Make it fit
your magnets.

/*
====================================================================
PARAMETRIC MAGNETIC CAR PLATE MOUNT BASE
80 x 36 x 7 mm | 2x Ø25 x 5 mm magnets
====================================================================

Features:
- Rounded rectangular base
- 0.8 mm top chamfer
- Two embedded magnet cavities
- 0.4 mm diametral clearance
- 0.2 mm vertical clearance
- 1.2 mm bottom floor
- 0.6 mm top cover
- Optional magnet visualization

Units: millimeters
*/

$fn = 100;


// ====================================================================
// 1. OUTER DIMENSIONS
// ====================================================================

base_length = 80.0;
base_width  = 36.0;
base_height = 7.0;

corner_radius = 10.0;
top_chamfer   = 0.8;


// ====================================================================
// 2. MAGNET PARAMETERS
// ====================================================================

magnet_dia   = 25.0;
magnet_thick = 5.0;

// Total diameter clearance:
// Ø25.0 + 0.4 = Ø25.4 mm cavity
clearance_dia = 0.4;

// Additional vertical clearance
clearance_h = 0.2;

cavity_dia    = magnet_dia + clearance_dia;
cavity_height = magnet_thick + clearance_h;


// ====================================================================
// 3. INTERNAL WALLS
// ====================================================================

// Material below magnet
floor_thick = 1.2;

// Material above magnet
top_cover = 0.6;

// Automatically calculate cavity Z positions
cavity_z_bottom = floor_thick;
cavity_z_top    = base_height - top_cover;


// ====================================================================
// 4. MAGNET POSITIONS
// ====================================================================

// Magnet 1
mag1_x = 20.0;
mag1_y = 18.0;

// Magnet 2
mag2_x = 60.0;
mag2_y = 18.0;


// ====================================================================
// 5. VALIDATION
// ====================================================================

assert(
    base_length > 0 && base_width > 0 && base_height > 0,
    "ERROR: Base dimensions must be positive."
);

assert(
    corner_radius > 0 &&
    corner_radius <= min(base_length, base_width) / 2,
    "ERROR: Invalid corner radius."
);

assert(
    top_chamfer >= 0 && top_chamfer < base_height,
    "ERROR: Invalid top chamfer."
);

assert(
    cavity_z_top - cavity_z_bottom >= cavity_height,
    str(
        "ERROR: Available cavity height = ",
        cavity_z_top - cavity_z_bottom,
        " mm; required = ",
        cavity_height,
        " mm."
    )
);

assert(
    abs(cavity_z_top - (base_height - top_cover)) < 0.001,
    "ERROR: Incorrect cavity top position."
);

assert(
    abs(
        (cavity_z_top - cavity_z_bottom) - cavity_height
    ) < 0.001,
    "WARNING: Cavity dimensions do not match the intended fit."
);

assert(
    base_width >= cavity_dia,
    "ERROR: Magnet cavity does not fit inside base width."
);

assert(
    mag1_x - cavity_dia / 2 > 0,
    "ERROR: Magnet 1 is too close to the left edge."
);

assert(
    base_length - mag2_x - cavity_dia / 2 > 0,
    "ERROR: Magnet 2 is too close to the right edge."
);

assert(
    abs(mag1_y - mag2_y) < 0.001,
    "WARNING: Magnets are not aligned on the same Y position."
);

assert(
    mag1_y - cavity_dia / 2 > 0 &&
    base_width - mag1_y - cavity_dia / 2 > 0,
    "ERROR: Magnet cavities are too close to the front or rear edge."
);


// ====================================================================
// 6. ROUNDED RECTANGLE
// ====================================================================

module rounded_rectangle(length, width, radius)
{
    hull()
    {
        translate([radius, radius])
            circle(r = radius);

        translate([length - radius, radius])
            circle(r = radius);

        translate([length - radius, width - radius])
            circle(r = radius);

        translate([radius, width - radius])
            circle(r = radius);
    }
}


// ====================================================================
// 7. OUTER BODY
// ====================================================================

module outer_body()
{
    straight_height = base_height - top_chamfer;

    union()
    {
        // Main body
        linear_extrude(height = straight_height)
            rounded_rectangle(
                base_length,
                base_width,
                corner_radius
            );

        // Sloped top chamfer
        translate([0, 0, straight_height])
            linear_extrude(
                height = top_chamfer,
                scale = [
                    (base_length - 2 * top_chamfer) / base_length,
                    (base_width  - 2 * top_chamfer) / base_width
                ]
            )
            rounded_rectangle(
                base_length,
                base_width,
                corner_radius
            );
    }
}


// ====================================================================
// 8. MAGNET CAVITY
// ====================================================================

module magnet_cavity(x, y)
{
    translate([
        x,
        y,
        cavity_z_bottom
    ])
    cylinder(
        d = cavity_dia,
        h = cavity_height
    );
}


// ====================================================================
// 9. COMPLETE MAGNETIC BASE
// ====================================================================

module magnetic_plate_base()
{
    difference()
    {
        // Solid outer body
        outer_body();

        // Magnet cavity 1
        magnet_cavity(
            mag1_x,
            mag1_y
        );

        // Magnet cavity 2
        magnet_cavity(
            mag2_x,
            mag2_y
        );
    }
}


// ====================================================================
// 10. OPTIONAL MAGNET VISUALIZATION
// ====================================================================

// Set true to preview magnet positions.
// The magnets are shown as transparent reference geometry.

show_magnets = false;

module magnet_preview(x, y)
{
    %translate([
        x,
        y,
        cavity_z_bottom
    ])
    cylinder(
        d = magnet_dia,
        h = magnet_thick
    );
}

if (show_magnets)
{
    magnet_preview(mag1_x, mag1_y);
    magnet_preview(mag2_x, mag2_y);
}


// ====================================================================
// 11. DIMENSION SUMMARY
// ====================================================================

echo("========================================");
echo("MAGNETIC PLATE BASE");
echo("Base length:", base_length, "mm");
echo("Base width:", base_width, "mm");
echo("Base height:", base_height, "mm");
echo("Magnet diameter:", magnet_dia, "mm");
echo("Magnet thickness:", magnet_thick, "mm");
echo("Cavity diameter:", cavity_dia, "mm");
echo("Cavity height:", cavity_height, "mm");
echo("Cavity bottom Z:", cavity_z_bottom, "mm");
echo("Cavity top Z:", cavity_z_top, "mm");
echo("Bottom floor:", floor_thick, "mm");
echo("Top cover:", top_cover, "mm");
echo("========================================");


// ====================================================================
// 12. FINAL RENDER
// ====================================================================

magnetic_plate_base();

Tip: avoid changing the validation, cavity, and final render sections unless you understand how the model is constructed.

• Measure magnet diameter and thickness with calipers if possible.
• Check the cavity size and magnet positions in OpenSCAD's preview and final render.
• Confirm the cavity and pause layer in the slicer's layer preview.
• Make sure the magnets are fully enclosed by plastic and cannot come loose.
• This is a DIY model; test fit and holding strength safely before mounting anything to a vehicle.