Creating Solid Models
Parametric Modeling Concept
• Parametric is a term used to describe a dimension’s
ability to change the shape of model geometry if the
dimension value is modified.
• Feature is a term used to describe the various
components of a model. For example, a part can
consists of various types of features such as holes,
grooves, fillets, and chamfers.
• Parametric modeler are featured-based, parametric,
solid modeling design program: SolidWorks, ProEngineer, Unigraphics (CSG and parametric),
AutoCAD’s Inventor, …..
Ken Youssefi
Engineering 10, SJSU
1
Sketching and Features
When discussing the mind-set needed for working with parametric
modelers, there are two topics that need to be expanded: Sketching
and Features
Sketching
• Take the word sketch literally. A sketch should be just
that, a sketch
• When sketching it is not necessary to create geometry
with accuracy. In other words the geometry need not be
created with exact dimension in mind.
• When dimensions are added, the sketch will change size
and shape. This is the essence of parametric modeling.
In short, the sketch need only be the approximate size and shape
of the part being designed. When dimensions are added, they
will drive the size and the shape of the geometry.
Ken Youssefi
Engineering 10, SJSU
2
Sketching – Drawing Tools
2D sketch menu
Line
Spline tool fits a curve
thru selected points
Circle
Arc
Rectangle
Rounding edges
Ken Youssefi
Engineering 10, SJSU
3
Exiting Sketch
To exit the sketch, right click and select Finish Sketch
Ken Youssefi
Engineering 10, SJSU
4
Dimensioning Sketch
Select the dimension icon
→ select the object to dimension (line),
you can also select two endpoints of a line → specify the desired value.
Over dimensioning (over-constrained) – an error message will appear if
there is redundancy in dimensioning. e.g., if you dimension both lines that
constitute the short side of the rectangle, the window below is activated;
decide which dimension to keep – Accept to make the last dimension the
driver, or Cancel to make the first dimension the driver.
Short
sides
Ken Youssefi
Engineering 10, SJSU
5
Editing a Sketch
Browser shows the
history of the model
The box was created by sketching a rectangle
1.25 x .75 and then extruded by .5 (depth)
Change the height from .75 to 1.0
.75
Select sketch and right click, choose Edit Sketch
Ken Youssefi
Engineering 10, SJSU
6
Editing a Sketch
Double click the dimension to be
changed and enter the new dimension
Click the Update icon to have the modification
take effect
Ken Youssefi
Engineering 10, SJSU
7
Constraints
Geometric constraints may be added to sketch to apply behavior to a specific
object or to create a relationship between two objects.
B
C
1 - It is desired to have AB always vertical.
2 - It is required to have AB = CD.
Constraints
A
D
Click the constraint icon
(perpendicular by default) to
see the constraint menu.
Ken Youssefi
Engineering 10, SJSU
8
Constraints
Choose Vertical from the constraint
menu and select the line.
Choose Equal from the constraint
menu and select both lines.
Ken Youssefi
Engineering 10, SJSU
9
Sketching – Modifying Tools
Original shape
Creates a duplicate of a selected object at a
specified distance
Offset shape
1. Click the Offset tool.
2. Click the sketch geometry you want to copy.
3. Move the cursor in the direction you want to place the offset geometry,
then click to create the new geometry.
4. Click to place the curve at the offset distance.
5. If desired, use the Dimension tool to set a specified offset distance.
1. Select the geometry to move. The Select button is on by default when
you open the Move tool.
2. Set the starting point for the move command. Once selected, you can
click anywhere in the graphics window or select the Precise Input check
box to enter X and Y coordinates of the base point into the Precise Input
toolbar.
Ken Youssefi
Engineering 10, SJSU
10
Sketching – Modifying Tools
1. Select the geometry to rotate. Click the Select button, and then select the
geometry in the graphics window. The Select button is on by default when
you open the Rotate tool.
2. Set the center point about which the geometry rotates. Once selected, you
can click a point in the graphics window or select the Precise Input check
box to enter X and Y coordinates of the center point into the Precise Input
toolbar.
3. Specify the rotation angle. Enter the angle, or click the arrow and select
the angle from the list. The field also shows the value dynamically as you
drag the pointer in the graphics window.
Sketch
Ken Youssefi
Center of rotation
Angle of rotation
Engineering 10, SJSU
11
Sketching – Modifying Tools
1. Select sketch geometry to mirror.
2. Select the mirror line (centerline) about which the sketch geometry is mirrored.
centerline
sketch
1. Select the geometry to copy. The Select button is on by default when you
open the Copy tool.
2. Set the starting reference point for the copy command. Once selected, you can
click anywhere in the graphics window or select the Precise Input check box to
enter X and Y coordinates of the base point into the Precise Input toolbar.
Ken Youssefi
Engineering 10, SJSU
12
Sketching – Modifying Tools
Use the Trim tool to trim curves or remove segments.
1. Click the Trim tool.
2. In the graphics window, pause over a curve to preview the trim,
then click to complete.
Segment to trim
1. Click the Extend tool.
2. In the graphics window, pause the cursor over a curve to preview
the extension, then click to complete.
Ken Youssefi
Engineering 10, SJSU
13
Sketching – Modifying Tools
1. Select the geometry to scale.
2. Set the start point from which the geometry will scale.
3. Sets the exact value by which to multiply the dimensions of the selected
geometry. The field also shows the value dynamically as you drag the
pointer in the graphics window.
Ken Youssefi
Engineering 10, SJSU
14
Design Intent
• In parametric modeling, dimensions
control the model.
• Design intent is how your model will
react when dimension values are
changed.
Ken Youssefi
Engineering 10, SJSU
15
Design Intent
The drawing shows the intent of the
designer that the inclined plane
(chamfer) should have a flat area
measuring 2.5 inches and that it should
start at a point 1.25 inches from the
base of the drawing. These parameters
are what the designer deemed
significant for this model.
2.50
2.50
1.25
4.00
Remember that the placement of dimensions is very
important because they are being used to drive the
shape of the geometry. If the 2.5 in. vertical dimension
increases, the 2.5 in. flat across the chamfer will be
maintained, but its angle will change.
Ken Youssefi
Engineering 10, SJSU
16
Design Intent
In this drawing, what is important
to the designer is the vertical
location and horizontal dimension
of the chamfer, rather than the flat
of the chamfer.
2.125
2.50
1.25
4.00
1.75
In the last drawing, the designer calls
for a specific angle for the chamfer. In
this case the angle of the chamfer
should be dimensioned.
30.0O
2.50
4.00
Ken Youssefi
Engineering 10, SJSU
17
Design Intent
Ken Youssefi
Engineering 10, SJSU
18
Design Notes
• Keep in mind that dimensioning scheme can
be changed at any time. You are not locked
into a specific design. You can also design
without dimensioning, rough out a sketch, and
then later go back and fully define it.
• Do not be concerned with dimensioning to
datum or stacked tolerances in the part. Those
issues can be addressed in the drawing layout.
Be more concerned with your design intent.
Ken Youssefi
Engineering 10, SJSU
19