Rectangle with one curved edge
I've embarrassed myself by asking stupid things on this list before;
I hope this isn't another. I'm trying to make a bit of a fiddly part.
It's to be a positive of an existing jaw which will later be a negative
(differenced) insert for a fit-over part.
The cross section is basically a rectangle with one side slightly
convex and the corners are slightly radiused. I had my first
printing (SLS) made without the convex face and the fit was
unacceptable. My question is: Is it possible to make an
intersection of an arc of a circle and a rectangle made by hulling
circles ?
Here's one of my attempts:
CX=9.525; // Cross section
CR=1; // Corner (fillet) Radius
X=CX-CR; // Cen to Cen of Circles
H=CX-9; // Cord height
R=(pow(CX,2)+(4pow(H,2)))/(8H);
$fn=64;
echo("radius= ",R);
module jawx(){
hull(){
translate([X/2-(1.15H),X/2])circle(CR); // 1.15 empirical
translate([X/2-(1.15H),-X/2])circle(CR);// to approx tang pt
translate([-X/2,X/2])circle(CR);
translate([-X/2,-X/2])circle(CR);
}
}
intersection(){ //
% linear_extrude(height=12) circle(r=R); // Extrude the disc
translate([2X-(.5H),0,0])
linear_extrude(height=12) jawx(); // Extrude rect jaw x-section
}
I'm still using that crufty OpenSCAD version 2012.05.26 on Debian
3.2.86-1 i686 GNU/Linux.
TIA for any clues.
Something like this:
intersection(){ //
linear_extrude(height=12)
circle(r=R); // Extrude the disc
translate([2X-(.5H),-CX/2,0])
cube([CX,CX,12]);
}
translate([2X-(.5H),0,0])
linear_extrude(height=12)
jawx(); // Extrude rect jaw x-section
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Don't be embarrassed. Even those who don't act makes mistakes.
Hull() doesn't help here.
To get a rectangle with rounded edges, intersect circles:
$fn = 120;
module arc_square(sx,sy,Rx,Ry) render()
intersection(){
translate([-Rx+sx/2,0]) circle(Rx);
translate([ Rx-sx/2,0]) circle(Rx);
translate([0,-Ry+sy/2]) circle(Ry);
translate([0, Ry-sy/2]) circle(Ry);
}
To round vertices, use offset:
offset(r) square([a,b], center=true);
To get both, a little math is needed:
a = 30; // rectangle width
b = 20; // rectangle height
e = 2; // rect. side bulge
Rx = e/2 + bb/e/8;
Ry = e/2 + aa/e/8; echo(Rx, Ry);
r = 3;
color("blue")
offset(r)
arc_square(a+2e-2r,b+2e-2r,Rx,Ry);
translate([0,0,2]) square([a,b],center=true); // just to compare
/*
Using Pythagoras
R^2 = (R-e)^2 + (a/2)^2
0 = -2eR + e^2 + (a/2)^2
R = e/2 + (a/2)^2 / e / 2
*/
Now just linear_extrude() this polygon.
BTW, to make a cylinder you don't need linear_extrude().
2017-04-05 21:57 GMT-03:00 John Tucker jart3@verizon.net:
I've embarrassed myself by asking stupid things on this list before;
I hope this isn't another. I'm trying to make a bit of a fiddly part.
It's to be a positive of an existing jaw which will later be a negative
(differenced) insert for a fit-over part.
The cross section is basically a rectangle with one side slightly
convex and the corners are slightly radiused. I had my first
printing (SLS) made without the convex face and the fit was
unacceptable. My question is: Is it possible to make an
intersection of an arc of a circle and a rectangle made by hulling
circles ?
Here's one of my attempts:
CX=9.525; // Cross section
CR=1; // Corner (fillet) Radius
X=CX-CR; // Cen to Cen of Circles
H=CX-9; // Cord height
R=(pow(CX,2)+(4pow(H,2)))/(8H);
$fn=64;
echo("radius= ",R);
module jawx(){
hull(){
translate([X/2-(1.15*H),X/2])circle(CR); // 1.15 empirical
translate([X/2-(1.15*H),-X/2])circle(CR);// to approx tang pt
translate([-X/2,X/2])circle(CR);
translate([-X/2,-X/2])circle(CR);
}
}
intersection(){ //
% linear_extrude(height=12) circle(r=R); // Extrude the disc
translate([2X-(.5H),0,0])
linear_extrude(height=12) jawx(); // Extrude rect jaw x-section
}
I'm still using that crufty OpenSCAD version 2012.05.26 on Debian
3.2.86-1 i686 GNU/Linux.
TIA for any clues.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
Minkowski() is a good way to radius corners.
On 6/04/2017 14:59, "Ronaldo Persiano" rcmpersiano@gmail.com wrote:
Don't be embarrassed. Even those who don't act makes mistakes.
Hull() doesn't help here.
To get a rectangle with rounded edges, intersect circles:
$fn = 120;
module arc_square(sx,sy,Rx,Ry) render()
intersection(){
translate([-Rx+sx/2,0]) circle(Rx);
translate([ Rx-sx/2,0]) circle(Rx);
translate([0,-Ry+sy/2]) circle(Ry);
translate([0, Ry-sy/2]) circle(Ry);
}
To round vertices, use offset:
offset(r) square([a,b], center=true);
To get both, a little math is needed:
a = 30; // rectangle width
b = 20; // rectangle height
e = 2; // rect. side bulge
Rx = e/2 + bb/e/8;
Ry = e/2 + aa/e/8; echo(Rx, Ry);
r = 3;
color("blue")
offset(r)
arc_square(a+2e-2r,b+2e-2r,Rx,Ry);
translate([0,0,2]) square([a,b],center=true); // just to compare
/*
Using Pythagoras
R^2 = (R-e)^2 + (a/2)^2
0 = -2eR + e^2 + (a/2)^2
R = e/2 + (a/2)^2 / e / 2
*/
Now just linear_extrude() this polygon.
