Unigraphics NX8 - Surface

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Surface View a topic Four Point Surface From Point Cloud Sheets From Curves Ribbon Builder Bounded Plane Midsurface Transition Patch Openings Through Points and From Poles

1. Four Point Surface Use the Four Point Surface command to create a surface by specifying four points. This is useful for creating base surfaces that support the surface based Class-A workflow. You can easily modify such a surface by increasing the degree and patch into a more complex surface with the desired shape. You must follow these point specifying conditions:   

No three selected points can be collinear. No two selected points can be the same or at the very same location in space. Four points must be specified to create the surface. If you specify three or fewer points an error message is displayed.

Four Point Surface Where do I find it? Application Modeling Menu Insert→Surface→Four Point Surface

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Create a surface using four points

1. Choose Insert→Surface→Four Point Surface to open the Surface by 4 Points dialog box. 2. Select the four surface corner points in the graphics window. You can specify the four points using any of the following methods: o Select an existing point in the graphics window. o Select any arbitrary point in the graphics window. o o

Define the coordinate location of a point using the Point Constructor Select a base point and create a point offset from the base point.

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Note The Snap Point options are useful when you want to specify an existing point on a particular curve or surface.

4. Four specified points 5. Specifying subsequent points displays a polygonal preview on the screen. You can modify any points before finalizing the shape of the surface. 6. Change the location of the points as required.

7. Relocated specified points 8. Click OK or Apply to create the surface.

9. Four Point Surface feature

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Four Point Surface options

Specify Points

Lets you select the first, second, third, and fourth points for the four point surface. Specify Point 1 - 4 Preview Select this check box to see a preview of the resulting surface.

Preview

2. Sheets From Curves This option lets you create bodies through selected curves.

Note Many illustrations in this section use solid fill shading to represent wire frame parts. The fill often hides portions of curves that would be visible in a wireframe model. The purpose is to represent the concepts with clearly recognizable figures at the loss of some technical viewing accuracy.

Local Settings When you choose Sheets From Curves, the following options appear: Cycle By Layer

Processes all selectable curves one layer at a time. To speed up the processing, you may wish to turn this option ON. This causes the system to create bodies by processing all selectable curves one layer at a time. All the curves defining a body must be on a single layer. Note Using the Cycle By Layer option can significantly increase processing performance. This option also significantly reduces the use of virtual memory. If you receive the message: Virtual Memory Exhausted, you may want to spread the wireframe geometry over several layers. But be sure to place all defining curves for a body on a single layer.

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Warnings Causes the system to stop processing and to display warning messages after generating bodies, if there are any warnings. You are warned about nonclosed planar loops of curves, and non planar boundaries. If you select OFF, you are not warned, and processing does not stop. Basic Procedure To convert curves to sheets, you must: 1. 2. 3. 4. 5.

Set the Cycle By Layer toggle switch as desired. Set the Warnings toggle switch as desired. Choose OK. Choose the curves you wish to sheet using the Class Selection Tool. Choose OK.

The message Creating Bodies appears during this stage of processing. The system then uses all selected curves to generate bounded planes, cylinders, extruded bodies, and truncated cones. Tips and Techniques You can generate bodies using any planar curve. Sheets From Curves creates the following bodies: 

Bounded planes - by forming planar closed loops (using the ends of curves) Note Single planar loops must be periodic.

  

Cylinders - by pairing circles and ellipses with coaxial centers. Cones - by pairing arcs with coaxial centers. Extruded bodies - by pairing conics and planar splines. They must be on parallel planes and one must project onto the other (via a translation perpendicular to the planes of the curves).

You can create bodies on one plane using: 

Loops of objects - These form a bounded plane. For example, the adjoining lines on any face of a simple rectangle.

You can create bodies between two parallel planes using:  

Coaxial arcs - For example, two circles with the same radius become a cylinder, and two circles having different radii become a cone. In both cases, they share the same axis and are parallel. Identical splines, parabolas, ellipses, hyperbolas - These form an extruded body; for example, the thickness of the sole of a shoe. Note Two coaxial conics do not always have to lie on parallel planes. An ellipse and arc on nonparallel planes can match and form a body if they are both segments of the same cylinder. These objects appear similar when viewed along their common axis. See the figure below.

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Sheets From Curves does not create spherical sections. Before using this option, you must create sheets at all sections of spheres. This option also does not create typical ruled sheets.

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Sheets From Curves Design Considerations

Sheets From Curves usually develops the sheets you desire. However, you will be successful if you follow certain design requirements: Guiding Lines Use guiding lines in ambiguous situations - You must connect defining arcs/ellipses if there are more than two, and they are coaxial and geometrically similar (that is, the same size in degrees but not necessarily in arc length). Otherwise the processor cannot determine which object to connect. See the figure below.

