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Parametric Modeling

Chapter 7. Parametric Modeling. Parametric Modeling Contents. Dimension References Promoting Parameters Promoting Dimension References Promoting Feature Dimensions Parameter Manager Driven/Dependent Parameters Auxiliary Variables Parameter Functions

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Parametric Modeling

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  1. Chapter 7 Parametric Modeling

  2. Parametric Modeling Contents • Dimension References • Promoting Parameters • Promoting Dimension References • Promoting Feature Dimensions • Parameter Manager • Driven/Dependent Parameters • Auxiliary Variables • Parameter Functions • Workshop 7-1, Pulley Model w/ Parameters December 17, 2004 Inventory #002176 7-2

  3. Parametric Modeling Dimension References • When sketches and features are created, their properties are controlled by what are called “dimension references”. Dimension references • Dimension references can be promoted to Design Parameters: • Allows parametric exchange of data. • Makes DM models more flexible to work with. • Is a key component in employing optimization (Sim) techniques. December 17, 2004 Inventory #002176 7-3

  4. Parametric ModelingPromoting Parameters • In the details box, click to promote a dimension reference to a design parameter “D”. • Use the default name or assign a more meaningful name (no spaces, underscore OK). • Notice, the value is no longer editable from the Details window. • Note: you cannot undo promotion of attached CAD parameters. December 17, 2004 Inventory #002176 7-4

  5. Parametric ModelingPromoting Dimension References • Dimension parameters: • Default sketch dimension names indicate the associated plane as well as the specific dimension. • Syntax is “Plane_reference.Dimension_type_and_number”. • Example: • Using the example below, the default name for the parameter reads “XYPlane.D4”. • XYPlane: indicates on which plane the dimension is located. • D4: indicates the specific dimension is Diameter number 4. • It can be easily changed. December 17, 2004 Inventory #002176 7-5

  6. Parametric ModelingPromoting Feature Dimensions • Feature dimensions: • Default feature dimension names indicate the operation as well as the dimension reference number (“FD” indicates Feature Dimension). • Syntax is “Operation_type.Feature_Dimension_number”. • Using the example below the default name for the parameter reads “Extrude1.FD1”. • The name contains 2 pieces of information: • Extrude1 indicates the parameter references the first extrusion created. • FD1 indicates it is parameter value 1 for the extrusion (see above; FD0= rotation angle, FD1= depth, FD2 = Z axis rotation) December 17, 2004 Inventory #002176 7-6

  7. Parametric ModelingParameter Manager • After specifying parameters DM uses the Parameter manager to work with them. • Click the “Parameter” button on the GUI to expose parameter manager tools. December 17, 2004 Inventory #002176 7-7

  8. Parametric ModelingParameter Manager… • The parameter manager window exposes 3 tabs allowing access to specific parametric tools: • Design Parameters tab: • Each design parameter is listed here. • Parameter values are reviewed and changed here. • Use the ‘#’ to add comments to parameter definitions. December 17, 2004 Inventory #002176 7-8

  9. Parametric ModelingParameter Manager… • Parameter/Dimension Assignment tab: • Lists a sequence of “left-hand-side = right-hand-side” assignments (equations) which are used to drive the model dimensions by the given Design Parameters. • The left-hand side is a reference to one of the plane/sketch or feature dimensions or a reference to an auxiliary “variable”. • The right-hand side is an arbitrary expression in +, -, *, and /, including parentheses, referencing Design Parameters (here, the syntax uses the '@' prefix) and feature dimensions, but also numeric constants or references to auxiliary variables. • Can also use ^ for exponential, and % for modulus (remainder of x/y) • Functions (discussed later) can also be used. December 17, 2004 Inventory #002176 7-9

  10. Parametric ModelingParameter Manager… • DesignModeler will evaluate the right-hand side of each expression, and use the resulting value to drive the dimension referenced in the left-hand side. • Design parameter names are preceded by @. • Comments can be added preceded by the #. • Example (from previous page): • XYPlane.R3 = @Hole_Size • Indicates that a design parameter named “Hole_Size” has been defined for a radial dimension reference lying on the XY plane. • A sample comment has been added to the parameter assignment. December 17, 2004 Inventory #002176 7-10

