project 7 - modeling a control arm

7/29/2019 Project 7 - Modeling a Control Arm

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Project 7: Modeling a Control Arm

In this project you will model this control arm.

The large end of the control arm is clamped to the shaft and tightened with a screw that goes through the

two tabs. When the shaft rotates, this moves the other end of the control arm and in turn moves a rod that

goes through the slot at the end of the arm.

Prerequisites

To model this part you must be able to:

Create sketches.

Create and constrain sketch curves.

Create holes.

Create bosses.


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Create pads.

Create edge blends.

Create datum planes.

Create datum axes.

Create extruded swept features.

The Dimensions of the Part

These are the overall dimensions of this part (in millimeters).

There is a counterbored hole drilled through both tabs.


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The right end of the part is split so that the cylindrical end can be tightened onto a control rod.

The Design Intent

When you have finished, you will want to be able to vary these dimensions:

The overall length of the part.

The radius at each end of the part.

The height of the central portion of the arm.

The height and length of the added material at the left end of the arm.

The height of the cylindrical material at the right end of the arm.

The dimensions of the slot in the left end of the arm.

The dimensions of the tabs.

The size of the split in the cylindrical material.

The Methods Used in This Project to Model the Part

In this project you will:

Use a sketch to create the basic shape of the part. Use a second sketch to add material to the top left side

of the part.


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Use a third sketch to create a slot in the left end of the part.

Use a boss feature to add cylindrical material to the right end of the part.

Create a hole in the cylindrical material.

Add a pad at the right end of the part to create material for two tightening tabs.

Round the end of the pad and add a counterbored hole through it.

Split the cylindrical material (and the pad) to create the two tabs that will allow this part be tightened

onto a control rod.

Task 1. Begin With a Standard Metric Part File

Open the standard metric part file, standard_mm, from the projects sub-directory.

If you want, you can save this part file in your own directory using a name such as ctrl_arm_1.

The standard part file uses the following layer standards:

Solid geometry on layers 1 through 20.

Sketch geometry on layers 21 to 40


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Curve geometry on layers 41 to 60

Reference geometry on layers 61 to 80Sheet bodies on layers 81 to 100

Drafting objects on layers 101 to 120

Start the Modeling application.

Leave the WCS in its default location and orientation.

If you need to, replace the current view with a TFR-TRI view.

This will be the naming convention throughout this project (with the slot on the left and the tab on the

right).

Task 2. Create the Sketch of the Basic Shape of the Arm

Your plan is to use sketches to model the basic shape of this part. That way you can change sketch

parameters to modify the dimensions of the part.

You want to create this sketch on the first layer reserved for sketches.

Make layer 21 the work layer.

Create a sketch on the XC-YC plane of the WCS.

- Have the system display this plane flat on the screen when the sketch is created.

- OPTIONAL: Name this sketch BODY.


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? Choose the Sketch icon or choose InsertSketch.? On the Sketch Tools dialog, turn the Change View Orientation option on.? Choose the Create icon.? You can use the default sketch name (SKETCH_000) or you can key in a name: BODY? Be sure the Sketch Plane option is set to XC-YC.? OKthe dialog.

Task 3. Create Freehand Sketch Curves of the Perimeter of the Arm

Create the sketch curves for the profile. Keep the lines out of the snap angle range.

- HINT: Use ShiftMB3 pop-up menu to change from lines to arcs and back.

? Choose the Basic Curves icon to display the Basic Curves dialog.? Be sure the Line icon is highlighted.? Be sure String Mode is on.? Leave the Point Method set to Infer.? Sketch a line.? Use ShiftMB3, select Arc.? Sketch an arc (using the Start, End, Point on Arc method).? Shift back to Line, and sketch the other line.? Shift back to Arc, and sketch the other arc (connecting one end to the first line before you indicate

the amount of curve).

Task 4. Check for Any Geometric Constraints Added by the System

You will want the ends of the lines and arcs to be tangent.

