constants.scad

LibFile: constants.scad

Constants for directions (used with anchoring), and for specifying line termination for use with geometry.scad.

To use, add the following lines to the beginning of your file:

include <BOSL2/std.scad>

File Contents

1. Section: General Constants

   • $slop – The slop amount to make printed items fit closely. 0.0 by default.
   • get_slop() – Returns the $slop value.
   • INCH – A constant containing the number of millimeters in an inch. 25.4
   • IDENT – A constant containing the 3D identity transformation matrix. ^[Mat]

2. Section: Directional Vectors

   • LEFT – The left-wards (X-) direction vector constant [-1,0,0].
   • RIGHT – The right-wards (X+) direction vector constant [1,0,0].
   • FRONT – The front-wards (Y-) direction vector constant [0,-1,0].
   • BACK – The backwards (Y+) direction vector constant [0,1,0].
   • BOTTOM – The down-wards (Z-) direction vector constant [0,0,-1].
   • TOP – The top-wards (Z+) direction vector constant [0,0,1].
   • CENTER – The center vector constant [0,0,0].
   • EDGE() – Named edge anchor constants
   • FACE() – Named face anchor constants

3. Section: Line specifiers

   • SEGMENT – A constant for specifying a line segment in various geometry.scad functions. [true,true]
   • RAY – A constant for specifying a ray line in various geometry.scad functions. [true,false]
   • LINE – A constant for specifying an unbounded line in various geometry.scad functions. [false,false]

Section: General Constants

Constant: $slop

Synopsis: The slop amount to make printed items fit closely. 0.0 by default.

Topics: Constants

Description:

A number of printers, particularly FDM/FFF printers, tend to be a bit sloppy in their printing. This has made it so that some parts won't fit together without adding a bit of extra slop space. That is what the $slop value is for. The value for this will vary from printer to printer. By default, we use a value of 0.00 so that parts should fit exactly for resin and other precision printers. This value is measured in millimeters. When making your own parts, you should add $slop to both sides of a hole that another part is to fit snugly into. For a loose fit, add 2*$slop to each side. This should be done for both X and Y axes. The Z axis will require a slop that depends on your layer height and bridging settings, and hole sizes. We leave that as a more complicated exercise for the user.

Note that the slop value is accessed using the get_slop() function. This function provides the default value of 0 if you have not set $slop. This approach makes it possible for you to set $slop in your programs without experiencing peculiar OpenSCAD issues having to do with multiple definitions of the variable. If you write code that uses $slop be sure to reference it using get_slop().

Calibration: To calibrate the $slop value for your printer, follow this procedure:

1. Print the Slop Calibration part from the example below.
2. Take the long block and orient it so the numbers are upright, facing you.
3. Take the plug and orient it so that the arrow points down, facing you.
4. Starting with the hole with the largest number in front of it, insert the small end of the plug into the hole.
5. If you can insert and remove the small end of the plug from the hole without much force, then try again with the hole with the next smaller number.
6. Repeat step 5 until you have found the hole with the smallest number that the plug fits into without much force.
7. The correct hole should hold the plug when the long block is turned upside-down.
8. The number in front of that hole will indicate the $slop value that is ideal for your printer.
9. Remember to set that slop value in your scripts after you include the BOSL2 library: ie: $slop = 0.15;
10. .
11. Note that the $slop value may be different using different materials even on the same printer.

Example 1: Slop Calibration Part.

include <BOSL2/std.scad>
min_slop = 0.00;
slop_step = 0.05;
holes = 8;
holesize = [15,15,15];
height = 20;
gap = 5;
l = holes * (holesize.x + gap) + gap;
w = holesize.y + 2*gap;
h = holesize.z + 5;
diff("holes")
cuboid([l, w, h], anchor=BOT) {
  for (i=[0:holes-1]) {
    right((i-holes/2+0.5)*(holesize.x+gap)) {
      s = min_slop + slop_step * i;
      tag("holes") {
        cuboid([holesize.x + 2*s, holesize.y + 2*s, h+0.2]);
        fwd(w/2-1) xrot(90) linear_extrude(1.1) {
          text(
            text=format_fixed(s,2),
            size=0.4*holesize.x,
            halign="center",
            valign="center"
          );
        }
      }
    }
  }
}
back(holesize.y*2.5) {
  difference() {
    union() {
      cuboid([holesize.x+10, holesize.y+10, 15], anchor=BOT);
      cuboid([holesize.x, holesize.y, 15+holesize.z], anchor=BOT);
    }
    up(3) fwd((holesize.y+10)/2) {
      prismoid([holesize.x/2,1], [0,1], h=holesize.y-6);
    }
  }
}

Example 2: Where to add $slop gaps.

include <BOSL2/std.scad>
$slop = 0.2;
difference() {
  square([20,12],center=true);
  back(3) square([10+2*$slop,11],center=true);
}
back(8) {
  rect([15,5],anchor=FWD);
  rect([10,8],anchor=BACK);
}
color("#000") {
  arrow_path = [[5.1,6.1], [6.0,7.1], [8,7.1], [10.5,10]];
  xflip_copy()
    stroke(arrow_path, width=0.3, endcap1="arrow2");
  xcopies(21) back(10.5) {
      back(1.8) text("$slop", size=1.5, halign="center");
      text("gap", size=1.5, halign="center");
  }
}

---

Function: get_slop()

Synopsis: Returns the $slop value.

Topics: Slop

See Also: $slop

Usage:

• slop = get_slop();

Description:

Returns the current $slop value, or the default value if the user did not set $slop. Always acess the $slop variable using this function.

---

Constant: INCH

Synopsis: A constant containing the number of millimeters in an inch. 25.4

Topics: Constants

Description:

The number of millimeters in an inch.

