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Trim or Extend Objects

May 20, 2011

       You can connect edges of objects through trimming or extending.

        When trimming or extending objects, you have to specify cutting edges or boundary to extend, then you can select objects to cut or extend. Pressing ENTER at the prompt of selecting entities, all entities are the possible boundaries, which calls hidden selection.

        If you want to select blocks as cutting edges, you can only use the single selection, Crossing, Fence, and Select All options.


Trim Objects

         You can clip, or trim, objects so they end at one or more implied cutting edges defined by other objects. You can also trim objects to the point at which they would intersect an implied cutting edge. When trimming objects, you first select the cutting edges and then specify the objects to trim, selecting them either one at a time or using the fence selection method.

        You can trim arcs, circles, lines, unclosed polylines, and rays. In which, arcs, circles, lines, polylines, rays, infinite lines, and viewports on a Layout tab can act as cutting edges.

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To trim an object

  1. Choose Modify > Trim.

  2. Select one or more cutting edges, and then press Enter.

  3. Select the object to trim.

  4. Select another object to trim, or press Enter to complete the command.

Modify toolbar\

Command line TRIM

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To trim objects, select the cutting edge (A), and then select the objects to trim (B) Result

      Holding down SHIFT while selecting objects, system extends object to the nearest boundary instead of trimming selecting object.

      In this example, you clean up the intersection of two walls smoothly by trimming.

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       Using variable selection methods while trimming several objects can help you select edges or objects more easily.

       In the following example, the cutting edges are selected using crossing selection.

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To trim several objects using the fence selection method

  1. Choose Modify > Trim.

  2. Select one or more cutting edges, and then press Enter.

  3. On the command line, type fence.

  4. Specify the first point of the fence.

  5. Specify the second point of the fence.

  6. Specify the next fence point, or press Enter to complete the command.

Modify toolbar \

Command line TRIM

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Select the boundary edge (A), and then specify the first point (B) and second point (C) of the fence Result

        
         You can trim objects to the nearest point of other objects. Selecting objects and clicking objects to trim, system specifies the nearest objects as the cutting edges. The following picture shows that the crossing boundary is smooth after trimming.

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Extend Objects

You can extend objects so that they end at a boundary defined by other objects. You can also extend objects to the point at which they would intersect an implied boundary edge. When extending objects, you first select the boundary edges, and then specify the objects to extend by way of selecting them one by one or using the fence selection method.

You can extend arcs, lines, two-dimensional polylines, and rays. Arcs, circles, ellipses, lines, splines, polylines, rays, infinite lines, and viewports on a Layout tab can act as boundary edges.

In this example, you extend the lines precisely to a circle, which is the boundary edge.

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To extend an object

  1. Choose Modify > Extend.

  2. Select one or more objects as boundary edges, and then press Enter.

  3. Select the object to extend.

  4. Select another object to extend, or press Enter to complete the command.

Modify toolbar\

Command line EXTEND

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To extend objects, select the boundary edge (A), and then select the objects to extend (B) Result

To extend an object to an implied boundary

  1. Choose Modify > Extend.

  2. Select one or more boundary edges, and then press Enter.

  3. On the command line, type edge mode.

  4. On the command line, type extend.

  5. Select the object to extend.

  6. Select another object to extend, or press Enter to complete the command.

Modify toolbar \

Command line EXTEND

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Select the boundary edge (A), and then select the objects to extend (B) Result

To extend several objects using the fence selection method

  1. Choose Modify > Extend.

  2. Select one or more boundary edges, and then press Enter.

  3. On the command line, type fence.

  4. Specify the first point of the fence.

  5. Specify the second point of the fence.

  6. Specify the next fence point, or press Enter to complete the command.

Modify toolbar \

Command line EXTEND

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Select the boundary edge (A), and then specify the first point (B) and second point (C) of the fence Result

TRIM can also be used to extend objects. At the prompts of selecting entities, holding down SHIFT and selecting objects to extend. As a result, the objects is extending instead of trimming.


Trim and Extend Wide Polylines

       System processes the center line if the object is 2D wide polyline. If the polyline is pyramid, the width of cutting edge keeps unchanged after trimming.

       When you extend a wide polyline, its centerline intersects the boundary edge. Because the end of the polyline is always cut at a 90-degree angle, part of the polyline may extend past the boundary edge. A tapered polyline continues to taper until it intersects the boundary edge. If this would result in a negative polyline width, the ending width changes to 0.

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A tapered polyline (A) continues to taper until it intersects the boundary edge (B) Result


         The ends of wide polylines are always square. Trimming a wide polyline at an angle leads to portions of the end to extend beyond the cutting edge. Trimming a spline-fit polyline deletes curve-fit information and converts spline-fit segments to ordinary polyline segments.


Trim or Extend in 3D

    You can trim or extend objects even the objects are in the different planes in 3D space.

     The system variable PROJMODE and EDGEMODE control the following project models:

  • XY plane of the Current UCS.

  • Current view plane.

  • 3D realty space (not projection).

         Attentively, when you trim or extend objects 3D space, the objects to cut or extend must be intersected with the boundary of 3D boundary. The objects to trim or extend may not concluding exactly if they do not intersect with each other when you work at the XY plane of the current UCS.


Commands Reference

EXTEND: Extends an object to meet another object

LENGTHEN: Changes the length of objects and the included angle of arcs

PROPERTIES: Controls properties of existing objects

TRIM: Trims objects at a cutting edge defined by other objects

System Variables Reference

EDGEMODE: Controls how the TRIM and EXTEND commands determine cutting and boundary edges

PROJMODE: Sets the current Projection mode for trimming or extending


 

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