hexapod-robot/2026-current/hardware/openscad/body.scad

// 2026 hexapod body: top + bottom plate, rebuilt from the Fusion 360 model
// fusion360/body-bottom/bottom v59.f3d (the `top` and `bottom` solids in
// "bottom v59.stp", which are newer than the top.dxf/bottom.dxf sketches).
//
// Plate geometry is written in the original's top-view coordinates
// (u, v) = (Fusion x, -Fusion z), so every number can be checked against
// the Fusion file. fusion_to_robot() turns that into the robot frame of
// robot/Config.h (+X forward, +Y left, +Z up): X = v, Y = -u.
// Z = 0 is the top face of the bottom plate.
//
// Deviations from the original (its bugs):
// - Left-front pivot boss at u = -50 instead of -50.894.
// - All six coxa servos present (the original has none at right front).
// - Hex nut wells share one orientation (the original's are rotated randomly).

use <../main-pcb-2026-11-13/main-pcb.scad>
include <servo.scad>

/* [Plates] */
PLATE_T  = 3.0;    // original: 3 mm, both plates
CAVITY_H = 27.0;   // inner gap; sized so the servo case ends 2 mm above the bottom plate

/* [Standoffs: split halfway, screw from the top into a captive nut] */
STANDOFF_D      = 15.0;
SCREW_D         = 3.1;
SCREW_GRIP      = 4.0;   // solid length of each half next to the split
COUNTERBORE_D   = 7.0;
NUT_AF          = 5.5;   // M3 nut across flats
STANDOFFS_UV    = [[35, 30], [-35, 30], [35, -30], [-35, -30]];

/* [Coxa servos] */
// Shaft axis per leg, in (u, v), with the direction the case extends from the shaft.
// Indices match robot/Config.h legs 0..5.
COXA_UV = [
    [ 50,  100, 230],  // 0 right front
    [ 65,    0, 180],  // 1 right mid
    [ 50, -100, 130],  // 2 right rear
    [-50, -100,  50],  // 3 left rear
    [-65,    0,   0],  // 4 left mid
    [-50,  100, -50],  // 5 left front (original boss at u = -50.894)
];
ARM_R        = 19.5;   // rounded arm end, centred on the coxa axis
PIVOT_BOSS_D = 14.0;   // under the bottom plate, carries the coxa bracket
PIVOT_BOSS_H = 2.0;

/* [Teensy, PCB and switch] */
TEENSY_CUT    = [23.78, 66.96];   // (u, v) size, centred
PCB_BOSSES_UV = [[17.89, 39.48], [-17.89, 39.48], [17.89, -39.48], [-17.89, -39.48]];
PCB_BOSS_D    = 5.0;
PCB_BOSS_H    = 1.0;              // PCB top face ends up 1 mm under the top plate
PCB_SCREW_D   = 2.5;
SWITCH_SLOT   = [[-4, 57], [4, 73]];
SWITCH_HOLES  = [[0, 55.5], [0, 74.5]];
SWITCH_HOLE_D = 2.0;
ENGRAVE_D     = 1.0;

/* [Battery bay on the bottom plate] */
BAY_RAIL_U   = [26.06, 29.06];   // inner/outer face of each rail, mirrored in u
BAY_V        = [-74.21, 31.79];  // open end at -v (rear), closed end at +v
BAY_STOP     = [[-16, 28.79], [16, 31.79]];
BAY_H        = 13.5;

/* [Rendering] */
SHOW_TOP     = true;
SHOW_BOTTOM  = true;
SHOW_PCB     = true;
SHOW_SERVOS  = true;
EXPLODE      = 0;      // mm; lifts the top half
PCB_USB_FRONT = false; // owner: Teensy USB faces away from the switch (rear)

/* [Hidden] */
$fa = 2; $fs = 0.3;
STANDOFF_SPLIT = CAVITY_H / 2;
TOP_Z = CAVITY_H + PLATE_T;

module fusion_to_robot() rotate([0, 0, -90]) children();

// linear_extrude with a convexity, so the preview shows holes correctly.
module lx(h) linear_extrude(h, convexity = 10) children();

// ---------- outline -------------------------------------------------------

function bez2(p, t) = (1-t)*(1-t)*p[0] + 2*(1-t)*t*p[1] + t*t*p[2];
function rev(l) = [for (i = [len(l)-1:-1:0]) l[i]];

NOTCH = [[-34.12, 111.31], [0, 71.93], [34.12, 111.31]];   // front/back notch
WAIST = [[60.03, 83.28], [49.86, 74.48], [50.13, 64.77]];  // corner arm -> side
FILLET_C = [65, 35];
FILLET_R = 15.5;
N = 24;

// Right half, front to back; the arm circles fill in the chords at the arm ends.
Q1 = concat(
    [for (i = [N/2:N]) bez2(NOTCH, i/N)],
    [for (i = [0:N]) bez2(WAIST, i/N)],
    [[49.5, 35]],
    [for (a = [180:5:270]) FILLET_C + FILLET_R * [cos(a), sin(a)]],
    [[65, 0]]);
RIGHT = concat(Q1, [for (p = rev(Q1)) [p[0], -p[1]]]);
OUTLINE = concat(RIGHT, [for (p = rev(RIGHT)) [-p[0], p[1]]]);

module outline_2d() {
    polygon(OUTLINE);
    for (c = COXA_UV) translate([c[0], c[1]]) circle(r = ARM_R);
}

module at_coxa(c) translate([c[0], c[1]]) rotate([0, 0, c[2]]) children();