You must use arcs (not ellipses) to generate cones. The system always generates truncated (nonpointed) cones. It is always safest to create guiding lines using arc endpoints. But you can connect any points on two circles if the guiding lines do not touch. If they do touch, you must use arc endpoints. See the figure below.

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"Soft Edge" Recognition - It is not necessary to create guiding lines to form a bounded plane if there are only two identical coaxial arcs limiting the plane. See the figure below.

Guiding Line Rules When in doubt - use a guiding line. In the figure below, area A shows that two coaxial arcs of the same size do not require guiding lines. The processor is able to match the partial arcs and the full arcs without additional help. However, in area B you must indicate whether the circles should form cones or cylinders. Area C requires you to match the 4 lower arcs with 4 upper arcs. Because there are more than 2 similar coaxial arcs you must connect the arc endpoints of the matched arcs. That requires eight guiding lines.

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Bounded Plane Rules Bounded plane object members must form a single unambiguous closed loop. A closed loop does not split and has no "dangling" object. Therefore the loop is reliably chainable.

In the example shown in the figure below, the boundary members of both front faces do not chain because the upper line segment extends outside of each boundary.

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Normally the solution is to create two segments. However, in this particular example, the following requirement further prevents sheet generation. Only two coplanar objects can share an endpoint. This option cannot reliably create a body if a boundary member object shares a common endpoint with more than one other object on that plane. In the figure below, even though you subdivide the dangling line, you still may not succeed in creating bodies the front faces. This is because each face has more than 2 coplanar objects that meet at a vertex. Notice that lines 1, 2, and 3, in the figure below, are all on the same plane. They also share a common endpoint. No. 1 effectively becomes a dangling line and that face is not turned into a sheet. Lines 1, 2, and 4 present the same problem in another plane. You must manually create sheets for these faces.

Bounded planes must not contain more than two colinear line segments. You cannot create a sheet if three or more sequential lines are colinear. In the figure below, the front slope is moved towards the center of its front face. The processor cannot create a bounded plane for the top sheet using the three colinear lines.

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You can generate a trimmed bounded plane if the interior objects do not touch or cross the boundary.

Assemblies Place multiple assembly components on separate layers. They often have curves that cross or touch. The figure below shows the bottom component trimmed by the base of the top component. The base of the top component is not turned into a sheet either.

Multiple components on a single layer can cause more than 2 curves on the same plane to share a common endpoint. Therefore, the bodies might not be properly created, or created at all. See the figure below.

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Invalid Sheets Trimmed Cylinders - You cannot generate a trimmed cylinder. The interior curves are either ignored or converted as usual.

Not all sheets are generated, such as unknown sheet types and sections of spheres. See the figure below.

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Error Messages and Warnings

The following is a list of errors and warning messages you might receive. The warning messages are only received when the Warnings option is turned ON: When all virtual memory is used, the following error message is displayed. If this message occurs, put wireframe components on different layers and use Cycle By Layer. Virtual Memory Exhausted

When the loop of curves is not closed, this warning is displayed. This usually occurs at the endpoints of two neighboring boundary curves. Occasionally this warning is displayed for legitimate planar strings which are not intended to form bounded planes. Planar Loop Is Not Closed

All of the curves which could not be attached to any loop on the plane, and not identified by the warning Planar Loop Is Not Closed, are displayed with the following warning message. This usually means that the curves are parts of loops which are disconnected. Occasionally this warning is displayed for open loops which form legitimate planar strings which are not intended to form bounded planes. Planar Loop(s) Are Not Closed

The following warning message means there are gap(s) in the chain of curves. Boundary Not Chainable

The following warning message means the curves of a bounded plane are not coplanar. Boundary Not Planar

The following warning message means the curves of a peripheral loop or hole, loop in a bounded plane intersect. Boundary Intersects

The following error messages mean that a sheet body could not be created from the specified surface. Unable to Create Sheet Body Unable to Create Planar Sheet Body

3. Bounded Plane Use the Bounded Plane command to create a planar sheet body enclosed by a set of end-connected planar curves. The curves must be coplanar and form a closed shape. To create a bounded plane, you must establish its boundary, and if necessary, define any internal boundaries (holes). You can define the boundaries by selecting individual curves, or you can use Selection Intent, as shown in the following animation.

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Two different bounded planes created on the same surface, one with holes and one without Selection Intent's Tangent Curves rule used to create a bounded plane without holes. Selection Intent's Region Boundaries rule used to create a bounded plane with holes Where do I find it? Application Modeling Toolbar Menu

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Surface→Surface Drop-down→Bounded Plane Insert→Surface→Bounded Plane

Create a bounded plane

1. Choose Insert→Surface→Bounded Plane. The Bounded Plane dialog box opens, and in the Planar Section group, Select Curve active.

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2. Specify the planar section by selecting an unbroken string of bounding curves or edges. They must be coplanar and form a closed shape.

