ENGT 122 – CAD I Chapter 14 - Blocks

What’s a Block?  Block - A group of objects combined to create a single object.  Can be named and saved for later retrieval (BLOCK).  Can be repeatedly inserted into a drawing at any time (INSERT).  Comprised of any number of objects, but treated as a single object that can be easily moved, rotated, scaled, and copied.

What’s a Block?  Individual objects comprising a block can be “recovered” using the EXPLODE command.  An inserted Block is referred to as a “Block Reference”.  Once created, a block can be modified (redefined), and all inserted block references will update accordingly.  Blocks can be “nested” within another block.

Some Advantages of Blocks  Allows a previously created drawing or portion of a drawing to be reused in the same drawing or another drawing without recreating it.  Allows extensive libraries of symbols and parts to be created, stored, and accessed at any time.  Reduces drawing time.  Assures standardized symbol conventions and part dimensions within the organization.

Some Advantages of Blocks  Greatly simplifies drawing changes.  Example: an assembly has 150 similar bolts. If the bolt specification changes, the block definition can be easily edited and the assembly will update to reflect the change on all bolts.  Greatly reduces drawing file size. The objects comprising a block are only stored once, during definition of the block. Each block insertion is merely a reference to the original block definition (ex: 500 block insertions of a bolt require little more storage requirements than a single bolt).

Block Example:  Standardized electrical symbol library can be created from Block entities and later used to create circuit diagrams.

DEMO 1:  Load file Demo1.dwg.  Show example of electrical symbol Block insertion

Learning Objectives  Create blocks with the BLOCK command.  Insert blocks with the INSERT command.  Split a block into individual objects using the EXPLODE command.  Learn to redefine a block.  Create drawing files using the WBLOCK command.  Redefine the insertion base point for a drawing.  Rename blocks and purge unused blocks.

Creating Blocks  Step 1: Create the objects to be grouped in the block using AutoCAD drawing commands, but note;  When inserted, each entity in the block will retain the properties of the layer it was created in or inherit the properties of the current layer according to table below: If you want objects in a block to: Create objects on these layers Create objects with these properties Retain original properties and layer when inserted Any but 0 (zero) Any but BYBLOCK Inherit properties and layer from the layer current during insert 0 (zero) BYLAYER Retain original layer but inherit specific individual properties according to current property settings Layer you want inserted block to be placed on BYBLOCK

Creating Blocks  Step 2: Make sure the objects to be placed in the block are visible. Then, issue the Make Block Command using command line, drop down menu, or toolbar. Command: BLOCK Command: BLOCK All methods bring up Block Definition dialog box. Draw Toolbar

Block Definition Dialog Box

DEMO 2:  Open file Demo2.dwg.  Create some geometry.  Demonstrate Make Block Commands and Block Definition dialog box;  BLOCK

Exercise 1:  Start a new drawing using an English template.  Set the current layer to Layer 0 and then create the simplified bolt shown (without dimensions). When inserted, this block will inherit the properties of whichever layer is current.  Using the bolt geometry, create a block named BOLT.  The base point should be at the location indicated.  Use the Delete option for the selected objects.  Save your file as Ex1.dwg. You will need it later. Base Point at midpoint

Inserting Blocks  Step 3 – Once created, the block is stored locally in the current drawing file.  To insert a copy of the block, the INSERT command can be used.  Set the current layer and/or adjust settings in the Properties toolbar before using INSERT;  Each block object will be placed on the current layer.  All block objects created on “Layer 0” will inherit properties from the current layer.  All block objects created with Properties set to BYBLOCK will inherit specific individual properties according to current property settings.

Inserting Blocks  A Block is inserted using the INSERT command; Command: INSERT Command: INSERT  Insert dialog box appears Draw Toolbar: Insert Block

Inserting Blocks  Insert dialog box allows;  A predefined block to be inserted, or  A drawing file to be inserted as a block.

DEMO 3:  Show the INSERT command using block made in Demo 2. Illustrate inserting;  A predefined block  An external file Demo3.dwg (title block) as a block.

