Converting entities and intersection curves in Solidworks - Deep Dive

Overview - Converting entities and intersection curves

What is it?

Converting entities and intersection curves are tools in SolidWorks that help you create new sketch lines based on existing edges or surfaces. Converting entities copies edges or faces into your sketch as lines or curves. Intersection curves create sketch curves where two surfaces or bodies meet. These tools make it easier to build complex shapes by reusing existing geometry.

Why it matters

Without these tools, you would have to redraw complex shapes manually, which is time-consuming and error-prone. They help keep your designs accurate and consistent by linking sketches to existing 3D geometry. This saves time and reduces mistakes, making your design process smoother and more reliable.

Where it fits

Before learning these tools, you should understand basic sketching and 3D modeling in SolidWorks. After mastering them, you can move on to advanced surface modeling and complex assemblies where precise geometry linking is crucial.

Mental Model

Core Idea

Converting entities and intersection curves let you trace existing 3D shapes into sketches to build new features accurately and quickly.

Think of it like...

It's like tracing a shadow on paper to capture the exact shape of an object without drawing it freehand.

┌───────────────────────────────┐
│        3D Model Surface       │
│   ┌───────────────────────┐   │
│   │                       │   │
│   │   Edge or Face to Use  │   │
│   │                       │   │
│   └───────────────────────┘   │
│               │               │
│               ▼               │
│      Convert Entities Tool    │
│               │               │
│               ▼               │
│       Sketch with Lines       │
└───────────────────────────────┘

Build-Up - 6 Steps

1

Foundation

Understanding Sketches and Edges

Concept: Learn what sketches and edges are in SolidWorks and how they relate.

Sketches are 2D drawings that define shapes for 3D features. Edges are the boundaries of 3D shapes. Knowing how sketches and edges connect helps you use tools that link them.

Result

You can identify which parts of a 3D model can be traced or referenced in sketches.

Understanding the relationship between sketches and edges is the base for using conversion and intersection tools effectively.

2

Foundation

Basic Use of Convert Entities Tool

Concept: Learn how to copy edges or faces into sketches using Convert Entities.

Select edges or faces on your 3D model, then use Convert Entities to create sketch lines or curves that match those edges. This creates a live link so if the model changes, the sketch updates.

Result

Your sketch now contains lines exactly matching the selected edges, ready for further modeling.

Knowing how to convert entities saves time and ensures sketches match the 3D model perfectly.

3

Intermediate

Creating Intersection Curves

🤔Before reading on: do you think intersection curves are just copies of edges? Commit to your answer.

Concept: Learn how to create curves where two surfaces or bodies intersect.

Use the Intersection Curve tool to select two surfaces or bodies. SolidWorks calculates the exact curve where they meet and adds it to your sketch. This is useful when edges don't exist but surfaces intersect.

Result

You get a precise sketch curve representing the intersection line between surfaces.

Understanding intersection curves helps you capture complex geometry that isn't defined by simple edges.

4

Intermediate

Linking Sketches to Model Changes

🤔Before reading on: do you think converted entities update automatically if the model changes? Commit to yes or no.

Concept: Learn how converted entities and intersection curves update when the 3D model changes.

Converted entities and intersection curves maintain a live link to the model. If the original edges or surfaces change, the sketch updates automatically. This keeps your design consistent without manual edits.

Result

Sketches stay accurate and reflect the latest model changes without extra work.

Knowing this live link prevents errors and saves time during design revisions.

5

Advanced

Using Intersection Curves in Complex Models

🤔Before reading on: do you think intersection curves can be used between non-planar surfaces? Commit to yes or no.

Concept: Learn how intersection curves work with complex, curved surfaces in advanced modeling.

Intersection curves work on any two surfaces, even curved or irregular ones. This allows you to create precise sketches for complex shapes like car bodies or consumer products where surfaces meet in 3D space.

Result

You can capture exact intersection lines for advanced surface modeling.

Understanding this expands your ability to model complex, real-world shapes accurately.

6

Expert

Managing Dependencies and Performance

🤔Before reading on: do you think too many converted entities slow down your model? Commit to yes or no.

Concept: Learn how heavy use of converted entities and intersection curves affects model performance and how to manage it.

Each converted entity or intersection curve creates a dependency link. Too many can slow down rebuild times or cause errors if upstream geometry changes drastically. Experts manage these by simplifying sketches or using reference geometry strategically.

Result

Your model remains efficient and stable even with complex linked sketches.

Knowing how dependencies affect performance helps you build robust, maintainable models.

