SolidworksHow-ToBeginner · 3 min read

How to Use Union in AutoCAD 3D: Step-by-Step Guide

In AutoCAD 3D, use the UNION command to combine two or more 3D solids into a single solid. Simply select the solids you want to merge, and AutoCAD will create one unified object without overlapping parts.

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Syntax

The UNION command syntax in AutoCAD 3D is straightforward. You start the command by typing UNION in the command line, then select the 3D solids you want to combine. After selection, press Enter to complete the union.

UNION: The command to merge solids.
Select solids: Choose two or more 3D solids to combine.
Enter: Confirms the selection and performs the union.

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Command: UNION
Select solids, surfaces, or regions to union:
Select solids, surfaces, or regions to union:
Press Enter to finish selection.

Output

The selected solids are combined into one single 3D solid.

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Example

This example shows how to union two 3D boxes into one solid.

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1. Draw two 3D boxes using the BOX command.
2. Type UNION and press Enter.
3. Select both boxes by clicking on them.
4. Press Enter to complete the union.
5. The two boxes become one solid that you can move or edit as a single object.

Output

Two separate boxes are merged into one solid object.

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Common Pitfalls

Common mistakes when using UNION include:

Trying to union objects that are not 3D solids (like surfaces or 2D shapes).
Not selecting all solids before pressing Enter, resulting in partial union.
Overlapping solids that cause unexpected geometry after union.

Always ensure your objects are 3D solids and fully selected before confirming.

autocad

Wrong:
Command: UNION
Select solids, surfaces, or regions to union:
Select only one solid and press Enter

Right:
Command: UNION
Select solids, surfaces, or regions to union:
Select all solids to combine
Press Enter

Output

Wrong: No union occurs with one solid selected. Right: Solids merge into one object.

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Quick Reference

Step	Action
1	Type UNION in command line
2	Select two or more 3D solids
3	Press Enter to complete
4	Result: One combined solid

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Key Takeaways

Use the UNION command to merge multiple 3D solids into one object.

Select all solids before pressing Enter to ensure complete union.

Only 3D solids can be unioned; surfaces or 2D objects won't work.

Union removes overlapping geometry and creates a single solid.

Check your selection carefully to avoid partial or failed unions.