OpenSCAD User Manual/MCAD

NOTE: WIP

Overview of MCAD Library

Download source: github dot com/openscad/MCAD

The MCAD library contains components commonly used in designing and making mockup mechanical designs. It is currently unfinished and you can expect some API changes, however many things are already working.

This library was created by various authors as named in the individual files' comments. All the files are licensed under the LGPL 2.1 (see creativecommons dot org/licenses/LGPL/2.1/ or the included file lgpl-2.1.txt), some of them allow distribution under more permissive terms (as described in the files' comments).

Usage

You can import these files in your scripts with use <MCAD/filename.scad>, where 'filename' is one of the files listed below like 'motors' or 'servos'. Some files include useful constants that are available with include <MCAD/filename.scad>, which should be safe to use on all included files (ie. no top level code should create geometry). (There is a bug/feature that prevents including constants from files that "include" other files - see the openscad mailing list archives for more details. Since the maintainers aren't very responsive, may have to work around this somehow)

If you host your project in git, you can do git submodule add URL PATH in your repo to import this library as a git submodule for easy usage. Then you need to do a git submodule update --init after cloning. When you want to update the submodule, do cd PATH; git checkout master; git pull. See git help submodule for more info.

Currently Provided Tools:

• regular_shapes.scad
  • regular polygons, ie. 2D
  • regular polyhedrons, ie. 3D
• involute_gears.scad (on Thingiverse):
  • gear()
  • bevel_gear()
  • bevel_gear_pair()
• gears.scad (Old version):
  • gear(number_of_teeth, circular_pitch OR diametrial_pitch, pressure_angle OPTIONAL, clearance OPTIONAL)
• motors.scad:
  • stepper_motor_mount(nema_standard, slide_distance OPTIONAL, mochup OPTIONAL)

Tools (alpha and beta quality):

• nuts_and_bolts.scad: for creating metric and imperial bolt/nut holes
• bearing.scad: standard/custom bearings
• screw.scad: screws and augers
• materials.scad: color definitions for different materials
• stepper.scad: NEMA standard stepper outlines
• servos.scad: servo outlines
• boxes.scad: box with rounded corners
• triangles.scad: simple triangles
• 3d_triangle.scad: more advanced triangles

Very generally useful functions and constants:

• math.scad: general math functions
• constants.scad: mathematical constants
• curves.scad: mathematical functions defining curves
• units.scad: easy metric units
• utilities.scad: geometric functions and misc. useful stuff
• teardrop.scad (www dot thingiverse dot com/thing:3457): parametric teardrop module
• shapes.scad: DEPRECATED simple shapes by Catarina Mota
• polyholes.scad: holes that should come out well when printed

Other:

• alphabet_block.scad
• bitmap.scad
• letter_necklace.scad
• name_tag.scad
• height_map.scad
• trochoids.scad
• libtriangles.scad
• layouts.scad
• transformations.scad
• 2Dshapes.scad
• gridbeam.scad
• fonts.scad
• unregular_shapes.scad

Umetric_fastners.scad

• lego_compatibility.scad
• multiply.scad
• hardware.scad

External utils that generate and process openscad code:

• openscad_testing.py: testing code, see below
• openscad_utils.py: code for scraping function names etc.

MCAD/regular_shapes.scad

2D regular shapes

This library is no longer the best way to create regular polygons — you can do this more efficiently with:

circle(radius, $fn=numberOfSides);

The regular polygon functions will be retained for compatibility and readability.

n-gons 2D shapes

Example:

Screenshot of regular 2D shapes with varying number of sides

use <MCAD/regular_shapes.scad>

radius = 5;

translate([00,0,0]) triangle(radius);
translate([10,0,0]) pentagon(radius);
translate([20,0,0]) hexagon(radius);
translate([30,0,0]) heptagon(radius);
translate([40,0,0]) octagon(radius);
translate([50,0,0]) nonagon(radius);
translate([60,0,0]) decagon(radius);
translate([70,0,0]) hendecagon(radius);
translate([80,0,0]) dodecagon(radius);

hexagon(radius, diameter, across_flats)

Specify one of these three arguments giving the radius from center to a vertex, the diameter between opposite vertices, or as across_flats, the distance between opposite sides.

ring(inside_diameter, thickness)

Example:

Screenshot of ring shape

use <MCAD/regular_shapes.scad>
ring(10, 5);

ellipse(width, height)

Example:

Screenshot of ellipse()

use <MCAD/regular_shapes.scad>
ellipse(30, 15);

egg_outline(width, length)

Example:

Screenshot of Egg_outline()

use <MCAD/regular_shapes.scad>
egg_outline(10, 15);

3D regular shapes

cone(height, radius, center = false)

Example:

Screenshot of cone()

use <MCAD/regular_shapes.scad>
cone(20, 10);

oval_prism(height, rx, ry, center = false)

This is a cylinder with unequal x and y dimensions specified here as radii.

