Flatten surfaces generates a planar surface from one or more contiguous non-planar surfaces.

The tool performs a geometric flattening to create a surface with minimum strain energy.

The flattening operation ignores the material properties of the part on which the surface is flattened. The resultant surface has no material properties.

Some uses for Flatten surfaces:

  • To evaluate the flat (cut) shape for a paint mask that is applied to a certain area of a part.

  • To evaluate the feasibility of a decal applied to a curved region of a part without undue strain or wrinkling.

  • To determine the cut shape of a composite ply given the outer mold line (OML) and the ply boundary.

  • To add features (cutouts, text curves, text wraps) to the flat surface and have them form back to the curved surface shape.

Manufacturers and assemblers often apply decals, wraps, or coverings to surfaces. While these typically come from flat sheets, the surfaces they adhere to aren’t always flat. Onshape’s Flatten surfaces tool generates a planar surface from one or more contiguous non-planar surfaces, allowing for a smoother application.

When you apply a planar sheet to a non-planar surface, it inevitably stretches and compresses. Onshape’s flatten surfaces tool performs geometric flattening to create a surface with minimal strain energy.

A flattened surface does not take the Material definition into account. The resultant flattened surface has no material properties.

This squeegee handle requires a textured grip covering.

Within the Part Studio, click the Show analysis tools icon in the bottom right corner of the graphics area. Select Flatten surfaces.

Select one or more contiguous faces to flatten. Then click the Flatten button to perform the flattening operation.

The Flatten surfaces tool provides multiple visualizations for feedback. Show facets reveals the mesh facets on both the original and flattened surfaces.

With Show facets disabled, Show edges enables edge display on the flattened surface.

Show checkerboard displays a checkerboard pattern on both the original and flattened surfaces. Adjust the scale of the pattern by entering the Checkerboard scale. Lower values result in larger checkerboard blocks, and higher values result in smaller ones.

Show distortion displays areas of the flattened surface that the flattening process geometrically distorts. Areas with distortion are shown in red or blue. Blue indicates tension or stretching, and red indicates compression or creasing. Areas of stronger color indicate areas with higher distortion values.

Check Show flattened to display the resultant surface.

Select an Origin about which to flatten the surface. If you do not select an origin, Onshape automatically chooses one for the flattened surface.

Further position the flattened surface by entering a Flattened offset or a Flattened angle value.

The Flatten surfaces tool does not create a part in the Parts list. Check Show export controls to reveal the Export options. Export the flattened surface to Parasolid or STL to obtain a physical representation of the surface in a file. If necessary, the file can then be imported back into the Part Studio using the Derived feature.

Alternatively, select your export format as SVG or DXF, and click the Export button to send the file to your device. You can then work on the decal in your external software, for example, Adobe Illustrator.

Close examination of this flattened surface reveals significant distortion near the bottom of the handle. Exit the Flatten surfaces tool and apply a split feature to add additional edges to the face.

Select Flatten surfaces and select an edge for the Rip edges. Click Flatten. The flattened surface has been split, or ripped, along the selected edge, alleviating the strain from stretching and creasing.

In a Part Studio:

  1. Click the Show analysis tools icon () in the bottom right corner of the graphics area. From the menu, select Flatten surfaces to open the dialog:

    Flatten surfaces dialog

  2. With the Faces to flatten field selected, select one or more contiguous faces in the graphics area.

    Faces to flatten

    Example of a partial soccer ball being flattened. Note that you must first press the Flatten button before results are displayed.

  3. Click to select the Rip edges field in the dialog, and then select any edges in the graphics area where the flattened surface should be ripped.

    Ripped edges

    Example of ripped edges used. Note that this helps to reduce distortion in the flattened surface. Compare with the image displayed under the Show distortion option below.

  4. Check the following optional display settings, and enter the appropriate input values:

    1. Show facets - Check to display the mesh facets on both the original and flattened surfaces.

      Flatten surface: Show facets

    2. Show edges - By default, the edges on the flattened surfaces are visible. Uncheck to hide these edges.

      Flatten surface: Show edges

      Show edges enabled (left) and disabled (right)

    3. Show checkerboard - Check to display a black and white checkerboard pattern overlaid on both the original and flattened surfaces.

