Ken Youssefi Introduction to Engineering, E10. 1

Introduction to Solid Modeling

Parametric (3D) Modeling

Ken Youssefi Introduction to Engineering, E10. 2

Why draw 3D Models?

• Less expensive than building a physical model.

• Can be used for presentations and marketing.

• 3D models can be altered easily, create more concepts

• 3D models are easier to visualize and interpret.• 3D models can be used to perform engineering

analysis, finite element analysis (stress, deflection, thermal…..) and motion analysis

• 3D models can be used directly in manufacturing, Computer Numerical Control (CNC).

Ken Youssefi Introduction to Engineering, E10. 3

Old designs - geometric

New designs - freeform

Ken Youssefi Mechanical Engineering Dept. 4

Radio Thermos

Coffee Press

Ken Youssefi Mechanical Engineering Dept. 5

Hull design

Freeform shapes

Ken Youssefi Introduction to Engineering, E10. 6

Basics of Finite Element Analysis (FEA) What is FEA ?

A complex problem is divided into a smaller and simpler problems that can be solved by using the existing knowledge of mechanics of materials and mathematical tools

Why FEA ?

Modern mechanical design involves complicated shapes, sometimes made of different materials that as a whole cannot be solved by existing mathematical tools. Engineers need the FEA to evaluate their designs

Ken Youssefi Introduction to Engineering, E10. 7

Basics of Finite Element AnalysisThe process of dividing the model into small pieces is called meshing. The behavior of each element is well-known under all possible support and load scenarios. The finite element method uses elements with different shapes. Elements share common points called nodes.

mesh analysis results

10-node Quadratic

Ken Youssefi Introduction to Engineering, E10. 8

Can Crusher

Ken Youssefi Introduction to Engineering, E10. 9

Computer Numerical Control (CNC)A CNC machine is an NC machine with the added feature of an on-board computer.

Machine Control Unit (MCU)

CNC machine

Tool exchanger2 The program path is generated by computer

A solid model of the part is created.

1 Program is entered into MCU via a flash

drive or created by onboard computer

3

Programmed path of cutter is displayed

4

Part is machined6

Programmed instructions

sent to CNC machine

5

Ken Youssefi Introduction to Engineering, E10. 10

CNC MachinesMachining Centers, equipped with automatic tool changers, are capable of changing 90 or more tools. Can perform milling, drilling, tapping, boring… on many faces.

Ken Youssefi Mechanical Engineering Department 11

CNC Face , 3-axis

Animation with Exploded View

Ken Youssefi Mechanical Engineering Dept., 12

Ken Youssefi Introduction to Engineering, E10. 13

Creating Solid ModelsParametric 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.

• Parametric models are featured-based, solid modeling design programs:

SolidWorks, Creo (PTC), Inventor by Autodesk Unigraphics, Catia, …..

• Feature-based is a term used to describe the various components of a model. A part can consist of various types of features such as holes, grooves, fillets, and chamfers.

Ken Youssefi Introduction to Engineering, E10. 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 Introduction to Engineering, E10. 15

Design Intent

2.50

4.00

1.25

2.50

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.

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.

Line not dimensioned

Ken Youssefi Introduction to Engineering, E10. 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.

2.50

4.00

1.25

2.125

Line not dimensioned

2.50

4.00

1.75

30.0OIn the last drawing, the designer calls for a specific angle for the chamfer. In this case the angle of the chamfer should be dimensioned.

Line not dimensioned

Ken Youssefi Introduction to Engineering, E10. 17

Design Intent

Ken Youssefi Introduction to Engineering, E10. 18

Parametric ModelingThe true power of parametric modeling shines through when design changes need to be made. The design modification is made by simply changing a dimension.

Since the counterbore is associated with the top surface of the ring, any changes in the thickness of the ring would automatically be reflected on the counterbore depth.

60

10

15

30Pattern: 8 Holes

Ken Youssefi Introduction to Engineering, E10. 19

Sketching and Features

• Take the word sketch literally. A sketch should be just that, a sketch.

• When sketching it is not necessary to create geometry with accuracy. Lines, arcs, and additional geometry need not be created with exact dimensions in mind.

When discussing the mind-set needed for working with parametric modelers, two topics need to be expanded: Sketching and Features

Sketching

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.

• When the dimensions are added, the sketch will change size and shape. This is the essence of Parametric Modeling.

Ken Youssefi Introduction to Engineering, E10. 20

Sketching and FeaturesFeatures

Create a feature from the sketch by extruding, revolving, sweeping, and lofting.

2.75

2.51.0

.25

.75

Create a 2D sketch and dimension it

Revolved featureExtruded feature

Ken Youssefi Introduction to Engineering, E10. 21

Creating Solids - Sweep

Sweep feature

Profile (section)

Path (guide)

A Sweep feature requires a profile and a path. The profile will follow the path to create the solid.

Ken Youssefi Introduction to Engineering, E10. 22

Creating Solids – Loft (different profiles)

• Sections (profiles) do not have to be sketched on parallel planes

• All sections must be either closed or open

Round profile

Round profile

Square profile

Ken Youssefi Introduction to Engineering, E10. 23

Creating Features from Sketches

Loft in SolidWorks

Ken Youssefi Introduction to Engineering, E10. 24

Applied FeatureApplied feature does not require a sketch. It is applied directly to the model.Fillets and chamfers are very common applied features.

Chamfer

Fillet

Applied Features

Ken Youssefi Introduction to Engineering, E10. 25

Shell – hollowing out a solid

Applied Features - Patterns

Ken Youssefi Introduction to Engineering, E10. 26

Linear (rectangular) pattern

Ken Youssefi Introduction to Engineering, E10. 27

Applied Features - PatternsLinear (rectangular) pattern1. Select direction 1 and 2

2. Select spacing in dir. 1 and 2

3. Select # of features in dir. 1 and 2

4. Select feature to pattern

Applied Features - Patterns

Ken Youssefi Introduction to Engineering, E10. 28

Circular (polar) pattern1. Select axis of rotation

2. Select spacing between features

3. Select # of features

4. Select feature to pattern