Depending on the technique you used to create the sketch curves, the system may have applied some

tangent constraints as you worked.

Check the sketch for tangencies between the arcs and lines.

? Choose the Show/Remove Constraints icon.? Run the cursor over each sketch curve.


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Task 5. Constrain the Ends of the Lines and Arcs to be Tangent

Add any tangencies you will need on these sketch curves.- Be careful to not select any end points.

? Choose the Constraints icon.? Choose the Geometric icon on the Constraints dialog.? Select one of the lines and its adjoining arc.? Choose the "Tangent" constraint from the list box.? Apply the dialog (use MB2 to OK the active option).? Continue through until all four tangencies have been applied.

Task 6. Constrain the Distance Between Arc Centers

Next you can constrain the size of these sketch curves to the dimensions required for the basic shape of this

part.

Constrain the distance between the two arc centers. - Use the default text height.

? Choose the Dimensional icon on the Constraints dialog.? Use the Infer method.? Use the Auto Placement positioning option.? Check that the default text height is 3.175.? Select each arc center.? Indicate a location for the dimensional constraint.


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? In the Current Expression text field, key in the required distance value between the arc centers.

Task 7. Constrain the Radius of Each Arc

Constrain the radius of each arc.

?Still using the Infer method, select an arc.

? Place the dimensional constraint.? Key in the radius value of the arc.? Do the same thing on the other arc.

Task 8. Constrain the Arc Centers to Be Horizontal

You will want the two arc centers to be constrained on the XC axis.

You could draw a reference line between the two arc centers, then constrain it with a horizontal geometric

constraint. But you can achieve the same result by constraining each arc center to the horizontal datum axis.

Use a "Point on curve" constraint to constrain an arc center to the horizontal datum axis.

- Then do the same thing on the other arc center.- When you are finished, Fit the view.

? Be sure the Constraints dialog is displayed.? Choose the Geometric icon.? Select an arc center.? Select the horizontal datum axis.? Choose the "Point On Curve" constraint.? Apply it.

Task 9. Constrain the Center of the Larger Arc to the Origin of the WCS

You would like to have arc center of the larger arc at the origin of the WCS.

Use a "Point On Curve" constraint to constrain the arc center of the larger arc to the vertical datum axis.


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? Select the arc center of the larger arc.? Select the vertical datum axis (parallel to YC).? Choose the "Point On Curve" constraint.? Apply it.

Fit the view.

Task 10. Prepare to Create the Solid. Cancel the Constraints dialog.

Deactivate the sketch.

Before you extrude this sketch, you want to place the datum geometry on an appropriate layer.

Move all the datum geometry to layer61.

? Choose the Move to Layer icon or choose FormatMove to Layer.? Use the Type option to display the Select By Type dialog.? Choose Datums.? OKthe dialog.? Choose Select All.? OKthe Class Selection dialog.? In the Destination Layer text field, key in 61.? OKthe dialog (or press Enter/Return

Task 11. Create the Solid

You are ready to create the solid by extruding the sketch.

You want this solid to be on a layer reserved for solids.



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Extrude the sketch.

? Choose the Extruded Body icon from the toolbar or choose InsertForm FeatureExtrude.? For the section string, select any sketch curve and OKthe dialog.? Use the Direction & Distance method.? If the direction arrow points upward, choose the Accept Default Direction option.

- If not, choose Reverse Default Direction.

? Key in the end distance value.? Be sure all the other values are zero.? OKthe dialog.

Task 12. Planning the Way to Add Extra Material Around the Slot

The next step is to add some extra material to the top of the control arm at the small end where a pin will

pass through a slot.

This material will have the same radius as the left end of this part.

If you associate both its left radius and right radius of the extra material to the end of the solid, it will

change if the dimensions on the first sketch are changed.

Optional: Change the view to Gray Thin Hidden Edges.

You will want this second sketch to be on its own layer.