// ---------- top plate -----------------------------------------------------

module top_plate_2d() {
    difference() {
        outline_2d();
        for (c = COXA_UV) at_coxa(c) servo_pocket_2d();
        square(TEENSY_CUT, center = true);
        for (s = STANDOFFS_UV) translate(s) circle(d = SCREW_D);
        for (b = PCB_BOSSES_UV) translate(b) circle(d = PCB_SCREW_D);
        translate(SWITCH_SLOT[0]) square(SWITCH_SLOT[1] - SWITCH_SLOT[0]);
        for (h = SWITCH_HOLES) translate(h) circle(d = SWITCH_HOLE_D);
    }
}

module switch_text() {
    for (t = [["ON", 49.3], ["OFF", 80.6]])
        translate([0, t[1]])
            text(t[0], size = 5.8, halign = "center", valign = "center",
                 font = "Liberation Sans");
}

module top_half() render(convexity = 10) {
    difference() {
        union() {
            translate([0, 0, CAVITY_H]) lx(PLATE_T) top_plate_2d();
            for (s = STANDOFFS_UV) translate([s[0], s[1], STANDOFF_SPLIT])
                cylinder(d = STANDOFF_D, h = CAVITY_H - STANDOFF_SPLIT);
            for (b = PCB_BOSSES_UV) translate([b[0], b[1], CAVITY_H - PCB_BOSS_H])
                cylinder(d = PCB_BOSS_D, h = PCB_BOSS_H);
        }
        for (s = STANDOFFS_UV) translate([s[0], s[1], 0]) {
            translate([0, 0, STANDOFF_SPLIT - 1]) cylinder(d = SCREW_D, h = SCREW_GRIP + 2);
            translate([0, 0, STANDOFF_SPLIT + SCREW_GRIP]) cylinder(d = COUNTERBORE_D, h = TOP_Z);
        }
        for (b = PCB_BOSSES_UV) translate([b[0], b[1], 0]) {
            translate([0, 0, CAVITY_H - PCB_BOSS_H - 1]) cylinder(d = PCB_SCREW_D, h = PLATE_T + 2);
            translate([0, 0, TOP_Z - 1]) cylinder(d = PCB_BOSS_D, h = 2);
        }
        translate([0, 0, TOP_Z - ENGRAVE_D]) lx(ENGRAVE_D + 1) switch_text();
    }
}

// ---------- bottom plate --------------------------------------------------

module bay_2d() {
    for (m = [1, -1]) scale([m, 1])
        translate([BAY_RAIL_U[0], BAY_V[0]])
            square([BAY_RAIL_U[1] - BAY_RAIL_U[0], BAY_V[1] - BAY_V[0]]);
    translate(BAY_STOP[0]) square(BAY_STOP[1] - BAY_STOP[0]);
}

module bottom_half() render(convexity = 10) {
    difference() {
        union() {
            translate([0, 0, -PLATE_T]) lx(PLATE_T) outline_2d();
            for (s = STANDOFFS_UV) translate([s[0], s[1], 0])
                cylinder(d = STANDOFF_D, h = STANDOFF_SPLIT);
            lx(BAY_H) bay_2d();
            for (c = COXA_UV) translate([c[0], c[1], -PLATE_T - PIVOT_BOSS_H])
                cylinder(d = PIVOT_BOSS_D, h = PIVOT_BOSS_H);
        }
        for (s = STANDOFFS_UV) translate([s[0], s[1], 0]) {
            translate([0, 0, STANDOFF_SPLIT - SCREW_GRIP - 1]) cylinder(d = SCREW_D, h = SCREW_GRIP + 2);
            translate([0, 0, -PLATE_T - 1])
                cylinder(d = NUT_AF / cos(30), h = STANDOFF_SPLIT - SCREW_GRIP + PLATE_T + 1, $fn = 6);
        }
    }
}

// ---------- PCB -----------------------------------------------------------
// Long axis along the body (robot X), holes on the PCB bosses, top face
// 1 mm under the top plate, Teensy up through the cut-out.

PCB_T = 1.6;
PCB_HOLE_CENTER = [22.89, 44.52];   // HOLE_GRID_CENTER in main-pcb.scad

module pcb_in_body() {
    translate([0, 0, CAVITY_H - PCB_BOSS_H - PCB_T])
        rotate([0, 0, PCB_USB_FRONT ? -90 : 90])
            translate([-PCB_HOLE_CENTER[0], -PCB_HOLE_CENTER[1], 0])
                main_pcb();
}

// ---------- assembly ------------------------------------------------------

module body_servos_uv() for (c = COXA_UV) translate([0, 0, TOP_Z]) at_coxa(c) hs485hb();

module body_assembly() {
    fusion_to_robot() {
        if (SHOW_BOTTOM) color("#3a3a3a") bottom_half();
        if (SHOW_TOP) translate([0, 0, EXPLODE]) color("#555555") top_half();
        if (SHOW_SERVOS) translate([0, 0, EXPLODE]) body_servos_uv();
    }
    if (SHOW_PCB) translate([0, 0, EXPLODE]) pcb_in_body();
}

body_assembly();