Design Intent: Effectively using Constraints in SolidWorks

Lecture 9, Part 2

IAT 106 Spatial Thinking and Communicating

Examples

http://idletigers.files.wordpress.com/2008/01/lego-bricks-high-resolution.jpg

http://www.allanblock.com/retainingwalls/Installation/Landscape/build/image/AngleOfRepose76.jpg

http://www.mcs.surrey.ac.uk/Personal/R.Knott/Fibonacci/fibnat.html

http://www.unbeatable.co.uk/articles/jvclt46dz7.jpg

16:9

IAT106: Design Intent M9 Pt2.3

Objectives

• Introduce concept of design intent

• Use constraints in SolidWorks to match design intent

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Design Intent

• What you intend a design to do.

• Some intentions can be modeled.

• Others not.

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Modelable Design Intent

• I intend that the Centre of Effort align with the Centre of Lateral Resistance.

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Un-modelable Design Intent

• I intend that a new boat design transforms the sport of sailing.

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A Square?• What is a square?

Square in SolidWorks1. Draw rectangle2. [Select one edge and define length

using Smart Dimension]

3. Select perpendicular edge, set relationship with previous edge as ‘equal’

4. Result: square!

A rectangle where sides and diagonals meet at right angles; or

All sides have equal size|AB| = |BC| = |CD| = |DA|And meet at right angles

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Constraint

Constraint refers to the degree of logical or mathematical dependence between or among variables.

In modeling we define geometry of objects, particularly:

– Size– Location– Orientation

Example model for demonstrating constraints

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Constraints in Parts

• Often think of constraints when creating assemblies

• But, constraints are just as useful when creating parts

http://www.seacadtech.com/torimoto/

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Types of Constraints

Size Location Orientation

Explicitdefined by user

AD = ABR = AB / 4

Center point on midpoint of diagonal

Angle DAB and ABC = 90°

Implicitselected by user

Equal Concentric Parallel

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Implicit Constraints

Closure Segment Overlap Endpoint / LineOverlap

Tangency

Parallelism Perpendicular Same Size Concentric

Coincident

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Creating Constrained Model

A: Create rough sketch

B: Define parameters and constraints on dimensions

C: Edit parameters to adjust geometry

D: Generate part using extrusion!

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Demo

• Let’s make a ‘cube’ with a hole through it!

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Setup to Sketch a Rectangle

• Select ‘Sketch’

• Select ‘Top Plane’ to draw rectangle

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Draw Rectangle

• Draw rectangle ‘roughly’ that looks like a ‘square’

• But notice that it is not a square yet

• What we need to do to make it square?

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Set ‘Equal’ Constraint on Edges

• Select lower-horizontal edge and select right-vertical edge(holding ‘Shift’ key’)

• Select ‘Equal’ from ‘Add Relations’ tools

• Notice selected items listed

• Notice “ = “ placed next to the lines selected

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Set ‘Dimension’ Constraint

• Select ‘Smart Dimension’

• Select lower horizontal edge

• A dimension will appear with a dialog box with an input field

• Drop down to see options

• Select ‘Link Value…’

• In the ‘Shared Values’ dialog box, type ‘SIZE’ in the name field; and press OK

• We created our first parameter!

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Parameter Value Changed

• Try changing the value on smart dimension; Let’s make it ‘0.05’

• What do you expect?

• Exit ‘Sketch’

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Use Parameter Defined

• Let’s use ‘SIZE’ parameter to define the height of the CUBE!

• Select ‘Sketch’ again

• Select ‘Front Plane’ from the ‘Part3’ after collapsing the tree

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Create Element to Constraint to Parameter

• Select ‘Trimetric’ view

• Select ‘Center Line’ from ‘Sketch’ toolbar

• Draw a construction line from one of the points on the square

• “CONSTRAINT” line VERTICAL

• Now, let’s define its size… or set it to ‘SIZE’ parameter

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Set Dimension Parameter

• Select ‘Smart Dimension’ one more time

• Select the ‘Center Line’ created

• Place the dimension element

• Select ‘Link Value’ while editing

• On the ‘Share Values’ dialog box, select Name pull-down menu to select “SIZE” parameter

• Voila! If you change the size of any line reading its value from “SIZE” all others will follow this change!

• Advantages?

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Create the “CUBE”

• Select “Extruded Boss/Base” command from “Features” toolbar

• Select one of the edges on the square to define the plane

• In ‘Extrude’ properties dialog:– Set ‘From’ as ‘Sketch Plane’– Set ‘Direction 1’ to ‘Up To

Vertex’– On the drawing, select the top

point on the center line (purple)

• Confirm all actions by selecting green ‘Check’ buttons!

• There you go, this is our parametric cube

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Challenge

• How can we create holes as shown in the figures?

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Equations and Link Values

Pros Cons

Equations –Easy to use–Limited set of functions

–Without good dimension names, can be difficult to set up–Can't change the driving (left-side) dimension

Link (Shared) Values

–Easy to use–Ties a single value together–Any linked valued can be changed, and the other updates

–Can provide a direct link only to another value–Hard to understand what's been linked–Limited scope

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Assignments

Reading

• Text: Chapter 4 “Modeling Fundamentals”

• Wikipedia:– Solid modeling: http://en.wikipedia.org/wiki/3D_modeling

– Constructive Solid Geometry (CSG): http://en.wikipedia.org/wiki/Constructive_solid_geometry

Pre-Lab (see next slide , and Pre-Lab document)

Reflective Blog/journal on parts modeling:

• Complete after finishing week 9 project deliverables

• 2 questions on webct

This Week’s Lab

• Step 2 of project– Create parts in SolidWorks– Sketch needed parts– Dimension them– Assign parts to group

members

• Don’t jump into SolidWorks too soon!– Spending more time preparing

and planning will save you time in the long run!

Pre-lab Assignment

• Sketch 2 parts from your AMT (nothing too simple)• Dimension• Label constraints• Label relationships

• Provide rough plan (sequence of sketches or brief description) outlining approximate steps to create parts in SolidWorks.

• See e.g. Feature-Planning Strategies (slide 31 in part 1 slides)