You anticipate that you will also need to use one of the datum axes.

Make the layer the datum geometry is on (layer 61) selectable.


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- Make the layer the sketch is on (layer 21) invisible.

Task 13. Create a Sketch for the Added Material Around the Slot

Create a sketch on the top face of the extruded solid.

- Again, be sure you will be looking down onto the part as you create the sketch curves.

- Define a reference direction that is parallel with the XC axis.

- OPTIONAL: Name this sketch PIN.

?Choose the Sketch icon.

? Be sure the Change View Orientation option is turned on.? Choose the Create icon.? On the Create Sketch dialog, check the selection step.? Be sure the sketch plane will be Face/Plane.? Use the default sketch name (SKETCH_001) or key in the name: PIN? For the attachment face, select the top face of the solid.? Select the Reference Direction Selection Step icon.? Be sure the reference direction will be Horizontal.? Use the "XC" datum axis to define the horizontal sketch direction.? OKthe dialog.

Task 14. Change to a Full Screen Cursor

Now that you are ready to create the profile of the added material, you will want to be able to line up sketch

curves with existing curves.

? Change to a full screen cursor.? Choose PreferenceSelection.? Turn the Crosshairs option on.? OKthe dialog.

Task 15. Create the Sketch Curves for the Added Material

Create the sketch curves for the second extrusion.

- Try to make these lines and arcs close to their final dimensions but within the edges of the solid.

- Keep the horizontal lines within the snap angle.

? Choose the Basic Curves icon.


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? Be sure the Line icon is highlighted on the Basic Curves dialog.? Sketch these lines and arcs within the edges of the solid.

- Use the same Shift+MB3 technique you used on the first sketch.

- Use the full screen crosshairs to draw the horizontal lines within the snap angle.

- Keep the lines within the snap angle.

Task 16. Check for Geometric Constraints Added by the System

You would expect to find that both lines have horizontal constraints.

Also, depending on exactly how you constructed the arcs, you may find some tangencies between the endsof arcs and lines. Both of these types of geometric constraints are critical.

Check the geometric constraints that were applied as you created these sketch curves.

? Use the Show/Remove Constraints dialog to display the constraints that have been added to thesesketch curves.

Task 17. Add Any Missing Horizontal Geometric ConstraintsIf you need to, add horizontal constraints to each horizontal line.

? Choose the Constraints icon on the Sketch Tools dialog.? Choose the Geometric icon on the Constraints dialog.? Select a line.? Choose the "Horizontal" constraint from the list box.? Apply it.

Task 18. Constrain the Ends of the Arcs and Lines to Be TangentBe sure there is "Tangent" geometric constraint at each tangential location on these curves.

? Be sure the Geometric icon is highlighted on the Constraints dialog.? Select a line and adjacent arc (avoiding control points).? Choose the "Tangent" constraint.? Apply it.? Continue until you have constrained all four tangencies.


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Task 19. Constrain the Distance Between Arc CentersYou need to define the distance between the two arc centers of this "extra material" sketch.

You want to use a dimensional constraint that will not overconstrain the sketch.Create a Parallel dimensional constraint between the two arc centers.

? Choose the Dimensional icon.? On the Constraints, dialog, choose the Parallel icon.? Select each arc center.? In the Current Expression text field, key in the required distance value between the two arc

centers.

Task 20. Constrain the Rounded Ends of the Sketch to Have the Same Radius

The rounded ends of this added material must maintain the same radius.


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You have constrained the lines adjoining the arcs to be horizontal and tangent. So you won't need to apply

equal radius constraints because whatever size you apply to one of the arcs, the other will become that sizealso.

Constrain the left arc of the sketch to be concentric with the left arc edge of the solid and to also share itsradius value.

Be sure the Geometric icon is highlighted.

Select the left sketch arc, then the left arc edge of the part (avoiding control points). Use the Control

key to highlight both the "Concentric" constraint and the "Equal Radius" constraints (use Ctrl+select).

