Curved groove gets wrong depth
I'm trying to make a groove in a bend, but I can't get it to have an even
depth. It gets shallower in the middle. Any ideas?
Code:
$fn=100;
function first(list) = list[0];
function tail(list) = [for (i=[1:len(list)-1]) list[i]];
function snd(list) = list[1];
module bend_2d(thickness, inner_radius, angle=90 /* 1->180 */) {
inner_r = inner_radius;
outer_r = inner_r + thickness;
angle_real = abs(angle);
invert = angle < 0;
mirror_vec_y = invert ? 1 : 0;
translate_y = invert ? thickness : 0;
translate([0, translate_y, 0]) // negative bends
mirror([0, mirror_vec_y, 0]) //
translate([0, outer_r])
difference() {
circle(outer_r);
circle(inner_r);
rotate(angle_real-90)
square(outer_r);
translate([-outer_r, -outer_r])
square([outer_r, outer_r*2]);
if (angle_real < 90)
square(outer_r);
}
}
/*
Make bent sheet metal
The bend list contains bend points and angles
as [length, angle]. The length refers to the length
of unbent metal before the bend.
The last angle can be undef, in which case no bend is produced.
Draws a 2d profile that must be extruded.
*/
module sheet_metal_2d(thickness, inner_radius, bend_list) {
task = first(bend_list);
straight = first(task);
angle = snd(task);
if (len(bend_list) > 1) {
outer_radius = inner_radius + thickness;
/* distance of bend */ /* distance due to straight
part rotation */
angle_abs = abs(angle);
// parameters for positive angles (around outside radius)
pos_bend_width = cos(angle_abs+270)*outer_radius;
pos_bend_height = sin(angle_abs+270)*outer_radius + outer_radius;
// parameters for negative angles (around inside radius, mirrored)
inv_bend_width = cos(90-angle_abs)*inner_radius;
inv_bend_height = sin(90-angle_abs)*inner_radius - inner_radius;
invert = angle < 0;
bend_width = invert ? inv_bend_width : pos_bend_width;
bend_height = invert ? inv_bend_height : pos_bend_height;
translate([bend_width, bend_height]) // to angle end
translate([straight, 0]) // to straight end
rotate(angle)
sheet_metal_2d(thickness, inner_radius, tail(bend_list));
} // endif
square([straight, thickness]);
if (angle != undef) {
translate([straight, 0])
bend_2d(thickness, inner_radius, angle);
}
}
/*
//bend_2d(3, 7, 60);
//bend_2d(3, 10, -70);
*sheet_metal_2d(1, 10, [ [20, -120], [30, 30] ]);
*linear_extrude(100)
sheet_metal_2d(5, 10, [ [40, 30], [60, -90], [10, -90], [40, -30], [60]
]);
*/
case = [ [200, 90], [200,90], [200, undef] ];
d = 2;
case_groove = [ [200-d, 90], [200-d*2,90], [200-d, undef] ];
difference() {
linear_extrude(135)
sheet_metal_2d(3, 10, case);
translate([0, d, 5])
linear_extrude(2) sheet_metal_2d(3, 10, case_groove);
}
--
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I think that instead of reducing the lengths of the groove you should just
reduce the bend radius by d instead.
I.e.
translate([0, d, 5])
linear_extrude(2) sheet_metal_2d(3, 10 - d, case);
You also need to set the convexity in the linear extrudes.
On 5 October 2016 at 10:16, Bananapeel lunatica.xiaoyu@gmail.com wrote:
I'm trying to make a groove in a bend, but I can't get it to have an even
depth. It gets shallower in the middle. Any ideas?
