Tutorial Attachment Edge Profiling

Using Attachment for Edge Profiling

You can use attachment in various ways to create edge profiles on objects. One method is to simply attach an edge mask to the edge of a parent object while using diff() so that the mask creates the desired edge profile. Most objects set the $edge_angle and $edge_length variables so make this easier to do.

Another way to apply edge treatments is to use some specialized modules for applying masks. Modules such as edge_mask() can for working with 3D masks, which may potentially change across their length. Modules like edge_profile() can extrude a 2D profile along specified edges.

3D Masking Attachments

To make it easier to mask away shapes from various edges of an attachable parent shape, there are a few specialized alternatives to the attach() and position() modules.

edge_mask()

If you have a 3D mask shape that you want to difference away from various edges, you can use the edge_mask() module. This module will take a vertically oriented shape, and will rotate and move it such that the BACK, RIGHT (X+,Y+) side of the shape will be aligned with the given edges. The shape will be tagged as a "remove" so that you can use diff() with its default "remove" tag. For example, here's a shape for rounding an edge:

include <BOSL2/std.scad>
module round_edge(l,r) difference() {
    translate([-1,-1,-l/2])
        cube([r+1,r+1,l]);
    translate([r,r])
        cylinder(h=l+1,r=r,center=true, $fn=quantup(segs(r),4));
}
round_edge(l=30, r=19);

You can use that mask to round various edges of a cube:

include <BOSL2/std.scad>
module round_edge(l,r) difference() {
    translate([-1,-1,-l/2])
        cube([r+1,r+1,l]);
    translate([r,r])
        cylinder(h=l+1,r=r,center=true, $fn=quantup(segs(r),4));
}
diff()
cube([50,60,70],center=true)
    edge_mask([TOP,"Z"],except=[BACK,TOP+LEFT])
        round_edge(l=71,r=10);

corner_mask()

If you have a 3D mask shape that you want to difference away from various corners, you can use the corner_mask() module. This module will take a shape and rotate and move it such that the BACK RIGHT TOP (X+,Y+,Z+) side of the shape will be aligned with the given corner. The shape will be tagged as a "remove" so that you can use diff() with its default "remove" tag. For example, here's a shape for rounding a corner:

include <BOSL2/std.scad>
module round_corner(r) difference() {
    translate(-[1,1,1])
        cube(r+1);
    translate([r,r,r])
        spheroid(r=r, style="aligned", $fn=quantup(segs(r),4));
}
round_corner(r=10);

You can use that mask to round various corners of a cube:

include <BOSL2/std.scad>
module round_corner(r) difference() {
    translate(-[1,1,1])
        cube(r+1);
    translate([r,r,r])
        spheroid(r=r, style="aligned", $fn=quantup(segs(r),4));
}
diff()
cube([50,60,70],center=true)
    corner_mask([TOP,FRONT],LEFT+FRONT+TOP)
        round_corner(r=10);

Mix and Match Masks

You can use edge_mask() and corner_mask() together as well:

include <BOSL2/std.scad>
module round_corner(r) difference() {
    translate(-[1,1,1])
        cube(r+1);
    translate([r,r,r])
        spheroid(r=r, style="aligned", $fn=quantup(segs(r),4));
}
module round_edge(l,r) difference() {
    translate([-1,-1,-l/2])
        cube([r+1,r+1,l]);
    translate([r,r])
        cylinder(h=l+1,r=r,center=true, $fn=quantup(segs(r),4));
}
diff()
cube([50,60,70],center=true) {
    edge_mask("ALL") round_edge(l=71,r=10);
    corner_mask("ALL") round_corner(r=10);
}

2D Profile Mask Attachments

While 3D mask shapes give you a great deal of control, you need to make sure they are correctly sized, and you need to provide separate mask shapes for corners and edges. Often, a single 2D profile could be used to describe the edge mask shape (via linear_extrude()), and the corner mask shape (via rotate_extrude()). This is where edge_profile(), corner_profile(), and face_profile() come in.

edge_profile()

Using the edge_profile() module, you can provide a 2D profile shape and it will be linearly extruded to a mask of the appropriate length for each given edge. The resultant mask will be tagged with "remove" so that you can difference it away with diff() with the default "remove" tag. The 2D profile is assumed to be oriented with the BACK, RIGHT (X+,Y+) quadrant as the "cutter edge" that gets re-oriented towards the edges of the parent shape. A typical mask profile for chamfering an edge may look like:

include <BOSL2/std.scad>
mask2d_roundover(10);

Using that mask profile, you can mask the edges of a cube like:

include <BOSL2/std.scad>
diff()
cube([50,60,70],center=true)
   edge_profile("ALL")
       mask2d_roundover(10);

corner_profile()

You can use the same profile to make a rounded corner mask as well:

include <BOSL2/std.scad>
diff()
cube([50,60,70],center=true)
   corner_profile("ALL", r=10)
       mask2d_roundover(10);

face_profile()

As a simple shortcut to apply a profile mask to all edges and corners of a face, you can use the face_profile() module:

include <BOSL2/std.scad>
diff()
cube([50,60,70],center=true)
   face_profile(TOP, r=10)
       mask2d_roundover(10);