Apply them.

Task 21. Create the Added Material

The sketch should now be fully constrained.

Cancel the Constraints dialog.


You are ready to create the added material at the pin end of this part.

Extrude the "added material" sketch.- Unite it with the solid).

Choose the Extruded Body icon.For the section string, select any sketch curve. OK the dialog. Use the Direction & Distance method.

If the direction arrow is pointing upward, use the default direction.Key in the End distance.

Be sure the other values are all zero.

Task 22. Prepare to Create a Slot Through the Added Material


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You will also need a slot through the small end of this control arm for the control pin to go through.

You could use a slot feature to do this.

Another way, however, would be to use a sketch. This will allow you to change the size of the addedmaterial and have the slot adjust accordingly.

Again, you would like to assign this sketch next sketch to its own layer.


You anticipate that you will need to use some of the datum geometry again.

Make layer 22 invisible.- Leave the datum geometry on layer 61 selectable.

OK the dialog.Unite the extruded body with the solid.

Task 23. Create a Sketch for the Control Pin Slot

Create this third sketch on the top face of the added material.

- Be sure you will be looking directly down onto the top face as you create the sketch curves.

- You can use the same method to define the horizontal direction of this sketch.- OPTIONAL: Name the sketch SLOT.

Use InsertSketch to display the Sketch Tools dialog.

Be sure the Change View Orientation option is turned on.

Choose the Create icon.

On the Create Sketch dialog, check the selection step.

Be sure the sketch plane will be a face.

Use the default sketch name (SKETCH_002) or key in the name: SLOTFor the attachment face, select the top face of the added material.


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Select the Reference Direction Selection Step icon.

Be sure the reference direction will be Horizontal.To define the horizontal sketch direction, select the same "XC" datum axis you used for the previous

sketch.

OK the dialog.

Fit the view.

Task 24. Create the Freehand Sketch Curves for the Pin Slot

Now you are ready to create the sketch curves for the slot.

Create the sketch curves within the perimeter of the added material.

- Create lines and arcs similar to the previous sketch.- Keep the horizontal lines within the snap angle.

Choose the Basic Curves icon.

Be sure the Line icon is highlighted on the Basic Curves dialog.

Sketch these lines and arcs within the edges of the solid.

- Use the same Shift+MB3 technique you used on the first sketch.

- Use the cross hairs to keep the lines within the snap angle.

Task 25. Constrain the Ends of the Arcs and Lines to be Tangent

Check the geometric constraints that were applied as you created these sketch curves.

You will probably find both lines to have horizontal constraints and, depending on exactly how you

constructed the arcs, tangencies between the arcs and lines. Both of these types of geometric constraints are

critical.

If you need to, add horizontal constraints to each horizontal line.

Add a "Tangent" geometric constraint at each tangent location on these curves.


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Task 26. Planning the Way to Constrain the Size of Both Ends of the Slot Sketch

What ever radius you apply to one of these arcs, the other will be the same because of the geometrichorizontal and tangency constraints on these sketch curves.

You will also want the length of the slot to be associated with the length of the extra material in case the

dimensions of the added material are changed.

Task 27. Constrain Both Arcs on the Slot Sketch

Constrain each arc to be concentric with the larger arcs of the added material.

Select an arc on the sketch, then select its companion arc edge on the part.

Choose the "Concentric" constraint, and Apply it. Do the same for the other sketch arc.

Task 28. Constrain the Size of Both Arcs on the Slot Sketch

Place a dimensional constraint on one of the slot arcs.


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Choose the Dimensional icon.

Select either sketch arc.Indicate a location for the radius constraint value.

In the Current Expressions field, key in the required radius value.

Task 29. Create the Slot for the Control Pin


Cancel the constraints dialog.

Deactivate this sketch.

You are ready to create the slot in the part.

For this task you won't need to extend the trim face.

