1
Objective
To learn to define and re-use libraries of symbols using AutoCAD blocks.
Exercise
1.Start a new drawing in AutoCAD.
2.Setup your drawing to convenient settings. You will use this drawing to define at least three new symbols, which you will later add to your floor plan. Note that this drawing only has to be large enough to accommodate three architectural symbols, not an entire floor plan.
3.Draw three generic symbols that you can find a use for in your architectural plans. These can be pieces of furniture, trees, plumbing fixtures, cars, appliances, drafting elements, etc. The best choices, of course, are objects that appear many times in a project, or in several projects. You will find some good examples of such symbols in the last part of this handout. You do not need to create door and window symbols, because these have already been drawn and provided for you. (Of course, if you have included a rough opening for a door or window with a different rough opening size than those found in the given symbol library, you will have to create your own symbol.)
Draw the symbols at full scale, but remember that they are going to be rather small when you put them in your plan. You want them to look interesting and neatly drawn, yet not including too many details. Do not hatch them, for instance. Excessive detail will increase your file size. Also do not include any anchor marks or other text annotation as shown in the example sheets. You must include at least one block to represent a shrub/tree/bush to be placed outside the floor plan.
Warning: do not slightly re-define a block from 95SYMLIB and present it as your own.
4.Make the symbols into blocks. When you are done drawing the symbols, you can aggregate all the entities in a symbol, and make it into a template object that can be inserted in many places. AutoCAD calls such a template object, a block. A block that you create is invisible in the drawing, until it is inserted. Once inserted, a block will behave like a single entity for selection commands and other editing commands. A block insertion is very cheap in terms of file space occupied, because AutoCAD only has to store the graphic information once even though it is used many times in the drawing.
Note that a single drawing can have as many BLOCK definitions, and as many insertions of each of those definitions as needed. Of course, if you do not use all these definitions in your drawing, they will still occupy space and contribute to the file size. Therefore, you should consider issuing the PURGE command on such a drawing to remove the unused BLOCK definitions. We will deal with the PURGE command later.
Invoke the BMAKE command either from the keyboard, “Draw-Block-Make” menu, or from the Draw toolbar (Make Block). Be careful to 1) enter a block name, 2) select the objects which are to make up the block, and 3) choose a base point.
After you define a block in a drawing, you can insert a block reference in the drawing as many times as necessary. Use this method to create blocks quickly.
Each block definition includes a block name, one or more objects, the coordinate values of the base point to be used for inserting the block, and any associated attribute data.
The base point is used as a reference for positioning the block when you insert it. Suppose you specify that the base point is at the lower-left corner of an object in the block. Later, when you insert the block, you are prompted for an insertion point. AutoCAD then aligns the block base point at the insertion point you specified.
Or enter the BLOCK command for a non-dialog version:
Command: BLOCK
Block name (or ?): <type in a name for your symbol>
Insertion base point: <pick/type an insertion point for the symbol>
Select objects: <select the objects comprising the symbol>
XX found
Select objects:
Either of these commands can be used to create a block, but the interaction is different for each and, as the following paragraphs warn, the status of the selected objects is different:
In some cases you will see that the original symbol disappears. This always happens with the non-dialog version, and only happens in the dialog version if the “Retain Objects” box is not checked. AutoCAD will erase the entities used to make a block definition, based on the assumption that you would be later inserting the block in your drawing. Do not reach for the UNDO command when you see this happen. Instead, if you want to get the original entities back, issue the OOPS command:
Command: OOPS
Note that the OOPS command has to be issued right after the BLOCK command in order to work.
Repeat the above steps to make at least two more blocks.
5.Write each of the above blocks into a separate file. AutoCAD provides the WBLOCK command to “export” a block as another drawing. A WBLOCK is simply a drawing file with the named symbol as the only object inside it. This allows you to use the symbol in other drawings. A WBLOCK appears in the directory listing with a “.DWG” extension attached to the file name you choose. Notice that you can use any drawing file as a WBLOCK and insert it in other drawings.
Command: WBLOCK
In the “Create Drawing File” dialog box, enter the name of a drawing file that does not yet exist.
Block name: <enter name for block inside the saved drawing file>
An alternative to creating WBLOCK files for each symbol is to create a “symbol library” as a single file. This will be demonstrated in class.
6.Save your work and plot the blocks on a single sheet. Use whatever scale you prefer.
7.Use the “Window NT Explorer (File Manager)” to display a directory listing of your files. This is just to make sure that the WBLOCK commands you issued earlier did create small drawing files on the disk.
8.Open your floor plan drawing. You will use the new symbols to embellish your old drawing.
9.Make an instance of each of the symbols you defined.
Issue the “Block” command from the “Insert” pull-down menu, or toggle the “Insert Block” tool from the “Draw” toolbar:
Click on the “Browse” button to select the name of one of the “.DWG” wblocks that you created in the last few steps.
