SG90 18-DOF Hexapod Walker

This is a desktop hexapod robot with six legs of three joints each (18 SG90 micro servos). It walks with tripod, wave and ripple gaits, turns on the spot and can lean its body in any direction. The body is a 164 x 124 mm chassis plate that holds the six hip servos. Above it, on four 30 mm standoffs, sits an electronics deck with a 10 mm M3 hole grid for your controller and a strap-down tray for a 2S 18650 pack. Each leg has three printed parts: a coxa hip bracket, a femur thigh link and a tibia foot link. It's aimed at hobby roboticists who want one clean leg set with consistent tolerances instead of a pile of mixed STLs.

All servo joints use the same two features. Every servo pocket is 23.4 x 12.8 mm with open M2 slots at each end, so SG90 and MG90S servos both fit without guessing the tab-hole spacing. Every pivot has a shallow recess for the stock single-arm horn plus a 6 mm access hole for the horn's centre screw. Put the horn in its recess and drill 1.6 mm pilots through the horn's own holes into the plastic, then fix it with two M2x6 self-tapping screws. The horn and part then press onto the spline and are secured with the servo's centre screw.

Assembly order, starting from the chassis:

1. Centre all 18 servos (90°) before fitting any horns.
2. Drop the six hip servos into the chassis plate from above, output shaft toward the plate edge, and clamp their tabs with M2x10 screws and nuts.
3. Bolt the four M3x30 standoffs to the chassis plate with M3x8 screws.
4. Fit a femur servo into each coxa bracket's side wall (flange on the outer face, body over the base) and clamp it with M2 screws.
5. Screw a horn into each coxa bracket's underside recess and press it onto a hip servo, pointing the leg straight out.
6. Fit a tibia servo into each femur link (flange on the face opposite the horn recess), then mount the femur link on the femur servo horn, horizontal.
7. Mount the tibia foot link on the tibia servo horn, pointing straight down.
8. Bolt the battery tray to the deck grid, strap in the 2S pack, fit the controller and UBEC, then screw the deck onto the standoffs.

Tuning notes: set each servo's zero in software rather than by re-indexing horns; a single spline tooth of error is easy to see on the tibia. SG90s can carry this frame (about 500 g) in a tripod gait. For heavier payloads, swap in MG90S servos, which fit the same pockets unchanged. Power the servos from a 5 V 5 A or larger UBEC, not from the controller's regulator.