add robotic_arm_attach

cad/robotic_arm_attach.scad

@@ -0,0 +1,41 @@
+include <threads.scad>;
+
+$fn=128;
+
+difference(){
+union(){
+linear_extrude(4)
+difference(){
+square([28.5,46.5]);
+translate([3.5,3])
+circle(d=2.5);
+translate([28.5-3.5,3])
+circle(d=2.5);
+translate([28.5-3.5,46.5-3])
+circle(d=2.5);
+translate([3.5,46.5-3])
+circle(d=2.5);
+translate([28.5/2,11.5])
+    for (i=[0 : 3]){
+rotate([0,0,i*90])
+translate([8,0])
+circle(d=4);
+    }
+}
+translate([0,0,4])
+linear_extrude(20)
+difference(){
+square([28.5,46.5]);
+translate([3.5,3])
+circle(r=5);
+translate([28.5-3.5,3])
+circle(r=5);
+translate([28.5-3.5,46.5-3])
+circle(r=5);
+translate([3.5,46.5-3])
+circle(r=5);
+}
+}
+translate([28.5/2,11.5, 8])
+metric_thread (diameter=6, pitch=1, length=20);
+}