blower housing

SolidWorks 2009 Training Manual

Exercise 11: Blower Housing

Getting Started With some models, where you should start is not obvious.

You may find it very tempting to start building your sweep by drawing the sweep profile first. It is best practice, however, to create the path and guide curves first so that the profile appears at the right point in history to apply P i e r c e relations to make the sweep work. This can present some difficulties because it is often helpful to use the profile to help build the path and guide curves.

I f you find that you must build the profile first and use it to construct the path and guide curves, you can copy the original profile to a new sketch which is driven by the path and guide curves.

In this part, the overall shape is a flat spiral, but the cross section of the involute shape changes in two directions as the sweep progresses. Making the profile grow taller around the sweep will mean that we use a spiral for the path and a spiral of a slightly larger pitch for the first guide curve. Making the sweep grow in width will be the work of a helix.

Procedure Open a new part from the PartJIN template and name it Blower Housing.

1 C r e a t e the path. The path should be the smallest spiral, since it is best practice to sweep to the outside of a curve when you can. Sweeping to the inside of a curve can create self-intersecting geometry i f the curvature of the path is too small.

Sketch a circle on the Front reference plane with a 4 inch diameter centered at the Origin, as shown.

Create this by following the steps as shown.

This lab reinforces the following skills:

Helix and Spiral on page 76.

Sweep with guide curves, on page 91.

Sweeping Along Model Edges on page 133.

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152 Exerc ise 11: Blower Housing


Next use the He l ix /Spi ra l tool with the sketched circle to create a spiral with the settings below:

For Def ined B y select Sp i ra l . For P i tch enter 0.750". For R e v o l u t i o n s enter 1. For Start a n g l e enter 0 and click

C o u n t e r c l o c k w i s e .

2 C r e a t e the f irst gu ide c u r v e . Draw a second circle again on the Front reference plane, this time with a 5 inch diameter centered at the Origin.

Use the settings below to create a second spiral which will function as a guide curve:

For Def ined B y select Sp i ra l . For P i tch enter 1.500". For R e v o l u t i o n s enter 1. For Start a n g l e enter 0 and click C o u n t e r c l o c k w i s e .

3 C r e a t e the s e c o n d gu ide c u r v e . Create a new plane with an Of fset D i s t a n c e of 0.200" from the Front reference plane.

Name it Helix_Plane.

Draw a third circle on Helix_Plane, with a 4.5" diameter, again centered at the Origin.

This time create a helix with the settings shown.

For Def ined B y select Height a n d R e v o l u t i o n . For Height enter 0.500". For R e v o l u t i o n s enter 1. For Start ang le enter 0 and click C o u n t e r c l o c k w i s e .

You do not need to make a tapered helix to compensate for the increasing diameter. We will accommodate that in the profile sketch.

You should now have two spirals and a helix.

Exerc ise 11: Blower Housing 153


Draw the profile. Open a sketch on the Top reference plane, and sketch a rectangle with two tangent arcs on the horizontal ends, turning two of the lines of the rectangle to construction geometry as shown.

To create involute shape, the spirals will drive the X dimension, so as the spirals get progressively further apart from one another, the X dimension of the sketch gets larger.

The Y dimension will be driven by the helix.

A d d s k e t c h points to the profi le s k e t c h . Add sketch points to the midpoints of the vertical lines. The points allow the spirals to drive the X dimension. The midpoint relations enable the Y dimension to be driven symmetrically.



Important!

7 A d d a n o t h e r s k e t c h point to the profi le. Add a sketch point to the construction line as shown

Do not place the point at the midpoint of the line, just on the line so that it only gets a C o i n c i d e n t relation. The point needs to be able to control the Y dimension and be able to slide back and forth, since the helix does not increase in diameter, but the spirals do.

8 A d d P i e r c e relat ion to hel ix. Add a P i e r c e relation between the new sketch point and the helix. Make sure to select the helix in the graphics window near the end where you want the point to touch it. There are three locations on the plane where the pierce would be correct: either end and the midpoint of the helix.

9 C r e a t e the s w e e p . Use the small spiral as the path, the large spiral as the first guide curve, and the helix as the second guide curve.

Check the intermediate profiles to see how the profile sketch follows the guide curves parametrically.

Also notice that the helix on one side drives the width of the involute symmetrically.

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10 E x t r u d e the outlet. Open a sketch on the outlet end of the involute, select the end face, and click C o n v e r t Ent i t ies .

Now extrude the sketch 2 .25".

Rename this feature Outlet.

11 Offset . Open a new sketch on the Front reference plane.

Select the smaller spiral from the FeatureManager design tree, and create a sketch offset at 0.200".

12 C o m p l e t e the s k e t c h . Complete the sketch with horizontal and vertical lines as shown.

Trim the lines and the spline to create a closed profile.

13 C r e a t e the body. Create a M id -P lane extrusion with a Depth of 0.900".



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14 D r a w outlet r ing s w e e p profi le. Open a new sketch on the Front reference plane.

Switch to H idden L i n e s R e m o v e d to make the sketch more visible.

Notice the sketch penetrates the solid body. In SolidWorks, sweeps are not always exact, so it is best practice to avoid creating line-on-line geometry. In this case, make the sweep interfere slightly with the main body to make sure that the new feature merges.

Create a P i e r c e relation between the endpoint of the arc and the edge of the Outlet.

Edge of Outlet

15 S w e e p the outlet r ing. Select the sketch from the previous step as the profile and the pierced edge as the path.

Use the option T a n g e n t propagat ion so the sweep will continue along the tangent edges, much like a fillet.

The result of the sweep is shown in a different color for illustration purposes.


SolidWorks 2009 Training Manua

16 C r e a t e e x t r u s i o n .

Open a sketch on the flat face as shown.

Sketch a circle centered on the Origin with a diameter of 4 .75".

Extrude the sketch a Depth of 0.550" with Draft of 5.

17 Mirror the feature. Mirror the extruded boss about the Front reference plane.

In t roduc ing: Insert , C u r v e , Spl i t L i n e s uses one or more curves to split one model Spl i t L i n e s face into two. They can be one or more connected sketch entities. They

must be oriented so that they will pass through model faces when projected normal to the sketch plane.

W h e r e to F i n d It Click Insert , C u r v e , Spl i t L i n e . Or on the Curves toolbar, click Spl i t L i n e B .

18 Spl i t l ine.

Open a sketch on the Front reference plane.

Draw a circle centered on the Origin with a diameter of 3.25".

Create a Spl i t L i n e feature splitting the two flat faces as shown.

Make sure the S i n g l e Direct ion option is cleared.



21 S h e l l . Shell the part using a T h i c k n e s s of 0.050".

For the F a c e s to R e m o v e , select the three faces that were created by the split lines in step 18 and step 19.

Notice that at the transition from the involute scroll to the straight outlet, there is a bit of tangent discontinuity. To correct for this, try using a spline to flow smoothly between the spiral and the straight line. A similar technique was shown in the coil spring case study.

Exerc ise 11: Blower Housing

blower housing

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