  11. Parametric ModelingDriven/Dependent Parameters • Driven parameters are parameters which take on values based on the value of a “driving” design parameter. • Goal: given the rectangular section shown here, with dimensions S1 for height and S2 for width, drive the value of the width according to the formula, S2 = 2*S1. S2 S1 • In DesignModeler we would proceed as follows: • Dimension the sketch height and width. • Create a design parameter called S1. • S1 will be our “driving” parameter. • Continued . . . December 17, 2004 Inventory #002176 7-11

  12. Parametric ModelingDriven/Dependent Parameters… • By inspecting the details for our sketch (previous page) we can see the width dimension assignment is called H1. • Remember!: The “H” in H1 indicates a horizontal dimension while the “V” in V2 indicates a vertical dimension. • From the Parameter/Dimension Assignments notice the dimension assignment for S1 is: • Knowing the “internal” parameter name for our driven parameter will be “XYPlane.H1” we can type the following formula in the Parameter/Dimension Assignment tab: December 17, 2004 Inventory #002176 7-12

  13. Parametric ModelingDriven/Dependent Parameters… • At this point we could verify our formula by simply changing values for S1, re-generating the model, and checking to make sure the width is always equal to 2*S1. • WAIT! If the regeneration of the model fails due to a mistake in our formula, we could encounter problems trying to undo the operation. • Fortunately DesignModeler contains a more elegant solution to validating parametric formulae: • By moving to the “Check” tab, parametric assignments are evaluated and the result displayed. • Let’s take a closer look at the Check feature . . . December 17, 2004 Inventory #002176 7-13

  14. Parametric ModelingDriven/Dependent Parameters… • The check window is split into two output sections: Parameter/Dimension Assignments Design Parameter Assignments • The sections are listed as “output” since each definition is displayed according to its definition as well as its output value. • In the above case, it can be seen that our parameter “S1” is assigned a value of 35.000 (design parameter section). • Similarly, our driven parameter “XYPlane.H1” evaluates to 70.000. • Since we wish to drive XYPlane.H1 to the value 2*S1 we verify the value of 70.000 makes sense. December 17, 2004 Inventory #002176 7-14

  15. Parametric ModelingAuxiliary Variables • Auxiliary variables are parameters that do not directly define a sketch or feature dimension. • Typically used as a constant value or factor. • Example: • Here we have defined 2 design parameters (@Height and @Length). • We now create a variable named “factor” using the formula shown. • Finally, we set the radius dimension “R5” equal to our variable. • Note, this example is for demonstration only. We could have simply directly defined R5 with the formula used to define the variable. December 17, 2004 Inventory #002176 7-15

  16. Parametric ModelingParameter Functions • Functions can be utilized to capture Design Intent and other relationships among parameters. • Functions are operations that return a single value • ABS(X) • EXP(X) • LN(X) • SQRT(X) • SIN(X) (in degrees) • COS(X) • TAN(X) • For X between –1 and +1. • ASIN(X) & ATAN(X) (return value between -90 & 90 degrees) • ACOS(X) (returns value between zero & 180 degrees) • Examples… • A=acos(-1) # evaluates to –90 • B=abs(X) # evaluates to |X| December 17, 2004 Inventory #002176 7-16

  17. Workshop 7-1, Pulley Model w/ Parameters • Goals: • Create a 3D model through sketching and extruding. • Add a revolved feature to represent the pulley’s groove. • Add a bolt hole pattern with one sketch that is based on a construction sketch. • Parameterize the model so the pulley size automatically updates the bolt hole pattern. A whole range of pulley sizes could now be simulated! • Start Page setup: • Choose to create new geometry, or >File>New • At the prompt, set the length unit to millimeter December 17, 2004 Inventory #002176 7-17