3. Preview of bounded plane after selecting a single string of face edges 4. (Optional) You can do the following:

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If there are discontinuous holes within the area bounded by the selected curves or edges that you do not want included in the bounded plane, select them as inner boundaries.

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Two holes specified by selecting them as inner boundaries Use Selection Intent rules to quickly select the closed shapes that define the bounded plane you want. 5. Click OK or Apply to create the bounded plane.

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Bounded Plane options

Planar Section Lets you select a closed string of end-to-end curves or solid edges to form the boundaries of the bounded plane. The bounding string can consist of single or multiple objects. Each object can be a curve, a solid edge, or a solid face. Select Curve

A hole in a bounded plane is defined as an internal boundary where the sheet is not created. You can create the bounded plane with or without holes, either by individual selection or by using Selection Intent rules.

4. Transition Use the Transition command to create a Transition feature at the intersection of two or more sectional curves. Surface drive24ward (meslab.org/mes)

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You can:  

Impose either a tangent or a curvature condition on the sections. Have a different number of elements for the sections.

If you do not use a surface to impose match conditions on a section, a tangent condition is imposed that is normal to the plane of the input section. The Transition feature is parametric and associative to any geometry used in its creation.

Three sections (numbered) form a Transition feature Where do I find it? Application Modeling Toolbar Menu

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Surface→Transition Insert→Surface→Transition

Create a Transition feature

1. Choose Insert→Surface→Transition. 2. Select the section elements for the first section. To aid selection, you can set the filter on the Selection bar to Curve, Edge or Sketch. 3. In the Continuity group, set the continuity to (G0) Position, (G1) Tangent, or (G2) Curvature and click OK. The section is added to the list in the sections window. 4. (Optional) Click Reverse Direction if you need to reverse the section direction. 5. Repeat this sequence for each section you want to add to define the Transition feature.

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6. Preview of Transition feature using two sections

7. As you add sections, a wireframe preview of the point mapping between each of the sections is automatically displayed.

8. Preview of Transition feature using three sections

9. After you have added all the sections, you can : o Dynamically edit, insert and delete any of the bridge curve coupling points using the options in the Support Curves group. o Dynamically edit the shape of the bridge curves using the options in the Shape Control group. o Preview the Transition feature before you create it. 10. In the Settings group, select the Create Surface check box to create the Transition feature as a surface. If you do not select this check box, only bridge curves are created. 11. Click OK or Apply to create the Transition feature.

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12. Transition feature

4.2.

Transition options

Sections Lets you select the elements for each section. The section elements can consist of splines, lines, arcs, conics, surface edges, sketches and so on. Select Curve

Reverse Direction

Lets you reverse the section direction so that bridge curves can be remapped.

Lets you specify the origin curve in each set of section curves. Specify Origin Curve Lets you add a new set of section curves. Add New Set List Shows a list of all the sections that you specified, their continuity, and their flow direction. List window

Select (or deselect) a surface to change the flow direction at the selected section. Changing the continuity of one section changes the continuity of all sections.

Constrain Faces

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Lets you select faces to specify the constrain surfaces. Select Face Support Curves Show All Points on Section

Displays all the section points of the selection section set. You can then select one of the section's points.

List window

Displays the coupling points of the selected section curve. Adds coupling points to the selected section curve. This option lets you add new coupling points and bridge curves to a section.

Add

You can click Add to insert a coupling point in the section in front of the currently selected point. The coupling point is added to the coupling point list, and a bridge curve is added between the selected section and another appropriate section that is determined by the software. Removes the selected coupling point from the section curve. This option lets you delete a coupling point from a section and its associated bridge curve from a section. The option becomes available when the selected coupling point has a coupling point associated with the other end of the bridge curve.

Remove When you delete a coupling point, it is removed from the coupling points list, and its related bridging curve is also removed. Lets you move the coupling point to another section curve. Move coupling point to other section

This option becomes available if it is possible to move the selected coupling point to another section. When you click the icon, the coupling point is removed from the list and moved to the appropriate section. Lets you specify the location of the coupling point.

Location

The slider becomes active when the point is a coupling point. It shows the correct positional value of that point on the section (0.0 to 1.00 relative to the section length). You can drag the slider to move the coupling point on the section.

Shape Control Displays a list of all the individual curves and bridge curves you want to edit. You can select bridge curves individually or as a group. Bridge Curve When you select a section that has the bridge curves you want to edit, this list updates automatically. Lets you specify the type of shape control method from the following options: Type

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Depth and Skew — Lets you change the depth and skew of the selected curve or group of bridge curves in a fashion similar to that used by the Bridge Curve command. drive24ward (meslab.org/mes)

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Tangent Magnitude — Lets you change the tangent magnitude of the selected curve or group of bridge curves. When you select a curve or a group of bridge curves from the Bridge Curve list, the curve is highlighted in the graphics window. You can then drag the Start and End sliders to shape them, or enter the required values in the data fields.

