SolidWorks 2010- P9 pot

On one side of the centerline, the dimension will be the distance from the centerline to the sketch segment or the radius of the shaft see Figure 5.9.. Select the Sketch tab on the Comma

D i m e n s i o n S k e t c h e s w i t h C e n t e r l i n e s 2 0 9

Dimension Sketches with Centerlines

By now you have surely become comfortable with adding dimensions to fully define

sketches Now it is time to introduce another cool dimensioning trick with sketches

As you know, clicking two points or sketch segments will define the distance between

the two entities But since your sketch has a centerline that represents the axis of

revolution for the part, you can use that centerline to define the diameter of the part

even though only half is shown in the sketch This is a great way to control the design

intent of the part since you are probably more apt to require the diameter controlled

rather than the radius Specifying the diameter of a sketch feature is extremely easy if

you already know how to add a dimension, as you will see in the following steps:

1 Select Smart Dimension in the shortcut bar.

2 Select the vertical centerline, and then select the short vertical

seg-ment at the bottom of the sketch

3 The dimension placement is important for how you want to define

the sketch On one side of the centerline, the dimension will be the distance from the centerline to the sketch segment or the radius of the shaft (see Figure 5.9)

F I g u R e 5 9 Defining the radius of a part

4 Move the mouse pointer to the other side of the centerline, and

the dimension changes to show the diameter of the shaft With the

dimension showing the diameter, click and release the left mouse button to place the dimension (see Figure 5.10).

F I g u R e 5 1 0 Defining the diameter of a part

5 In the Modify window, make the diameter 1.000, and click the green

check mark

6 Making a dimension a diameter also works with points on the sketch

With the Dimension tool still active, select the centerline again, and select the undefined endpoint of the small arc, as shown in Figure 5.11

F I g u R e 5 1 1 Defining the diameter from a point on the sketch

7 Move the mouse pointer to the opposite side of the centerline again to

make the dimension a diameter dimension, and accept its location

8 In the Modify window, add the value 900 for the diameter of the

shaft at the end of the arc

9 In addition to lines and points, you can also specify the diameter

for an arc at the tangency Select the centerline again, but this time press and hold the Shift button on your keyboard while selecting the large arc (see Figure 5.12)

M i r r o r a S k e t c h 2 1 1

F I g u R e 5 1 2 Defining the diameter for an arc at the tangent point

10 Move the mouse pointer to the other side of the centerline, and accept

the dimension once it changes to a diameter dimension In the Modify

window, specify the value 1.100, and click the green check mark.

Rather than specifying the radius of the arc, this approach specifies the

diam-eter of the shaft at the largest part of the arc, allowing the radius and length of

the arc to float depending on the other dimensions in the sketch

Mirror a Sketch

Mirroring a sketch or part of a sketch is a great time-saver when areas of the

sketch are symmetric Using a centerline as the mirror point, items that you

select can be mirrored so they take on the relations and dimensions specified in

the original section If you haven’t used another CAD package that has a mirror

function, the length of the mirror line does not matter; instead, the actual angle

used is important This should become clear as you use the Mirror tool in the

next few steps

1 Before mirroring the sketch, you need to finish dimensioning some

items Select the small vertical segment that makes up the 1.00 eter, and place the dimension to the side In the Modify window, add

diam-the value 250.

O

A centerline resenting the axis

rep-of revolution for a part can be used to define the diameter

of the part.

2 Next, select the horizontal line at the bottom of the sketch Then

select the under-defined point at the end of the short arc, and place the dimension so that it is shown as a vertical dimension In the

Modify window, make the value 350.

3 Press Esc on the keyboard to exit the dimension mode.

4 Double-click the scroll wheel or press F on your keyboard to fit the

entire sketch into the graphics area

5 Select the Sketch tab on the CommandManager, and click the Mirror

Entities button

6 Select all the sketch entities that are not centerlines The easiest way

to do this is to window over the sketch selecting all the items Then while holding the Ctrl key on the keyboard, deselect the centerlines

7 Ensure that Copy is selected in the Mirror PropertyManager.

8 Next click the Mirror About field in the Mirror PropertyManager.

9 In the graphics area, select the horizontal centerline A yellow

pre-view will show what the mirrored entities will look like in the ics area (see Figure 5.13)

graph-10 Click the green check mark in the PropertyManager to accept the

mirror sketch entities The sketch now contains the mirror image of the lower half of the shaft above the mirror line with the same size and relations defined in the original section (see Figure 5.14)

M i r r o r a S k e t c h 2 1 3

F I g u R e 5 1 3 Preview of mirrored entities

F I g u R e 5 1 4 Part of a sketch created through mirroring

Trim Sketch entities

Even the most perfectly planned sketch will require segments to be trimmed As you build your sketch by adding sketch entities, you will often be required to trim

a segment using an existing sketch entity as the trimming plane Even the est line that is not properly terminated will cause issues when you attempt to cre-ate a feature In your sketch, you will be adding one last sketch entity that will be used to complete the profile, and you will need to trim all the segments to create one continuous profile But first you need to add the last entity Here’s how:

small-1 Select the Circle command in the shortcut bar.

