Tutorial 6: Quadcopter Drone Frame

Goal#

Design a true-X quadcopter frame for 5-inch propellers: 225 mm motor-to-motor diagonal, a 3 mm thick bottom plate with four integrated 16 mm wide arms (the arms are part of the 3 mm plate), a 2 mm top plate, 16 x 16 mm motor mounting patterns (M3), and a central 30.5 x 30.5 mm stack pattern for a flight controller and speed controller. The same sketch is used to cut carbon fibre plates on a CNC router, or to print the frame.

The project demonstrates a symmetric design where one quarter is drawn and everything else is mirrored or patterned, and where every important dimension flows from a few parameters. It also gives you practice with typical hobby standards: bolt patterns that are fixed by hardware and must be exact.

What you'll learn#

• Setting up a design driven by hardware standards.
• Laying out an X-frame with polar geometry and construction lines.
• Drawing one arm and using a Circular Pattern for the other three.
• Creating mounting hole patterns that match motors and stacks.
• Making bottom and top plates and spacing them with standoffs.
• Weight reduction pockets and checking mass.
• Exporting DXF for CNC cutting and STL for printing.

Prerequisites#

• Tutorials 1 and 2.
• Familiarity with Circular Pattern. See Mirror and Patterns.
• Understanding that carbon plate cutting needs sharp-corner relief and minimum internal radius of the router bit (for a 2 mm bit use at least 1 mm).

Hardware and standards#

These are typical values for this class of frame; check them against the datasheet of your actual motors and boards.

Parameters#

Steps#

Part A: Bottom plate outline#

1. New design. Name it Quad Frame. Add parameters.
2. Create components. Make components Bottom Plate, Top Plate, Standoffs (optional) to keep bodies separate.
3. Sketch. In Bottom Plate start a sketch on XY. Draw a construction line from the origin at 45 degrees with length motor_r (112.5 mm). Use Line (L), press X to toggle construction, set angle with a dimension between the line and the X axis (arm_ang).
4. Motor circle. At the end of the construction line draw a circle with diameter 30 mm (the motor base boss area). Use Circle > Center Diameter.
5. Arm outline. Draw two lines parallel to the construction line, offset arm_w/2 on each side, running from the motor circle tangent back toward the center. The easy way: use Sketch > Offset on the construction line with distance arm_w/2 both directions (offsets of construction geometry produce normal lines, which you can toggle). Terminate them at the central body region.
6. Central body. Draw a Center Rectangle at the origin of body_l x body_w (70 x 44 mm). Trim away the portions of lines inside the rectangle. Fillet the rectangle corners with a 5 mm radius.
7. Trim and clean. Use Trim (T) to remove the inner part of the motor circle, leaving only the outer semicircle merged into the arm. Check that the profile is a single closed boundary for one arm plus body.
8. Pattern the arm. Select the arm lines and the circle portion and use Create > Circular Pattern in the sketch: Objects = arm geometry, Center Point = origin, Quantity = 4, Angle = 360 deg. Delete the pattern's overlapping segments in the body area with Trim. This leaves one closed outline with four arms.
9. Check closed profile. Click inside the shape; the whole outline highlights as one profile. If it breaks into pieces, find the small gap.

Part B: Holes#

10. Motor holes. At the motor circle center, draw a center rectangle motor_pat x motor_pat as construction, rotated to match arm direction (the pattern is square in the motor's frame, so it is rotated 45 degrees with the arm). Place 4 points at corners and draw circles 3.2 mm diameter. Draw a center circle of 12 mm diameter for the motor shaft/bell clearance. If you drew these on one arm only, Circular Pattern them around the origin (quantity 4).
11. Stack holes. Centered at the origin, a construction square stack_pat x stack_pat, with four 3.2 mm circles at its corners. Turn the square construction so the pattern is aligned with the frame axes (0 deg), or at 45 degrees; your choice should match your arrangement of USB port. Dimension to the origin and use Symmetric constraints.
12. Center cable hole. 20 mm circle at the origin between the stack holes helps wires pass through. Skip it if you want the plate stiffer.
13. Standoff holes. Four 3.2 mm holes. A typical 5 inch frame places the standoffs front and rear of the stack. Use X = +/-30 mm, Y = +/-16 mm (inside the 70 x 44 mm body and clear of the 30.5 mm stack holes; verify against your battery and electronics).
14. Battery strap slots. Two slots 20 x 3 mm at Y = +/-14 mm, X = 0 (clear of the 20 mm cable hole, whose edge is at 10 mm, and of the stack holes, whose edges start at X = 13.65 mm), using Create > Slot > Center to Center Slot.