Available only when Type is set toDepth and Skew. Depth

Changes the depth of the selected bridge curve. You can either drag the Depth slider or enter the required values in the data field. For an example, see Changing the depth value of the selected bridge curve. Available only when Type is set toDepth and Skew.

Skew

Changes the skew angle of the selected curve or bridge curve . You can either drag the Skew slider or enter values the required values in the data fields. For an example, see Changing the skew angle of the selected bridge curve. Available only when Type is set to Tangent Magnitude.

Start

You can drag the Start slider to shape the start of the curve or enter the required values in the data field. For an example, see Changing the start value of the selected curve. Available only when Type is set to Tangent Magnitude.

End

You can drag the End slider to shape the end of the curve or enter the required values in the data field. For an example, see Changing the end value of the selected curve.

Continuity Lets you assign the type of mating condition for the sections. Select from the following options:

Continuity

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G0 (Position) G1 (Tangent) G2 (Curvature)

Note A surface must be selected to use G2 (Curvature). You cannot assign G1 (Position) or G2 (Tangent) continuity to the faces comprising the bottom of a Transition feature. Settings

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Create the Transition feature as a surface. Create Surface Note Only bridge curves are created if this check box is not selected.

5. Through Points and From Poles The Through Points and From Poles free form features options use the same interactive creation techniques, so they are described together in this section. Through Points - Lets you define a rectangular array of points through which the body will pass. The body interpolates each specified point. Using this option, you have very good control over the body in the sense that it always passes through the points that you specify. From Poles - Lets you specify points as poles (vertices) of a control net which defines the shape of the sheet. Using poles gives you much better control of the overall shape and character of the body. Using this option also gives you a much better chance of avoiding unwanted undulations (reversals of curvature) in the sheet.

The options on the Through Points and From Poles dialogs are the same. Through Points and From Poles Dialog Options Patch Type Lets you create a body containing a single patch or multiple patches. Closed Lets you select a method for closing a multiple patch sheet body. Along Row Lets you specify the row degree (1 to 24) for a multiple patch. For a single patch, the system Degree determines the row degree from the row with the highest number of points. Column Lets you specify the column degree for a multiple patch (up to one less than the number of Degree specified rows). For a single patch, the system sets this to one less than the number of specified rows. Points Lets you define the points by choosing a file that contains them. From File

5.1.

Create a Through Points & From Poles surface

To create a body using Through Points or From Poles, you must:

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1. Choose a Patch Type. 2. For multiple patch, choose a Closed Along method for closing the sheet body. 3. For multiple patch, enter the degrees for rows and columns. You do not have to specify degrees for single patch. 4. Specify rows of points or poles to be used to create the body, using either the Point Specification Method dialog or by using specifying a file containing the point definitions. Patch Type Single creates a body consisting of only one patch. Multiple creates a body consisting of a rectangular array of single patches.

Closing the Patch Closed Along lets you choose a method for closing a multiple patch sheet body using the following options: Neither Rows Columns Both

The sheet body begins and ends with the specified points. The first column of points/poles becomes the last. The first row of points/poles becomes the last. Closes the body in both directions (rows and columns).

If you choose to close the body in both directions or you close the body in one direction and the other direction the ends are planar, a solid body is created.

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Degrees for Single Patch Bodies For a single patch body, the system determines both the row and column degrees for you, depending on the points/poles and rows that you specify. The Row Degree (U direction) comes from the row with the highest number of points. The Column Degree (V direction) is equal to one less than the number of rows you specify. Note The minimum number of rows or points per row is two (minimum degree of one) and the maximum number of rows or points per row is 25 (maximum degree of 24 + 1). The sheet shown in the figure below has 4 rows of points, so its column degree (V degree) is equal to 3 (=4-1). The largest number of points in any row is 6, so the rows degree (U degree) is equal to 5 (=6-1).

Degrees for Multiple Patch Bodies For a multiple patch body, you must specify degrees for the rows and columns. The Row Degree can be any number from 1 to 24. The default is 3. The Column Degree can be set to any number from one to one less than the number of rows you specified. The default is 3.

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Note The minimum number of rows or points per row is two (minimum degree of one) and the maximum number of rows or points per row is 25 (maximum degree of 24). For example in the figure below, the row degree can be set to any number from 1 to 4. The column degree is equal to 3.

Points/Poles Once you have specified the degree and set the Patch Type and Closed Along parameter values, you must specify the points in one of the following ways:  

Choose OK, then specify the rows of points using the Ordered Point Constructor, or the rows of poles using the Point Constructor. Choose Points From File and specify the name of the file containing the point definitions. It must be a Rows of Points type file.

If you use the first method, when you have specified two or more rows of points (enough to satisfy the degree), you are prompted with two options: All Points Specified Creates the body and returns you to the dialog. Specify Another Row Lets you specify another row of points for the body you are creating.

