Altium NEXUS Documentation

Arc

Modified by Susan Riege on Mar 20, 2019

Parent page: PCB Objects

Two placed Arcs; on the left is a Full Circle Arc, on the right is an Arc selected for editing.

Summary

An arc is a primitive design object. It is essentially a circular track segment that can be placed on any layer. Arcs can have a variety of uses in PCB layout. For example, they can be used when defining component outlines on the overlay layers, or on a mechanical layer to indicate the board outline, edges of cut outs, and so on. They also can be used to produce curved paths while interactively routing. Arcs can be open or closed to create a circle (often referred to as a full circle arc).

As well as the standard arc, there is a second type of arc available, referred to as a keepout arc. These can be placed on a signal layer to create a layer-specific barrier, or no-go region. Refer to the Keepout Arc page for more information.

Availability

Arcs are available for placement in both PCB and PCB Library Editors. There are four arc placement modes available (Center, Edge, Any Angle, and Full Circle).

  • In the PCB Editor - to place an arc:
    • Choose the required standard arc mode from the Place » Arc submenu.
    • Right-click then choose the required standard arc mode from the Place » Arc submenu.
    • Choose the required mode from the PCB Editor Active Bar. The drawing objects are accessed via the last button on the bar (as shown below), click and hold anywhere on that button to access all drawing objects. The last used menu button will become the current Active Bar button.

  • In the PCB Library Editor - to place an arc:
    • Choose the required standard arc mode from the Place menu
    • Choose the required mode from the PCB Library Editor Active Bar. The drawing objects are accessed via the button shown below, click and hold anywhere on that button to access all drawing objects. The last used menu button will become the current Active Bar button.

Placement

The way in which an arc is placed depends on the particular method of placement that you have chosen to invoke. Four different methods of arc placement are supported:

  • Place arc by center – this method enables you to place an arc object using the arc center as the starting point.
  • Place arc by edge – this method enables you to place an arc object using the edge of the arc as the starting point. The arc angle is fixed at 90°.
  • Place arc by edge (any angle) – this method enables you to place an arc object using the edge of the arc as the starting point. The angle of the arc can be any value.
  • Place full circle arc – this method enables you to place a 360° (full circle) arc.

Placing an Arc Starting at the Center

Command pages: Place Arc by Center

After launching the command, the cursor will change to a cross-hair and you will enter arc placement mode. Placement is made by performing the following sequence of actions:

  1. Click or press Enter to anchor the center point of the arc.
  2. Move the cursor to adjust the radius of the arc then click or press Enter to set it.
  3. Move the cursor to adjust the start point for the arc then click or press Enter to anchor it.
  4. Move the cursor to change the position of the arc's end point then click or press Enter to anchor it and complete placement of the arc.
  5. Continue placing further arcs or right-click or press Esc to exit placement mode.

Placing an Arc Starting at the Edge

Command pages: Place Arc by Edge

After launching the command, the cursor will change to a cross-hair and you will enter arc placement mode. Placement is made by performing the following sequence of actions:

  1. Click or press Enter to anchor the start point for the arc.
  2. Move the cursor to change the position of the arc's end point then click or press Enter to anchor it and complete placement of the arc.
  3. Continue placing further arcs or right-click or press Esc to exit placement mode.

Placing an Arc Starting at the Edge (any angle)

Command pages: Place Arc by Edge (Any Angle)

After launching the command, the cursor will change to a cross-hair and you will enter arc placement mode. Placement is made by performing the following sequence of actions:

  1. Click or press Enter to anchor the start point for the arc.
  2. Move the cursor to adjust the radius of the arc then click or press Enter to anchor the center point.
  3. Move the cursor to change the position of the arc's end point then click or press Enter to anchor it and complete placement of the arc.
  4. Continue placing further arcs or right-click or press Esc to exit placement mode.

Placing a Full Circle Arc

Command pages: Place Full Circle

After launching the command, the cursor will change to a crosshair and you will enter arc placement mode. Placement is made by performing the following sequence of actions:

  1. Click or press Enter to anchor the center point of the arc.
  2. Move the cursor to adjust the radius of the arc then click or press Enter to set it and complete placement of the arc.
  3. Continue placing further arcs or right-click or press Esc to exit placement mode.

Additional Placement Actions

Additional actions that can be performed during placement are:

  • For all methods (excluding full circle arcs), press the Spacebar before defining the arc's end point to render the arc in the opposite direction.
  • Press the L key to flip the arc to the other side of the board – note that this is only possible prior to anchoring the arc's start/center point.
  • Press the + and - keys (on the numeric keypad) or use the Shift+Ctrl+Wheelroll shortcuts to cycle forward and backward through all visible layers in the design to change placement layer quickly.
  • Press the Tab key to open the Arc mode of the Properties panel from where properties for the arc can be changed on-the-fly. When this is done interactive editing will pause so that the panel can be used, click the  button that appears in the center of the workspace to return to the interactive arc placement mode or press Esc.
While attributes can be modified during placement (Tab to open the Properties panel), keep in mind that these will become the default settings for further placement unless the Permanent option on the PCB Editor – Defaults page of the Preferences dialog is enabled. When this option is enabled, changes made will affect only the object being placed and subsequent objects placed during the same placement session.

Graphical Editing

This method of editing allows you to select a placed arc object directly in the workspace and graphically change its size, shape or location.

When an arc object is selected, the following editing handles are available:

  • Click and drag A to adjust the radius.
  • Click and drag B to adjust the end points (start and end angles).
  • Click anywhere on the arc away from editing handles then drag to reposition it. Alternatively, click and drag on the arc center-point. While dragging, the arc can be rotated or mirrored:
    • Press the Spacebar to rotate the arc counterclockwise or Shift+Spacebar for clockwise rotation. Rotation is in accordance with the value for the Rotation Step, defined on the PCB Editor – General page of the Preferences dialog.
    • Press the X or Y keys to mirror the arc along the X-axis or Y-axis.

If attempting to graphically modify an object that has its Locked property enabled () button in the Properties panel), a dialog will open asking for confirmation to proceed with the edit. If the Protect Locked Objects option is enabled on the PCB Editor – General page of the Preferences dialog and the Locked option for that design object is enabled as well, that object cannot be selected or graphically edited. Click the locked object to select it then disable the Locked property in the List panel or disable the Protect Locked Objects option to graphically edit the object.

Non-Graphical Editing

The following methods of non-graphical editing are available:

Editing via the Properties Panel

Properties page: Arc Properties

The properties of an Arc can be edited in the PCB editor's Properties panel, which allows editing of all item(s) currently selected in the workspace.


The properties of a standard arc.

During placement, the panel can be accessed by pressing the Tab key.

To access the properties of a placed arc:

  • Double-click on the Arc's perimeter.
  • Right-click on the Arc perimeter then select Properties from the context menu.
  • If the Properties panel is already active, click on the Arc's perimeter to select it.

Editing via the List Panel

Panel pages: PCB List, PCB Filter, PCBLIB List, PCBLIB Filter

The List panel allows you to display design objects from one or more documents in tabular format, enabling quick inspection and modification of object attributes. Used in conjunction with appropriate filtering - by using the applicable Filter panel, or the Find Similar Objects dialog - it enables the display of just those objects falling under the scope of the active filter – allowing you to target and edit multiple design objects with greater accuracy and efficiency.

 

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