proe surfacing - module 5
Post on 11-Sep-2014
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Module 5: Surface Modeling using BoundariesLab ExercisesIf you are ready to start on the exercises for this module, please click the links below. Exercise 1: Creating Boundary Surfaces on the Shaver Exercise 2: Creating Surfaces on the Air Filter Cover (Challenge) Exercise 3: Adding Control Points to the Air Filter Cover (Challenge) Exercise 4: Creating Draft Surfaces (Challenge)
Lecture ReviewIf you would like to review a text-based version of the materials presented in this lecture, please click here.
IntroductionSurfaces by boundaries are one of the most powerful and flexible surface creation tools that you can use to capture design intent. You use them while creating continuous surface features. As the name suggests, the surfaces are created with the boundary edges defined with curves or edges. You can apply edge tangency conditions for aligning the shape of the surface with the adjoining geometry. You can modify the structure of surfaces by modifying the curves that define the shape of the surfaces or the surfaces directly. You can also use direct surfacing tools such as, Blend Section to Surfaces, to reduce the multiple steps required for creating such features. These tools are used to reduce the design development time. Solid and surface modeling techniques are used together effectively for modeling a part quickly with greater feature control.
ObjectivesAfter completing this module, you will be able to: Describe boundary surfaces. Describe types of boundary surfaces. Create a surface with boundaries. Apply constraints at the boundary edges of surfaces. Create blending surfaces using Blend tools.
Surface Modeling using Boundaries
You can create a surface by defining its boundaries in one or two directions. You can select datum curves, datum points, solid, or surface edges as boundaries. You can apply Edge Tangency conditions for aligning the shape of the surface with the adjoining geometry. Continuity conditions like tangency or curvature continuity are usually defined at the ends of the surface. This help you define constraints to the surface with the adjacent surfaces, edges, or curves. You can modify the surface geometry to smoothen the surface patches that are created. You can create different types of surfaces using boundaries. o Blended: The surface is a blend between reference entities that are selected, such as datum curves. You can create blended surfaces in one or two directions. o Conic: The surface created follows the geometric rules of conics. These are used in special cases such as styling products where a smooth transition is required between surfaces. o Approximate: The blended surface is approximated through some fit curves and by specifying a smoothening factor. o N-sided: The surface is defined using more than four boundary edges.o
Advanced options: Create advanced surfaces using the Advanced option in the Insert drop-down menu.
Blended surfaces are used to create a smooth quilt that connects several sections. The first and last entities selected in each direction define the surface boundary. Adding more section entities in between enables you to define the surface shape with greater control. Blended surfaces can be created with curves available in one direction. The surface created thus passes through the curves. Blended surfaces can also be created when a curve network is available in two directions. The surface created thus passes through the curves in both directions. For blended surfaces defined in two directions, the outer boundaries must form a closed loop.
Manipulating Blended Surfaces
Any surface created with default system conditions may not satisfy your design need. You will have to tweak the shape to get the desirable surfaces. Pro/ENGINEER Wildfire provides tools that enable you to manipulate the blended surfaces while you are in Feature Creation mode. You can manipulate blended surfaces by: o Controlling the Boundary Conditions Defining tangency or curvature continuity conditions at the boundary edges. o Defining Blend Control Points You change the patch structure using different options. o Defining the Boundary Influence Placing the surface in conjunction with other surfaces and defining how the newly created surface is influenced by the other geometry lying next to it.
Controlling the Boundary Conditions
You control the boundary conditions of the blended surface using the following types of edge alignments: o Free No tangency conditions are set along the boundary. Tangent The blended surface is tangent to the reference surface along the boundary. o Curvature The blended surface has curvature continuity across the boundary. o Normal The blended surface is normal to the reference surface or datum plane. For checking boundary conditions, you can use curvature plots as shown in the slides.o
About the figures: Free Edge Alignment Notice the curvature plot at a cross-section of the created surface. It has zero value. Tangent Edge Alignment Notice the curvature plot at a cross-section of the created surface. Notice the joined curvature at the surface joint. The curvature is unequal at the joint. Curvature Edge Alignment Notice the curvature plot at a cross-section of the created surface. The heights of the curvatures are matched at the joint. Normal Edge Alignment Notice the curvature plot at a cross-section of the created surface.
Defining Control Points
Surfaces are affected by the condition of the geometry that is used as references to define them. When there are curve segments present in the curves used to define a surface, the surface displays patches. Sometimes the number of patches in the surfaces are far greater than what is acceptable. Generally, surfaces with patches pose modeling problems in downstream features, for example, creating a shell. It is always advisable to create a smooth blended surface rather than surfaces with patches. Pro/ENGINEER enables you to remove unnecessary patches using Control Points. You use the Control Points option to: o Connect logical sets of vertices.o o
Eliminate unnecessary small surfaces and extra edges thus achieving a smoother surface. Avoid undesirable twisting and stretching of surfaces.
To blend the points, you can select: o Vertices of the datum curves or edges used to define the boundary.o
Datum points that lie on the curve.
To add control points to a boundary blend surface you can: o Select the Control Points option from the Boundary Blend dashboard.o o
Add sets of points on each boundary to control the patch definitions. Define them automatically by selecting the other re-parameterization options.
Defining the Boundary Influence
Most surfaces that are created are never placed in isolation. They are placed in conjunction with the other surfaces. Also you need to create shapes in which surfaces flow from one to the other smoothly. You can manipulate the boundaries of the blended surface by defining the boundary influence of the adjacent surfaces. This constraint is used in situations where surface defining curves are available only in one direction. In such a case, you can control the geometry of a blended surface so that the shape and properties of the side curves are propagated into the shape of the blended surface. In essence, the use of boundary influence makes the side edges of the blended surface tangent to the side edges of the reference.
Conic surfaces are used quite often in styling products where a smooth transition is required between surfaces. It is a best practice to use conic fillets over radial fillets to prevent problems related to curvature at the surface transitions. You can use conic fillets to resolve such problems. Conics are widely used in auto styling. In the top figures in the slide, a radius fillet and a conic fillet are defined on the edge of the surfaces. Notice the curvature at the edge where the fillet begins. In the radius fillet, the curvature abruptly changes, but in the conic fillet the curvature gradually increases. There is a smooth transition from the flat surface to the fillet. You can create a conic surface by picking two opposite boundary curves and one control curve. The control curve can be a Shoulder or Tangent curve. o Shoulder CurveThe surface passes through the control curve. In this case, the control curve defines the location of conic shoulders for each cross-section of the surface. o Tangent CurveThe surface does not pass through the control curve. In this case, the control curve defines the line, which passes through the intersections of the conic sections asymptotes. Rules for selecting curves/edges, while creating conic surfaces: o Only single-segment composite curves can be selected as boundary or control curves. o When selecting with the Chain option, the chain cannot have more than one edge/curve component.
Conic Surfaces (cont.)
You can sketch complex shapes such as elliptical, parabolic, and hyperbolic sections for conic surfaces by using conic arcs. To create a conic arc, you select the location for the first endpoint, the location for the second endpoint, and a third intermediate or shoulder location. You can dimension conic sections using the RHO parameter to control the shape of the cross-sections. o Using the RHO parameter: You can dimension the endpoints and specify a value for the RHO parameter (similar to a radius dimension) to control the size and shape of the conic. You can only specify values between 0.05 and 0.95 for the RHO parameter. Based on the values, you get different shapes for the conic section: 0.05 to < 0.50 = Elliptical 0.5 = Parabolic > 0.50 to 0.95 = Hyperbolic 2-1 = Quadrant of an Ellipse Pro/ENGINEER Wi