5.2.

Tips and Techniques

When specifying creation points or poles, you should select them by row in approximately the same order. Otherwise, you might get undesirable results. The figures below show different object selection orders and the resulting bodies.

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6. From Point Cloud From Point Cloud lets you create a sheet body that approximates a large "cloud" of data points, typically produced by scanning or digitizing. While there are some restrictions, this function lets you create a body from a large number of points with a minimum amount of interaction. The resulting sheet body is much "smoother" than one created from the same points using the Through Points method, but is not as close to the original points. From Point Cloud Feature Dialog Options Select Points Points From File U Degree V Degree #U Patches #V Patches Coordinate System

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Lets you select points when this icon is active. Lets you define the points by choosing a file that contains them. Let you control the degree of the sheet body in both U and V directions. The default degree of 3 can be changed to any value from 1 to 24. (The default of 3 is recommended.) Let you specify the number of patches in each direction. The combination of degree and patches in each direction controls the distance error between the input points and the generated sheet body. Consists of a vector approximately normal to the sheet body (corresponding to the Z axis of the coordinate system), and two vectors that indicate the U and V directions of the sheet body (corresponding to the X and Y axes of the coordinate system). drive24ward (meslab.org/mes)

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Lets you define the boundary of the sheet body that you are creating. Lets you create another sheet body without leaving the dialog. Opens the Confirm Upon Apply dialog after you choose Apply, letting you preview the results, and accept, reject or analyze them. This option is common to Selection Steps dialogs.

In general, there are few requirements for the points you can use to create a sheet body with this function. There is no restriction on the number of points, other than available virtual memory. The degree and number of patches in the resulting sheet body is controlled by you, and is not determined by the number of specified points. There is no requirement on the organization of the points that are input. They may or may not be organized in "scan lines". Part of the information you must supply is a temporary coordinate system. The intended sheet body must not "fold under itself" when viewed along the Z axis of this coordinate system; that is, for any given point in this view there must be only one, unambiguous place it can exist on the sheet body. Basic From Point Cloud Procedure Following is the general procedure to create a From Point Cloud body. Also, see the abbreviated "quick" method procedure. 1. 2. 3. 4. 5. 6.

Select the points, or specify a file that defines the points. Specify the U and V degree of the surface. Specify the number of patches in the U and V directions. Specify the local U-V coordinate system. Specify the boundary around the desired points. Choose OK or Apply to create the sheet body.

The "Quick" Method If you do not intend to specify a particular coordinate system, and you do not need to specify a boundary around the desired points, you can use this "quick" method: 1. 2. 3. 4.

Orient your view so that you are looking down on the shape of the desired sheet body. Drag a selection rectangle to enclose the desired points. Enter the desired values for the degrees and patches. Choose OK or Apply to create the sheet body.

6.1.

From Point Cloud Options

Select Points

This is a required step, and the first step in creating a From Point Cloud sheet body. Notice that, when the dialog first appears, the Select Points icon is active. There are two ways you can specify the points:

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Select the points by clicking and dragging a rectangle or by selecting them individually. Robust selection is available, so you can add or remove points from those selected. As soon as you select points, a boundary is displayed that encloses all the selected points, and the U and V directions are displayed by vector arrows. As you select and deselect points, the size of the boundary changes.

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Choose Points From File, then specify one or more files containing the point definitions. Each point file must be a Series of Points type file.

Note If you use more than one point file, only the name of the last point file is stored in the POINT_FILE object attribute. #U Patches, #V Patches These options let you specify the number of patches in each direction. The combination of degree and patches in each direction controls the distance error between the input points and the generated sheet body. The number of patches you should specify depends on the degree of the sheet body in the corresponding direction, the shape of the data in that direction, and the tolerance you are trying to achieve. A general rule of thumb is that you need one patch each time the slope varies as much as 90 degrees in the corresponding direction. You can use fewer segments with higher degrees. Coordinate System The coordinate system that you choose consists of a vector approximately normal to the sheet body (corresponding to the Z axis of the coordinate system), and two vectors that indicate the U and V directions of the sheet body (corresponding to the X and Y axes of the coordinate system). You have five options for defining the coordinate system: View of Selection WCS Current View Specified CSYS Specify New CSYS

The U-V plane is in the plane of the view, and the normal vector is normal to the view. The U vector points to the right, and the V vector points up. The current Work Coordinate System. The coordinate system of the current work view. Selects the coordinate system previously defined by using Specify New CSYS. If a CSYS has not been defined, this will behave just like Specify New CSYS. Brings up the CSYS Subfunction, which you can use to specify any coordinate system.

