> Taper a face with advanced taper

Taper a face with advanced taper
With the standard Taper command, you can only taper planes, cones, and cylinders. You must use Advanced when you need to taper other types of surfaces. The primary difference between Taper and Advanced is that the resulting face of an advanced taper operation may not retain its original curvature. The face may be transformed into a freeform surface to satisfy the taper restrictions.
An advanced taper is defined by the following parameters:
The fixed elements that anchor the selected faces to be tapered. These are either specific edges on the faces, or neighboring faces that meet the selected faces at common edges. The fixed edges in relation to the draft direction determine whether material is added or removed in the taper operation. In this sense, the fixed edges are analogous to a draft plane.
The draft direction that can be any valid direction in 3D space. For axial faces (such as cylinders and cones) the draft direction is not limited to the surface axis, as is the case with tapering by draft plane.
The absolute draft angle measured with respect to the fixed edges and the draft direction.
A constant angle or constant opposite shape that controls the final curvature of the tapered face. When a constant angle is specified, Creo Elements/Direct Modeling maintains the angle between the draft direction and the tapered faces, along the fixed edges, as constant. However, this may alter the shape of edges common with opposite faces of the tapered face. To avoid this, the constant opposite shape option can be used to retain the general shape of an edge common with a specified opposite face. This applies to any faces that meet the taper faces at common edges, on the opposite side of the fixed edges with respect to the draft direction.
The draft plane for a draft point is defined by a plane through the draft point with the W direction of the plane is equal to the draft direction.
The draft point can be defined either by the draft direction or by the user. It is also possible to specify a maximum or minimum point of an edge or face as a draft point.
If you select the Keep as Feature option, a taper feature is created and you will find its icon in the Structure Browser. You can easily change a taper feature. When a taper feature created with the Advanced Taper command becomes invalid, its name is displayed in red in the Structure Browser.
Note that the constant angle and constant opposite shape options are effectively mutually exclusive. In most tapering operations, especially those involving non-planar faces, a constant angle will lead to an adjusted opposite face, and a constant shape will result in a variable angle between the draft direction and the tapered faces. A constant shape is often desired when designing top elements that should keep their shape at visible edges for aesthetic reasons. In general, the constancy to apply depends upon the nature of the model being constructed.
The figure shows a rib (1) tapered with both types of constancy; a constant angle (2) and a constant opposite shape defined as the top face of the rib (3).
 As with tapering by draft plane, blends can also be preserved in advanced taper operations. Creo Elements/Direct Modeling removes specified blends, tapers the faces, and then replaces the blends. For this reason, you cannot specify the edges defined by a blend as fixed edges in a taper operation. An original (unblended) edge can be used as a fixed edge by specifying the face that defines the pre-blended edge.It is also possible to taper faces created by an imprint operation. However, the fixed edges in this case must touch the imprint.
To taper a face with advanced taper (fixed edges),
1. Click Modeling and then, in the Engineering group, click Taper. The Taper dialog box opens.
3. Select the faces or features to taper:
Click Faces, then click on the face to taper. Hold the Shift key to select multiple faces.
Click Taper Feat and select a taper feature in the Structure Browser to adjust an existing taper. You can identify a taper feature by the icons (applied) or (not applied).
4. Click Fixed Elems, then click on the fixed edges to act as the anchor for the tapered faces. You can click the edges themselves, or click the faces that meet the taper faces at the common edges.
5. If any blends will be affected by the modification,
a. Click Redo Blend.
b. To include affected faces other than the default, click Control, then click on the blend faces. Creo Elements/Direct Modeling will recalculate these blends so they fit smoothly.
6. Click Draft Dir and set the draft direction in the viewport.
7. Type the absolute draft angle in the Abs Angle box.
8. Select the Constant element relative to the tapered faces:
Select Angle, then type the desired angle between the draft direction and the tapered faces along the fixed edges.
Select Opp Shape, then click a face that will become a constant opposite face to restrict the shape a mutual edge of the tapered faces.
9. Click Keep as Feature to create a taper feature in the Structure Browser so you can activate and deactivate the taper, or quickly adjust the taper later.
10. Click to complete the operation.
Limitations
When tapering faces, you can add or remove material. You can even add and delete faces, edges, and vertices. Use the Preview tool to see the impact of changes before accepting them.
Fixed edges must not be parallel to the draft direction anywhere on the edges.
When you select the option to retain specified blends, the edges defined by the blends cannot be used as fixed edges in the taper operation.
When a constant opposite shape is specified, none of the edges on the face to remain constant can touch the fixed edges.
The faces to be tapered and those providing a constant shape must meet at some common edge.
When a face is specified as a constant shape, only the edges on this face common to the taper faces are affected by the constancy criterion.
A constant shape will be retained exactly when the specified opposite faces are planar. If the shape is non-planar, then its projection to the plane orthogonal to the draft direction will remain constant. The plane is taken to be at the point on the opposite faces that is farthest from the fixed edges.
When you create a taper feature, the Constant must be Angle and cannot be Opp Shape.
If you click the Redo Blend check box, the system will attempt to recreate the blend with the same blending options. However, in some situations that may not be possible. If the blend was created with the RollAtSharp or RollAtSmooth options, the blend may be recreated without those options.