Inventor 2010: Plastic part design
Published Sun 10 May 2009
Plastic part design tools that have been available on Autodesk Labs are now integrated into Inventor's toolset.
Since the dawn of computers, one of their key benefits has been the ability to automate functions that would previously have been repetitive and laborious. Within the field of 3D CAD, this is perfectly illustrated in the creation of complex, but standardised features. In Inventor 2010 the new Plastic Part Design tools enable users to create standard, but complex, plastic part features such as grills, bosses, lips and grooves, automatically and intelligently. This not only saves time during the design cycle, but allows the user to concentrate on design challenges, rather than geometry wrangling issues.
Mounting bosses: If you open any injection moulded component you’ll find a series of plastic bosses. These are used to hold internal components in place (such as PCBs, ) and external forms together. Inventor provides a single feature operation for the creation of such features with a number of options to satisfy both functional and aesthetic requirements.
Grills and vents: The grill feature provides a simple dialog box that can help form geometry that is usually hard to build manually. A sketch is used to define the boundary edges, islands, ribs and spars within a single operation. If you’re working on a flat face, the sketch is added to that face, but when building a more complex surface, you can create a sketch and project it onto the surface. When working with non-linear profiles (using splines, circles and arcs) a good tip is to ensure that your sketch elements for ribs or spars extend beyond the profile boundary, otherwise you run the risk of having incorrectly terminated geometry.
Snap fit: These are common in many products and can be incredibly hard to build manually, particularly when they need to interface with complex forms. The Inventor snap fit feature provides an automated tool for creating both hook and loop type features. Once the basic positioning requirements are defined, the system builds the preview and allows adaptation of that form to achieve the required shape/functionality. This is done either by dialling in specifics or by dynamically dragging/dropping.
Lip and grooves: The lip function offers a set of tools for creating those features found where two or more components interface and the join needs to be closed out. This can be for functional or cosmetic reasons, or both. This single command will create both lips and grooves based on model edges or custom sketches (if you have something a little more complex). Users have full control over how the features are formed, and draft and recess or cutting dimensions can be added.
Rest features: The rest feature is used to create those odd features often found within plastic parts that are both adding and removing material at the same time. Commonly used to provide a mounting position for other components or an aesthetic feature, rests are typically incredibly hard to add manually. The new feature enables the use of profiles and linear distances for a flat face or a surface to create a more complex form. These features will respect all shells already applied where possible which should make design change more robust.
Rule-based fillets: Rule-based fillets differ from standard fillets in that they are not assigned to specific edges on a model. Instead they are typically assigned to a feature (such as a pocket or boss) and the system calculates which edges need to be filleted. The controls allow the user to define exactly how the system selects which edges are rounded off while it handles the rest. While for simple geometry this won’t make much difference, the power of rule-based definition comes into play when handling complex design change and complex forms, as the rule-based nature of the tool makes the rebuilding of those features much more robust.
Conclusion
The plastic part features bring a highly intelligent approach to defining commonly used features that are a part of almost every injection moulded component. If there's a criticism to be levelled at the tools at present, it’s that commonly used feature set-ups can’t be stored with ease. The good news is that features can be re-used within a single model or if the same forms are to be used on different products, they can be formalised and distributed as iFeatures. When you consider the widespread use of spark erosion within the moulding industry, the ability to reuse the same electrodes to create common features within a core or cavity is essential.