      1. Checkerboard scale - Sets the checkerboard pattern scale. Lower values result in larger patterned blocks. Higher values result in smaller patterned blocks.

        Flatten surface: Show checkerboard

        Show checkerboard; Checkerboard scale: 25

    4. Show distortion - Displays areas of the flattened surface where there is geometrical distortion as a result of the flattening process in magenta. The stronger the color, the more that distortion occurs.

      1. Distortion scale - Sets the sensitivity level of distortion that is reported. Higher values increase distortion sensitivity (reporting more distortion). Lower values decrease the distortion sensitivity (reporting less distortion).

        Flatten surface: Show distortion

    5. Show flattened - Displays the flattened result. This allows you to toggle the flattened result on or off.

      1. Flattened position (mate connector) - Select a mate connector to position the flattened surface result in a location other than below the selected surfaces.

        Flatten surface: Flattened position (mate connector)

      2. Flattened offset - If a mate connector is used for the Flattened position, enter a positive or negative numerical value to offset this position along the mate connector's Z axis.

      3. Flattened angle - If a mate connector is used for the Flattened position, enter a positive or negative angle degree value to offset this position about the mate connector's Z axis.

    6. Origin - Select a vertex used as the origin point for the resultant flattened surface.

      Flatten surface: Origin

  5. Click Show export controls to display the export options:

    Show export controls

    1. Export Format - Select from a list of file format options: PARASOLID, STL, DXF, or SVG.

    2. Export inner edges - Exports the inner edges if the Faces to flatten contain multiple faces.

      Example

    3. Export button - Click the Export button to have the final flattened surface results downloaded to your device.

  6. Click Flatten to display the final flattened surface resulting from the dialog inputs.

Flattening to obtain a decal or paint mask surface.

One use of the Flatten surfaces tool is to extract a flat surface out of multiple non-planar surfaces, used as a decal or paint mask.

In the following image, the side view appears to be a perfect circle. In reality you will need to extract the curved surface, flatten it, apply a decal, and then apply the decal on the curved surface:

Flattening a curves surface for decal application

Using the Flatten surfaces tool to obtain the decal cutout:

Using Flatten surface to obtain the decal cutout

Once you have the surface, check Show export controls, select either SVG or DXF as your export format, and click the Export button to send the file to your device. You can then work on the decal in your external software, for example, Adobe Illustrator.

Exporting inner edges

The same example as above is exported without and with Export inner edges selected (under the Show export controls section of the dialog):

Export inner edges example

Export inner edges disabled (left) and enabled (right)

Flattening a pipe

In this example, a pipe is unrolled. This is a surface that can be developed and adding a rip produces a flat surface with no distortion:

Flattening a pipe surface

Setting the origin to the vertex at the top of the pipe allows you to visualize how the surface flattens along the pipe edge:

Setting the origin for the pipe's flattened surface

Car hood

This example shows a scanned surface of a car hood brought into Onshape as a mesh import. Typically, you want to create a paint protection film (PPF) from this surface. This is useful on hoods, fenders, front surfaces of headlights, and other curved surfaces. The import is flattened and shows little distortion:

Hood scoop Flattened surface example

  • Some options require pressing the Flatten button again if they are updated. For example, if a Rip edge is added, or an Origin selected.

  • The Flatten surfaces tool does not create a part in the Parts list. Export the flattened surface to obtain a representation of the surface in a file. This file can then be imported back into the Part Studio, if required.

    Imported flattened surface

    Example of an imported flattened surface. The surface was exported using a PARASOLID file format, imported into the document, and imported into a Part Studio using the Derived feature.

  • Flatten surfaces does not provide perfect accuracy. You should not use Flatten surface to obtain critical or fine measurements for use in calculations. It should be used to provide general dimensions to wrap things like decals around non-planar surfaces.