Code:
$fn=100;
function first(list) = list[0];
function tail(list) = [for (i=[1:len(list)-1]) list[i]];
function snd(list) = list[1];
module bend_2d(thickness, inner_radius, angle=90 /* 1->180 */) {
inner_r = inner_radius;
outer_r = inner_r + thickness;
angle_real = abs(angle);
invert = angle < 0;
mirror_vec_y = invert ? 1 : 0;
translate_y = invert ? thickness : 0;
translate([0, translate_y, 0]) // negative bends
mirror([0, mirror_vec_y, 0]) //
translate([0, outer_r])
difference() {
circle(outer_r);
circle(inner_r);
rotate(angle_real-90)
square(outer_r);
translate([-outer_r, -outer_r])
square([outer_r, outer_r*2]);
if (angle_real < 90)
square(outer_r);
}
}
/*
Make bent sheet metal
The bend list contains bend points and angles
as [length, angle]. The length refers to the length
of unbent metal before the bend.
The last angle can be undef, in which case no bend is produced.
Draws a 2d profile that must be extruded.
*/
module sheet_metal_2d(thickness, inner_radius, bend_list) {
task = first(bend_list);
straight = first(task);
angle = snd(task);
if (len(bend_list) > 1) {
outer_radius = inner_radius + thickness;
/* distance of bend */ /* distance due to straight
part rotation */
angle_abs = abs(angle);
// parameters for positive angles (around outside radius)
pos_bend_width = cos(angle_abs+270)*outer_radius;
pos_bend_height = sin(angle_abs+270)*outer_radius + outer_radius;
// parameters for negative angles (around inside radius, mirrored)
inv_bend_width = cos(90-angle_abs)*inner_radius;
inv_bend_height = sin(90-angle_abs)*inner_radius - inner_radius;
invert = angle < 0;
bend_width = invert ? inv_bend_width : pos_bend_width;
bend_height = invert ? inv_bend_height : pos_bend_height;
translate([bend_width, bend_height]) // to angle end
translate([straight, 0]) // to straight end
rotate(angle)
sheet_metal_2d(thickness, inner_radius, tail(bend_list));
} // endif
square([straight, thickness]);
if (angle != undef) {
translate([straight, 0])
bend_2d(thickness, inner_radius, angle);
}
}
/*
//bend_2d(3, 7, 60);
//bend_2d(3, 10, -70);
*sheet_metal_2d(1, 10, [ [20, -120], [30, 30] ]);
*linear_extrude(100)
sheet_metal_2d(5, 10, [ [40, 30], [60, -90], [10, -90], [40, -30],
[60]
]);
*/
case = [ [200, 90], [200,90], [200, undef] ];
d = 2;
case_groove = [ [200-d, 90], [200-d*2,90], [200-d, undef] ];
difference() {
linear_extrude(135)
sheet_metal_2d(3, 10, case);
translate([0, d, 5])
linear_extrude(2) sheet_metal_2d(3, 10, case_groove);
}
--
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Curved-groove-gets-wrong-depth-tp18537.html
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On 2016-10-05 11:16, Bananapeel wrote:
I'm trying to make a groove in a bend, but I can't get it to have an
even
depth. It gets shallower in the middle. Any ideas?
I did not study your code in all detail, it seemed complex to me.
Below you have another approach that creates something almost similar to
your code (the parameter values may be off). In this version the groove
depth is constant in the "bend".
$fn=100;
module rounded_square(width=10,height=10,radius=1)
{
hull() {
for(iy=[-1:2:1]) {
for(ix=[-1:2:1]) {
translate([ix*(width-radius),iy*(height-radius)])circle(radius);
}
}
}
}
module box(dx=10,dy=10,dz=10,th=1,inner_r=3)
{
linear_extrude(dz,convexity=10)
difference() {
rounded_square(dx+th,dy+th,inner_r+th);
rounded_square(dx,dy,inner_r);
}
}
width = 200;
height = width/2;
thickness = 3;
inner_radius = 10;
d = 1.5;
difference()
{
box(dx=width,dy=height,dz=135,th=thickness,inner_r=inner_radius);
union() {
translate([0,0,thickness])
linear_extrude(thickness,convexity=10)
rounded_square(width+d,height+d,radius=inner_radius+d);
translate([-250,0,0])cube([500,500,500],center=true);
}
}
Carsten Arnholm
Thanks, reducing the bend radius did the trick.
--
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