2 Move the mouse pointer to the middle of the sketch, onto the point

where the two large arcs merge, and click the left mouse button

3 Move the mouse pointer away from the point selected until the radius

of the circle is about 150, as shown next to the mouse pointer in Figure 5.15 Click and release the left mouse button to create the circle

F I g u R e 5 1 5 Using the Circle command

4 Open the shortcut bar, and select Trim Entities.

In the Trim PropertyManager, you will notice there are five different ways to use the Trim tool Each has its strengths and weaknesses, and rather than show you how to use each of them at this point, we’ll just briefly touch on each of them

Power Trim The Power Trim option allows you to trim multiple sketch

enti-ties by dragging the mouse pointer across the segments to be trimmed This is

Tr i m S k e t c h E n t i t i e s 2 1 5

extremely helpful when you have many items that would be too tedious to

indi-vidually select

Corner Trim The Corner Trim tool trims or extends line segments to create

a corner If a selected segment is too short to meet where the obvious corner

should be created, the segment will extend

Trim Away Inside The Trim Away Inside tool allows you to select two sketch

entities and then trim away nonclosed sketch entities that intersect with both

of the selected entities or none of them An example of a closed sketch entity

would be a circle That means even if a circle crosses both of the selected items,

it could not be trimmed with the Trim Away Inside option

Trim Away Outside The Trim Away Outside tool acts the same as the Trim

Away Inside option except sketch entities that fall outside the two entities

selected can be trimmed

Trim To Closest The Trim To Closest option is my most frequently used trimming

option We find that this option is the most useful since it trims anything to the

nearest sketch entity without the need to preselect a trimming entity In fact, in

this particular sketch, it will be the option that will be used to clean up the profile

To perform the trim, do the following:

1 Select Trim To Closest in the Trim PropertyManager.

2 Select the two arc segments that fall inside the circle to trim off the

segment

3 Then, select the two segments of the circle that fall inside the sketch

profile to remove them, making one continuous profile

4 Click the green check mark in the PropertyManager to exit Trim.

5 Since the ends of the large arcs were trimmed back, the relationship

to the original endpoint was lost You need to ensure that the arcs are still connected to the endpoint of the horizontal centerline to maintain the integrity of the sketch While holding the Ctrl key on your keyboard, select one of the large arcs and the endpoint of the horizontal centerline

6 Release the Ctrl key, and select the coincident relation in the context

toolbar

7 Add the coincident relation to the second large arc as well.

8 Select Smart Dimension in the shortcut bar, and click the remaining

section of the circle at the middle of the sketch

9 Place the radius dimension, and enter the radius value of 100 in the

Modify window

10 Now, select the vertical centerline of the sketch, and hold the Shift

button on the keyboard while selecting the middle arc segment

11 Place the dimension, and set the value to 1.250 in the Modify window,

as in Figure 5.16

12 The sketch should be fully defined, as you will be able to tell by all the

sketch segments shown in black and the words Fully Defined in the status bar If the sketch is not fully defined, recheck your sketch for all relationship and dimensions

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F I g u R e 5 1 6 A trimmed sketch segment

Revolve the Sketch

Now that you have fully defined the sketch that makes up the profile for the

lamp shaft, you can create the revolved part All that is required in the sketch is

that a centerline be present to use as an axis of revolution and that all the sketch

entities be on one side of the centerline only The profile that will be used must

also be a closed profile, but since you created the sketch with an obvious

divid-ing line, SolidWorks will be able to place a line along the centerline to close the

sketch To revolve the part, do the following:

1 Select the Features tab on the CommandManager, and click the

Revolved Boss/Base button

2 A SolidWorks message box will prompt you stating that the sketch

needs to be closed and asking whether you would like to cally close the sketch Since you do need it to be closed, click Yes

automati-N O t e Depending on how the sketch was created, SolidWorks will not always be able to properly determine how to close the sketch This sketch is fairly simple, and it will have no problem, but if there is any doubt, it would not be a bad idea to close the sketch manually with a line connected to the two open ends of the sketch

3 Since there is more than one centerline in the sketch, the Revolve

tool doesn’t know which one will be used to revolve the sketch This can be seen by the lack of a selected axis of revolution in the Revolve PropertyManager This means that you must select the vertical center-line that makes up the axis of the sketch manually (see Figure 5.17)

F I g u R e 5 1 7 Selecting a centerline around which to rotate the sketch

The preview in the graphics area will show what the revolved part will look like when created

4 In the Revolve PropertyManager, the only options that you need to be

concerned with are Revolve Type and Angle Of The Revolution The

Revolve Type setting should already be set to One-Direction, and the angle should be set to 360° If that is the case, click the green check mark to create the revolved part The base feature for the lamp shaft has been created! See Figure 5.18