Under the Hood

Convert Entities works by creating a parametric link between the sketch and the selected model edges or faces. It copies the geometry's exact shape into the sketch plane, maintaining references so changes propagate. Intersection Curves calculate the 3D intersection line mathematically between two surfaces or bodies, then project that line into the sketch plane as a curve.

Why designed this way?

These tools were designed to reduce manual sketching errors and speed up modeling by reusing existing geometry. Parametric links ensure models stay consistent during changes. Alternatives like manual tracing were error-prone and inefficient, so parametric conversion and intersection were chosen for accuracy and automation.

┌───────────────┐       ┌───────────────┐
│ 3D Model Edge │──────▶│ Convert Entity│
└───────────────┘       └───────────────┘
         │                      │
         ▼                      ▼
┌─────────────────┐     ┌───────────────┐
│ Intersection of  │────▶│ Intersection  │
│  Two Surfaces   │     │ Curve Tool    │
└─────────────────┘     └───────────────┘
         │                      │
         ▼                      ▼
┌───────────────────────────────┐
│        Sketch Geometry         │
└───────────────────────────────┘

Myth Busters - 3 Common Misconceptions

Quick: Does Convert Entities create independent sketch lines that never change? Commit yes or no.

Common Belief: Convert Entities just copies edges as static lines that don't update.

Reality: Convert Entities creates live links that update the sketch if the original model edges change.

Why it matters: Believing they are static leads to confusion when sketches unexpectedly change or don't update, causing design errors.

Quick: Can Intersection Curves only be created between flat surfaces? Commit yes or no.

Common Belief: Intersection Curves only work on flat or simple surfaces.

Reality: They work on any surfaces, including complex curved ones.

Why it matters: Limiting their use prevents capturing important geometry in complex models, reducing design accuracy.

Quick: Does using many converted entities always improve model performance? Commit yes or no.

Common Belief: More converted entities always make the model better and faster.

Reality: Too many linked entities can slow down rebuilds and cause errors.

Why it matters: Ignoring performance impact can make models slow and unstable, frustrating users.

Expert Zone

1

Converted entities maintain parametric links that can break if upstream geometry is deleted or heavily modified, requiring careful model management.

2

Intersection curves can be used to create reference geometry for advanced features like lofts or boundary surfaces, not just sketches.

3

Using selection filters and temporary axes can improve precision when selecting edges or surfaces for conversion in complex models.

When NOT to use

Avoid using Convert Entities or Intersection Curves when the geometry is unstable or frequently deleted, as this breaks links. Instead, use manual sketches or reference geometry that is more stable. For very simple shapes, manual sketching may be faster.

Production Patterns

In professional CAD workflows, Convert Entities is used to maintain design intent by linking sketches to existing features. Intersection Curves are common in automotive and aerospace industries for surface modeling where precise intersections define part boundaries. Experts combine these tools with configurations and design tables for scalable models.

Connections

Parametric Modeling

Builds-on

Understanding how converted entities create parametric links helps grasp the core of parametric modeling where changes propagate automatically.

Geometric Constraints

Same pattern

Both converted entities and geometric constraints maintain relationships between sketch elements and model geometry, ensuring design consistency.

Cartography (Map Tracing)

Similar pattern

Tracing map features onto paper to create accurate maps is like converting entities—both capture existing shapes precisely to build new representations.

Common Pitfalls

#1 Trying to convert entities from edges not visible or selectable in the current sketch plane.

Wrong approach:

Using Convert Entities on edges behind or outside the sketch plane without adjusting view or plane.

Correct approach:

Change the sketch plane or use Intersection Curves to capture geometry not on the sketch plane.

Root cause:

Misunderstanding that Convert Entities only works on edges visible and intersecting the sketch plane.

#2 Overusing Convert Entities on many edges causing slow model rebuilds.

Wrong approach:

Converting all edges of a complex model into one sketch indiscriminately.

Correct approach:

Select only necessary edges or break sketches into smaller parts to improve performance.

Root cause:

Not realizing each converted entity adds dependency and rebuild cost.

#3 Using Intersection Curves between bodies that do not actually intersect.

Wrong approach:

Selecting two bodies with no overlapping surfaces and expecting an intersection curve.

Correct approach:

Verify bodies intersect or use other methods like projected curves if no intersection exists.

Root cause:

Assuming Intersection Curves work without actual surface intersection.

Key Takeaways

Converting entities and intersection curves help you reuse existing 3D geometry in sketches, saving time and improving accuracy.

These tools create live links so sketches update automatically when the model changes, maintaining design consistency.

Intersection curves capture complex intersections between surfaces that edges alone cannot represent.

Overusing these tools can slow down your model, so use them thoughtfully and manage dependencies carefully.

Mastering these tools is essential for advanced modeling and professional CAD workflows.