Undercut detection in Solidworks - Step-by-Step Guide

Introduction

Undercut detection helps you find areas on a 3D model that are hard to reach or mold because they stick out or are hidden. This is important when designing parts for manufacturing, especially for molds, to avoid costly mistakes.

When designing a plastic part that will be made using injection molding and you need to check if the mold can open without issues.

When preparing a model for casting and want to find areas that might trap the mold or cause defects.

When reviewing a complex part to ensure all surfaces can be accessed by tools or machines during production.

When you want to identify features that require special tooling or side actions in the mold.

When validating a design before sending it to manufacturing to reduce rework and delays.

Steps

Step 1: Open your 3D model

- SolidWorks main window

Your part or assembly is displayed in the workspace

Step 2: Click on the 'Evaluate' tab

- CommandManager toolbar

Evaluation tools become visible

Step 3: Select 'Undercut Analysis'

- Evaluate tab

Undercut Analysis property manager opens on the right side

Step 4: Choose the direction of pull

- Undercut Analysis property manager

The tool knows which way the mold will open

Step 5: Click 'Calculate'

- Undercut Analysis property manager

Undercut areas are highlighted on the model in red

Step 6: Review the highlighted areas

- 3D model workspace

You see exactly where undercuts exist that may cause manufacturing issues

Step 7: Adjust your design or note the undercuts for tooling

- 3D model workspace or design tree

You can fix or plan for the undercuts before manufacturing

Before vs After

Before

3D model shows all surfaces with no visual indication of undercuts

After

Undercut areas are highlighted in red on the model, showing exactly where issues exist

Settings Reference

Pull Direction

📍 Undercut Analysis property manager

Defines the direction the mold will open to detect undercuts correctly

Default: Use default axis

Tolerance

📍 Undercut Analysis property manager

Sets the sensitivity for detecting undercuts, smaller values find smaller features

Default: 0.05 mm

Highlight Color

📍 Undercut Analysis property manager

Changes the color used to show undercut areas on the model

Default: Red

Common Mistakes

Not setting the correct pull direction

The tool will highlight wrong areas or miss real undercuts if the mold opening direction is wrong

Always select the correct pull direction matching the mold opening before running the analysis

Ignoring small undercuts due to high tolerance

Small but critical undercuts can cause manufacturing problems if not detected

Use a smaller tolerance value to catch all relevant undercuts

Summary

Undercut detection finds hard-to-manufacture areas on 3D models.

Set the mold opening direction correctly to get accurate results.

Use the tool early to avoid costly manufacturing issues.

Practice

1. What is the main purpose of undercut detection in SolidWorks molding design?

easy

A. To find areas that may cause problems during mold release

B. To calculate the weight of the molded part

C. To determine the color of the plastic material

D. To measure the surface roughness of the mold

Solution

1. Step 1: Understand undercut detection purpose

   Undercut detection identifies areas that can trap the part in the mold.

2. Step 2: Relate to molding process

   These problem areas affect mold release and manufacturing quality.

3. Final Answer:

   To find areas that may cause problems during mold release -> Option A

4. Quick Check:

   Undercut detection = problem areas in molding [OK]

Hint: Think about what stops a part from coming out of a mold [OK]

Common Mistakes:

• Confusing undercut detection with weight calculation
• Thinking it measures color or surface finish
• Assuming it checks material properties

2. Which step is essential before running undercut detection in SolidWorks?

easy

A. Adding fillets to all edges

B. Applying a texture to the model

C. Changing the color of the part

D. Setting the correct pull direction

Solution

1. Step 1: Identify key setup for undercut detection

   The pull direction defines how the mold opens and affects detection results.

2. Step 2: Understand impact of pull direction

   Incorrect pull direction leads to wrong undercut identification.

3. Final Answer:

   Setting the correct pull direction -> Option D

4. Quick Check:

   Pull direction setup = correct undercut detection [OK]

Hint: Always set pull direction before checking undercuts [OK]

Common Mistakes:

• Skipping pull direction setup
• Confusing texture or color with detection setup
• Thinking fillets affect undercut detection directly

3. Given a part with a pull direction set incorrectly, what is the likely output of the undercut detection tool?

medium

A. The tool crashes with an error

B. All edges flagged as undercuts

C. No undercuts detected even if they exist

D. Undercuts detected only on flat surfaces

Solution

1. Step 1: Analyze effect of wrong pull direction

   Wrong pull direction means the tool looks from the wrong angle.

2. Step 2: Predict detection result

   It misses real undercuts, showing none detected.

3. Final Answer:

   No undercuts detected even if they exist -> Option C

4. Quick Check:

   Wrong pull direction = missed undercuts [OK]

Hint: Wrong pull direction hides real undercuts [OK]

Common Mistakes:

• Assuming tool crashes on wrong pull direction
• Thinking all edges get flagged
• Believing detection only works on flat surfaces

4. You ran undercut detection but the results seem incorrect. Which of the following is the most likely cause?

medium

A. The pull direction was not set properly

B. The part color was changed after detection

C. The model has no fillets

D. The software version is outdated

Solution

1. Step 1: Identify common error in detection setup

   Incorrect pull direction is the main cause of wrong undercut results.

2. Step 2: Eliminate unrelated causes

   Color changes, fillets, or software version usually do not affect detection output directly.

3. Final Answer:

   The pull direction was not set properly -> Option A

4. Quick Check:

   Incorrect pull direction = wrong detection results [OK]

Hint: Check pull direction first when results look wrong [OK]

Common Mistakes:

• Blaming color or fillets for detection errors
• Ignoring pull direction setup
• Assuming software version causes detection errors

5. You have a complex molded part with multiple undercuts. How can you use SolidWorks undercut detection to improve your design for manufacturing?

hard

A. Ignore undercuts and rely on manual inspection only

B. Set the correct pull direction, identify undercuts, then modify design to remove or reduce them

C. Change the part color to highlight problem areas

D. Add fillets to all edges without checking undercuts

Solution

1. Step 1: Use undercut detection properly

   Set the pull direction correctly to get accurate undercut locations.

2. Step 2: Modify design based on detection

   Adjust or remove undercuts to ease mold release and reduce manufacturing issues.

3. Step 3: Avoid ineffective actions

   Ignoring undercuts or just changing colors does not solve molding problems.

4. Final Answer:

   Set the correct pull direction, identify undercuts, then modify design to remove or reduce them -> Option B

5. Quick Check:

   Correct pull direction + design changes = better molding [OK]

Hint: Detect undercuts, then redesign to avoid molding problems [OK]

Common Mistakes:

• Ignoring undercuts in design process
• Thinking color changes fix molding issues
• Adding fillets without checking undercuts