Blog Published: 07/12/2018

Blogger - Graham Mansfield

Autodesk Inventor Professional - Where would we be without rules?

Designing with Parameters
Most modern mechanical CAD software employs parametrics, a method of driving geometry with parameters so that when the parameters change, the geometry also changes. The ability to create relationships between parameters using equations is also standard. With parametrics, design modifications can be performed quickly, without the redrawing required by non-parametric CAD packages. Parametric modifications can be performed in several ways: with a spreadsheet, script, or by manually changing the dimensional values associated with a digital model. A single change can ripple through a large model and all the downstream models that consume it.

Standard Parametric Capabilities
There are numerous capabilities which enable you to:
  • Define the size and shape of features, and control the relative positions of components within assemblies. Specify the size of a cover plate as: Height = Width/16 with equations that defines the relationships between the parameters.
  • Define parameters relating dimensions to functional requirements. This includes the cross-sectional area of a part to have certain proportions and withstand a certain load: Area = Load/Material Strength*Factor of Safety
  • Link a spreadsheet to a part or assembly and drive the parameter values from cells in the spreadsheet. Parameters can also be exported to a bill of materials (BOM) and a parts list.
Autodesk Inventor Professional has a parameters tool for viewing and editing parameters, creating user-defined parameters and linking to a spreadsheet. Model parameters are created automatically when you define a sketch dimension, create a feature, or add an assembly constraint.

With Inventor Professional, you can create user parameters which are more general than model parameters, which can be used to convey functional requirements. User parameters can also be driven by a spreadsheet. You can use user parameters in equations. If you use the same parameters in many parts, such as force or material, you can define the parameters in templates used to create new part files. Custom parameters are created through the application programming interface (API). However, Inventor Professional does also have the capability to handle boolean, string and multi-value parameters (since Inventor 2011).

Designing with iLogic
As useful as parametric modelling can be, it also has limitations, as equations and relationships between numbers can never fully define the variations within a family or range of products. Take a simple panel used on a building fa├žade for instance. Parametrics takes care of the resizing and shaping of the panel with no problem, but what about if we need to add stiffeners above a certain panel size, change the fastener arrangement when the panel is a particular shape, or quickly switch between a number of different flange styles. This is where iLogic excels. As we often say – if the designer can form a logical description in plain English for how they wish the model to be configured, then this can be translated into an iLogic rule. So we are seeing design rules that previously resided in the experienced CAD designer’s mind / Excel spreadsheet / Word document, embedded in the CAD model, or even controlled globally - independent of each model - courtesy of external iLogic rules. The designers brain space is now free for more innovation, and importantly, the company is not vulnerable when that designer is unavailable for any reason – the intelligence is in the models.

iLogic is not primarily a generative tool, meaning that it does not normally create geometry on an individual component level. However, there are some exciting new iLogic capabilities in Inventor Professional 2019 that allow generative assembly design – assemblies can be constructed from scratch using the components and constraints determined by iLogic rules.

Does iLogic have limitations? While it goes beyond the traditional capabilities of parametric design and can greatly improve your sales engineering and time to quote, it is not an engineer-to-order (ETO) tool. Historically, ETO packages have been used to create products with customer specifications that require unique engineering design or significant customisation and usually result in a unique set of components, sales quotes, bills of material and production routings.

Embracing Configurator 360
This is where Autodesk’s Configurator 360 platform can take the iLogic model and publish to the Autodesk cloud service, delivering benefits such as a catalogue branded product configurator in a website, downloadable content on demand such as RFA, IFC, STP, PNG and more, request for quotation facility, all instantly deployable without the need for dedicated servers. It’s certainly a valuable way to start to capture customer trends and requirements for popular products which could assist in helping you keep stocks under control.

Should you wish to explore what’s possible with one of your models or assemblies, then please do not hesitate to contact Excitech’s manufacturing team for more information on 01992 807444

About the author

  • Graham Mansfield

Graham Mansfield

Business Manager - Manufacturing

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