smooth section transitions example

wall_thickness = 2;
section1_heigth = 50;
section1_radius = 20;

section2_heigth = 50;
section2_radius = 10;

section3_heigth = 15;
section3_radius = 15;

section4_heigth = 15;
section4_radius = 5;

difference() {
    union() {
        cylinder(h=section1_heigth, r=section1_radius);
        translate([0,0,section1_heigth]) cylinder(h=section2_heigth, r1=section1_radius, r2=section2_radius);
        translate([0,0,section1_heigth + section2_heigth]) cylinder(h=section3_heigth, r1=section2_radius, r2=section3_radius);
        translate([0,0,115]) cylinder(h=section4_heigth, r1=section3_radius, r2=section4_radius);
    }

    union() {
        cylinder(h=section1_heigth, r=section1_radius - wall_thickness);
        translate([0,0,section1_heigth]) cylinder(h=section2_heigth, r1=section1_radius - wall_thickness, r2=section2_radius - wall_thickness);
        translate([0,0,section1_heigth + section2_heigth]) cylinder(h=section3_heigth, r1=section2_radius - wall_thickness, r2=section3_radius - wall_thickness);
        translate([0,0,section1_heigth + section2_heigth + section3_heigth]) cylinder(h=section4_heigth, r1=section3_radius - wall_thickness, r2=section4_radius - wall_thickness);
    }
}