mandolin-body-fender.py

"""
Parametric Fender-style solid mandolin body for the matching bolt-on neck.

Units: millimeters.
Coordinate system matches mandolin_fender_style_neck.py:
- Nut is at X = 0
- Neck centerline is Y = 0
- Nominal high-course bridge/saddle line is at X = scale
- Neck heel/pocket end is at X = nut_to_heel_end

Default design intent:
- 13.875 in / 352.425 mm scale
- Body top at Z = 0, body extends downward to Z = -body_thickness
- Recessed Fender-style neck pocket
- 4 neck screw clearance holes through the body, aligned to the neck pilot holes
- 2 bridge mounting holes near the scale line
- 2 tailpiece mounting holes behind the bridge

Run:
    python mandolin_fender_style_body.py

Exports:
    mandolin_fender_style_body.step
    mandolin_fender_style_body.stl
    mandolin_body_and_neck_reference.step  # if mandolin_fender_style_neck.py is importable

CadQuery install example:
    conda install -c conda-forge cadquery
"""

from __future__ import annotations

from dataclasses import dataclass
import cadquery as cq

MM_PER_INCH = 25.4


@dataclass(frozen=True)
class BodyParams:
    # Match the neck script defaults
    scale: float = 13.875 * MM_PER_INCH           # 352.425 mm
    nut_to_heel_end: float = 10.25 * MM_PER_INCH  # 260.35 mm
    heel_length: float = 55.0
    heel_width: float = 39.0
    heel_pocket_clearance: float = 0.35

    # Body proportions: roughly mandolin-sized solidbody, not a full ES/archtop mandolin
    body_thickness: float = 34.0
    pocket_depth: float = 16.0
    body_start_extra: float = 18.0       # body extends this far forward of pocket start
    body_length: float = 285.0           # from body_start_x to strap-end/tail end
    upper_bout_width: float = 175.0
    waist_width: float = 150.0
    lower_bout_width: float = 255.0

    # Mounting holes
    neck_screw_clearance_dia: float = 4.2
    neck_screw_counterbore_dia: float = 9.0
    neck_screw_counterbore_depth: float = 4.0

    # Bridge / tailpiece mounting holes. These are just sensible pilots/clearance holes;
    # adjust to match your actual bridge and tailpiece hardware.
    bridge_hole_dia: float = 3.2
    bridge_post_spacing: float = 42.0
    bridge_x_offset_from_scale: float = 2.0       # slightly behind nominal scale line

    tailpiece_hole_dia: float = 4.0
    tailpiece_hole_spacing: float = 38.0
    tailpiece_x_offset_from_scale: float = 76.0

    # Optional wire/string-through reference holes, disabled by default
    stl_tolerance: float = 0.08
    stl_angular_tolerance: float = 0.2


P = BodyParams()


def make_body_blank(p: BodyParams) -> cq.Workplane:
    """Make a small offset-waist Fender-ish mandolin solidbody."""
    pocket_start_x = p.nut_to_heel_end - p.heel_length
    x0 = pocket_start_x - p.body_start_extra
    x1 = x0 + p.body_length

    # Key longitudinal stations
    xn = x0 + 8.0                         # neck-side upper shoulder
    xu = x0 + 60.0                        # upper bout
    xw = x0 + 132.0                       # waist
    xl = x0 + 215.0                       # lower bout
    xt = x1 - 6.0                         # rounded tail

    # Outline points, clockwise, using splines for a smooth guitar/mandolin body.
    # Widths are total widths, so y uses half width.
    pts = [
        (xn, -p.heel_width * 0.78),
        (xu, -p.upper_bout_width * 0.50),
        (xw, -p.waist_width * 0.50),
        (xl, -p.lower_bout_width * 0.50),
        (xt, -p.lower_bout_width * 0.34),
        (x1, 0.0),
        (xt, p.lower_bout_width * 0.34),
        (xl, p.lower_bout_width * 0.50),
        (xw, p.waist_width * 0.50),
        (xu, p.upper_bout_width * 0.50),
        (xn, p.heel_width * 0.78),
    ]

    body = (
        cq.Workplane("XY")
        .moveTo(*pts[0])
        .spline(pts[1:])
        .close()
        .extrude(-p.body_thickness)
    )

    # Soften the front/back perimeter a bit. If your CadQuery install complains about
    # the selector, comment these two lines out; the flat functional features remain.
    body = body.edges("|Z").fillet(4.0)
    body = body.edges("<Z or >Z").fillet(1.5)
    return body


def make_neck_pocket_cutter(p: BodyParams) -> cq.Workplane:
    pocket_start_x = p.nut_to_heel_end - p.heel_length
    width = p.heel_width + 2.0 * p.heel_pocket_clearance
    length = p.heel_length + 0.8

    # Cuts from body top Z=0 downward to pocket floor at -pocket_depth.
    return (
        cq.Workplane("XY")
        .box(length, width, p.pocket_depth + 0.2, centered=(False, True, False))
        .translate((pocket_start_x - 0.4, 0, -p.pocket_depth - 0.1))
    )


def cut_neck_mounting_holes(body: cq.Workplane, p: BodyParams) -> cq.Workplane:
    pocket_start_x = p.nut_to_heel_end - p.heel_length
    screw_xs = [pocket_start_x + p.heel_length * 0.34, pocket_start_x + p.heel_length * 0.74]
    screw_ys = [-p.heel_width * 0.27, p.heel_width * 0.27]

    for x in screw_xs:
        for y in screw_ys:
            through = (
                cq.Workplane("XY")
                .center(x, y)
                .circle(p.neck_screw_clearance_dia / 2.0)
                .extrude(-p.body_thickness - 1.0)
                .translate((0, 0, 0.5))
            )
            body = body.cut(through)

