2.4 Editing commands and modifiers

Editing commands and modifiers are essential tools for refining and adjusting your CAD drawings. These tools allow you to trim, extend, fillet, chamfer, stretch, and lengthen objects with precision, giving you full control over your design's details.

Mastering these editing techniques is crucial for creating accurate and polished drawings. From simple modifications like trimming excess lines to complex operations like dynamic grip editing, these commands form the backbone of efficient CAD work and are key to bringing your design ideas to life.

Object Trimming and Extension

Using the TRIM Command

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• The TRIM command cuts an object at a specified boundary defined by one or more other objects
• When using TRIM, select a cutting edge and then specify the object to be trimmed
• The portion of the object that is not needed is removed (discarded)
• Polylines, lines, arcs, and rays can all be used as boundaries for trimming
• The EDGEMODE system variable controls how the boundary edges are selected for TRIM
• Example: Trim a line extending past a circle by selecting the circle as the cutting edge

Using the EXTEND Command

• The EXTEND command extends an object to meet another object (boundary edge)
• When using EXTEND, select a boundary edge and then specify the object to be extended
• The object will be lengthened until it meets the selected boundary
• Polylines, lines, arcs, and rays can all be used as boundaries for extending
• The EDGEMODE system variable controls how the boundary edges are selected for EXTEND
• Example: Extend a line to meet the endpoint of an arc by selecting the arc as the boundary

Corner Filleting and Chamfering

Creating Rounded Corners with FILLET

• The FILLET command creates a rounded corner between two objects
• When using FILLET, specify a fillet radius and then select the two objects to be filleted
• The fillet arc is tangent to the selected objects at the endpoints
• If the objects being filleted are polylines, the PEDITACCEPT system variable must be set to 1 to retain the polyline after the operation
• Example: Create a 0.5 unit radius fillet between two perpendicular lines

Creating Beveled Corners with CHAMFER

• The CHAMFER command creates a beveled (angled) corner between two objects
• When using CHAMFER, specify chamfer distances and then select the two objects to be chamfered
• The chamfer line connects the selected objects at the specified distances from their endpoints
• The CHAMFERA and CHAMFERD system variables control the default chamfer distances
• If the objects being chamfered are polylines, the PEDITACCEPT system variable must be set to 1 to retain the polyline
• Example: Create a chamfer with a distance of 1 unit on the first line and 2 units on the second line

Object Stretching and Lengthening

Stretching Objects with STRETCH

• The STRETCH command stretches objects while maintaining connectivity and associations
• When using STRETCH, specify a stretch frame and then select the objects to be stretched
• Objects that cross the stretch frame boundary will be stretched, while objects completely inside the frame will be moved
• STRETCH maintains connectivity between stretched objects and adjoining geometry
• Example: Stretch one side of a rectangle to make it longer, while keeping the opposite side in place

Changing Object Length with LENGTHEN

• The LENGTHEN command changes the length of an object
• When using LENGTHEN, you can specify an incremental length, percentage of total length, or total length
• LENGTHEN can be used on lines, arcs, open polylines, and elliptical arcs
• Example: Change the length of a line to 75% of its original length
• Example: Increase the length of an arc by 2 units

Dynamic Editing with Grips

Grip Modes and Functions

• Grips are small squares that appear on selected objects and allow for dynamic editing
• Grips can be used to move, stretch, scale, rotate, and mirror objects
• The "Stretch" grip mode moves or stretches objects and is the default mode
• The "Move" grip mode moves objects without stretching them
• The "Rotate" grip mode rotates objects around a base grip point
• The "Scale" grip mode scales an object by a specified scale factor
• The "Mirror" grip mode mirrors objects across a temporary mirror line

Examples of Grip Editing

• Example: Stretch one corner of a polyline rectangle by clicking and dragging its grip
• Example: Rotate a block reference by selecting its base grip and using the Rotate grip mode
• Example: Scale a group of objects uniformly using grips and the Scale grip mode
• Example: Move a line segment to a new location by selecting its midpoint grip and dragging

Combined Editing Commands

Breaking and Joining Objects

• The EXPLODE command breaks a block or polyline into its component objects, allowing them to be edited individually
• The JOIN command joins multiple objects into a single object, which can then be edited as a unit
• The BREAK command creates gaps in objects, which can then be fileted, chamfered, or joined as needed
• Example: Explode a polyline, fillet its corners, then join it back into a single polyline

Aligning and Modifying Polylines

• The PEDIT command converts a polyline into individual line and arc segments for editing with FILLET and CHAMFER
• The ALIGN command aligns objects with other objects in 2D or 3D space
• Example: Convert a rectangle polyline to lines, chamfer the corners, then use PEDIT to recreate the polyline
• Example: Align a group of lines to be parallel to an existing edge using the ALIGN command