Engineering Design & Material Selection

Focus on the application of the content

0. Planning

1. Concept Development

2. System-Level Design

3. Detail Design

4. Testing & Refining

5. Production Ramp-Up

Product Development Process Phases

1. Identifying lead users

2. Identifying competitive products

3. Collecting user needs

4. Define product requirements

5. Develop alternative design concepts and evaluate to select one and build test concept prototypes

Concept Development invloves…

1. Defines what rather than how

2. Defined in early stage of product development process

3. Not latent

4. Solution-independent

Definition of requirement

1. Effectively communicate and define goals

2. Capture user expectations in binding contract

3. Ensure product fitness

Why the need for well-defined requirements?

1. Explicit (widely understood)

2. Unfulfilled (diff. to address)

3. Latent (currently unaddressed)

Types of user needs

Should weigh less than 4kg and must be protected against dust

Well formulated requirements

Generating a variety of concepts, Utilizing creativity and classification to fill gaps in the explored solution space (ex. Pugh Concept Screening Matrix)

Approach for concept generation phase

Using selection tool to justify a personal or team favorite and preferring solutions that are already implemented in existing products

Pitfalls of concept selection methods

1. Isometric 1:1:1, a and b=30°

2. Dimetric 1:1:1/2, a= 42° and b=7°

3. Trimetric free, 30°<a<45° and b<=30°

List the three axonometric projections

Orthogonal projections, Sections, Detail views

Main views in technical drawings include

1. Choose principal view

2. Choose other required views and cuts

3. Draw views and cuts

4. Add dimensions

5. Verify

Technical drawing process

C

Top view below front view, object before projection plane

1st Angle

Top view above front view, object behind projection plane

3rd Angle

1. Full section

2. Half section

3. Local section

3 Types of Sections

C-C

Antriebsstrang

Drivetrain

Federung

Suspension

Motor Shaft

1. Intra-feature (Independent)

2. Inter-feature (Dependent)

3. Composite (two or more features)

4. Pattern (recurring relation features)

Feature types

1. Define rough geometry

2. Define geometric constraints

3. Evaluate Model (constraint solver)

4. Create variants by changing values and constraints

Parametric modeling guide aids to

Parts sharing some similarities

Part families definition

Fused Deposition Modeling

uPrint SE Plus, Stratasys

0.254 mm and 203 × 203 × 152 mm

Layer Height and maxiumum build envelope

STL file exportation in CAD

Cause of triangulation error

Taxonomy of Projections

While the dimensions can be measured in parallel projections the perspective projection is closer to the eye’s perception. Parallel projections are used in technical drawings, because all elements with equal length are equally dimensioned.

Difference Parallel vs Perspective Projection

Axonometric Projections

Oblique Projections

Mechanical Systems

1. Single person transport electric vehicle

2. Target of elderly or ppl w/o license

3. Max speed of 10,20,30 km/h

4. Range of 65 to 120 km

5. 300 kg empty weight

6. 160 kg payload

Infos to Kyburz PLUS II

1. 3D wireframe models

2. 3D surface models

3. 3D solid models (B-reps, Solid Primitives)

Types of 3D models

Boolean Set Operations

faces, edges and vertices

Boundary-representations consist of

Models can easily be changed and updated through the CAD interface or linked spreadsheets

Pros parametric modeling

a) Vertical, Horizontal, Perpendicular, Tangent, Perpendicular

b) Distance, Angle, Diameter, Radius

a)Basic Geometric Constraints vs. b) Dimensional Constraints

there is a sufficient amount of constraints and no degrees of freedom are left unconstrained

When a sketch is fully constrained…

Recolving = non-intersecting sketch, Sweeping = profile is sweept along a defined curve

3 Modeling operations

B-rep

What is the main solid representation used in CAD sytems?

Continuity conditions ensure smooth transitions while avoiding visible discontinuities. This enhances both the aesthetic appeal and functional accuracy of the design.

Why is it important to use continuity conditions to connect curves and surfaces to represent freefrom objects ?

1. Bézier curves define a network of control points in approximated or interpolated form.

2. The Bézier curves degree is defined by the #control points minus 1.

3. If one point is moved the whole curve is affected.

Bézier curves

1. B-Splines are composite curves and a generalized form of Bézier curves

2. If the knot intervals are equal lenghts, the knot vector is uniform

3. The degree of each curve is k-1

4. Moving one point won’t affect the whole spline

B-spline

1. Non-uniform rational B-splines increase the generality of B-splines allowing almost any freeform curve/surface

2. Knot values can be non-uniformly spaced

3. Control points can be weighted

NURBS

1. Extruding an object from several profiles

2. Common applications in wing, hull and forged object design

3. Object created by interpolating a series of sections

Lofting

1. Bézier curves and surfaces

2. B-splines

3. NURBS

3D surface models include

A feature represents the engineering meaning of the geometry of a part or assembly

Definition feature

parametrize curves and surfaces using control points

The three 3D surface models can