Part C: Extrude#

15. Extrude. Press E. Selecting regions inside the outline but outside holes and slots creates the plate. Distance plate_b. Operation New Body. Check that holes remain empty.
16. Weight relief. Optional: on each arm cut a long slot 50 x 6 mm centered on the arm centerline from 40 to 90 mm from the plate center (clear of the body and of the motor boss), leaving 5 mm rails on each side of the 16 mm arm. Make a slot sketch on the arm centerline and extrude Cut through all; pattern with a four-fold circular pattern.
17. Fillets. Press F. Select vertical outer edges of the plate, radius 2 mm. For sharp inside corners (where arms meet the body), radius 3 mm. These reduce crack starts in carbon plate.

Part D: Top plate#

18. Top plate sketch. A common top plate is just the central body, without the arms. Create it as a derived shape: in the Top Plate component, sketch on an Offset Plane at plate_b + stand_h above XY, project the bottom plate body outline (use Project, P, on the outline edges). Keep only the central rectangle region and its fillets and the four standoff holes.
19. Extrude. plate_t upward. Name the body Top.
20. Camera mount slot. Cut a 19 mm x 2 mm slot for the camera mount, and an antenna hole of 6 mm diameter at the rear.

Part E: Standoffs and fasteners#

21. Standoff. In the Standoffs component, sketch a hexagon 6 mm across flats (Create > Polygon > Circumscribed Polygon, circle diameter 6 mm) on the bottom plate top at a standoff hole; extrude stand_h = 25 mm; then use the Hole command, diameter 2.5 mm (M3 tap drill), 8 mm deep on both ends. Setting Hole Tap Type to Tapped in the Hole dialog adds M3 x 0.5 threads (ISO Metric profile).
22. Pattern. Use Rectangular Pattern or copy/paste with Move to place the four standoffs.
23. Bolts. Optional: Insert > Insert McMaster-Carr Component for M3 screws, for realism; see the McMaster-Carr page in Components. Do this only if you intend to render.

Part F: Motor and props check#

24. Placeholder motor. Make a body cylinder 28 mm diameter x 20 mm tall at each motor center to represent a 2207 motor; verify arm clearance. Make a disc 127 mm diameter x 1 mm for the propeller and check prop-to-prop distance: the center spacing between adjacent motors is wheelbase / sqrt(2) = 159 mm, so 127 mm props leave 32 mm of air.
25. Mass. Assign a material: right-click the body > Physical Material and pick a library material (carbon fibre if listed, or ABS). Check Properties for mass; a hand estimate for the bottom plate in carbon fibre (about 1.6 g/cm3) is roughly 40 g, so treat the library value as authoritative.

Part G: Export#

26. DXF. Right-click the bottom plate sketch in the browser > Export DXF. Do the same for the top plate. Check units in the DXF with your CAM software.
27. STL. Right-click the body > Save as Mesh to print in PETG or nylon-carbon; use 100 percent infill on arms.

Checkpoints#

• Motor center to center across the diagonal: 225.0 mm. Use Inspect > Measure between two motor holes pattern centres.
• All four arms identical; quick test: use Inspect > Measure from the origin to each motor center (112.5 mm each).
• All mounting holes: 3.2 mm; minimum web between hole and edge: 3 mm (general guidance).
• Frame mass fits your target.

Variations#

1. Change wheelbase to 150 mm for a 3 inch cinewhoop and watch the layout adapt.
2. Add a unibody top plate with integrated camera cage.
3. Make a deadcat geometry by changing the arm angles.
4. Hollow 3D printed arms with a 2 mm wall.
5. Add a 3D-printed GPS mount using the snap tutorial.

Troubleshooting#

Related#

• Mirror and Patterns for circular patterns.
• Hole and Thread for the M3 tapping options.
• Tutorial 8 covers CNC milling concepts, which also apply to router cut plates.