Extrude the slot sketch downward to the bottom face of the solid.

- Subtract it from the solid.

Choose the Extruded Body icon. Select the sketch curves.

Use the Trim to Face/Plane method.Point the direction arrow downward.

Use the Do Not Extend Trim Face option.

Select the bottom face.

OK the dialog.

Be sure all the values in the Extruded Body dialog are set to zero.

OK it.

Subtract this extrusion from the solid.

Task 30. Planning the Way to Add the Cylindrical Material to the Arm

The right end of this part must be cylindrical with a hole in it that will fit over a control rod.


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One way to add this material is to create a boss on the top face of the arm. (Another way would be to

extrude a sketch.)

You do, however, want the diameter of this boss to be remain exactly the same as the diameter of the large

arc of the sketch (in case the sketch value for this arc is changed).

You can guarantee this if you use the expression for the diameter of the boss that was used to define theradius of this sketch curve.

Task 31. Find the Name of a Specific Expression

There are several ways you can find the name of a specific expression used for a specific value:

You can activate the sketch that has the dimensions you want to look at (SKETCH_000 or BODY).

Or you can display the Model Navigator, place the cursor over the name of the feature you want to

query, then use the Properties option on the MB3 pop-up menu to display all of the expressions used in that

feature.

Or you can use InformationExpression List AllBy Reference to display all the expressions used for each feature that has been created in the part.

Find the expression that defines the 30 mm radius of the large arc in the first sketch (most likely p1 or

p2).

Task 32. Add the Cylindrical Material at the Right End of the Arm



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Make layer 23 (the third sketch) and layer 61 (the datum geometry) invisible.

Create the boss on the face of the part.

- For its diameter, use the expression name in a formula that will create a diameter value for the boss.

Choose the Boss icon from the toolbar or choose

InsertForm FeatureBoss.

For the placement face, select the top face of the part near its right end.

On the Boss dialog, key in the parameters.

- For the diameter value, use a formula with the name of the expression you looked up.

Task 33. Position the Boss

Position the center of the boss within the center of the arc at the right edge of the part.

Choose the Point Onto Point icon on the PositioningMethod dialog.

Select the left arc edge of the part.

Use the Arc Center method.

Task 34. Create a Hole in the Boss

Next you need to create the hole for the control rod that this arm will be attached to.

This hole must go all the way through the cylindrical material of the the right end of this part.


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Create a simple thru hole on the top face of the boss.

Choose the Hole icon on the toolbar or choose

InsertForm FeatureHole.

Choose the Simple option.

For the planar placement face, select the top face of the boss.

For the thru face, select the bottom face of the part.

Key in the diameter of the hole.

Task 35. Position the Hole

Position this hole along the central axis of the boss.

Choose the Point Onto Point icon.

Select the top edge of the boss.

Use the Arc Center method.

Task 36. Planning the Way to Construct Tabs on the Right End

of the Cylinder

To finish this part you will need to split the right end of the cylindrical material and create two tabs that a

tightening screw will go through to tighten this control arm onto a shaft.

You could create material for each tab separately or create just one tab then mirror it.

For this project, however, you decide that it would be better to create enough material for both tabs then

split all the material at this end of the part.


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Task 37. Planning the Datum Geometry That Will Be Required

You plan to build the pad on a datum plane that is parallel with another datum plane constructed through

the center of the part. If you then associate the height (Z length) of the pad with the offset value betweenthe two datum planes, you can keep it centered in the part.

Task 38. Create the Reference Geometry That Will Be Required

The first datum plane must cut through the center of the part vertically.

You would like this reference geometry for this task to be on its own layer.


Create a datum plane that passes through axes of the cylindrical material at each end of this part.

Choose the Datum Plane icon from the toolbar orchoose InsertForm FeatureDatum Plane.

Select the cylindrical face at the right end of the part, then

the cylindrical face at the left end.

Select the vertical arrow at each end of the part.