Example:

Screenshot of oval_prism()

use <MCAD/regular_shapes.scad>
oval_prism(20, 15, 5);

oval_tube(height, rx, ry, wall, center = false)

Difference of two scaled cylinders. Note this does not give a wall of even thickness if the cylinders are elliptical -- you would need to use offset for that.

Example:

Screenshot of oval_tube()

use <MCAD/regular_shapes.scad>
oval_tube(20, 10, 5, 1);

cylinder_tube(height, radius, wall, center = false)

Example:

Screenshot of cylinder_tube()

use <MCAD/regular_shapes.scad>
cylinder_tube(20, 10, 1);

triangle_prism(height,radius)

Example:

Screenshot of triangle_prism()

use <MCAD/regular_shapes.scad>
triangle_prism(20,10);

triangle_tube(height,radius,wall)

Example:

Screenshot of triangle_tube()

use <MCAD/regular_shapes.scad>
triangle_tube(20,10, 1);

pentagon_prism(height,radius)

Solid pentagon shape

pentagon_tube(height,radius,wall)

Hollow pentagon shape

hexagon_prism(height,radius)

Similar to above

hexagon_tube(height,radius,wall)

Similar to above

heptagon_prism(height,radius)

Similar to above

heptagon_tube(height,radius,wall)

Similar to above

octagon_prism(height,radius)

Similar to above

octagon_tube(height,radius,wall)

Similar to above

nonagon_prism(height,radius)

Similar to above

decagon_prism(height,radius)

Similar to above

hendecagon_prism(height,radius)

Similar to above

dodecagon_prism(height,radius)

Similar to above

torus(outerRadius, innerRadius)

Example:

Screenshot of torus()

use <MCAD/regular_shapes.scad>
torus(30, 15);

torus2(r1, r2)

Example:

Screenshot of torus2()

use <MCAD/regular_shapes.scad>
torus2(30, 5);

oval_torus(inner_radius, thickness=[0, 0])

Example:

Screenshot of oval_torus()

use <MCAD/regular_shapes.scad>
oval_torus(20, thickness=[4, 8], $fn=50);

triangle_pyramid(radius)

Example:

Screenshot of triangle_pyramid()

use <MCAD/regular_shapes.scad>
triangle_pyramid(20);

square_pyramid(base_x, base_y, height)

Example:

Screenshot of square_pyramid()

use <MCAD/regular_shapes.scad>
square_pyramid(10, 20, 30);

egg(width, length)

NOTE: I couldn't get egg() to work at the time of creating this document.

To Fix egg(): replace 'cube(' with 'square(' at line 254 pos 40 on regular_shapes.scad

MCAD/involute_gears.scad

NOTE regarding bevel gears: Two bevel gears mesh when they have the same cone distance, circular pitch (measured at the cone distance), and pressure angle.

bevel_gear_pair()

bevel_gear_pair (gear1_teeth = 41, gear2_teeth = 7, axis_angle = 90, outside_circular_pitch=1000)

bevel_gear()

bevel_gear (
    number_of_teeth=11, 
    cone_distance=100, 
    face_width=20, 
    outside_circular_pitch=1000, 
    pressure_angle=30,
    clearance = 0.2, 
    bore_diameter=5,
    gear_thickness = 15, 
    backlash = 0, 
    involute_facets=0, 
    finish = -1) 

    Bevel Gear Finishing Options:
    bevel_gear_flat = 0;
    bevel_gear_back_cone = 1;

More INFO:

• number_of_teeth number of teeth
• cone_distance Important to the angle of your gear teeth. See Cone Distance
• pressure_angle Part of the terms that, taken together, make up the gear tooth profile. See Pressure_angle
• bore_diameter Size of hole in middle of gear
• outside_circular_pitch Roughly, this is the circumference of the gear. This is one of the most important measurements, and is worth looking up more precisely. See Pitch_circle. This indirectly controls the gear radius. Your gear's overall diameter is roughly the outside_circle_pitch / 360 * number_of_teeth. For example, 1000 / 360 * 36 would result in a gear approx 100mm in diameter.
• finish Special parameter. Setting this equal to bevel_gear_flat (0) vs bevel_gear_back_cone (1) changes whether your gear looks like a flat bevel gear, or whether a back cone (similar to the 'cone' before) is used. See Back Cone
• gear_thickness Bit of a misnomer. This is not the "typical" gear definition of thickness. Instead, it has nothing to do with the teeth of your gear and instead asks how tall of a cylinder the gear teeth should be placed on top oc

gear()

gear (
    number_of_teeth=15,
    circular_pitch=false, diametral_pitch=false,
    pressure_angle=28,
    clearance = 0.2,
    gear_thickness=5,
    rim_thickness=8,
    rim_width=5,
    hub_thickness=10,
    hub_diameter=15,
    bore_diameter=5,
    circles=0,
    backlash=0,
    twist=0,
    involute_facets=0,
    flat=false)

