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), I showed a subtractive manufacturing approach that models a globoid worm gear couple by using OpenSCAD's powerful Boolean operations. The fully parameterized code mainly relies on two major subtractions, the first subtraction cutting a worm by differencing a helically extruded 2D gear spline from a cylinder, and the second subtraction cutting a single gear tooth by differencing three extreme worm positions from an appropriate blank. This tooth is then cloned and unioned into a full-blown gear. While the code functions in F5 preview mode (CSG), it executes quite slowly in F6 render mode (CGAL) and also struggles with numerical issues, mainly due to excessive vertex refinement, which 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, resulting in a much lower vertex count. As a result, it renders much faster in both modes, and the objects it creates are less prone to malformation from numerical instabilities. The code heavily utilizes two of my favorite libraries: 1. The [ShortCuts.scad library](https://www.thingiverse.com/thing:644830) defines an extensive set of abbreviations for most OpenSCAD language primitives as well as a set of macros for more complex operations useful in daily programming life. Its mnemonic naming convention and the help_shortcuts() function, which outputs a cheat sheet to the console, make them easy to remember and understand. Here's 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 based on 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(), ... 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 visualizing stuff like the profiles() module that visualizes the clearing parameter, or animation that allows outputting 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.