Pick the place where you want the symbol to be anchored when prompted for the “Insertion point.” All subsequent scaling and rotation of the block (when it is inserted) will be about this insertion point. If you did a good job of drawing the symbol at the right scale, you should be able to use scale factors of 1 or -1 most of the time. You will often have to rotate blocks when you insert them. In some cases, use of the UCS can help achieve this easily. The prompts will look similar to this:
Insertion point: X scale factor <1>/Corner/XYX:
Y scale factor (default=X):
Rotation angle <0>:
Command:
Note that if you are not changing the scale factor or the rotation angle, you can quickly accept the default answers simply by pressing (or more conveniently, the right mouse button) at the command prompts. This way, you can quickly insert a number of blocks without taking your hand off the mouse.
Repeat the above process to make instances of at least three different symbols that you created earlier.
10.Insert the supplied symbol library from the hard disk into your drawing. First, set the ATTREQ (attribute required) system variable to 0 (zero) by entering the following command. Also set View-Display-Attribute Display to Off. (One can also do this directly by setting the ATTDISP system variable to 0.)
Command: attreq
Enter new value for ATTREQ <1>: 0
Command: attdisp
Normal/ON/OFF <ON>: off
The blocks in 95SYMLIB.DWG were created with attributes attached to them. These include manufacturer name, catalog number, etc. If the ATTREQ variable is set to on (1), you will have to fill in all attribute variables each time you insert a new block. Turning ATTREQ off (0) hides this additional step. You will learn about attributes in a later assignment.
Follow the above procedure for inserting WBLOCK, but this time, choose the file “95SYMLIB.DWG” copies from the course homepage ( You will have to “unzip” the file since it has been packed to save disk space. Double clicking on the zip file should unpack the drawing file.
This will not seem to make any change to the drawing display, but your file will increase in size because of the additional block definitions that just got inserted. These block definitions will only become visible when you choose to instance (insert) them using the INSERT BLOCK command. Insert the file of blocks at 0.,0. at an X and Y scale of 1.
- Insert symbols for door and windows in your floor plan. You will not need to indicate a file this time because the definition of the block now lives inside the current drawing. However, you will need to provide a block name. The names appear in the handout, but for doors and windows, the name can be derived from the context of the door or window. For instance, “36x08hdr” indicates a 36” wide hinged door for an 8” thick wall. The insertion base point is at the hinge of the door; if you use endpoint or intersection object snapping, you should be able to place the door quite easily. You will have to answer the usual questions (scale, rotation) about the placement of the symbol.
Be precise when locating insertion points. Use Object Snapping to ensure that symbols snap to drawing features (such as door jambs snapping to wall breaks.) Also, make sure symbol rotations are exact. If they are to be 90 degrees, type “90” instead of “eyeballing.”
If you have set ATTREQ to 0, you can skip to step 12.
After you have answered the usual block insertion questions you will be prompted for a series of questions regarding the properties of every individual door you inserted. These extra questions appear because, when the relevant block was defined, special types of entities called “attributes” were included in the block definitions. You can think of attributes as essentially being questions, the answers to which will be posed at block insertion time, and will be remembered by AutoCAD and stored in the drawing file along with the block instantiation information. Note that there are a number of different types of attributes, some of which do not pose any questions at block insertion time; others, like the ones in the door and window symbols are invisible; and still others have constant values.
Respond to the attribute questions with your own data each time you insert a door or window block. The answers shown below are only examples:
Enter attribute values...
MANUFACTURER <ANDERSON>: Turner
CATALOG NUMBER <4123412>: 2345C3
ROUGH OPENING HEIGHT <80>:
DOOR MATERIAL <HOLLOW CORE>: Solid Core
FRAME MATERIAL <METAL>: Wood
12.Insert other symbols from the symbol library as desired, and make other improvements to the drawing. You will be graded based on the imaginative use of the blocks and not on the number of instantiations. So strive for a clean drawing that conveys information rather than noise.
- Remove the definitions of unused blocks from the drawing. As mentioned earlier, you can use the
PURGE command (or File-Drawing Utilities-Purge menu command) to do this.
Command: PURGE
Using the “Blocks” option will get rid of all unused block definitions from the drawing. For each type of information that is about to be purged, AutoCAD will ask you to confirm. Once a block definition has been purged from the drawing, it cannot be inserted in the drawing. Therefore, for the list of blocks that you are asked about, delete only the ones that you are sure you won’t be using.
14.Add a fence to the outside of the floor plan. Either use a block for each section of the fence or use the MEASURE or DIVIDE command to assist in adding blocks as fence posts.
- Save the drawing, and plot the floor plan. Make sure you specify very small line weights for the block instances that will be small on the plot - otherwise, they will come out as black blobs. (Don’t worry if you are not able to change the line weight of an inserted block - they have been created with the line weight (and color) “ByLayer” and will only inherit the line weight of the layer on which they are inserted.
16.Backup your work.
CAD Fundamentals ISymbol LibraryAutoCAD