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Shanghai Jiao Tong University 1 UG: Free Form Feature ME 250: Design & Manufacturing I School of Mechanical Engineering.

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Presentation on theme: "Shanghai Jiao Tong University 1 UG: Free Form Feature ME 250: Design & Manufacturing I School of Mechanical Engineering."— Presentation transcript:

1 Shanghai Jiao Tong University 1 UG: Free Form Feature ME 250: Design & Manufacturing I School of Mechanical Engineering

2 Shanghai Jiao Tong University 2 Outline Introduction Create and Edit Splines Create Surfaces Summary

3 Shanghai Jiao Tong University 3 Introduction Create the curves used to construct sheet bodies. Create the sheet bodies that will define the surfaces that make up the solid.

4 Shanghai Jiao Tong University 4 Examples

5 Shanghai Jiao Tong University 5 Examples

6 Shanghai Jiao Tong University 6 Examples

7 Shanghai Jiao Tong University 7 Objectives Create simple well-defined geometry that captures the design intent. Analyze the sheet bodies/curves for continuity and flow as well as their relationship to surrounding geometry. Edit the sheet bodies/curves in the areas that need modifications.

8 Shanghai Jiao Tong University 8 Free Form Modeling Process Point _ based Curve _based Sheet _ based Free Form Feature Create/Analysis/Edit Form Feature & Operation Feature Sew/Thicken/Trim Body Solid Sheet Extract Sew/Thicken Note:  Point _based sheet is non parametric  Curve _based sheet is parametric (Smart Sheet) 100%  Sheet _based sheet is most parametric

9 Shanghai Jiao Tong University 9 Free Form Modeling Process General Process :  Create & Analysis Spline (Optional) :  Build “Primary Sheet” :  Build “Transition Sheet” :  Analysis Face : Analysis → Face  Edit Free Form Feature Note: Using Edit→ Features → Parameters… or Using MB3 pop menu on node within PNT 。  Build Solid Body :

10 Shanghai Jiao Tong University 10 Curves Most Free Form Modeling applications will require the use of a previously created edge or generating curve. It is important to control the complexity of these curves, as the complexity will be passed on to its associated body.

11 Shanghai Jiao Tong University 11 Curves

12 Shanghai Jiao Tong University 12 Curves Points, Lines Conics Arc, Ellipse, Parabola, Hyperbola, A General Conic Splines Law curves

13 Shanghai Jiao Tong University 13 A General Conic When 0.001

14 Shanghai Jiao Tong University 14 Rho

15 Shanghai Jiao Tong University 15 Law Curve Law Curve uses a combination of X, Y, and Z components to define a law spline. You can define both two and three-dimensional law splines.

16 Shanghai Jiao Tong University 16 Helix

17 Shanghai Jiao Tong University 17 Splines Splines created in Unigraphics are NURBS (Non-Uniform Rational B- Splines). They are created using defining data(points, slope and curvatures), poles or as the result of another operation.

18 Shanghai Jiao Tong University 18 Spline Segments Single segment curve Multiple segment curve Single segment splines are an excellent first choice to simple model. Multiple segment splines are used to generate more complex sheet/solid bodies.

19 Shanghai Jiao Tong University 19 Spline Degree The degree of a spline refers to degree of the polynomial expression that defines it mathematically. Y=ax 3 +bx 2 +cx+d This equation has a degree of 3.

20 Shanghai Jiao Tong University 20 Spline Degree Single segment spline degree = number of points or poles – 1 Multiple segment spline degree = number of points or poles – number of segments Splines can have a minimum degree of 1 and a maximum degree of 24.

21 Shanghai Jiao Tong University 21 Spline Degree A 3 degree multiple segment spline and a 4 or 5 degree single segment spline are recommend.

22 Shanghai Jiao Tong University 22 Continuity The term continuity refers to the change in flow of curve. A curve can have C0, C1, C2 continuity. The continuity types reflect the geometry combinations used in the creation of a curve.

23 Shanghai Jiao Tong University 23 Continuity C0 continuity is continuous with respect to position and contains a corner. C1 continuity is continuous with respect to tangency and contains a tangent point. C2 continuity is continuous with respect to position, slope, and curvature.