More INFO:

• number_of_teeth number of teeth. Note that since circumference=2πr∝number_of_teeth the distance_between_gears∝total_number_of_teeth*pitch Basically if you have two gears, any two gears with the same sum number of teeth also fit at that distance.
• circular_pitch, diametral_pitch proportional to the size of the teeth. (TODO proportionality constant)
• pressure_angle
• clearance
• flat Makes the module a 2d object. This way you can `linear_extrude` it yourself.

The module has a lot of 'extra' features.

• rim_thickness Thickness of edges(where it contacts.
• gear_thickness Thickness inside, it cuts out a circle to make the inside flatter if smaller than rim thickness.
• rim_width How far from the edge the gear is made at the
• hub_thickness, hub_diameter, thicker bit in the center.
• bore_diameter hole in center, for an axle, for instance.=
• circles Makes the given number of holes around the center to save material
• backlash
• twist Twist in linear extruding. Used for making helical gears. (e.g.chevron/herringbone or worm drive gears)
• involute_facets

Example:

 gear(number_of_teeth=20, circular_pitch=200, flat=true);

Tests

test_gears()

Example:

Demonstration of output from test_gears()

use <MCAD/involute_gears.scad>
test_gears();

test_meshing_double_helix()

Example:

Screenshot of output of testing_meshing_double_helix()

use <MCAD/involute_gears.scad>
test_meshing_double_helix();

test_bevel_gear()

Example:

Screenshot of test_bevel_gear

use <MCAD/involute_gears.scad>
test_bevel_gear();

test_bevel_gear_pair()

Example:

Screenshot of test_bevel_gear_pair()

use <MCAD/involute_gears.scad>
test_bevel_gear_pair();

test_backlash()

Example:

Screenshot of test_backlash()

use <MCAD/involute_gears.scad>
test_backlash ();

MCAD/teardrop.scad

The teardrop shape can be used to make printing vertical holes easier for the 3d printer by avoiding steep overhangs.

Example:

Screenshot of Teardrop Shaped Cutouts

 use <MCAD/teardrop.scad>
 
 difference() {
     cube([5, 60, 40], center=true);
     translate([0, -15, 0]) teardrop(radius=6, length=20, angle=90);
     translate([0,   0, 0]) teardrop(radius=5, length=20, angle=60);
     translate([0,  15, 0]) teardrop(radius=4, length=20, angle=45);
 }

MCAD/stepper.scad

The stepper's shaft is pointing in negative Z-direction. The stepper's round front plate is flush with the Z-Plane.

Example:

Screenshot of Stepper Motors

 include <MCAD/stepper.scad>
 
 for (size = [NemaShort, NemaMedium, NemaLong]) {  
   translate([50, size*100,0])  motor(Nema34, size, dualAxis=false);
   translate([150,size*100,0])  motor(Nema23, size, dualAxis=false);
   translate([250,size*100,0])  motor(Nema17, size, dualAxis=true);
   translate([350,size*100,0])  motor(Nema14, size, dualAxis=true);
   translate([450,size*100,0])  motor(Nema11, size, dualAxis=true);
   translate([550,size*100,0])  motor(Nema08, size, dualAxis=true);
 }
 % translate([0, 150, 0.01]) cube([600, 200, 0.1]); 

MCAD/nuts_and_bolts.scad

Example:

Screenshot of M3 capscrew, nut, bolt, and clearance holes

 use <MCAD/nuts_and_bolts.scad>
 include <MCAD/units.scad>

 $fn=50;

 //M3 is an alias for 3. It is defined in units.scad

 // cap screw
 boltHole(M3, length=10);
 // clearance hole for cap screw
 %translate([0, 7, 0])
   boltHole(M3, length=10, tolerance=0.3);
 // nut
 translate([7, 0, 0]) 
   nutHole(M3, tolerance=0.0);
 // nut hole
 %translate([7, 7, 0]) 
   nutHole(M3, tolerance=0.3);
 // bolt
 translate([14, 0, 0]){
    boltHole(M3, length=10);
    rotate([180,0,0])nutHole(M3, tolerance=0.0);}

MCAD/2Dshapes.scad

Example:

Screenshot of various 2D shapes

 use <MCAD/2Dshapes.scad>
 
 ellipse(width=50, height=80);
 
 translate([100, 0, 0]) pieSlice([50, 100], start_angle=0, end_angle=250);
 
 translate([210, 0, 0]) donutSlice(20,50,0,300);
 
 translate([320, 0, 0]) ngon(6, 50, center=false);