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Scott Alfter
2018-07-20 14:22:28 -07:00
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parametric_bracket.scad Executable file
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// parametric extrusion brackets
// Scott Alfter
// 20 July 2018
// settings
nominal_extrusion_width=20;
screw_diameter=5;
gap=0.4; // adjust for your process
thickness=2.8;
// uncomment one of the following to render
//corner_bracket();
//t_bracket();
double_t_bracket();
// other constants needed later
tw=(nominal_extrusion_width+gap+2*thickness); // total width
iw=(nominal_extrusion_width+gap+thickness)/2; // dimension from center of cube to center of hole
// top-level modules
module corner_bracket()
{
corner();
translate([0,tw,0])
tube();
translate([tw,0,0])
rotate([0,0,90])
tube();
translate([0,0,tw])
rotate([90,0,0])
tube();
translate([tw,0,tw])
brace();
translate([0,tw,tw])
rotate([0,0,90])
brace();
translate([tw,tw,0])
rotate([-90,0,0])
brace();
}
module t_bracket()
{
t();
translate([0,0,tw])
rotate([90,0,0])
tube();
translate([0,0,-tw])
rotate([90,0,0])
tube();
translate([tw,0,0])
rotate([0,0,90])
tube();
translate([tw,0,tw])
brace();
translate([tw,0,-tw])
rotate([180,0,0])
brace();
}
module double_t_bracket()
{
dt();
translate([0,0,tw])
rotate([90,0,0])
tube();
translate([0,0,-tw])
rotate([90,0,0])
tube();
translate([tw,0,0])
rotate([0,0,90])
tube();
translate([0,tw,0])
tube();
translate([tw,0,tw])
brace();
translate([tw,0,-tw])
rotate([180,0,0])
brace();
translate([0,tw,tw])
rotate([0,0,90])
brace();
translate([0,tw,-tw])
rotate([180,0,90])
brace();
translate([tw,tw,0])
rotate([-90,0,0])
brace();
}
// lower-level modules
module brace() // a pair of braces
{
d=tw/2-4;
translate([0,-d,0])
brace_sub();
translate([0,d,0])
brace_sub();
}
module tube() // four panels to make a tube
{
translate([0,0,-iw])
panel();
translate([0,0,iw])
panel();
translate([-iw,0,0])
rotate([0,90,0])
panel();
translate([iw,0,0])
rotate([0,90,0])
panel();
}
module corner() // three panels and three edges in a corner
{
translate([0,iw,iw])
edge();
translate([iw,0,iw])
rotate([0,0,90])
edge();
translate([iw,iw,0])
rotate([0,90,0])
edge();
translate([0,0,-iw])
panel();
translate([0,-iw,0])
rotate([90,0,0])
panel();
translate([-iw,0,0])
rotate([0,90,0])
panel();
}
module t() // three panels and two edges in a T
{
translate([iw,0,iw])
rotate([0,0,90])
edge();
translate([iw,0,-iw])
rotate([0,0,90])
edge();
translate([0,-iw,0])
rotate([90,0,0])
panel();
translate([0,iw,0])
rotate([90,0,0])
panel();
translate([-iw,0,0])
rotate([0,90,0])
panel();
}
module dt() // two panels and four edges in a double-T
{
translate([0,iw,iw])
edge();
translate([0,iw,-iw])
edge();
translate([iw,0,iw])
rotate([0,0,90])
edge();
translate([iw,0,-iw])
rotate([0,0,90])
edge();
translate([0,-iw,0])
rotate([90,0,0])
panel();
translate([-iw,0,0])
rotate([0,90,0])
panel();
}
// basic components
module panel() // basic unit: a square plate with a hole, centered on the origin
{
d=tw/2;
translate([0,0,-thickness/2])
linear_extrude(thickness, convexity=10)
difference()
{
polygon([[-d,-d],[-d,d],[d,d],[d,-d]]);
circle(d=screw_diameter+gap, $fn=45);
}
}
module edge() // a stick to fill in the corners where panels meet
{
d1=tw/2;
d2=thickness/2;
translate([0,0,-d2])
linear_extrude(thickness, convexity=10)
polygon([[-d1,-d2],[d1,-d2],[d1,d2],[-d1,d2]]);
}
module brace_sub() // a diagonal brace
{
d=tw/2;
translate([0,thickness/2,0])
rotate([90,0,0])
linear_extrude(thickness, convexity=10)
polygon([[-d,-d],[d-3,-d],[-d,d-3]]);
}