added the smallest unit value to the ploygon in order to ensure they overlap and union correctly

modules/idt.scad

@@ -1,6 +1,14 @@
 // creates 1 side of the idt
-module delay_line(lambda = 1, n_fingers = 1, finger_length = 50, gap = 0, thickness = 0) {
-    // code
+module delay_line(
+    lambda = 1, 
+    n_fingers = 1, 
+    finger_length = 50, 
+    gap = 0, 
+    thickness = 0
+) {
+
+    // just a very small value that allows the polygons to overlap nicely
+    esp = $fs;
     l45 =lambda*5/4;
     l2 = lambda/2;
     l4 = lambda/4;
@@ -24,8 +32,8 @@ module delay_line(lambda = 1, n_fingers = 1, finger_length = 50, gap = 0, thickn
         [b+f, l2],
         [b+f, l2+l4],
         [b, l2+l4],
-        [b, l4*5-l4],
-        [0, l4*5-l4]
+        [b, l4*5-l4 + esp],
+        [0, l4*5-l4 + esp]
     ];
     union () {