevent edge chipping.0.5 mm × 45° chamfer to the bottom plate perimeter to eliminate elephant's foot print squish.Open Modify → Change Parameters. Change plate_thick from 4.0 mm to 6.0 mm, and slot_travel from 6.0 mm to 10.0 mm. Watch the entire solid body update smoothly with zero timeline errors or broken sketch references!