Designing Functional Brackets with AI CAD
Brackets are one of the most common things people print. They're also a great test of an AI CAD tool because they require precise hole placement, specific angles, and structural thinking. This tutorial walks through designing a real mounting bracket from scratch using FreeTextToCAD.
What We're Building
A right-angle wall-mounting bracket to hold a small shelf or tray:
- 100mm horizontal arm (mounts to shelf)
- 80mm vertical arm (mounts to wall)
- 4mm thickness throughout
- Three M4 clearance holes per arm (4.5mm diameter)
- A triangular gusset for rigidity
Writing the Prompt
"An L-shaped bracket, 4mm thick. The horizontal arm is 100mm long and 40mm wide, with three 4.5mm holes evenly spaced along the center. The vertical arm is 80mm tall and 40mm wide, with three 4.5mm holes evenly spaced. Add a triangular gusset on the inside corner of the L, filling the space between 10mm from the bend on each arm. The gusset should be 4mm thick."
Break this down: we've named the shape (L-bracket), specified all dimensions (arms, width, thickness), described the holes (count, size, spacing), and added the gusset with its own dimensions.
Common Bracket Mistakes to Avoid
Forgetting clearance on holes
Always specify M4 clearance holes as 4.5mm (not 4mm). The extra 0.5mm ensures the bolt slides in without threading into the plastic.
Too thin at the bend
The inside corner of an L-bracket is a stress concentration point. If your bracket is for any meaningful load, add a gusset or increase thickness to at least 5–6mm at the bend.
No flat bottom for printing
L-brackets need to be oriented flat to print without supports. If the model comes out in a weird orientation, use the feedback: "The bracket should be oriented with the horizontal arm flat on the print bed."
Iterating on the Design
After generating the initial model, inspect it carefully. Common refinements for brackets:
- "Move the holes to be exactly 15mm from each end, not evenly spaced"
- "Make the gusset larger: extend it 30mm along each arm"
- "Add a second row of holes 15mm from the first row"
- "Round the outer corners with a 5mm radius"
Print Settings for Structural Brackets
- Material: PETG or ABS for any bracket that will bear weight. PLA is fine for light duty.
- Infill: 40–60% gyroid or honeycomb
- Perimeters: at least 4 (1.6mm at 0.4mm nozzle)
- Layer height: 0.15–0.2mm for good layer adhesion
- Orientation: flat on the bed, not standing upright
See also: Wall Thickness Guide and CAD Tolerances for 3D Printing.