Joystick Handle

Goal – Reproduce the Logitech Wingman Joystick Controller plastic handle shown. Create a parametric CAD model with Siemens Nx Ideas, then export an .stl file for 3D prototype print.

Joystick CAD Model Process

All handle geometry measurements taken by hand with calipers, ruler and dividers. I do not have a digital scanner and image files cannot be imported into the Nx Ideas modeler.

My original effort to duplicate the handle was a single, complex surface part with numerous coordinate systems to create structure. The grip and head portions of the part model went well, however, problems emerged while trying to create additional features. First, large portions of the part surface darkened into the background, so the part was only partially visible. Then, I could not zoom up to the part, (as often needed) like it was encased in glass. The problems only got worse as I tried to add features. After numerous troubleshooting iterations, it became clear that it is not possible to create a single-part, complex-surface CAD model such as this, with this software.

Solution to display issues involved converting the single joystick part into an assembly (illustration 1.0.0). Further, I used associative copy functionality of Nx Ideas to make it an assembly of copies. The joystick assembly-model performs perfectly now.

The joystick handle assembly contains a layout-handle part (made entirely of reference curves) and context-assemblies with source and target parts used to join, cut and shell the final handle part.

An exploded view in Illustration 1.0.0 below indicates joystick part instances assembly-joined and cut to final shape. Items 8 and 9 are created from Item 7. The two layout parts (items 2 and 10) are for design reference and do not have a direct effect on the part file exported to print.

Reference curves are used extensively in the joystick models for two reasons. Part handle surfaces are made entirely of lofted cross-sections and because reference curves can be re-used for any Boolean operation.

My first consideration when starting a model is design of a coordinate-system structure. Item 11 is the only part with just 2 coordinate systems(CS2 and CS3). In the rest of the parts, CS3 has children. The side boss has the most coordinate systems with 26 and is one of two models (the cutter-base) where CS3 is a grandfather. Model design will likely change, so CS part structures need to be adjustable as possible.

In this project, the second step is to create reference curves for lofted and extruded features. I begin with a sketch of the desired cross-sectional shape of necessary curves to create the features. Extruded features are simple joins or cutting operations (I did not use equations, draft angles, etc…). Lofted features, on the other hand, have multiple sketches in a number of planes to create part surfaces. To save time, I copied and pasted the first set of unique cross-section curves into other planes (where necessary) to create that feature. Shape of part surfaces are modified by changing values in coordinate-system property tables and dimensioned sketch curves.

With exception to the layout-handle model, made only of reference curves, the last step(s) to create joystick parts are loft and extrude operations. For further details, please click links in the part list below.

CAD Model Details with image galleries

Results

People at Computer Aided Technology CATI part printer and scanner supplier in Brookfield Wisconsin were kind enough to print the PVC plastic joystick handle prototype part in Illustration 1.1.0. Red stains on the part in bottom-view images are from modeling clay used to weight down the handle for pictures.

The prototype handle feels just like the original Logitech joystick, so I am happy with the general size of the final part. However, there are sharp creases in the printed handle at locations in the CAD model where parts intersect. The surface transitions need to be more smooth. The cobra-face shape could also be improved. Specifically, the straight edges of the cheeks should be curved round, especially down toward the tip of the nose.

Conclusion

Complex surfacing is much easier and faster with Siemens Nx. Youtube video demonstrations of the Nx Realize Shape surfacing tool are amazing. Coincidentally, there is one video to make a joystick handle. Realize Shape tool reminds me of the old SDRC Ideas surface and harness design shape tools, but is much more powerful. I love that picture files can be added to the Nx part for reference and how well class A surfaces can be stretched to shape while maintaining integrity. I look forward to using it.

Back to the Nx Ideas Joystick Handle. The next model iteration will have smoother edges and surface transitions. Also improvements to the face shape. I want to change sketch curve types in the layout-face part (illustrations 10.4.0 to 10.11.0) from two circular and supporting straight curves, to a parabola, for a more rounded and continuous-cut chin.

Tweak dimensions of cross-section curves in models to minimize rough surface transitions. Additional fillet-type parts (like item 4) in the assembly may further smooth surface transitions between joystick parts. Ideas may not be able to make complex surface models (such as this) as quickly and easily as Realize Shape, but I can approximate Nx surface models with Ideas to create an acceptable and error-free final product.

Finger ridges could also be added to the joystick handle grip. There are many possibilities.