            # Counterbore from the back face. Because the body extends negative Z,
            # this is placed at the bottom/back side.
            counterbore = (
                cq.Workplane("XY")
                .center(x, y)
                .circle(p.neck_screw_counterbore_dia / 2.0)
                .extrude(p.neck_screw_counterbore_depth)
                .translate((0, 0, -p.body_thickness - 0.05))
            )
            body = body.cut(counterbore)
    return body


def cut_bridge_and_tailpiece_holes(body: cq.Workplane, p: BodyParams) -> cq.Workplane:
    bridge_x = p.scale + p.bridge_x_offset_from_scale
    tailpiece_x = p.scale + p.tailpiece_x_offset_from_scale

    for y in [-p.bridge_post_spacing / 2.0, p.bridge_post_spacing / 2.0]:
        hole = (
            cq.Workplane("XY")
            .center(bridge_x, y)
            .circle(p.bridge_hole_dia / 2.0)
            .extrude(-p.body_thickness - 1.0)
            .translate((0, 0, 0.5))
        )
        body = body.cut(hole)

    for y in [-p.tailpiece_hole_spacing / 2.0, p.tailpiece_hole_spacing / 2.0]:
        hole = (
            cq.Workplane("XY")
            .center(tailpiece_x, y)
            .circle(p.tailpiece_hole_dia / 2.0)
            .extrude(-p.body_thickness - 1.0)
            .translate((0, 0, 0.5))
        )
        body = body.cut(hole)

    return body


def add_reference_marks(body: cq.Workplane, p: BodyParams) -> cq.Workplane:
    """Add shallow engraved centerline and scale-line marks for layout sanity checks."""
    pocket_start_x = p.nut_to_heel_end - p.heel_length
    x0 = pocket_start_x - p.body_start_extra + 10.0
    x1 = x0 + p.body_length - 20.0

    centerline = (
        cq.Workplane("XY")
        .box(x1 - x0, 0.7, 0.6, centered=(False, True, False))
        .translate((x0, 0, -0.35))
    )
    scale_mark = (
        cq.Workplane("XY")
        .box(1.0, 70.0, 0.6, centered=(True, True, False))
        .translate((p.scale, 0, -0.35))
    )
    pocket_end_mark = (
        cq.Workplane("XY")
        .box(1.0, 50.0, 0.6, centered=(True, True, False))
        .translate((p.nut_to_heel_end, 0, -0.35))
    )
    return body.cut(centerline).cut(scale_mark).cut(pocket_end_mark)


def build_body(p: BodyParams = P, reference_marks: bool = True) -> cq.Workplane:
    body = make_body_blank(p)
    body = body.cut(make_neck_pocket_cutter(p))
    body = cut_neck_mounting_holes(body, p)
    body = cut_bridge_and_tailpiece_holes(body, p)
    if reference_marks:
        body = add_reference_marks(body, p)
    return body


def try_build_body_and_neck_reference(body: cq.Workplane, p: BodyParams) -> cq.Workplane | None:
    """Optional assembly reference if the neck script is next to this file."""
    try:
        import mandolin_fender_style_neck as neck_script
    except Exception:
        return None

    neck = neck_script.build_model(neck_script.P)

    # Drop the heel bottom onto the pocket floor. The neck script's heel bottom is at Z=0.
    neck = neck.translate((0, 0, -p.pocket_depth))
    return body.union(neck)


if __name__ == "__main__":
    body = build_body(P)
    cq.exporters.export(body, "mandolin_fender_style_body.step")
    cq.exporters.export(body, "mandolin_fender_style_body.stl", tolerance=P.stl_tolerance, angularTolerance=P.stl_angular_tolerance)

    ref = try_build_body_and_neck_reference(body, P)
    if ref is not None:
        cq.exporters.export(ref, "mandolin_body_and_neck_reference.step")
        print("Exported mandolin_body_and_neck_reference.step")

    bridge_x = P.scale + P.bridge_x_offset_from_scale
    tailpiece_x = P.scale + P.tailpiece_x_offset_from_scale
    print("Exported mandolin_fender_style_body.step")
    print("Exported mandolin_fender_style_body.stl")
    print(f"Body top: Z = 0; body back: Z = {-P.body_thickness:.3f} mm")
    print(f"Neck pocket floor: Z = {-P.pocket_depth:.3f} mm")
    print(f"Pocket start X: {P.nut_to_heel_end - P.heel_length:.3f} mm")
    print(f"Pocket end X: {P.nut_to_heel_end:.3f} mm")
    print(f"Nominal scale line X: {P.scale:.3f} mm")
    print(f"Bridge holes X: {bridge_x:.3f} mm, Y: +/-{P.bridge_post_spacing / 2.0:.3f} mm")
    print(f"Tailpiece holes X: {tailpiece_x:.3f} mm, Y: +/-{P.tailpiece_hole_spacing / 2.0:.3f} mm")