How to Turn Multiple Lines into a Polyline in AutoCAD

In AutoCAD, converting multiple individual lines, a series of connected line segments, or even a Multiline (MLINE) object into a single, editable polyline is a fundamental task that streamlines your drafting process and enhances drawing efficiency. This conversion ensures your designs are cohesive and easier to manipulate.

Several commands are available for this purpose, each suited to different scenarios.

Essential Commands for Polyline Conversion

Here's a quick overview of the key commands you'll use:

Command	Purpose	Objects Handled
`PEDIT`	Polyline Edit: Converts lines/arcs to polylines, joins segments, and modifies existing polylines.	Lines, Arcs, Splines, Polylines
`JOIN`	Combines co-linear or end-to-end lines, arcs, or polylines into a single object.	Lines, Arcs, Polylines
`EXPLODE`	Breaks down complex objects, such as Multilines, blocks, or polylines with width, into simpler components.	MLINEs, Blocks, Polylines (with width), Associative arrays
`BOUNDARY`	Creates a closed polyline or region from an enclosed area defined by existing objects.	Lines, Arcs, Circles, Polylines (forming a boundary)
`PRESSPULL`	Extrudes 2D closed areas into 3D solids or surfaces, or presses/pulls existing 3D faces.	Closed boundaries (defined by lines, polylines)

Step-by-Step Methods

Let's explore the most common methods for converting various line types into polylines.

1. Converting Individual Line Segments Using PEDIT

The PEDIT (Polyline Edit) command is the most versatile tool for transforming individual, connected line or arc segments into a single polyline.

Steps:

Start PEDIT: Type PEDIT (or PE) in the command line and press Enter.
Select Object: You will be prompted to "Select polyline or [Multiple]:".
- If you select a single line or arc that is not already a polyline, AutoCAD will ask: "Do you want to turn it into one? [Yes/No] ". Press Enter to accept Yes.
Join Segments: Once the selected object is a polyline, enter J (for Join) and press Enter.
Select Additional Objects: Select all other connected line, arc, or polyline segments you want to join to the first one. Ensure these segments meet precisely end-to-end.
Confirm and Exit: Press Enter to complete the selection, then press Enter again to exit the PEDIT command.

All selected, connected objects will now form a single polyline. For more details, refer to the Autodesk Knowledge Network on Using PEDIT to Join Objects.

2. Joining Multiple Objects with the JOIN Command

The JOIN command provides a quicker way to combine multiple co-linear or end-to-end lines, arcs, and polylines into a single polyline.

Steps:

Start JOIN: Type JOIN (or J) in the command line and press Enter.
Select Objects: Select all the lines, arcs, and polylines you wish to join.
Confirm: Press Enter.

AutoCAD will attempt to join all selected objects that are continuous and co-linear or meet precisely at their endpoints. This command is often more direct than PEDIT for simple joining tasks. For further information, see the Autodesk Help on the JOIN command.

3. Converting a Multiline (MLINE) Object to a Polyline

An AutoCAD Multiline (MLINE) object is a single object composed of two or more parallel lines. To convert a Multiline into a standard polyline, a two-step process is usually required.

Steps:

Explode the Multiline: Type EXPLODE (or X) in the command line and press Enter. Select the Multiline object and press Enter again. This action will break the Multiline into its individual constituent lines.
- Insight: When you select a Multiline and explode it, it converts into its component lines, effectively making it ready for polyline conversion.
Join the Exploded Lines: Now that you have individual lines, use either the PEDIT command (as described in Method 1) or the JOIN command (as described in Method 2) to combine these individual lines into a single polyline.
- Using PEDIT:
  1. Start PEDIT, select one of the exploded lines, and confirm Yes to turn it into a polyline.
  2. Enter J for Join, then select the remaining exploded lines.
  3. Press Enter twice to complete the command.
- Using JOIN:
  1. Start JOIN.
  2. Select all the exploded lines.
  3. Press Enter.

This process ensures that a complex Multiline object is transformed into a manageable polyline. The EXPLODE command is detailed further in the Autodesk Help documentation.

4. Creating a Polyline from a Closed Boundary with BOUNDARY

If you have multiple lines that form a closed area, the BOUNDARY command can automatically generate a polyline or region from that enclosed space. This is particularly useful for creating a single, continuous boundary object.

Steps:

Start BOUNDARY: Type BOUNDARY (or BO) in the command line and press Enter.
Pick Internal Point: In the Boundary Creation dialog box, ensure "Object Type" is set to Polyline. Click the "Pick Points" button.
Select Internal Area: Click inside the closed area formed by your lines. AutoCAD will highlight the detected boundary.
Confirm: Press Enter.

A new polyline will be created exactly on top of the existing boundary, allowing you to select and manipulate it independently. Learn more about the BOUNDARY command in Autodesk Help.

Using PRESSPULL with Closed Line Boundaries

While not directly converting lines to a 2D polyline, the PRESSPULL command is a powerful tool in AutoCAD that works with closed boundaries formed by lines (including polylines) to create 3D solids. After you've successfully created a closed polyline from your multiple lines, you can use PRESSPULL to extrude that 2D shape into a 3D object.

Steps:

Start PRESSPULL: Type PRESSPULL in the command line and press Enter.
Pick Inside Boundary: Click inside a closed area defined by your lines or a polyline.
Define Height: Drag your cursor to specify the extrusion height, or enter a value.
Confirm: Click or press Enter.

This will create a 3D solid from your 2D outline. This functionality is distinct from creating a 2D polyline but is a common next step for designers using closed line work. For more on this, refer to the Autodesk Help documentation for PRESSPULL.

By mastering these commands, you can effectively manage and transform your line geometry in AutoCAD, ensuring precision and efficiency in your drawing projects.