// basic parameters for the locking mechanism
kerf = 0.1;       // laser kerf to account for
slot = 0.2;       // slot widht: material thckness
rodlength = 30;   // length of a rim / rod
rodbase = 0.01;   // base width, necessary for drawing using hull
tabhook = 3;      // trapezioid shape length     
tab = 2;          // width of a tab
snapratio = 0.75; // trapezioid angle between 0 (full tab gap and 1 full push through)
// make the buildplate of triangles and squares
projection(){
    for(i=[0:1:3])translate([i*50,110,0])triangle();
        for(i=[0:1:3])translate([i*50 + 55,80,0])rotate([0,0,180])triangle();
    for(i=[0:1:5])translate([i*38,30,0])square();
for(i=[0:1:5])translate([i*38,70,0])square();
}
// a square
module square(){
    translate([0,0,0])rotate([0,0,0])edge();
translate([0,-rodlength,0])rotate([0,0,90])edge();
translate([rodlength,-rodlength,0])rotate([0,0,180])edge();
translate([rodlength,0,0])rotate([0,0,270])edge();  
  
hull(){
        translate([0,0,0])rotate([0,0,0])cube([rodlength,rodbase,slot]);
translate([0,-rodlength,0])rotate([0,0,90])cube([rodlength,rodbase,slot]);
translate([rodlength,-rodlength,0])rotate([0,0,180])cube([rodlength,rodbase,slot]);
translate([rodlength,0,0])rotate([0,0,270])cube([rodlength,rodbase,slot]);  
}     
}
// the triangle shape
module triangle(){
translate([0,0,0])rotate([0,0,0])edge();
translate([rodlength/2,-sin(60)*rodlength,0])rotate([0,0,120])edge();
translate([rodlength,0,0])rotate([0,0,240])edge();
hull(){
translate([0,0,0])rotate([0,0,0])translate([0,-rodbase,0])cube([rodlength,rodbase,slot]);
translate([rodlength/2,-sin(60)*rodlength,0])rotate([0,0,120])translate([0,-rodbase,0])cube([rodlength,rodbase,slot]);
translate([rodlength,0,0])rotate([0,0,240])translate([0,-rodbase,0])cube([rodlength,rodbase,slot]);
}
}
// the locking edge design
module edge(){
    translate([0,-rodbase,0]){
difference(){
union(){
cube([rodlength,rodbase,slot]);
translate([tabhook,rodbase,0])cube([rodlength/2-2*tabhook,slot,slot]);
hull(){translate([tabhook/2,rodbase+slot,0])cube([rodlength/2-tabhook,0.01,slot]);
translate([tabhook,rodbase+slot+tab,0])cube([rodlength/2-2*tabhook,0.01,slot]);}
hull(){
    translate([rodlength/2,rodbase,0])cube([rodlength/2,0.01,slot]);
    translate([rodlength/2+tabhook/2,rodbase+tab+slot,0])cube([rodlength/2-tabhook,0.01,slot]);}
}
translate([rodlength/2+snapratio*tabhook,rodbase,-0.01])cube([rodlength/2-2*snapratio*tabhook,slot,slot+0.02]);
}}
}