24 Shanghai Jiao Tong University 24 Spline By Poles Through Points Fit

25 Shanghai Jiao Tong University 25 By Poles When a spline is defined "By Poles", it gravitates toward the points you select (referred to as poles), but does not pass through them (except at the endpoints). Curve Type Curve Degree

26 Shanghai Jiao Tong University 26 Through Points A "Through Points" spline passes through all the points you select (these are the defining points). Curve Type Curve Degree Slopes Curvatures

27 Shanghai Jiao Tong University 27 Slopes Automatic Slope Vector Component Direction to Point Vector to Point Slope of Curve Angle

28 Shanghai Jiao Tong University 28 Curvatures Curvature of Curve Enter Radius

29 Shanghai Jiao Tong University 29 Fit Fit Method Curve Degree

30 Shanghai Jiao Tong University 30 Points

31 Shanghai Jiao Tong University 31 Analysis spline

32 Shanghai Jiao Tong University 32 Edit Splines

33 Shanghai Jiao Tong University 33 Specify constraint

34 Shanghai Jiao Tong University 34 Edit Splines

35 Shanghai Jiao Tong University 35 Example

36 Shanghai Jiao Tong University 36 Example

37 Shanghai Jiao Tong University 37 Free from feature Insert-Surface

38 Shanghai Jiao Tong University 38 Free from feature

39 Shanghai Jiao Tong University 39 Through the Points Through Point From Poles From Poles gives you better control of the overall shape and character of the body than does the Through Points. The use of poles also minimizes unwanted undulations in the face of the free form feature. From Point Cloud This is a simple way to create a sheet body that approximates a large "cloud" of data points, typically produced by scanning or digitizing.

40 Shanghai Jiao Tong University 40 A Ruled Body Section strings are on opposing ends of the sheet body.

41 Shanghai Jiao Tong University 41 A Ruled Body Pick Section String 1 and continue to click OK until the cue line prompts you for Section String 2. Pick Section String 2 Select an Alignment string. Type in the appropriate values for the Tolerance, Temp u Count and Temp u Count

42 Shanghai Jiao Tong University 42 Through Curve Bodies Through Curve option specify rows defined by section strings. The amount of section strings can vary between 2 and 150.

43 Shanghai Jiao Tong University 43 Through Curve Bodies Pick the strings. Set the Patch type. Set the Alignment. Verify the V degree Type a value in the Tolerance text box. Select the appropriate constraint for the first and last section strings.

44 Shanghai Jiao Tong University 44 Through Curve Mesh Through Curve Mesh creates a sheet body by defining primary and cross strings.

45 Shanghai Jiao Tong University 45 Through Curve Mesh Pick the first primary curve. This can be made up of a series of continuous curves. Pick the next primary curve. Pick the first cross curve. Repeat this step until you pick all cross curves. Pick a Spine String if needed. Select the appropriate constraint for the first and last section strings.

46 Shanghai Jiao Tong University 46 Swept Features Swept Features create sheet or solid bodies using a profile swept along one, two, or three guide strings. You can specify one section string, with a maximum of 400. If the spine is used, the body limits are controlled by the length of the spine curve.

47 Shanghai Jiao Tong University 47 Section Body You can use the Section option to construct bodies through cross sections that you define using conic, cubic, and quintic construction techniques. To comply with industry standards, and to make data transfer easy, the Section option produces a body with B-surfaces as output. A typical application for sections would be in the design of an aircraft fuselage, or auto body panel.

48 Shanghai Jiao Tong University 48 Section Body A typical application for sections would be in the design of an aircraft fuselage, or auto body panel. To comply with industry standards, and to make data transfer easy, the Section option produces a body with B-surfaces as output.

49 Shanghai Jiao Tong University 49 Use the Section Option You can use the Section option to construct bodies through cross sections that you define using conic, cubic, and quintic construction techniques.

50 Shanghai Jiao Tong University 50 End points-Apex-Shoulder

51 Shanghai Jiao Tong University 51 Slope

52 Shanghai Jiao Tong University 52 Analysis and edit

53 Shanghai Jiao Tong University 53 Analysis

54 Shanghai Jiao Tong University 54 Analysis

55 Shanghai Jiao Tong University 55 Analysis

56 Shanghai Jiao Tong University 56 Extension Sheet Body The length of extension can be either a specified distance or a percentage of the existing sheet body.

57 Shanghai Jiao Tong University 57 Surface Fillet This creates an unparameterized sheet tangent to two sheets or faces that is either circular or conical in a cross-sectional shape.

58 Shanghai Jiao Tong University 58 Offset This creates an offset sheet body from a face of a solid of from another sheet body.

59 Shanghai Jiao Tong University 59 Quilt You can combine a group of sheet bodies in to one sheet body with one face to simplify operations requiring these faces.

60 Shanghai Jiao Tong University 60 Bridge Create a sheet that spans a gap between two existing sheets. The resultant sheet matches either curvature or tangency of the two existing sheets.

61 Shanghai Jiao Tong University 61 Thicken Sheet Create a solid body from a sheet body by giving volume and mass to the sheet.

62 Shanghai Jiao Tong University 62 Mouse Model

63 Shanghai Jiao Tong University 63 Exercise A beautiful or cool cap


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