  18. 1 Workshop 7-1, Pulley Model w/ Parameters Create a sketch on the XYPlane: In Tree, click on >XYPlane to activate it Toolbar: “Look At” • [Sketching] > Draw > Circle Note: selecting the Sketching tab after selecting a plane changes to Sketching mode and automatically creates a new sketch if one does not exist December 17, 2004 Inventory #002176 7-18

  19. 2 3 4 5 Workshop 7-1, Pulley Model w/ Parameters Create a sketch on the XYPlane (cont’d): • Select origin for center of circle • Put the cursor near the global origin. You should see a “P” appear near your cursor, indicating an auto-constraint will be applied. Click once with the left mouse button. • Select an arbitrary point for diameter of circle • Click on the screen to define the radius of the circle. The actual value does not matter, as we will dimension this next. • [Sketching] > Dimensions > General • RMB and choose Diameter dimensioning, then click on the circle. Click again on the screen to place the dimension. • Details View: Dimensions > D1 • Click on the text box value next to “D1”. This will highlight the text entry field. Enter “60” for the value of D1. This redefines the diameter as 60 millimeters. December 17, 2004 Inventory #002176 7-19

  20. 9 8 7 6 Workshop 7-1, Pulley Model w/ Parameters Extrude the circle to create a cylinder • Graphics View: Select Iso View ball • Select the light-blue iso-ball on the triad to change to isometric view. • Toolbar: Extrude • Select the Extrude icon on the 3D Features Toolbar. • Details View: FD1, Depth (>0) • Select the text entry box next to “FD1, Depth (>0)” in the Details View. Enter a value of “10” to extrude the sketch 10 millimeters in the positive z-direction. • Toolbar: Generate • Select the Generate icon on the Toolbar to generate the cylinder. December 17, 2004 Inventory #002176 7-20

  21. 11 10 Workshop 7-1, Pulley Model w/ Parameters Toolbar: “Look At” icon (XYPlane is already active) Toolbar: “New Sketch” (creates Sketch2 on XY plane) [Sketching] > Draw > Polygon n=5 • Put the cursor near the global origin. You should see a “P” appear near your cursor, indicating an auto-constraint of “Coincident Point” will be applied. Click once with the left mouse button to define the center of the polygon. • Put the cursor near the positive Y axis. You should see a “C” appear near the cursor indicating the point is coincident to the Y axis. Click once with the left mouse button to define the top vertex location. December 17, 2004 Inventory #002176 7-21

  22. 13 12 Workshop 7-1, Pulley Model w/ Parameters Dimension the 5 sided polygon [Sketching] > Dimensions > Vertical • Dimensions the polygon as shown at right. • Select the text entry box next to “V2” and enter a value of 20 mm. December 17, 2004 Inventory #002176 7-22

  23. 14 ! 15 Workshop 7-1, Pulley Model w/ Parameters Create the holes for the bolt pattern: Note: XYPlane is still active Toolbar: “New Sketch” icon (creates Sketch3 on XY plane) Toolbar: “Look At” icon [Sketching] > Draw > Circle • Put the cursor near the top vertex until a “P” appears near your cursor, indicating an auto-constraint will be applied. Click to define the center of the circle then drag the cursor to define the circle radius. • Repeat the above step at each of the (5) vertices of the polygon. • IMPORTANT:watch for the “R” to appear next to the cursor before clicking to define each radius. This indicates the new circle is radially constrained to the previous circle. Note: if you inadvertently fail to apply auto constraints, you can undo the selection and try again, or use >Constraints tab and apply them manually. December 17, 2004 Inventory #002176 7-23

  24. 17 16 Workshop 7-1, Pulley Model w/ Parameters Dimension the top circle: [Sketching] > Dimensions > Diameter • Click on the top circle created in step 14. • Specify 5mm diameter in the dimension Detail. • Note: vary the dimension several times to see if all circles update to the new value. Can use >Dimensions>Animate too! Remember to make final dimension 5 mm before moving on to the next step. 8 mm December 17, 2004 Inventory #002176 7-24