With the View of Selection method, if you rotate the view (or modify it in some other way) after selecting points, this coordinate system may be different from the Current View coordinate system. (Or, if you select from a view other than the work view in a multiview layout, the View of Selection coordinate system is different from the Current View coordinate system.) It is important to remember that the normal vector of this coordinate system does not need to be exact. It simply must satisfy the requirement that, when the points are viewed down this vector, they not form a sheet body that folds under itself. Many vectors can meet this requirement (see the figure below).

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If a normal vector is specified that violates this requirement, the resulting sheet body will be dramatically different and probably not what you want. As soon as you specify a coordinate system, the boundary is redisplayed, as projected onto the new U-V plane.

6.2.

Boundary

The default boundary for the sheet body is generated by projecting all selected data points onto the U-V plane (see the Coordinate System section). The minimum rectangle that encloses those points is found and projected along the normal vector onto the cloud of points. This is the option called Minimum Box. Sometimes this default boundary is not appropriate for your data, and you need to define the boundary yourself. For example, arrows in the figure below indicate areas inside the boundaries that have no points.

Unconstrained areas such as this within the boundaries can result in wild twists in the sheet body, as shown in the figure below. Areas that were unconstrained, because they did not contain any points, are erratic in the sheet body produced.

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In a case such as this, you may wish to specify a different quadrilateral (four sided polygon) to be projected onto the point cloud. You do this by specifying four corner points, which are projected onto the U-V plane along the normal axis. The resulting quadrilateral must be convex. The figure below shows an acceptable quadrilateral shape and two unacceptable shapes.

Initially the Minimum Box option is specified. To specify a boundary other than the default, choose Specify New Boundary from the Boundary option menu. The Point Constructor dialog is displayed and the Cue line prompts you to specify the first corner. As points 2 through 4 are specified, they are connected by straight lines, finally forming a quadrilateral. After you successfully specify the new boundary, the Specified Boundary option is displayed on the button. If you choose the Minimum Box or Specified Boundary option, the chosen boundary is displayed in the graphics window. Note that specifying a new boundary does not change the U-V plane of the coordinate system. However, the U and V vectors do change direction within the plane, as shown in the figure below. The direction of the U vector is determined by connecting the midpoint of the 1-4 segment to the midpoint of 2-3. The direction of the V vector is determined by connecting the midpoint of the 1-4 segment to the midpoint of 2-3. The direction of the V vector is determined by connecting the midpoint of 1-2 to the midpoint of 3-4 (the V vector is not necessarily perpendicular to the U Vector). the origin is the intersection of these two lines.

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If you specify a new boundary, or toggle the Boundary option menu between Minimum Box and Specified Boundary, the temporary display of the coordinate system and boundary is updated.

6.3.

Creating the Sheet Body

When all your options are correctly set, choose OK to complete point selection, then choose Apply or OK to create the sheet body. (If you choose Apply, and the sheet body is not what you want, the From Point Cloud dialog is still displayed. You can then change options and generate the sheet body again.) After the sheet body is created, the Fit Information dialog is displayed, showing the Average and Maximum deviation of the sheet body from the data points. Also, the data point that is the maximum distance from its intended position on the sheet body is highlighted. In most cases, the system is able to produce a sheet body (if not, an error message is displayed). The sheet that is created may be close to the points or, in some cases, the result may be dramatically erratic. Inspecting visually and with the available analysis tools is the only sure method of determining if the sheet body meets your needs. The Average deviation and Maximum deviation are an analysis of the distance the sheet body differs from the original points in the direction of the normal to the U-V plane. The true 3D distance from the sheet body to the points is never greater than this number and it is usually less. These numbers are most useful for comparing the results from two different sets of input parameters. You can use Analysis→ Distance to find the true 3D distance for the maximum error point. To try again with different parameters, choose Undo to delete the sheet body just created. You can then change any of the parameters and choose Apply again. Error Messages Memory limits exceeded. Reduce the number of points, the degree or number of patches. The above message is displayed when the operation has required more memory than is currently available. This usually results from too many points, too large a degree, too many patches, or some combination of the above. Select fewer points and/or reduce the value of the input parameters. You will need at least %n data points to produce a sheet body. The above error message is displayed when the number of points selected are not at least (Row Degree + #Row Patches) * (Column Degree + #Column Patches). In this case, you must select more points or reduce the value of some of the parameter values.

Surface


[NX8-HELP] SURFACE

29

Points too sparse to constrain sheet body. Use more points, reduce the degree or restrict the boundary. The above error message is displayed when the number of points and/or their distribution on particular patches, is not large enough. The distribution of the points on the proposed surface is very important each patch on the proposed surface has to have a decent number of points lying on it. You can avoid this problem by using small numbers of patches. Remember, too, that this function is designed to be used on very dense sets of points, like the ones you get from laser scanners. It may not work well if you do not have a sufficient number of points. Degree must be in the range 1 to 24. The above message is displayed when the U Degree or V Degree fields are out of the specified range. Specified boundary must be a convex quadrilateral. The above error message is displayed if the specified four corners are projected onto the U-V plane and connected and they do not form a convex quadrilateral.