BTW, to make a cylinder you don't need linear_extrude().
2017-04-05 21:57 GMT-03:00 John Tucker jart3@verizon.net:
I've embarrassed myself by asking stupid things on this list before;
I hope this isn't another. I'm trying to make a bit of a fiddly part.
It's to be a positive of an existing jaw which will later be a negative
(differenced) insert for a fit-over part.
The cross section is basically a rectangle with one side slightly
convex and the corners are slightly radiused. I had my first
printing (SLS) made without the convex face and the fit was
unacceptable. My question is: Is it possible to make an
intersection of an arc of a circle and a rectangle made by hulling
circles ?
Here's one of my attempts:
CX=9.525; // Cross section
CR=1; // Corner (fillet) Radius
X=CX-CR; // Cen to Cen of Circles
H=CX-9; // Cord height
R=(pow(CX,2)+(4pow(H,2)))/(8H);
$fn=64;
echo("radius= ",R);
module jawx(){
hull(){
translate([X/2-(1.15*H),X/2])circle(CR); // 1.15 empirical
translate([X/2-(1.15*H),-X/2])circle(CR);// to approx tang pt
translate([-X/2,X/2])circle(CR);
translate([-X/2,-X/2])circle(CR);
}
}
intersection(){ //
% linear_extrude(height=12) circle(r=R); // Extrude the disc
translate([2X-(.5H),0,0])
linear_extrude(height=12) jawx(); // Extrude rect jaw x-section
}
I'm still using that crufty OpenSCAD version 2012.05.26 on Debian
3.2.86-1 i686 GNU/Linux.
TIA for any clues.
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
one side slightly convex
using that crufty OpenSCAD version 2012.05.26
Thus no offset()
Admin - PM me if you need anything, or if I've done something stupid...
Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above.
The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
View this message in context: http://forum.openscad.org/Rectangle-with-one-curved-edge-tp21097p21102.html
Sent from the OpenSCAD mailing list archive at Nabble.com.
2017-04-06 0:33 GMT-03:00 MichaelAtOz oz.at.michael@gmail.com:
one side slightly convex
using that crufty OpenSCAD version 2012.05.26
Thus no offset()
Does it have minkowski() ?
module offset(r) {
very_big = 1e16; // something greater then the children size
render()
if(r>0)
minkowski(){
children();
circle(r);
}
else
difference(){
square(very_big-1,center=true);
minkowski(){
difference(){
square(very_big,center=true);
children();
}
circle(-r);
}
}
}
Ronaldo,
Why does your offset square example above have slightly curved edges? It
should have straight edges and rounded corners and does when I try it.
On 6 April 2017 at 05:22, Ronaldo Persiano rcmpersiano@gmail.com wrote:
2017-04-06 0:33 GMT-03:00 MichaelAtOz oz.at.michael@gmail.com:
one side slightly convex
using that crufty OpenSCAD version 2012.05.26
Thus no offset()
Does it have minkowski() ?
module offset(r) {
very_big = 1e16; // something greater then the children size
render()
if(r>0)
minkowski(){
children();
circle(r);
}
else
difference(){
square(very_big-1,center=true);
minkowski(){
difference(){
square(very_big,center=true);
children();
}
circle(-r);
}
}
}
OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
2017-04-06 7:24 GMT-03:00 nop head nop.head@gmail.com:
Ronaldo,
Why does your offset square example above have slightly curved edges? It
should have straight edges and rounded corners and does when I try it.
You are right. The second image is a wrong image. That is what I should
have include instead:
I should correct myself in the statement that hull() would not help here.
It is possible to do it just with hull, without offset() or minkowski().
But the the math would be a little more complicate and I mention it here
for completeness. The solution would be the intersection of the rounded
edge rectangle with 4 big triangles with rounded vertices (a hull of 3
circles) well dimensioned and positioned.
Do you have access to a CAD program that produces a DXF file?
The simple way would be to draw the profile in cad using your exact
dimensions and then import it into OpenSCAD.
http://forum.openscad.org/file/n21113/rect.jpg
--
View this message in context: http://forum.openscad.org/Rectangle-with-one-curved-edge-tp21097p21113.html
Sent from the OpenSCAD mailing list archive at Nabble.com.
Bit of a necropost here but I had a similar question with rounded corners and
though I'd share my formulae, which combine and outer/inner cube and
cylinders to create beveled corners
module beveled_rect(w,d,h,r){
union() {
translate([r,r,h/2]) cylinder(r = r, h = h, center = true);
translate([w-r,r,h/2]) cylinder(r = r, h = h, center = true);
translate([r,0, 0]) cube([w-(r*2),r,h]);
translate([r,d-r,h/2]) cylinder(r = r, h = h, center = true);
translate([w-r,d-r,h/2]) cylinder(r = r, h = h, center = true);
translate([r,d-r, 0]) cube([w-(r*2),r,h]);
translate([0, r, 0]) cube([w,d-(r*2),h]);
}
}
module beveled_rect_bot(w,d,h,r){
union() {
translate([r,r,h/2]) cylinder(r = r, h = h, center = true);
translate([w-r,r,h/2]) cylinder(r = r, h = h, center = true);
translate([r,0, 0]) cube([w-(r*2),r,h]);
translate([0, r, 0]) cube([w,d-r,h]);
}
}
This of course focuses on bevelled/rounded corners, but one could just as
easily do the same logic with the whole edge.
As I make formulae etc I'll be posting them to my own wiki as well:
https://wiki.phormix.com/pub/index.php?title=OpenSCAD_Modules
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