  25. 19 18 20 Workshop 7-1, Pulley Model w/ Parameters Extrude Sketch 3 to create the bolt holes Toolbar: Extrude • Details: • Operation: “Cut Material” • Type: “Through All” • “Generate” December 17, 2004 Inventory #002176 7-25

  26. 22 21 Workshop 7-1, Pulley Model w/ Parameters Create a sketch to revolve around the pulley in order to define the pulley groove • Click on >ZXPlane in Tree to make it active • Toolbar: “New Sketch” • Toolbar: “Look At” icon • Sketching: Draw > Rectangle • Draw a rectangle in the approximate location shown at right December 17, 2004 Inventory #002176 7-26

  27. Workshop 7-1, Pulley Model w/ Parameters Dimension the sketch • [Sketching] > Dimensions Using the dimension toolbox add dimensions as shown here December 17, 2004 Inventory #002176 7-27

  28. 24 29 28 27 25 26 Workshop 7-1, Pulley Model w/ Parameters Create the pulley groove by revolving the sketch > Modeling>ZXPlane > Sketch4 • Toolbar: Revolve • Click on the Z axis in the graphics window • Click >Apply • Change the Operation to “Cut Material” • Change “FD1, Angle” to 360 • Generate the feature • Click on the Blue Triad ISO Ball as desired. December 17, 2004 Inventory #002176 7-28

  29. Workshop 7-1, Pulley Model w/ Parameters With the pulley model completed as shown here we will now create a parameter for the pulley’s diameter and define several expressions to control the pulley’s features. December 17, 2004 Inventory #002176 7-29

  30. 30 31 Workshop 7-1, Pulley Model w/ Parameters [Modeling Tree] >XYPlane > Sketch1 • In the Sketch1 Detail check the box next to D1 This action will immediately cause a dialog box to be displayed containing the default dimension name. • Enter “Pulley_Dia” in the dialog box to name the parameter then OK. December 17, 2004 Inventory #002176 7-30

  31. Workshop 7-1, Pulley Model w/ Parameters Note: we have now made the pulley diameter a parametric value. Since our goal is to “drive” the other dimensions to automatically reflect any diameter change, we’ll now create several expressions for that purpose. In particular, there are 2 dimensions we need to control, the hole pattern dimension and the pulley’s groove radius (see below). Recall the original dimensions were: Pulley_Dia = 60 Hole pattern = 20 Groove radius = 28 The desired formulae are: • Hole pattern placement • Dimension = (Pulley_Dia) / 3 • Pulley groove diameter. • Dimension = (Pulley_Dia)/2 - 2 December 17, 2004 Inventory #002176 7-31

  32. 32 Workshop 7-1, Pulley Model w/ Parameters Activate the parameter manager via the toolbar icon Toolbar: Parameters • Click on the “Parameter/Dimension Assignments” tab to enter equations. • NOTE: Your default parameter names may be different depending on the order and type of >Dimensions placed. • Click on your various sketches in the Tree to display your default names in the Detail Window • This equation is for the overall size of the bolt pattern that lies on the XY plane. • This equation is for the groove sketch radial dimension line. This sketch lies on the ZX plane. Hole Pattern Size is Dia/3 The Groove is placed at “Dia/2 minus 2mm” . The “minus 2” insures it always cuts a 2mm deep groove. December 17, 2004 Inventory #002176 7-32 Note: Your default parameter names may be different

  33. Workshop 7-1, Pulley Model w/ Parameters Return to the “Design Parameter” tab Experiment with new values for “Pulley_Dia” and click “>Check” tab after each change. Notice the “driven” dimensions can be viewed and evaluated with their updated values. Pulley_Dia = 40 mm Pulley_Dia = 150 mm December 17, 2004 Inventory #002176 7-33 Note: Your default parameter names may be different

  34. Workshop 7-1, Pulley Model w/ Parameters Once again, experiment with new values for “Pulley_Dia”, this time “generating” the model after each change. Note how all model dimensions update simultaneously. This could represent an entire range of pulley sizes (part family) or a series of design variations to used in optimization. December 17, 2004 Inventory #002176 7-34

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