7. Ribbon Builder Use the Ribbon Builder command to build a sheet body between an input profile and an offset profile. In the following animation, a sheet body is created between the spline and its offset profile.

Where do I find it? Application Modeling Toolbar Menu

7.1.

Surface→Surface Drop-down→Ribbon Builder Insert→Surface→Ribbon Builder

Create a ribbon sheet

1. Choose Insert→Surface→Ribbon Builder. 2. In the Ribbon Builder dialog box, in the Profile group, click Select Curve curve or edge(s) representing the shape of the ribbon sheet you want to create.

Surface

and select the


[NX8-HELP] SURFACE

30

3. Under Offset View, select an object that defines the direction in which to view the offset. You can use either of the available vector constructor options to define the vector. 4. Under Offset, specify the distance for the offset. 5. 6. 7. 8.

(Optional) Click Reverse Direction to reverse the displayed direction of the offset. Specify the angle for the offset. (Optional) Under Settings, specify the Distance Tolerance and Angle Tolerance values. Click OK or Apply to create the Ribbon Sheet feature.

7.2.

Ribbon Builder options

Profile Lets you select the profile defining the shape of the ribbon surface. Select Curve Offset View Lets you select an object that defines the direction in which to view the offset. 

Offset View



Vector Constructor: Opens the Vector dialog box. Inferred Vector: This is the default vector type. Click to see the Vector list. Select the required vector type, then select objects supported by that vector. You can change the vector and select new objects as needed.

Offset Distance

Reverse Direction

Specifies the distance for the offset.

Reverses the displayed direction of the offset specified with Offset View.

Specifies the angle for the offset. Angle

See the Ribbon Builder example that illustrates how different Distance and Angle values change the output.

Settings Distance Tolerance

Specifies the distance tolerance. The default value is taken from Modeling Preferences. You can change this value.

Angle Tolerance

Specifies the angle tolerance. The default value is taken from Modeling Preferences. You can change this value.

7.3.

Ribbon Builder example

The following example illustrates the different outputs you get when you specify different Distance and Angle values for the selected spline (in the center).

Surface


[NX8-HELP] SURFACE

31

8. Midsurface The Midsurface function is used mainly from the Advanced Simulation application, but it is available here in Modeling as well. Advanced Simulation's model idealization uses a simplified model whose behavior can be utilized to model the behavior of a more complicated system. This is performed using the Midsurface feature. The model idealization process allows you to create a midsurface feature that resides in a single target solid. There can only be one midsurface feature in a target solid. For a description of how to use this option, please see the discussion for Midsurface in the Advanced Simulation Help.

8.1.

Patch Openings

Use the Patch Openings command to create sheet bodies to close openings in a set of faces. You can:       

Patch an opening using a single patch type or a sequence of patch types. Create special surfacing to patch joggles. Patch one part of a larger opening, such as in a notch. Smooth the edges of an opening by creating face extensions along the edges. Suppress the parametric feature that created the hole. Control the shape and flow of the patching surface by using dividing curves to break up the opening. Create the patches as one feature, or as multiple features.

Surface


[NX8-HELP] SURFACE

32

The image shows the command used to patch a collection of sewn sheet bodies.

— Selected edges of openings to patch — Patch Openings feature Where do I find it? Application Modeling Toolbar Menu

8.2.

Surface→Surface Drop-down→Patch Openings Insert→Surface→Patch Openings

Patch multiple openings

1. On the Surface toolbar, from the Surface Drop-down list, select Patch Openings or choose Insert→Surface→Patch Openings. In the Patch Openings dialog box, in the Face to Patch group, Select Face

is active.

2. Select the faces that have openings that you want to patch.

3. In the Opening to Patch group, click Select Edge and in the graphics window, select the edges of the openings you want to patch. For this example, edges of multiple openings are selected.

Surface


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4. In the Settings group, from the Output list, select Multiple Features. 5. Click OK to create a separate patch for each opening.

8.3.

Patch Openings dialog box

Type Specifies the methods for creating the Patch Openings feature. Approximates the opening and fills it with a series of patches. Quilted Patch Type list

N-sided Area Patch

Surface

Creates an N-sided patch surface with an unrestricted number of curves or edges that form a simple, open, or closed loop.


[NX8-HELP] SURFACE

34

Creates a mesh sheet body to fill the gaps. Mesh By Removing Edges

Extension Only

Removes the edges surrounding the opening and merges the surrounding faces.

Extends the edges of the opening in a direction that is tangential to the surrounding faces.

Patches a notch or a cutout area of a larger opening. Notch

Joggle

Patches an area of a larger opening, where the boundary of the opening lies on multiple planes.

