When you bake a cake, make a pie, or cook a souffle you follow a recipe and the recipe dictates the final result. Inventor’s sheet metal environment is not much different as it is the sheet metal styles that act as the recipe dictating the resultant flat pattern.

Sheet Metal Style Defaults

Let’s start with the Sheet Metal Style Defaults. Using this dialog, you set the defaults used when placing sheet metal features.

Inventor Sheet Metal Default Styles Dialog

Unchecking Use Thickness from Rule allows you to specify the thickness, ignoring the thickness set in the rule. The Material drop-down provides another method of setting the active material. This is no different than the material list accessed from the iPropertiers dialog or from the Material Browser dialog.

What you specify in this dialog are used only as the defaults. You can override these settings with each feature you place. Here for example as three tabs of the Flange feature, all used to override the setting specified as the defaults.

Inventor Sheet Metal Feature Override Defaults

Sheet Metal Styles – Rules

Both the Sheet Metal Rules and Unfold Rules are styles, managed via the Styles and Standard Editor. This means that a global library can be defined for all parts to use, but it is flexible for local edits to occur.

In this example, I select the Default rule and click New to use it as the starting template for my new rule. I set the Material, Thickness, Gap, and Unfold Rule (more on Unfold Rules later). The values set here also adjust the sheet metal parameters which are auto-generated when you active the Sheet Metal Environment.

Use the Flat Pattern Bend Angle drop-down to change how the Bend Angle is measure… outside-in (A) or inside-out (B). When dealing with punches the flat pattern can show the punch in its 3D form, in a 2D representation (sketch), or as a simple Center Mark.

Inventor Sheet Metal Rules Style Dialog

The Bend tab is all about the bend, as in the Relief Shape, Bend Radius, and Bend Transition. If using a straight or round relief the options for relief size become available. The Minimum Remnant is a neat feature in that this sets how much dangling material is acceptable when the bend is not applied to the entire edge. If the amount of material left is less than the Minimum Remnant it is automatically removed

The Bend Transition manages how the bend blends into the intersecting faces. There are five options available, all that appear in the flat pattern. The folded model will appear with no transition type, except in the case of Trim, where it is shown in the folded model.

Inventor Sheet Metal Rules Style Dialog Bend

With the Corner tab, you set the desired relief shape for both 2 bend and 3 bend intersections

Inventor Sheet Metal Rules Style Dialog Corner

Here’s the difference between Full Round and Intersection

Inventor Sheet Metal 3 Bend Corner

Sheet Metal Styles – Unfold Rules

When bending metal the material deforms, both elongating on the outside and going into compression on the inside of the bend. The Unfold Rule defines how your sheet metal model unfolds, as in what is the amount of correction to account for the deformation of the material. Autodesk Inventor provides three options within the Sheet Metal Styles to define the correction.

Linear approximation (aka KFactor)

As discussed earlier, when metal is bent the inside face is compressed and the outer face is elongated (stretched). The line between the compression and elongation is referred to as the neutral axis. The ratio of the neutral axis location and the thickness of the material is the kFactor.

Inventor Sheet Metal Unfold Rule kFactor

Bend Tables

When you want to manage the correction value as it changes with different bend radii, angle, and material thickness you will want to use the Bend Table option. With Bend Tables, you plot the correction value against the Angle and Radii. As it can get intense consider using the Export option to export the data to a spreadsheet, making it easier to populate the information.

Inventor Sheet Metal Unfold Rule Bend Table
Custom Equations

I’ll be honest that I have absolutely zero experience with custom equations, mostly because the situation to use them has never presented itself. To quote the help “Custom equations that provide uniform deformation within specified angular bounding conditions

Inventor Sheet Metal Unfold Rule Custom Equation

Inventor Sheet Metal Styles in Action!

And That’s a Wrap

So this is the final piece to our deep-dive into Inventor Sheet Metal. If you are just joining us on this voyage make sure to start with the first article in the series Holy Sheet Metal Batman!


Feature Image “Orange Filling” by Phil! Gold