Example 1:

include <BOSL2/std.scad>
square(2*INCH, center=true);

Example 2:

include <BOSL2/std.scad>
cube([4,3,2.5]*INCH, center=true);

---

Constant: IDENT

Synopsis: A constant containing the 3D identity transformation matrix. ^[Mat]

Topics: Constants, Affine, Matrices, Transforms

See Also: ident()

Description:

Identity transformation matrix for three-dimensional transforms. Equal to ident(4).

---

Section: Directional Vectors

Vectors useful for rotate(), mirror(), and anchor arguments for cuboid(), cyl(), etc.

Constant: LEFT

Synopsis: The left-wards (X-) direction vector constant [-1,0,0].

Topics: Constants, Vectors

See Also: RIGHT, FRONT, BACK, TOP, BOTTOM, CENTER

Description:

Vector pointing left. [-1,0,0]

Example 1: Usage with anchor

include <BOSL2/std.scad>
cuboid(20, anchor=LEFT);

---

Constant: RIGHT

Synopsis: The right-wards (X+) direction vector constant [1,0,0].

Topics: Constants, Vectors

See Also: LEFT, FRONT, BACK, TOP, BOTTOM, CENTER

Description:

Vector pointing right. [1,0,0]

Example 1: Usage with anchor

include <BOSL2/std.scad>
cuboid(20, anchor=RIGHT);

---

Constant: FRONT

Aliases: FWD, FORWARD

Synopsis: The front-wards (Y-) direction vector constant [0,-1,0].

Topics: Constants, Vectors

See Also: LEFT, RIGHT, BACK, TOP, BOTTOM, CENTER

Description:

Vector pointing forward. [0,-1,0]

Example 1: Usage with anchor

include <BOSL2/std.scad>
cuboid(20, anchor=FRONT);

---

Constant: BACK

Synopsis: The backwards (Y+) direction vector constant [0,1,0].

Topics: Constants, Vectors

See Also: LEFT, RIGHT, FRONT, TOP, BOTTOM, CENTER

Description:

Vector pointing back. [0,1,0]

Example 1: Usage with anchor

include <BOSL2/std.scad>
cuboid(20, anchor=BACK);

---

Constant: BOTTOM

Aliases: BOT, DOWN

Synopsis: The down-wards (Z-) direction vector constant [0,0,-1].

Topics: Constants, Vectors

See Also: LEFT, RIGHT, FRONT, BACK, TOP, CENTER

Description:

Vector pointing down. [0,0,-1]

Example 1: Usage with anchor

include <BOSL2/std.scad>
cuboid(20, anchor=BOTTOM);

---

Constant: TOP

Aliases: UP

Synopsis: The top-wards (Z+) direction vector constant [0,0,1].

Topics: Constants, Vectors

See Also: LEFT, RIGHT, FRONT, BACK, BOTTOM, CENTER

Description:

Vector pointing up. [0,0,1]

Example 1: Usage with anchor

include <BOSL2/std.scad>
cuboid(20, anchor=TOP);

---

Constant: CENTER

Aliases: CTR, CENTRE

Synopsis: The center vector constant [0,0,0].

Topics: Constants, Vectors

See Also: LEFT, RIGHT, FRONT, BACK, TOP, BOTTOM

Description:

Zero vector. Centered. [0,0,0]

Example 1: Usage with anchor

include <BOSL2/std.scad>
cuboid(20, anchor=CENTER);

---

Function: EDGE()

Synopsis: Named edge anchor constants

Topics: Constants, Attachment

Usage:

• EDGE(i)
• EDGE(direction,i)

Description:

A shorthand for the named anchors "edge0", "top_edge0", "bot_edge0", etc. Use EDGE(i) to get "edge". Use EDGE(TOP,i) to get "top_edge" and use EDGE(BOT,i) to get "bot_edge(i)". You can also use EDGE(CTR,i) to get "edge" and you can replace TOP or BOT with simply 1 or -1.

---

Function: FACE()

Synopsis: Named face anchor constants

Topics: Constants, Attachment

Usage:

• FACE(i)

Description:

A shorthand for the named anchors "face0", "face1", etc.

---

Section: Line specifiers

Used by functions in geometry.scad for specifying whether two points are treated as an unbounded line, a ray with one endpoint, or a segment with two endpoints.

Constant: SEGMENT

Synopsis: A constant for specifying a line segment in various geometry.scad functions. [true,true]

Topics: Constants, Lines

See Also: RAY, LINE

Description:

Treat a line as a segment. [true, true]

Example 1: Usage with line_intersection:

include <BOSL2/std.scad>
line1 = 10*[[9, 4], [5, 7]];
line2 = 10*[[2, 3], [6, 5]];
isect = line_intersection(line1, line2, SEGMENT, SEGMENT);

---

Constant: RAY

Synopsis: A constant for specifying a ray line in various geometry.scad functions. [true,false]

Topics: Constants, Lines

See Also: SEGMENT, LINE

Description:

Treat a line as a ray, based at the first point. [true, false]

Example 1: Usage with line_intersection:

include <BOSL2/std.scad>
line = [[-30,0],[30,30]];
pt = [40,25];
closest = line_closest_point(line,pt,RAY);

---

Constant: LINE

Synopsis: A constant for specifying an unbounded line in various geometry.scad functions. [false,false]

Topics: Constants, Lines

See Also: RAY, SEGMENT

Description:

Treat a line as an unbounded line. [false, false]

Example 1: Usage with line_intersection:

include <BOSL2/std.scad>
line1 = 10*[[9, 4], [5, 7]];
line2 = 10*[[2, 3], [6, 5]];
isect = line_intersection(line1, line2, LINE, SEGMENT);

---