Creates a feature set using the Edge Patch method from the Mold Mold Wizard application. This option is only available when you create Wizard Face patches. Patch

Surface


[NX8-HELP] SURFACE By Suppression

35 Identifies features associated to the edges that make up the opening and suppresses them to fill the hole. This option is only available during the create mode. No new features are created.

Note Mold Wizard Face Patch and By Suppression are not available when you edit patches. Face to Patch Lets you select faces that have openings that you want to patch. Select Face

The selected faces are sewn together and openings are determined after the system internally sews the faces. Faces which cannot be sewn are ignored.

Preselect Sheet Bodies check box

Automatically selects all sheet bodies.

Opening to Patch Lets you select edges that define the openings you want to patch. Select Edge

You can select or deselect an entire opening by selecting one of the edges of an opening. You can only select edges that NX identifies as belonging to an opening.

Dividing Curve Lets you specify a bridge curve between two points on the selected edge to divide the opening into two regions. Select Curve

The region on one side of the curve is patched.

Limits Lets you limit the area around the opening to create a partial patch sheet body. When multiple openings are selected for patching, you can specify limits for only one of the openings. Limit Point 1 Limit Point 2

Sets a start and end point for limiting the patch. Location options are available for both points. Provides options for creating limits.

Select Curve Actions

Lets you select a curve to define the limit points. NX uses the start and end points of the selected curve as Limit Point 1 and Limit Point 2 respectively. Reverses the limit points.

Reverse Deselects any selected limit points. Remove Limit Points

Surface


[NX8-HELP] SURFACE

36

Joggle Options Available when Type is set to Joggle.

Specify Point

Lets you specify points that define the boundary of the limit path for creating the shelf surface.

Point list Shelf Length

Sets the length of the shelf surface. Sets a rounding radius for the shelf surface.

Shelf Radius Cutout Length

The shelf is created by extruding the edges of the shelf length and rounding off the end of the extrusion by the shelf radius. Sets the length of the cutout for the joggle. Sets a rounding radius for cutout for the joggle.

Cutout Radius

The system creates a shape similar to the shelf to cut out the base surface in preparation to create the joggle patch.

Settings Specifies the type of patch that is output.

Output list

Single Feature

Creates a single feature that includes all the openings.

Multiple Features

Creates a different feature for each patched opening.

Sew

Sews all the patches with the sheet body that has the opening to create one sheet body. Note This option works only when you patch openings on a sheet body.

Ignores gaps and allows you to select all openings. Ignore Gaps and Exterior Openings check box

When you select this check box, you can:  

Filter small openings between faces, such as slivers. NX evaluates each opening to determine if a sheet body can be created to patch it. Select exterior openings. Use this option when a cylindrical body has openings at both ends. You can patch either of the two ends.

Extension Distance

Surface

Available when Type is set to Extension Only. Specifies the distance to extend the edges of an opening. drive24ward (meslab.org/mes)

[NX8-HELP] SURFACE Distance Tolerance

37

Sets the value for the Distance Tolerance. For more information, see Modeling Preferences — General.

Mục lục Surface ......................................................................................................................................................................... 1 1.

2.

3.

4.

5.

6.

7.

8.

Four Point Surface ............................................................................................................................................ 1 1.1.

Create a surface using four points ........................................................................................................... 2

1.2.

Four Point Surface options ....................................................................................................................... 3

Sheets From Curves .......................................................................................................................................... 3 2.1.

Sheets From Curves Design Considerations ............................................................................................. 5

2.2.

Error Messages and Warnings ............................................................................................................... 11

Bounded Plane ............................................................................................................................................... 11 3.1.

Create a bounded plane ......................................................................................................................... 12

3.2.

Bounded Plane options .......................................................................................................................... 13

Transition ....................................................................................................................................................... 13 4.1.

Create a Transition feature .................................................................................................................... 14

4.2.

Transition options .................................................................................................................................. 16

Through Points and From Poles ..................................................................................................................... 19 5.1.

Create a Through Points & From Poles surface ...................................................................................... 19

5.2.

Tips and Techniques ............................................................................................................................... 22

From Point Cloud ............................................................................................................................................ 23 6.1.

From Point Cloud Options ...................................................................................................................... 24

6.2.

Boundary ................................................................................................................................................ 26

6.3.

Creating the Sheet Body ......................................................................................................................... 28

Ribbon Builder ................................................................................................................................................ 29 7.1.

Create a ribbon sheet ............................................................................................................................. 29

7.2.

Ribbon Builder options ........................................................................................................................... 30

7.3.

Ribbon Builder example ......................................................................................................................... 30

Midsurface ..................................................................................................................................................... 31 8.1.

Patch Openings ...................................................................................................................................... 31

8.2.

Patch multiple openings ......................................................................................................................... 32

8.3.

Patch Openings dialog box ..................................................................................................................... 33

Surface


Unigraphics NX8 - Surface

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