About Sheet Metal Flat Patterns

Use a flat pattern, which is the shape of the sheet metal part before it is formed, to create drawings for manufacturing.

What's New: 2024.2

Use a flat pattern, which is the shape of the sheet metal part before it is formed, to create drawings for manufacturing.

Flat patterns show bend lines, bend zones, punch locations, and the shape of the entire part with all bends flattened and bend factors considered.

Important: The flat pattern command is disabled in a multi-body part file. Use Make Components or Make Part to create a unique part file for each body and then open the derived part to flatten.

Create Flat Pattern creates a flat pattern within the sheet metal part feature browser. A set of flat pattern edit commands are active while the model is displayed in the flat pattern state, including:

Conversion of a sheet metal part to a standard part automatically deletes the sheet metal flat pattern. Any time you delete a flat pattern in a sheet metal part, you also delete all of the flat pattern views in associated drawings.

Create Flat Pattern calculates the material and layout required to flatten a 3D sheet metal model.

The part browser displays a Flat Pattern node, and the flattened state of the model displays when this node is active. After you create a flat pattern, you can switch between the folded part state and the flat pattern state.

When you edit the 3D model, the flat pattern updates automatically. If a model revision results in an invalid flat pattern, a dialog box indicates any error conditions that exist in the flat pattern. You can accept and continue working, although the error warnings persist until the error conditions are eliminated.

You cannot flatten features that require material deformation, such as louvers or dimples. If you place these features onto sheet metal faces using the Punch Tool command, they are represented as 3D features on the flat pattern. They can also be represented using a selected sketch or with a centermark. Sketched and placed features can have unpredictable results, so use Punch Tool to add these shapes to your sheet metal part.

If you cannot unfold a model (for example, flange features that overlap in the flat pattern), a warning dialog box indicates intersecting features. You can Edit or Cancel the dialog box, or you can Accept the intersecting errors. If you accept, the flat pattern is developed with intersecting features. Subsequent feature creation in the folded model displays the dialog box until you edit the features that intersect in the flattened state.

Physical Properties in Drawings of Flat Patterns

Physical iProperties (including but not limited to: mass and volume) calculate differently depending upon the folded or flat state of the model. Any alternative punch representations present in your flat pattern impacts physical iProperties as does the last calculated model state (folded or flat with any edits in the flat).

Export of Flat Patterns

You can export a flat pattern in STEP format, SAT format, or as an AutoCAD DWG or DXF file. Full layer support (color, line type, and lineweight) is provided for flat patterns saved in DWG or DXF formats.

Orientation of Flat Patterns

When you create a flat pattern, you can use the A-Side Definition command on the ribbon to mark any face in a sheet metal part as Up. The A-side face highlights to indicate the punch direction. If no A-side face is present when you create the flat pattern, the software creates the A side, and adds a browser entry

You can delete the A side it as long as no flat pattern exists. Changing the orientation of the flat pattern reflects on the A side that highlights when you select the browser node. If a change causes the compute of the A side to fail, you can right-click the A-side browser node and pick a new A side, which results in a new A-side browser node.

Use options on the context menu to highlight the A side, and adjust the orientation, punch representation, and bend angle measuring. If you click the command Show A-Side, you place all A-side faces into the preselection set of the document.

Sometimes various member files of a sheet metal iPart require unique orientations of their flat pattern. Save uniquely named flat pattern orientations to specify the orientation in the iPart table.

Note: Take care when creating drawings of flat patterns. Bend and punch notes that indicate a direction do so relative to the defaulted front side view that is placed during view creation. This view is based on the front face seen in the flat pattern state of the model.

Display of 3D Features in Flat Patterns

3D features added to the folded model using the Punch tool offer the most flexibility in flat patterns. You can display these features as:
  • A 3D feature
  • An alternative sketch representation
  • A sketch with centermark
  • A centermark only

These display options are not available for punch features added to a flat pattern. 3D features that are placed in a folded model using iFeatures display as they are modeled. If these features remove material (for example, a cut), the flat pattern correctly represents the flattened sheet stock. If these features add material, the features display on the flat pattern as they are modeled

Note: Parts that are converted to sheet metal sometimes have 3D features that cannot be formed using the uniform thickness of the sheet stock. These features display in the flat pattern as they are modeled.
Note: In some cases, cut features in a sheet metal part show only as lines or arcs in the flat pattern. The following conditions can cause this display:
  • The feature is cut at an angle to the face on which it was applied.
  • Chamfers or rounds are added to the edges of the cut feature.

Edits to Flat Pattern

Using commands on the ribbon, Sheet Metal tab, you can add features to your flat pattern that assist with manufacturing. When you add features while the model is displayed as a flat pattern, they do not become part of the part model. When the model returns to the Folded Model state, these features do not display in the part feature history tree .

Note: If you want to add model features while the model is in a flattened state, first add an Unfold feature to the model. If these features cross over a bend zone, when the model returns to the folded state using a Refold feature, they deform as expected.

Drawings of Flat Patterns

The Drawing Manager uses the flat pattern to create the flat pattern view. If you delete the flat pattern, that view is lost.

When creating drawings of flat patterns, remember that bend and punch notes that indicate a direction are relative to the flat pattern view shown in the model. Up is toward you relative to the shown (or named) view and Down is away from you relative to the shown (or named) view.

Physical iProperties (including but not limited to: mass and volume) calculate differently depending upon the folded or flat state of the model. Any alternative punch representations present in your flat pattern impacts physical iProperties as does the last calculated model state (folded or flat with any edits in the flat).

Flat Pattern Extents

Flat patterns require a certain amount of material on the flat sheet stock. This material foot print varies in length and width depending on the orientation of the flat pattern. These properties update each time the flat pattern is updated or reoriented.

In Inventor, the length, width, and area are available in Drawing Manager (and using the API) as Sheet Metal Properties listed as: FLAT PATTERN EXTENTS LENGTH, FLAT PATTERN EXTENTS WIDTH, and FLAT PATTERN EXTENTS AREA.