Engineering design is full of repetitive tasks: updating a family of parts to a new dimension standard, generating variants of a product for different customer specifications, or ensuring that a set of interrelated parameters remains consistent when one changes. Done manually, these tasks consume significant engineering time and introduce the risk of human error. Inventor’s iLogic feature is designed to automate exactly this type of work — and it is accessible to engineers who are not software developers.
Autodesk Inventor Professional is available from GetRenewedTech for €46.99 per year. iLogic is included in Inventor Professional (not Inventor LT), making it available to any user of the full Inventor package.
What Is iLogic?
iLogic is a rule-based automation system built into Inventor. Rules are written in a simplified version of Visual Basic (VB.NET), but Inventor provides a comprehensive library of built-in functions that mean most common automation tasks require minimal or no direct coding — you reference parameters by name and the syntax is largely intuitive even without programming experience.
iLogic rules can be triggered:
- When a parameter changes
- When a specific parameter exceeds a threshold
- When a file is opened or saved
- Manually, from a user interface form you create yourself
Understanding Parameters Before Writing Rules
iLogic works with Inventor’s parameters. Before writing any rules, open the Parameters dialog (Manage > Parameters) and review the user parameters and model parameters already in your file. These are the variables your rules will read and write. Good parameter naming is essential: a parameter named ShaftDiameter is far easier to work with in iLogic than one named d0.
Rename key parameters in the Parameters dialog before creating rules. The parameter name is what you will use in all your rule code, and changing it later requires updating all references.
Creating Your First Rule
Open the iLogic browser via Tools > iLogic > iLogic Browser. Right-click in the Rules pane and select Add Rule. Give it a descriptive name like Wall Thickness Validation. The iLogic code editor opens with a simple VB.NET editor.
A simple rule that ensures wall thickness is always at least 3mm might look like this:
If WallThickness < 3 Then
WallThickness = 3
MessageBox.Show("Wall thickness has been set to the minimum of 3mm.")
End IfClick the green Run button to test the rule. If WallThickness is a user parameter in your file, iLogic will evaluate the condition and take action accordingly.
Driving Suppression of Features
One of the most powerful iLogic applications is controlling which features are active in a model based on a parameter value. For example, a part that comes in a standard and reinforced variant might have additional ribs in the reinforced version. Rather than maintaining two separate files, use a parameter called Variant (with values Standard or Reinforced) and a rule that suppresses or unsuppresses the rib features accordingly:
If Variant = "Reinforced" Then
Feature.IsActive("ReinforcingRibs") = True
Else
Feature.IsActive("ReinforcingRibs") = False
End IfThis technique — driving feature suppression from a parameter — is the foundation of configurable product families in Inventor. Instead of dozens of separate part files, you have one intelligent part that adapts to a configuration parameter.
Building User Forms for Non-Engineers
iLogic Form Designer allows you to create custom user interfaces for your rules, making it possible for non-engineers (sales staff, project managers) to configure variants without understanding the underlying model. Go to Tools > iLogic > Form Editor to design a form.
Drag and drop controls onto the form:
- Numeric parameters — text boxes or sliders
- Boolean parameters — checkboxes
- String/list parameters — drop-down lists
Bind each control to a parameter by double-clicking it and selecting the parameter name. Add an Update button that runs your rules when clicked. Now a non-technical user can select from a dropdown of configurations, enter a dimension, and click Update to see the model regenerate instantly.
Automating Drawing Updates
iLogic rules can also drive Inventor drawings. A rule can automatically change the drawing title block fields, update revision levels, switch between sheet sizes, or show/hide certain views based on the model’s current configuration. This ensures that drawings always match the model state without manual intervention.
iParts and iAssemblies — The Enterprise-Level Approach
For large product families with many standard variants (fasteners, extrusions, standard components), iParts and iAssemblies provide a tabular configuration approach. An iPart is a part family where each row in an Excel-like table defines a variant (different dimensions, different suppressed features). iLogic works alongside iParts, adding conditional logic that goes beyond what a simple table can express.
Handling Errors Gracefully
Production iLogic rules should handle edge cases and invalid inputs. Use error handling to catch conditions where a user has entered an impossible dimension:
If Length < Width Then
MessageBox.Show("Length cannot be less than Width. Please correct the values.")
Length = Width
End IfBuilding validation into your rules prevents invalid model states that would require manual investigation to diagnose.
For manufacturers, product designers, and engineering firms that deal with configurable products or high volumes of similar designs, iLogic in Inventor Professional (€46.99 from GetRenewedTech) offers a return on investment that is difficult to quantify but easy to feel: less time repeating the same design adjustments, fewer errors from manual parameter updates, and the ability to generate entire product variants in seconds rather than hours.