F I g u R e 5 1 8 Preview of a revolved part

A d d a T h r e a d e d B o s s 2 1 9

Now you need to add a few more features to complete the model

Add a Threaded Boss

In lieu of adding separate fasteners to assemblies, it is often advantageous to

build the fastening feature directly into the part In this instance, a threaded boss

is needed to attach the lamp shaft to the lamp base that would be held in place

with a nut Some designers enjoy modeling threads on a part because they want

to show how the threads actually look on the part Although this approach is

very pleasing to look it, it is often still a waste of system resources, not to

men-tion time in modeling the threads Instead of taking the time to model threads

onto a part, we always encourage designers to use the Cosmetic Thread option

Using the Cosmetic Thread option in SolidWorks, a simple representation of

the thread is shown in the part and assembly The information also transfers

well onto the drawing, giving the reader a representation of the thread that

adheres to common drawing standards and that also displays the pertinent

thread information for the manufacturer

N O t e Although it is not the case for this project, there will be times when modeling a true thread is required In those times, the advantages of the actual thread geometry far outweigh the disadvantages For example, if your part model

is to be used for injection-molded parts, using a cosmetic thread may not work with your process, and you would be forced to actually make the thread

Before you can add the threads to the lamp shaft, you first need to add a

boss to the bottom of the shaft This is the portion of the shaft that goes into

the hole in the top boss of the lamp base The next few steps should be pretty

straightforward to you at this point since we have covered this process before

1 Rotate the part around to give you access to the bottom view of the part.

2 Select Extruded Boss/Base in the shortcut bar.

3 Select the bottom face of the revolved part to insert a sketch for the

threaded boss

4 Select the Circle tool in the shortcut bar, and select the origin of the

sketch that corresponds to the center point of the circular face

5 Create a circle and add a diameter dimension of 750 using the Smart

Dimension tool selected in the shortcut bar (see Figure 5.19)

6 Click the Exit Sketch button in the confirmation corner to initiate

the Extrude command

F I g u R e 5 1 9 Sketching a boss

7 In the Depth field in the Extrude PropertyManager, set the depth of

extrusion to 375, and click the green check mark.

8 Click or hover over the SolidWorks logo on the menu bar Select

9 Select the top circular edge of the boss (see Figure 5.20).

F I g u R e 5 2 0 Specifying an edge for a cosmetic thread

A d d a T h r e a d e d B o s s 2 2 1

10 In the Cosmetic Thread PropertyManager, select the Standard field to

display a list of available thread standards From the list, select Ansi Inch After you specify the standard, two additional fields that pertain

to the Ansi Inch thread standard will appear below the field In the first of the two new fields, the Type field, ensure that the Machine Threads option is specified

11 Below the Type field, the second new field is used to specify the

thread In previous versions of SolidWorks, you were required to manually enter the thread size Unless you already knew the size

of the thread you were going to specify, you would need to look up the thread that worked with the diameter of the boss selected In SolidWorks 2010, based on the diameter of the selected edge, the Size field should already be set to the most thread callout Many times the coarse thread is considered the most common, but for this design, you require a fine thread since the length of the boss is only 375″ To select the fine thread, click the Size field, and select the 3/4-10 thread size, as shown in Figure 5.21

F I g u R e 5 2 1 Specifying the thread size in the Cosmetic Thread

PropertyManager

12 Make sure that the End Condition setting, near the bottom of the

Thread Settings section, is set to Up To Next This will make the

cosmetic thread end at the next feature, which is where the boss ends

on the shaft

Th r e a d Si z e

The callout that you used here is a standard thread callout that can be preted by most manufacturers in the United States Each part of the callout gives the machinist the information necessary to create the thread

inter-The first part, ¾, refers to the actual nominal size of the thread

13 Click the green check mark to create the thread on the boss A circle

shown in a dash line will be added to the part to represent the minor diameter of the thread, and the shaded thread will be shown on the cylindrical face of the boss, as in Figure 5.22

F I g u R e 5 2 2 Minor diameter of a thread

N O t e If you do not see a shaded thread as shown in Figure 5.22, you’ll need to update your document properties In the Document Properties tab

of the Options window, click Detailing in the left pane, and then select the Shaded Cosmetic Thread option in the Display Filter section

A d d a R e v o l v e C u t 2 2 3

Add a Revolve Cut

The next feature you need to add to the lamp shaft is a revolved cut that will be

used to create a thread relief at the base of the threaded boss A thread relief is

often preferred by machinists since it makes it easier for them when they cut the

threads to remove the material that comes off the cutting tool A thread relief can

be done a few different ways, but we like to make the smallest diameter of the relief

slightly smaller than the minor diameter of the thread The relief does not need to

be very large, just large enough to allow the machinist to remove the material

To create the thread relief, you need to create a profile of the cutout that will

be revolved around the axis The profile is different from the one that you used

for the shaft itself since the profile is not connected to the axis That and being

a cut are the only two things that are different about this revolve feature for this

part But first, you need to add a couple of features to the boss to complete it

prior to creating the revolve cut; follow these steps:

1 Select the Chamfer tool in the shortcut bar.

2 Select the bottommost circular edge of the boss.

3 In the Chamfer PropertyManager, set the Distance value to 025, as

shown in Figure 5.23

F I g u R e 5 2 3 Adding a chamfer to the boss

4 Accept all the other defaults and select the green check mark to

cre-ate the chamfer on the threaded boss