AutoCAD tips and lisp

In teaching AutoCAD for so long I find lots of simple things people may have missed or overlooked along the way. Different people approach AutoCAD from different angles. It is often I learn new things with each class I teach.

The two most frustrating things for new users to remember are to look at and read the command prompt and to remember to hit enter when they are done selecting objects. In every entry level class I warn new students about this. The trim and extend commands have two selection sets and are the commands that seem to catch them the most. In R13 the stretch command doesn’t give you a crossing window by default as it did in R12 and this is also a trouble spot.

When producing drawings every day we don’t have time to try all the commands and check out every prompt. Even an advanced user can benefit from taking a one day productivity class to get some new ideas.

Scale & Rotate

More experienced users also need to read the command prompt and question all the choices. For instance, the scale and rotate commands have a reference option. This reference option can get you out of hot water sometimes. One client had a drawing that had been arbitrarily scaled down several times to fit on a smaller sheet instead of changing the plot scale factor. They needed to add dimensions and the dimensions were all wrong due to the scaling. With the known length of just one line, 7" full scale, and the wrong length in the drawing file, we were able to scale the whole drawing up with the reference option. Using the scale command and selecting all the objects we referenced the wrong length and then gave it the new length. Problem solved.

ARRAY

Array has an option to specify a "Unit cell" for the distance between rows and columns. Most users have never tried this. Unit cell simply allows you to pick two points. It will array the selected objects the X & Y distance between the two points you picked. This works well for ceiling grids. So - in place of giving a distance between rows, pick two points for a Unit cell distance.

UNDEFINE & REDEFINE

AutoCAD allows you to UNDEFINE commands. The most popular command to undefine is the END command. By typing UNDEFINE at the command prompt and then the command name the average user can not access the command. To get the command you simply type a period before the command name " . end". Now, if you type "end" by mistake at a command prompt it won't dump you out of AutoCAD. To return the command for good use the REDEFINE command.

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OBJECT SELECTION

Methods of SELECTING OBJECTS

Before R12 of AutoCAD we had only a few ways of selecting objects: Last, Previous, one at a time, and by a rectangular window (crossing and regular).
R12 added in new selection options:
Fence (crossing line great for extend and trim)
Window Polygon
Crossing Polygon
Group
ALL

SHIFT-PICK to REMOVE OBJECTS

One of the most surprising things is to see someone selecting objects to move, erase, or copy, and cancel if they get one item in the selection set they don't want. Most of us know if we type "R" for remove at the Select objects prompt and touch on the object it will remove it from the selection set. Then we have to type "A" to add again. With Release 12 they included a feature to save time in removing objects from the selection set. While selecting objects, if you select an object you don't want, simply hold down the shift key and select the object to remove it from the selection set.

Command: ERASE
Select objects: 1 found
Select objects: 1 found
Select objects: r
Remove objects: 1 found, 1 removed
Remove objects: a
Select objects: 1 found
Select objects: 
Command:

Release 12 you simply hold down the shift key and pick the item to remove it from the selection set.

OBJECT CYCLE for SELECTING OBJECTS

In AutoCAD before Release 12 we could count on the fact that the object we created last was on top for selection purposes. Release 12 made it hard to select the object we thought should be on top. If you have more than one line on top of each other it is hard to select the top line. Release 13 fixes all that with Object Cycle. If you are at a Select objects prompt you can hold down the CTRL key and pick with the first mouse button to turn Cycle on. Let off CTRL key and keep picking to Cycle through the objects near your first pick. When the object is highlighted that you want to select hit enter. Great feature!

Command: ERASE 			Hold down the CTRL key and pick over several items.
Select objects: [Cycle on]	Hit the pick button to cycle through objects
				ENTER when the correct item is highlighted.
[Cycle off]1 found     
Select objects:
Command:

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EDITING TIPS

MEASURE & DIVIDE by BLOCK

One of my favorite tips would be to use measure and divide by BLOCK. I tried to used measure and divide for years before I realized they could be useful. Measure and divide simply insert points under the selected object. Then you must use object snap "node" to access the points accurately. It is much nicer to have measure or divide place a block at the locations in place of the points. A good example of this would be to layout parking stalls along a curved polyline.

Command: measure
Select object to measure:
Segment length\Block: B (for block)
Block name to insert: parking  (the block you use must be in this drawing)
Align block with object? Y or N
Segment length: 1

TRIM & EXTEND

Release 12 gave us the Fence option. Fence is a crossing line to select objects. When trimming or extending objects don't select them one at a time, select them by Fence.

Release 13 added the ability to trim or extend to extended entities. If you toggle the Edge option to Extend, AutoCAD will pretend the object you selected as cutting edges or boundary edges extend out to infinity in both directions.

EXTEND
Select boundary edges: (Projmode = UCS, Edgemode = No extend)
Select objects: 1 found
Select objects:
Select object to extend\Project\Edge\Undo: E (for edge mode)
Extend\No extend (No extend): E
Select object to extend\Project\Edge\Undo:

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DIMENSIONING TIPS

RETURN to SELECT DIMENSION

Here it's hard to know where to start. I feel the least used dimension feature is RETURN to select. When doing a horizontal dimension you can hit RETURN (Enter on modern keyboards) to simply select the line. No need to go ENDpoint to ENDpoint. The AutoCAD prompt says "First extension line origin or RETURN to select: ". Most people pick two endpoints. If the line is the correct length, simply hit return (enter) and pick the line. This option also appears with the Aligned, Angular, Baseline, and Continue dimensions. Give it a try!

Command: dimlinear
First extension line origin or RETURN to select: (hit ENTER)
Select object to dimension:
Dimension line location (Text\Angle\Horizontal\Vertical\Rotated):
Dimension text -5.1681-:

Command: _dimaligned
First extension line origin or RETURN to select: (hit ENTER)
Select object to dimension:
Dimension line location (Text\Angle):
Dimension text <4.51>:
Command:

Command: _dimangular
Select arc, circle, line, or RETURN: (hit ENTER)
Angle vertex:
First angle endpoint:
Second angle endpoint:
Dimension arc line location (Text\Angle):
Dimension text <305.84>:
Command:

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