Extended modules > Creo Elements/Direct Sheet Metal > Import sheet metal parts > Handling non-planar surfaces
  
Handling non-planar surfaces
You can add a Creo Elements/Direct Sheet Metal material attribute to a part containing a range of non-planar geometry types created in Creo Elements/Direct Modeling or other 3D CAD applications. The Creo Elements/Direct Sheet Metal Unfold 2D button allows you to unfold the following non-planar surface types:
Cylindrical surfaces
If you want Creo Elements/Direct Sheet Metal to handle a part including cylindrical surfaces, attach material to the part. Examples of different types of cylindrical surfaces are shown below.
When you have attached material to a part including cylindrical surfaces, you can process that part just like any other sheet metal part created in Creo Elements/Direct Sheet Metal. The following figure shows a part with cylindrical surfaces plus the flat for that part.
The Unfold dialog box includes a special Cylinder Allowance area which enables you to set the relative position of the neutral phase (also known as neutral fiber) for cylindrical bends. The notional plane in which the length of the cylindrical sheet metal part remains unchanged with respect to the flat is known as the "neutral fiber" or "neutral phase". The location of this neutral phase relative to the material thickness ("T") is defined by a parameter known as the k-factor.
Conical surfaces
If you want Creo Elements/Direct Sheet Metal to handle a part including conical surfaces, attach material to the part. Examples of different types of conical surfaces are shown below.
If you use a spline or any other non-ruled function or an ellipse to create the cone, be sure that the cone cross-section is circular along its entire axis. The Creo Elements/Direct Modeling commands Lift Angular (with linear profiles) and Variable Radius Blend (along a linear edge) produce perfect cones with tangential edges.
When you have attached material to a part including conical surfaces, you can process that part just like any other sheet metal part created in Creo Elements/Direct Sheet Metal. The following figure shows part with conical surfaces plus the flat for that part.
The Unfold dialog box includes a special Cone Allowance area which enables you to set the relative position of the neutral phase (also known as neutral fiber) for conical bends. The neutral phase is a notional plane in which the length of the conical sheet metal part remains unchanged with respect to the flat. The location of this neutral phase relative to the material thickness (T) is defined by a parameter known as the k-factor.
Linear swept b-spline surfaces
If you want Creo Elements/Direct Sheet Metal to handle a part including linear swept B-spline surfaces, attach material to the part. An example of a part created through a linear sweep of a B-spline part is shown below.
When you have attached material to a part including linear swept B-spline surfaces, you can process that part just like any other sheet metal part created in Creo Elements/Direct Sheet Metal. The following figure shows a part with linear swept B-spline surfaces plus the flat for that part
If your part consists of linear swept B-spline body (without any planar surfaces apart from the side faces), please note that Creo Elements/Direct Sheet Metal cannot automatically place the flat on a workplane because no workplane is located on the curved surfaces of the part. However, you can use the following Output to options for such parts:
Creo Elements/Direct Drafting
MI File
Text File
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You can attach a material attribute to parts containing spherical or free-form surfaces or parts having an elliptical cross-section. However, you cannot unfold such parts in Creo Elements/Direct Sheet Metal.
The K-Factor
The plane in which the length of a curved sheet metal part remains unchanged is identified by the "neutral phase". The portions on either side of this neutral phase become longer or shorter.
The location of this neutral phase relative to the material thickness ("T") is described in terms of a parameter known as the "k-factor". ANSI (American National Standard Institute) defines this k-factor as the offset of the neutral phase relative to "T", while DIN (Deutsche Industrienorm) defines the k-factor as the offset of this neutral phase relative to "T/2".
Both conventions are illustrated in the following figure.
When unfolding a part including cylindrical or conical surfaces, you can specify the applicable k-factor in the Unfold dialog box.
Side faces
Creo Elements/Direct Sheet Metal allows you to correctly unfold side faces that have features like chamfers. You can also control tool handling to display geometrical details of inner tools in the flat. For details, see Controlling the information output to the flat.