Be sure there are two "Through Face Axis" constraints.

Apply the dialog.

Task 39. Create a Second Datum Plane


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You want the next datum plane to be parallel with the first one and to be offset away from it 1/2 the

required height of the pad.

Create a second datum plane parallel to and offset from the first towards the front of the part.

Select the first datum plane.

Be sure the constraint is "Offset To Plane".

Depending on the direction of the arrow, in the Offset field, key in a positive or negative value (either 7

or -7).

Apply the dialog.

Task 40. Planning the Way to Place the Pad

The wall thickness of the cylindrical material is 14 mm. The tab material must extend 12 mm out from the

right end of the cylinder.

If you created a datum plane that was tangent to the hole in this material, you could use it to position one

end of the pad. Then, if you made the pad 26 mm, it would satisfy the design intent.

Task 41. Create a Third Datum Plane

One way to create a datum plane tangent to the face of the hole is to first create a datum plane through the

axis of the cylinder. Then you can use it to create another datum plane that is parallel with it and tangent to

the face of the hole.

Create a datum plane through the axis of the cylinder and along the YC axis of the WCS.


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If you need to, display the Datum Plane dialog.

Select the cylindrical face at the right end of the part.

Be sure the constraint is "Through Face Axis".Apply the dialog.

Task 42. Create a Forth Datum Plane

You are ready to create another datum plane (the one you will use to position the left end of the pad).

Create a datum plane parallel with the third datum plane and tangent to the inside face of the hole.

- Optional: Check your work by looking at the TOP view of the part.

Select the third datum plane (the plane that is parallel with the YC axis).

Select the cylindrical face of the hole.

Select the arrow on the face of the hole that points to the right.Be sure the constraints are "Parallel To Plane" and "Tangent To Face".

Apply the dialog.

Optional: Change the view to a TOP view.

Task 43. Creating the Last Datum Plane

You will remember that you had planned to keep the tab material (pad) centered between the top and

bottom of the cylinder in case there is a design change.

Create a datum plane that is centered horizontally between the top face of the boss and bottom face of the

part.


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? Select the top face of the boss (and be sure both edges on this face are highlighted before youaccept it).? Select the bottom face of the part.? Be sure the constraints are "Center Plane" and "Parallel Plane".? OKthe dialog.

Task 44. Find the Name of an Expression You Will Need

You figure that you now have all the datum planes in place that you will need for this task.

When you create the pad, you will want to use the name of the expression that defines the offset distance

between the two datum planes in the height value for the pad (the offset value is 7 mm).

Then, any required change of the thickness of this tab would be accomplished by changing the offset value

of the datum plane.

Find the name of the expression you will need to use as one of the parameters of the pad (most likely

p20).- Write it down.

- HINT: Use the List All By Reference option.

Task 45. Preparing to Create the Material for Both Tabs

You anticipate that you will need to use the datum axis parallel with the XC axis to define the horizontal

direction of the pad.

Make the datum geometry on layer 61 selectable.

To make your picks easier, you can blank some of the datum

geometry that you will not need for the next task.

Blank all the datum geometry except these.


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Task 46. Create the Material for the Tabs on the Vertical Datum Plane

The pad you are going to create will be placed on the back side of the offset datum plane.

This is the task where you will need to use the expression that defines the offset value between the twocentral datum planes (pxx=7 mm).

Create a rectangular pad on the offset vertical datum plane. - Be sure to create the pad on the correct side

of the datum plane (its back side).

- For a horizontal reference, use the datum axis that is parallel with the XC axis.- Use the expression for the offset in the formula for the Z Length of the pad (and be sure to double it!).

? Choose the Pad icon from the toolbar or choose InsertForm FeaturePad.? Use the Rectangular method.? For the planer face, select the offset datum plane.? Accept or flip the feature side arrow (you want it to point towards the back of the part).? For the horizontal reference, select the "XC" datum axis.? On the Pad dialog, key in the parameters of this feature.

