Globoid worm and gear combi 2.0 OpenSCAD

thingiverse

In my post [globoid worm gear drive - parametric OpenSCAD code with large ratio range](https://www.thingiverse.com/thing:2776688) from 2018 I showed a subtractive manufacturing approach that models a globoid worm gear couple by use of OpenSCADs mighty Boolean operations. The fully parametrized code mainly uses two major subtractions, a first subtraction that cuts a worm by differencing a helically extruded 2D gear spline from a cylinder, and a second subtraction that cuts a single gear tooth by differencing 3 extreme worm positions from an appropriate blank. This thooth is then cloned and unioned into a full-blown gear. While the code works in F5 preview mode (CSG), it executes quite slow in F6 render mode (CGAL) and also has to fight with numerical issues (mainly because of excessive vertex refinement) that can lead to errors during such a render operation. Meanwhile I have simplified the method to use only the second major subtraction, while the worm, and especially the part of it used as cutting tool, is explicitly calculated (which leads to a much lower vertex count). As a result it renders much faster in both modes and the objects it creates are much less prone to malformation from numerical instabilities. The code makes heavy use of two of my favorite libraries. 1. The [ShortCuts.scad library](https://www.thingiverse.com/thing:644830) defines an extensive set of abbreviations for most of the OpenSCAD language primitives as well as a set of makros for more complex operations useful in the daily programming life. Because of its mnemonic naming convention and the help_shortcuts() function which outputs a *cheat sheet* to the console, they are easy to remember and understand. Sorry for that, but it simplifies things so much and increases the readability of the code significantly once you are used to it. Here a short excerpt: ``` union() -> U() difference() -> D() translate() -> T(), Tx(), Ty(), Tz() scale() ->S(), Sx(), Sy(), Sz() rotate() -> R(), Rx(), Ry(), Rz() forN(r, N) place N clones of children() around a circle with radius r ... ``` 2. The [Naca_sweep.scad library](https://www.thingiverse.com/thing:900137) contains all the functionality to skin (=extrude) objects on the basis of an affine representation explicitly calculated by OpenSCAD functions. The main function sweep() expects a sequence of polygons each properly placed in 3D space, which it triangulates and feeds into polyhedron(). This lib also defines identically named functions T(), Tx(), ... and so on for respective operations over affine representations (lists of 2D or 3D points). The code should be easy to handle. It contains a parameter section, tons of comments and all the lines (commented out) needed to produce a full blown system, print output, single components and visualising stuff like the profiles() module that visualises the clearing parameter, or animation that allows to output an animated sequence of a drive. Note that animation() reads (and therefore expects) previously exported STL objects to speed up display to a bearable extent.