Creating Emboss Features

Contents

• 42.1 Introduction
  • 42.1.1 Arguments
• 42.2 Options
  • 42.2.1 Convexity
  • 42.2.2 Profile location
  • 42.2.3 Sidewalls
    • 42.2.3.1 Tapered sidewalls
    • 42.2.3.2 Specifying multiple angles for tapered sidewalls
    • 42.2.3.3 Ruled sidewalls
    • 42.2.3.4 Swept sidewalls
    • 42.2.3.5 Supplying your own sidewall
  • 42.2.4 Overflow
    • 42.2.4.1 Specifying interior overflow behaviour
    • 42.2.4.2 Specifying laminar overflow behaviour
  • 42.2.5 Returning the embossed feature separately
• 42.3 Constraints
  • 42.3.1 Topological constraints
  • 42.3.2 Orientation constraints

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42.1 Introduction

The functions PK_BODY_emboss and PK_FACE_emboss provide you with generic, high-level functionality for adding protruding (pad) or indented (pocket) emboss features to a target body, the general shape of which can be described using supplied profiles.

• PK_BODY_emboss provides global emboss functionality, letting you add emboss features across a whole body in one operation.
• PK_FACE_emboss provides local emboss functionality, letting you add emboss features to a selected set of faces within a body.

For both functions, Parasolid automatically creates sidewalls for emboss features, based on a range of criteria you supply.

Figure 42-1 Creating pad and pocket emboss features on a target body

42.1.1 Arguments

In order to create an emboss feature, you need to supply:

• A target body (for PK_BODY_emboss) or a set of faces from the same body (for PK_FACE_emboss) that the emboss feature is placed onto
• A profile that describes the shape of the emboss on that target
• An end cap that describes how far the emboss feature should protrude from the target (for pads) or indent into the target (for pockets)

Parasolid then creates a sidewall around the profile, limited by the target (or the specified faces) and the end cap, and based on further constraints supplied in the form of options to the function (described in Section 42.2, “Options”). The received bodies are described in more detail in the following table:

Figure 42-2 Orientation of input bodies in pad and pocket emboss features

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42.2 Options

In addition to the input bodies, you can supply an extensive set of options that further describe the nature of the emboss feature. This section describes the options that are available.

The table below provides a summary of the options that you can specify in both PK_BODY_emboss_o_t and PK_FACE_emboss_o_t.

tolerance

convexity

profile_on

sidewall_data

overflow_data

unite

update

42.2.1 Convexity

You can choose the convexity of the emboss features that Parasolid creates using the convexity option. By default, Parasolid creates both protruding embosses (pads) and indented embosses (pockets), but if required, you can specify that only one or other type is created.

When a non-default convexity is specified, attempting to create an emboss feature of the opposite convexity results in the error PK_emboss_bad_position.

42.2.2 Profile location

By default, the profile you specify can be located anywhere. However, if required, you can use the profile_on option to indicate that the profile must be located on either the target or the end cap.

42.2.3 Sidewalls

A major part of the emboss functionality involves the construction of the sidewall, and Parasolid provides you with a number of different methods and controls for you to specify its final appearance.

Parasolid can construct a sidewall for you using one of three methods:

• Tapered sidewalls can be created based on a specified draw direction and taper angle.
• Ruled sidewalls can be created using the normals of faces in the supplied profile.
• Swept sidewalls can be created based on a specified sweep direction.

In all three cases, the geometry of the sidewall is formed by a set of ruled surfaces that pass through the boundary of the profile.

In addition to these methods of internal construction, you can supply a sidewall yourself.

The data required for sidewalls is supplied using the sidewall_data option, which uses the PK_emboss_sidewall_data_t sub-structure.

42.2.3.1 Tapered sidewalls

If the sidewall field of sidewall_data is PK_emboss_sidewall_tapered_c, then Parasolid creates sidewalls that are tapered between the specified target and end cap, usually based on a supplied draw direction and taper angle.

Figure 42-3 Pad emboss feature with tapered sidewalls

For tapered sidewalls, you should also set the following fields (some of which are optional).

taper_method

draw_direction

taper_angle

offset

top_surface

Figure 42-4 Pad emboss feature with normal tapered sidewalls

Tapered sidewalls (when taper_method is not PK_taper_method_offset_c) are generally constructed such that they draft outwards from the end cap body to the target body. This ensures that the emboss feature created will be non die-lock, that is, it would be physically possible to draw the part from a mold in the specified draw direction. You can model a die-lock emboss feature, such as a dovetail, by supplying a negative taper_angle .

42.2.3.2 Specifying multiple angles for tapered sidewalls

By default, if tapered sidewalls are created then a single taper angle is used for all faces in the sidewall. However, you can specify that different taper angles are used for any of the faces in the sidewall, as shown in Figure 42-5.

Figure 42-5 Pad emboss feature with tapered sidewalls using different angles

For sidewalls with multiple taper angles, you should set the following fields:

n_multi_taper_edges

multi_taper_edges

multi_taper_angles

42.2.3.3 Ruled sidewalls

If the sidewall field of sidewall_data is PK_emboss_sidewall_ruled_c, then Parasolid creates sidewalls that are ruled along the normals of the faces in the supplied profile.

No additional information needs to be supplied in order to create this type of sidewall.

Figure 42-6 Pad emboss feature with ruled sidewalls

42.2.3.4 Swept sidewalls

If the sidewall field of sidewall_data is PK_emboss_sidewall_swept_c, then Parasolid creates sidewalls that are swept.

For swept sidewalls, the sweep direction is taken from the specified draw_direction , which must be a unit vector. No other information needs to be supplied.