Exercise 2A:  Use the same drawing file from Exercise 1 (Ex1.dwg) and create the geometry shown using a new layer called JOINT with color = Magenta (no dimensions).  Then create a new layer called BOLTBLOCK using color = Green, linetype = continuous, linewight = 0.7.  Set the current layer to Layer BOLTBLOCK.

Exercise 2B:  Use the INSERT command to insert 3 copies of your block named BOLT as shown below.  Notice the blocks inherit the properties of the current layer (BOLTBLOCK ). Why?  Save your file as Ex2.dwg. You will need this later.

Editing Block Definitions  A bock is treated as a single object, but is comprised of multiple objects.  To make a change in a block, it must first be “Exploded” to divide it into its components.  Use the INSERT command with the Explode option to insert the block in an exploded state, or…  Or use the EXPLODE command on a previously inserted block. Command: EXPLODE DDMenu: Modify > Explode Modify Toolbar: Explode

Editing Block Definitions  Once in the exploded state, the individual objects comprising the block can be edited and modified.  After making the required changes, the block can be “Redefined” as follows;  Reissue the BLOCK command.  Reselect the objects comprising the block.  Provide the original block name  AutoCAD will issue a warning, “Block is already defined, Do you want to redefine it?”  Select “YES”.  The block is now redefined and incorporates the changes you made. All blocks inserted previously with this name will update accordingly! Wowee!

DEMO 4:  Open Demo4.dwg.  Insert an exploded version of diode.  Redefine diode and view update.  Insert a non-exploded version of resistor.  Use EXPLODE to explode resistor.  Redefine resistor and view update.

Exercise 3A:  If not currently open, reopen drawing Ex2.dwg which you saved in the previous exercise.  Away from the existing objects, insert a copy of your block named BOLT using the Explode option.  Use STRETCH to increase the length of the exploded bolt by 2”.  Then Set the current layer to layer 0 and add some simple threads using COPY or ARRAY. Exploded Bolt block

Exercise 3B:  Use the modified bolt geometry to redefine your block called BOLT. Use the Retain option for selected objects, and use the same base point as previously.  Respond YES to the message Bolt already defined, do you want to redefine it?  Your bolts should all update by increasing in length. Base Point at midpoint

End Lesson 30

Block Layers Review of Layers as pertaining to blocks: If you want objects in a block to: Create objects on these layers Create objects with these properties Retain original properties and layer when inserted Any but 0 (zero) Any but BYBLOCK Inherit properties and layer from the layer current during insert 0 (zero) BYLAYER Retain original layer but inherit specific individual properties according to current property settings Layer you want inserted block to be placed on BYBLOCK

DEMO 5:  Open file Demo5.dwg.  Show how object creation layer affects block insert properties and layer.

Nested Blocks  Nested Block  If the BLOCK command is issued to create a block, and another block is selected as one of the objects, a nested block is formed (one within another).  The depth of nesting is unlimited.

DEMO 6:  Load Demo6.dwg.  Show Nested block.  Create a small circuit using existing blocks.  Convert circuit into a larger block with nesting.

WBLOCKS  Blocks are stored locally in the drawing file they were created in and are not directly accessible in other drawings.  The WBLOCK command (called Write Block) overcomes this deficiency.  Any drawing file can be inserted as a block.  WBLOCK  glorified save command that creates a drawing file from a portion of your current file.  selected objects  predefined block  or the entire drawing  These new drawing files can then be inserted as blocks in any other drawing file.

WBLOCKS To Create a WBLOCK:  Command: WBLOCK  Displays Write Block dialog box.

DEMO 7:  Load file Demo7.dwg.  Show the WBLOCK command using;  A predefined block  Entire drawing  Selected objects  Show WBLOCK insert.

Exercise 4A:  Open a new drawing.  Create a layer called BLOCKS (any color & line type).  Make layer BLOCKS current, then set the Properties Control for color, linetype, and lineweight to BYBLOCK.  Create the objects shown below without dimensions.

Exercise 4B:  Create a Wblock named SmallBolt using the geometry and base point indicated. Save it where you can find it!  Create a Wblock named BigBolt using the geometry and base point indicated. Save it where you can find it!  Create a Wblock named nut using the geometry and base point indicated. Save it where you can find it!  Save your file. Base Point at midpoint Wblock named SmallBolt WBlock named BigBolt WBlock named Nut Base Point Base Point at midpoint

Exercise 4C:  Open a new drawing file and create the geometry shown below (without dimensions).  Create a new layer called BOLT (any color & line type).  Make BOLT the current layer.

