thick = 3; //thickness of the material
offset = 0.45; //enter offset characteristic to the laser cutter

radius = 100;   //radius of the ring
joints = 20;    //number of joints
joint_depth = 10;   //joint depth


module shade_ring(radius, joints, joint_depth){
    difference(){
    cylinder(r=radius, h=thick);
    cylinder(r=radius-joint_depth*2, h=thick);

    rotate( 360/(joints*2), [0,0,1])
     for ( i = [0:joints] ) {
      rotate( i*360/joints, [0, 0, 1])
       translate( [0, radius-joint_depth, 0] ) cube(size=[thick-offset, joint_depth, thick]); 
     };

     for ( i = [0:joints] ) {
      rotate( i*360/joints, [0, 0, 1])
       translate( [0, radius-joint_depth*2, 0] ) cube(size=[thick-offset,joint_depth,thick]); 
     };
    }
 
}; //module shade_ring

module shade_ring_cut(radius, joints, joint_depth, angle){
intersection(){
    translate([-radius*2,0,0]) cube(size=[radius*4, radius*2, radius*2]);
    rotate([0,0,angle]) translate([-radius*2,-radius*2,0]) cube(size=[radius*4, radius*2, radius*2]);
    
   difference(){
    cylinder(r=radius, h=thick);
    cylinder(r=radius-joint_depth*2, h=thick);

    rotate( 360/(joints*2), [0,0,1])
     for ( i = [0:joints] ) {
      rotate( i*360/joints, [0, 0, 1])
       translate( [0, radius-joint_depth, 0] ) cube(size=[thick-offset, joint_depth, thick]); 
     };

     for ( i = [0:joints] ) {
      rotate( i*360/joints, [0, 0, 1])
       translate( [0, radius-joint_depth*2, 0] ) cube(size=[thick-offset,joint_depth,thick]); 
     };
    };
    };
};//module shade_ring_cut


projection(cut = true){
shade_ring(radius, joints, joint_depth);
// 1/3 (120degree)
translate([300,0,0]) shade_ring_cut(radius, joints, joint_depth, angle=120);
// Half (180degree)
translate([600,0,0]) shade_ring_cut(radius, joints, joint_depth, angle=180);
}