- For the height value, use a formula with the name of the expression you looked up.

Task 47. Position the Pad

You are ready to begin constraining this pad, but you don't want to overconstrain it.


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Position the horizontal centerline of the pad on the horizontal datum plane.

Choose the Line Onto Line icon.

For the target edge, select the horizontal datum plane.

For the tool edge, select the horizontal centerline of the pad.

Position a control point at the left end of the pad on the datum plane tangent to the hole.

Choose the Point Onto Line icon.

For the target edge, select the datum plane tangent to the face of the hole.

For the tool edge, select a point on the left edge of the pad.

Task 48. Planning a Way to Round the End of the Tab Material

The end of each tab must be rounded.

You decide that you can use a blend feature on the upper andlower edge of the pad. If you used a value of 1/2 the width (Y length) of the pad, the two blends wouldcreate the required circular end.


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Task 49. Find the Name of an Expression You Will Need

You will need to know the name of one of the length expressions used to create the tab.

Find the expression that was used to define the pad's Y length (most likely p22).

- Write it down.- HINT: Use the Model Navigator.

Task 50. Round the End of the Tab

Blend the upper and lower edges of right end of the pad.

Choose the Edge Blend icon from the toolbar or choose InsertFeature OperationEdge Blend.

On the Edge Blend dialog, be sure the blend type is Edge.Select the top and bottom edges of the pad.

In the Default Radius field, key in the radius value of these blends.- Use a formula with the name of the expression you looked up.

OK the dialog.

Task 51. Create a Counterbored Hole in the Tab

Before you split the right end of the cylindrical material, you can create the counterbored hole through the

tab material.


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Create a counterbored hole all the way through through the pad.

- Place it on the front face of this material.

? Choose the Hole icon.? Choose the Counterbore icon.? For the placement face, select the front face of the pad.? For the thru face, select the back face of the pad.? Key in the values for the counterbore diameter, the counterbore depth, and the hole diameter.

Task 52. Position the Counterbored HolePosition the hole at the arc center of the rounded end of the tab.

Choose the Point Onto Point icon.

Select the arc at the end of the pad.

Choose Arc Center.


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Task 53. Planning a Way to 'Split' the Cylindrical Solid and the Tab

Your last task is to subtract a portion of the material at the right end of this part to creat a separation in the

cylindrical material.

One way to do this is to create a sketch the width of this separation on the top face of the cylinder, then

extrude (and

subtract) it downward through the solid (including the pad).

If you plan and place the sketch carefully, you can use it to vary the size of the "split" in this material.


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Task 54. Create a Sketch That Will 'Split' the Cylindrical Solid and the Pad

You would like to place this sketch on its own layer. You can also make some of the reference geometry

invisible (but you will need to use the horizontal datum arrow later).

Unblank all of the part.

Change the work layer to layer 24.

Make layer 62 invisible.

- Be sure that the horizontal datum axis remains selectable.

Create a sketch on the top face of the cylinder.

- Be sure that you will be looking down onto the part as you create the sketch curves.- Use the same datum axis you used before to define the horizontal direction of the sketch plane.

- OPTIONAL: Name this sketch SPLIT.

Choose the Sketch icon.Be sure that the Change View Orientation option is on.

Choose the Create icon.

On the Create Sketch dialog, be sure that the Attachment

Face/Plane icon is highlighted.

Be sure that the Sketch Plane option is set to Face/Plane.

You can accept the system name for this sketch

(SKETCH_003) or key in SPLIT.

Be sure the reference direction is set to Horizontal.Select the top face of the cylinder.

Be sure the direction arrow is pointing upward.Choose the Reference Direction icon (or choose OK).Choose the datum axis that is parallel with the XC axis.OK the dialog.

Task 55. Create the Freehand Sketch Curves

You know that you must be able to position the sketch curves rather carefully to achieve the effect you

want.