Exercise 4D:  Set your Properties Controls as shown below. Use INSERT to Insert block SmallBolt shown in green  Adjust Property controls as shown below and Use INSERT to Insert block Bigbolt shown in yellow.  Adjust Property controls as shown below and Use INSERT to Insert two blocks nut shown in red.

Defining Base Points  When a drawing file (i.e. WBLOCK created by Entire Drawing option) is used for block insertion, the base point defaults to the drawing origin.  If the file is frequently used as a block, it’s desirable to reset the base point to a specific location.  BASE command accomplishes this.  Open the drawing file to be used as a block.  Issue the BASE command; Command: BASE DDMenu: Draw > Block > Base  Select a new base point and resave the file.

DEMO 8:  Open file Demo8A.dwg and show contents. Then close it.  Open file Demo8B.dwg and Insert Demo8A.dwg as a block with original BASE.  Edit the BASE in Demo8A.dwg using the BASE command, then save it.  Insert Demo8A.dwg as a block with new BASE.

Editing WBlock Definitions  Redefining an externally referenced block (one from another file) will update the block locally but not in the source file.  WBLOCKS and Drawing files used as blocks should be edited directly in the source file and re-saved.

Renaming Blocks  A block can be renamed using the RENAME command: Command: RENAME DDMenu: Format > Rename…  Rename dialog box displays.  Select the name to change.  Enter a new name and pick the Rename To button.  Select OK.  Rename can be used for other entities too.

DEMO 9:  Open Demo9.dwg.  Rename some of the blocks.  RENAME can be used for other entities.

Deleting Unused Blocks  To remove unused blocks from the drawing use the PURGE command. DDMenu: File > Drawing Utilities > Purge… Command: PURGE  Purge dialog box displays.  Expand the tree labeled Blocks. Only unused blocks will be visible.  “Non-purgable” items can be viewed by selecting view items you cannot purge.  Nested blocks can be purged by selecting Purge nested items. PURGE can be used for other entities too!

DEMO 10:  Open Demo10.dwg.  Delete all blocks then insert a couple blocks.  Show the PURGE command.  PURGE can be used for other entities.

Exercise 5:  Create the objects shown. Then generate a block for each using the name indicated and the Delete option.  Insert a copy of each block.  Rename the blocks as follows: CIRCLE  ROUND; RECTANGLE  BOX; HEX  POLYGON  Try to PURGE the blocks.  Delete the inserted blocks, then try PURGE again. Block: CIRCLE Block: RECTANGLE Block: HEX

End Lesson 31

End Lesson 32

The End

RETIRED MATERIAL

Creating Blocks  Step 1: Create the objects to be grouped in the block using AutoCAD drawing commands, but note;  When inserted, each entity in the block will retain the properties of the layer it was created in or inherit the properties of the current layer according to table below: If you want objects in a block to: Create objects on these layers Create objects with these properties Retain original properties and layer when inserted Any but 0 (zero) Any but BYBLOCK Inherit properties and layer from the layer current during insert 0 (zero) BYLAYER Retain original layer but inherit specific individual properties according to current property settings Layer you want inserted block to be placed on BYBLOCK

Inserting Blocks Affect of Scale Factor:  Block can be mirrored during insertion by using a negative scale factor.  If X-Scale negative  mirrors about Y-axis.  If Y-Scale negative  mirrors about X-axis. Basepoint

Nested Blocks  Nested Block  If the BLOCK command is issued to create a block, and another block is selected as one of the objects, a nested block is formed (one within another).  The depth of nesting is unlimited.  Special rules for how layers, colors, and linetypes are affected in a nested block:  If an inner block has objects on Layer 0, or objects with linetype or color specified BYBLOCK, the objects acquire the properties of the first fixed layer encountered in a higher level nest.  If no fixed layers are found, the Layer 0 and BYBLOCK objects acquire color = white, linetype = continuous, line weight = default.