Dimensional constraints in AutoCAD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a dimensional constraint in AutoCAD?

A dimensional constraint controls the size or distance of objects, keeping them fixed or related to other objects in a drawing.

intermediate

How does a dimensional constraint differ from a geometric constraint?

Dimensional constraints control size or distance, while geometric constraints control shape and position relationships like parallelism or perpendicularity.

beginner

What happens when you change a dimensional constraint value in AutoCAD?

The related object resizes or moves automatically to maintain the specified dimension, keeping the design consistent.

beginner

Name two common types of dimensional constraints in AutoCAD.

Linear constraints (control length or distance) and angular constraints (control angles between lines).

beginner

Why are dimensional constraints useful in design and drafting?

They help keep drawings accurate and consistent, making it easier to update designs without errors.

What does a dimensional constraint control in AutoCAD?

A Color of objects

B Size or distance of objects

C Layer visibility

D Text font style

Dimensional constraints control the size or distance of objects to keep them fixed or related.

Which type of dimensional constraint controls the angle between two lines?

A Linear constraint

B Perpendicular constraint

C Parallel constraint

D Angular constraint

Angular constraints control the angle between two lines.

What happens when you update a dimensional constraint value?

A The drawing color changes

B The layer is locked

C The object resizes or moves accordingly

D The text size changes

Updating a dimensional constraint changes the object size or position to maintain the dimension.

Which of these is NOT a dimensional constraint?

A Parallelism between two lines

B Angle between two lines

C Distance between two points

D Length of a line

Parallelism is a geometric constraint, not a dimensional constraint.

Why use dimensional constraints in your drawing?

A To keep designs accurate and easy to update

B To change colors automatically

C To add text labels

D To hide layers

Dimensional constraints keep designs accurate and consistent, making updates easier.

Explain what dimensional constraints are and how they help in AutoCAD drawings.

Think about how you keep measurements fixed or related in a drawing.

Describe the difference between dimensional and geometric constraints with examples.

One controls measurements, the other controls relationships.

Practice

1.

What is the main purpose of dimensional constraints in AutoCAD?

easy

A. To change colors of objects automatically

B. To fix sizes and angles so parts stay consistent when edited

C. To create 3D models from 2D drawings

D. To export drawings to other file formats

Solution

1. Step 1: Understand the role of dimensional constraints

   Dimensional constraints fix sizes and angles in drawings to keep parts consistent.

2. Step 2: Compare options with this role

   Only To fix sizes and angles so parts stay consistent when edited describes fixing sizes and angles; others describe unrelated tasks.

3. Final Answer:

   To fix sizes and angles so parts stay consistent when edited -> Option B

4. Quick Check:

   Dimensional constraints = fix sizes and angles [OK]

Hint: Remember: constraints keep sizes fixed when editing [OK]

Common Mistakes:

• Confusing constraints with color or export features
• Thinking constraints create 3D models
• Assuming constraints change object appearance

2.

Which command is used in AutoCAD to add dimensional constraints?

DIMCONSTRAINT has options like Linear, Radial, and Angular.

easy

A. DIMCONSTRAINT

B. DIMSTYLE

C. DIMEDIT

D. DIMLINEAR

Solution

1. Step 1: Identify the command for dimensional constraints

   The command DIMCONSTRAINT is used to add dimensional constraints with options like Linear, Radial, Angular.

2. Step 2: Check other commands

   DIMSTYLE changes styles, DIMEDIT edits dimensions, DIMLINEAR adds linear dimensions but not constraints.

3. Final Answer:

   DIMCONSTRAINT -> Option A

4. Quick Check:

   Command for constraints = DIMCONSTRAINT [OK]

Hint: Use DIMCONSTRAINT to fix sizes and angles [OK]

Common Mistakes:

• Choosing DIMSTYLE which only changes appearance
• Confusing DIMEDIT with adding constraints
• Selecting DIMLINEAR which is dimension type, not constraint

3.

Given a rectangle with a horizontal linear dimensional constraint set to 100 units, what happens if you try to stretch the rectangle's width to 120 units?

medium

A. AutoCAD shows an error and stops the action

B. The width changes to 120 units ignoring the constraint

C. The width stays at 100 units due to the constraint

D. The rectangle changes height instead of width

Solution

1. Step 1: Understand the effect of a linear dimensional constraint

   A linear dimensional constraint fixes the length to a set value, here 100 units.

2. Step 2: Predict behavior when stretching width

   Trying to stretch width to 120 units will not change it because the constraint keeps it at 100 units.

3. Final Answer:

   The width stays at 100 units due to the constraint -> Option C

4. Quick Check:

   Constraint fixes size = width stays 100 [OK]

Hint: Constraints prevent size changes despite stretching [OK]

Common Mistakes:

• Assuming width changes ignoring constraints
• Thinking height changes instead of width
• Expecting an error message from AutoCAD

4.

Which of the following is a common mistake when applying dimensional constraints in AutoCAD?

Consider this code snippet: DIMCONSTRAINT Linear 50 applied to a line.

medium

A. Applying a constraint without selecting the object first

B. Using DIMCONSTRAINT with a value less than 100

C. Applying constraints only to circles

D. Using DIMCONSTRAINT without specifying Linear, Radial, or Angular

Solution

1. Step 1: Check correct syntax for DIMCONSTRAINT

   The command requires specifying the type: Linear, Radial, or Angular before the value.

2. Step 2: Identify the mistake in options

   Using DIMCONSTRAINT without specifying Linear, Radial, or Angular shows missing type, which causes error. Other options are either allowed or irrelevant.

3. Final Answer:

   Using DIMCONSTRAINT without specifying Linear, Radial, or Angular -> Option D

4. Quick Check:

   Specify constraint type = required [OK]

Hint: Always specify constraint type before value [OK]

Common Mistakes:

• Skipping object selection before applying constraint
• Thinking value must be above 100
• Applying constraints only to circles

5.

You have a mechanical part drawing with multiple connected lines. You want to keep the angle between two lines fixed at 45 degrees and the length of one line fixed at 150 units. Which combination of dimensional constraints should you apply?

hard

A. Apply an Angular constraint of 45 degrees and a Linear constraint of 150 units

B. Apply two Radial constraints of 45 and 150 units

C. Apply a Linear constraint of 45 degrees and an Angular constraint of 150 units

D. Apply only a Linear constraint of 150 units

Solution

1. Step 1: Identify constraints needed for angle and length

   Angle fixed at 45 degrees requires an Angular constraint; length fixed at 150 units requires a Linear constraint.

2. Step 2: Match constraints to options

   Apply an Angular constraint of 45 degrees and a Linear constraint of 150 units correctly applies Angular for angle and Linear for length. Other options mix types incorrectly or miss angle constraint.

3. Final Answer:

   Apply an Angular constraint of 45 degrees and a Linear constraint of 150 units -> Option A

4. Quick Check:

   Angle = Angular, Length = Linear [OK]

Hint: Use Angular for angles, Linear for lengths [OK]

Common Mistakes:

• Mixing Radial with angle or length incorrectly
• Swapping Angular and Linear constraint types
• Applying only one constraint when two are needed