One way to do this is to anchor its left end of the sketch to the arc center of the hole.


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If you create two lines at the left end of the sketch, you will be able to associate the endpoint between themat the arc center position of the hole.

Make all the datum geometry on layer 61 invisible.

Create the sketch geometry that you will need.

- Keep all of these lines within the snap angle.

- HINT: Sketch these curves away from the part.

Choose the Basic Curves icon.

Be sure that the Line icon is highlighted.

Create these five lines.

Task 56. Check the Geometric Constraints Added by the System

Check that horizontal and vertical constraints were applied as you drew these sketch curves.

- If any are missing, add them.

Choose the Show/Remove Constraints icon.

Run the cursor over all five lines.

Task 57. Constrain Two Lines to Be Equal

It will be important for the left end of this sketch to exactly straddle the datum plane that goes through the

cylindrical material.


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Constrain the two vertical lines on the left end of the sketch to be equal length.

Choose the Constraints icon.

Choose the Geometric icon on the Constraints dialog.

Select each line (zoom in and avoid any control points).

Choose the "Equal Length" constraint from the list box and Apply it.

OK the dialog

Task 58. Constrain the Size of the Sketch Curves

You are ready to constrain this sketch to its correct shape.

Constrain the length and width of the sketch.- While the width (2mm) is critical, the length must just be long enough to completely clear the tab

material.

Choose the Dimensional icon on the Constraints dialog.

Use the Infer icon to add a horizontal dimensional constraint to the top horizontal line.

Add a vertical dimensional constraint to the right vertical line.

Task 59. Position the Sketch

You are ready to position this sketch on the solid. You want the control point between the two vertical lines

on the left side of the sketch to be coincident with the arc center of the cylinder.

Position the point between the two vertical lines of the sketch coincident on the arc center of the hole.

- You can use the arc centerpoint of either circle.

- HINT: Zoom in very close on the end of the sketch!


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Choose the Geometric icon.

Select the arc center symbol (cross) of the hole.Zoom in very close on the left end of the sketch, then select the end point between the two equal length

lines.

Choose the "Coincident" constraint from the list box. Be sure both the arc center and the arc arehighlighted, then

Apply the dialog.

Task 60. Extruding the Sketch to Create the Gap


Cancel the Constraints dialog.


You are ready to "split" the cylindrical material.

To be sure that the solid will cut all the way through the part correctly, you can extend the trim face.

Extrude the sketch downward to the bottom face of the cylinder.

- Extend the trim face.- Subtract the extrusion from the solid.


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Choose the Extruded Body icon.

Select the sketch.

Choose Trim to Face/Plane.

If you need to, Reverse Default Direction of the arrow.

Select the bottom face.

Turn the Extend Trim Face option on.

OK the dialog.

On the Extruded Body dialog, be sure all of the parametersare set to zero/

OK the dialog.

Subtract the extruded sketch from the solid.

Task 61. Clean Up Part

You can do a little clean up to finish this project.


- Make all the other layers invisible.

Task 62. Modify the Part

There are many dimensions you can modify on this part without "breaking" it. Of course there is a limit tothe amount of variation you can introduce.


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You can vary these dimensions:

The overall length of the part (by changing the dimensional

constraint on the sketch).

The radius at each end of the part (by changing the sketch dimensions).

The height of the central portion of the arm (by changing the parameter of the extrusion).

The height and length of the added material at the left end of the arm (by changing the parameters of thesketch and the extrusion).

The height of the cylindrical material at the right end of the arm (by changing the parameters of the

boss).

The dimensions of the slot in the left end of the arm (by changing the parameters of the sketch and the

extrusion).

The dimensions of the tabs (by changing the parameters of the pad the tabs are fashioned from and theoffset value of the datum plane the pad was created on).

The size of the split in the cylindrical material (by changing the parameters of the sketch and its

extrusion).

This completes the project.

project 7 - modeling a control arm

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