Rotate extrude help needed

I have hit the wall on this one, and you’re going to laugh, because it’s probably so simple.

I need to make a disc 35mm across, 3mm thick, with a rounded edge.

To that end, I was able to create the points to make a polygon rectangle 17.5 X, 3mm Y and that extrudes fine into a disc 35mm across with square edges.

The problem comes in when I try to create a circle at the end, 1.5mm radius, centered at X17.5, Y1.5. I’ve tried a few ways, but nothing works.

Could anyone offer some guidance on this? I’m tearing my hair out at this point.

Edited 2 time(s). Last edit at 04/28/2022 08:28PM by andy.wpg.

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"I have noticed that even those who assert that everything is predestined and that
we can change nothing about it still look both ways before they cross the street"

-Stephen Hawking

Adapted from the previous thread [reprap.org]

// chamfercyl - create a cylinder with round chamfered ends
module chamfercyl(
   r,              // cylinder radius
   h,              // cylinder height
   b=0,            // bottom chamfer radius (=0 none, >0 outside, <0 inside)
   t=0,            // top chamfer radius (=0 none, >0 outside, <0 inside)
   offset=[[0,0]], // optional offsets in X and Y to create
                   // convex hulls at slice level
   slices=10,      // number of slices used for chamfering
   eps=0.01,       // tiny overlap of slices
){
    astep=90/slices;
    hull()for(o = offset)
       translate([o[0],o[1],abs(b)-eps])cylinder(r=r,h=h-abs(b)-abs(t)+2*eps);
    if(b)for(a=[0:astep:89.999])hull()for(o = offset)
       translate([o[0],o[1],abs(b)-abs(b)*sin(a+astep)-eps])
          cylinder(r2=r+(1-cos(a))*b,r1=r+(1-cos(a+astep))*b,h=(sin(a+astep)-sin(a))*abs(b)+2*eps);
    if(t)for(a=[0:astep:89.999])hull()for(o = offset)
       translate([o[0],o[1],h-abs(t)+abs(t)*sin(a)-eps])
          cylinder(r1=r+(1-cos(a))*t,r2=r+(1-cos(a+astep))*t,h=(sin(a+astep)-sin(a))*abs(t)+2*eps);
}

$fn=60;
chamfercyl(35/2,3,-0.5,-0.5);  // chamfer both edges
color("red") translate ([-36,0,0]) chamfercyl(35/2,3,-0.0,-0.5); // chamfer top edge
color("blue") translate ([36,0,0]) chamfercyl(35/2,3,-0.5,-0.0); // chamfer bottom edge 

Thanks for that, I’ll give it a try in the morning. I did do a search for rotate extrude, but nothing showed up in the results.

---

"I have noticed that even those who assert that everything is predestined and that
we can change nothing about it still look both ways before they cross the street"

-Stephen Hawking

That worked, thanks!

I woke up at 4am this morning and ran downstairs to try the following. I guess I was thinking about it in my sleep! :-)

$fn=100;
union()
{
rotate_extrude(convexity = 10)
translate([27, 0, 0])
circle(r = 1.5, $fn = 100);
}
translate([0,0,-1.5])
cylinder(3,27,27);

I'm not sure if the union is necessary, I didn't try without it. This is a quick and dirty acceptable version, yours is much more elegant.

---

"I have noticed that even those who assert that everything is predestined and that
we can change nothing about it still look both ways before they cross the street"

-Stephen Hawking

Why not
hull() {
rotate_extrude(convexity = 10, $fn = 100)
translate([27, 0, 0])
circle(r = 1.5, $fn = 100);
}
?

Maybe faster

rotate_extrude(convexity = 10, $fn = 100) {
union() {
translate([27, 0, 0]) {
circle(r = 1.5, $fn = 100);
}
square([27, 1.5]);
}
}

Edited 2 time(s). Last edit at 07/26/2022 10:55AM by F14Claude.

I will try that! Thanks!

---

"I have noticed that even those who assert that everything is predestined and that
we can change nothing about it still look both ways before they cross the street"

-Stephen Hawking