Figure 42-7 Pad emboss feature with swept sidewalls

42.2.3.5 Supplying your own sidewall

If the sidewall field of sidewall_data is PK_emboss_sidewall_supplied_c, then you can supply your own pre-constructed sidewall to use in the emboss operation. The sidewall itself is supplied using the sidewall_body field in the sidewall_data structure.

The sidewall supplied must be a sheet body, and is usually duct-like in shape. A supplied sidewall must be manifold and must not be disjoint. It should also be large enough to reach both the target and end cap.

When supplying a sidewall yourself, the profile received by Parasolid may be PK_ENTITY_null.

Figure 42-8 Pad emboss feature with user-supplied sidewalls

42.2.4 Overflow

Sometimes, the target body (for PK_BODY_emboss), or the supplied target faces (for PK_FACE_emboss) may not provide a complete base for the emboss feature. In other words, some of the profile’s projection along the sidewall lies outside the target area, and prevents the emboss feature from being completely defined.

In such cases, Parasolid can either trim the emboss feature so that it fits in the available area, or modify the feature so that it overflows onto adjacent faces.

Figure 42-9 shows an example where the profile’s projection overflows the target body on several sides. The resulting pad has been successfully created by trimming the pad on two overflow boundaries, and creating a new swept sidewall on the third boundary.

Figure 42-9 Creating an emboss feature using a profile that overflows the target

You use the overflow_data structure in both PK_FACE_emboss_o_t and PK_BODY_emboss_o_t to control emboss overflow behaviour. It has the following fields:

interior_overflow

laminar_overflow

sweep_direction

laminar_walled

Overflow behaviour is different at laminar edges in the target body than it is at non-laminar, or interior, edges. Both interior overflow and laminar overflow are specified using a PK_emboss_overflow_t sub-structure.

42.2.4.1 Specifying interior overflow behaviour

Interior overflow behaviour only applies to local emboss operations performed using PK_FACE_emboss. You should not specify interior overflow behaviour for a global emboss operation using PK_BODY_emboss.

If a locally created emboss feature overflows an interior edge on a target body, then several approaches are possible, depending on the configuration of the faces adjacent to the edge, and the information provided in the interior_overflow field.

• At a concave edge, the approach is always to trim the emboss feature to the adjacent face.
• At a convex edge, the emboss feature can be trimmed by extending the adjacent face so that it meets the end cap. Alternatively, the emboss feature can be extended so that it overflows onto the adjacent face.

Convex and concave edges along an interior boundary are determined by the direction in which the adjacent faces bend with respect to the direction of the emboss feature:

• An edge is convex if its adjacent outer faces bend away from the emboss feature
• An edge is concave if its adjacent outer faces bend towards from the emboss feature

The convexity of a given edge is therefore dependent on whether you are creating a pad or a pocket.

Figure 42-10 and Figure 42-11 show the result of mixed and added overflow on a pad and a pocket respectively. Notice that the concave and convex edges are reversed for the pocket example, compared to the pad example. In each case, the face specified in the call to PK_FACE_emboss is shown in blue.

Figure 42-10 Trimming pads at interior edges

Figure 42-11 Trimming pockets at interior edges

42.2.4.2 Specifying laminar overflow behaviour

If an emboss feature overflows a laminar edge on a target sheet body, when using either global or local emboss, Parasolid’s general approach is to attempt to trim the emboss back to the laminar edge. The precise behaviour of overflow in these circumstances is actually a combination of two pieces of information:

• How to trim the sidewall at the laminar edge in order to finish the emboss feature suitably
• Whether or not to add new side faces in order to preserve the original laminar edges on the target.

You control the first of these using the laminar_overflow field, which can take any of the following values.

Figure 42-12 Trimming emboss features at laminar edges

You can control whether additional side faces are created during laminar overflow using the laminar_walled field of overflow_data . If PK_LOGICAL_true, side faces are created from the laminar edges whose surfaces are the ruled or swept surfaces used to trim the sidewall. Figure 42-13 shows the swept overflow result from Figure 42-12 with an additional side face. By default, side faces are not created at laminar edges.

Figure 42-13 Adding additional side faces at laminar edges

42.2.5 Returning the embossed feature separately

By default, Parasolid returns a single body containing the embossed feature. Alternatively, you can choose to leave the target body unaltered and return the faces of the embossed feature in the tracking information for the function. You do this by specifying the value of the unite field of the options structure as follows:

Figure 42-14 Embossed feature returned united or separate by PK_FACE_emboss

In Figure 42-14, the profile overlaps the target sheet body with the end cap positioned above as shown in diagram (a). By default, PK_FACE_emboss returns the embossed attached to the target body. If unite is set to PK_emboss_unite_sidewall_no_c, however, the embossed feature is returned separately (with the target unaffected).

If you choose to have the embossed feature returned separately, you can limit the sidewalls by treating the interior overflow boundary as a laminar overflow boundary; for details of laminar overflow processing, see “Specifying laminar overflow behaviour” in Section 42.2.4, “Overflow”. Limiting the sidewalls is done by setting the interior_overflow field of the overflow_data structure to PK_emboss_overflow_laminar_c. Figure 42-15 shows the difference in setting interior_overflow to PK_emboss_overflow_mixed_c and to PK_emboss_overflow_laminar_c.

Figure 42-15 The effect of interior_overflow on the embossed feature.

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42.3 Constraints

For emboss operations to be successful, Parasolid places a number of constraints on both the topology supplied to the operation, and the orientation of the input bodies. This section describes the constraints that you should be aware of.

42.3.1 Topological constraints

The topology of the input bodies are checked for their suitability for the emboss operation. The following constraints should also be observed:

42.3.2 Orientation constraints

You should observe a number of constraints regarding the orientation of the various bodies received by PK_BODY_emboss:

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