Autocad 2D Dynamic Blocks

Dynamic blocks in the Autocad 2D interface are blocks that can be modified to show different variations of the block, for example variable window sizes, or screw lengths, or rotations. So we end up with one block but define different lengths, size, rotation, etc, as you place it into your drawing. Dynamic blocks are made dynamic by adding various parameters and actions to those parameters. These can also be modified using their grips or properties. Incidentally, before AutoCAD introduced its Block Editor this was done using the programming code AutoLisp.

An example of this type of block would be a plan view of a window with varying lengths where we add dynamic stretch to a standard window block. First create a new file from your metric template, with drawing limits of 10 by 6 metres. Then create a window: Rectangle > 1000 x 150 - this will be the Plan view of the window. Next create a block from it, naming it 1000-2000 window. Specify the base point as the bottom left corner, and uncheck Scale Uniformly. Then test the block to ensure that it works. Save the Autocad file; the block now resides within this drawing file.

Now we open the Block Editor from the Ribbon or type bedit into the Command Line. Select your new window block, whereupon the Block Authoring palette will open. Note the Parameters panel on the left. Choose the Linear option and type V into the Command Line (for value set). Then type I for Increment and type in the distance of 100. Autocad then asks you for the minimum distance; type in 1000 and a maximum of 2000. We then specify the start point by clicking on the bottom left of the object, and the end point of the bottom right. We also choose the label location below the window; a title tag Distance 1 will appear. Next select the Parameter (Distance 1) and right-clicking on it choose Grip Display at the top of the list. Type 1 for the right side (2 would be both sides).

The next step is to select the Stretch tool on the Actions tab, then click on the Distance 1 Parameter and specify a Parameter Point of the arrow Grip on the right. Now define the stretch by clicking and dragging a crossing window to select the right hand side of the window. Select objects by again dragging a crossing selection around the right hand side of the window and finish by hitting the Enter key on your keyboard. Zoom out to see the ten vertical bars to the right: these are the 100mm incremental distances you specified above. Note also the Stretch icon on the bottom right. If it's not there right-click on it to make it visible. You can later right-click on this to edit the block. Now close the Block Editor on the top right of the Ribbon and choose to Save the changes.

Test the block by selecting it; note the blue Grip icon. Pull it to the right to see the increments appear. Alternatively you can drag the grip and punch in the distance required. Also type DI for distance, and click on both end points to check the window length. Keep saving throughout the process since it's easy to close the file instead of the block editor.

The possibilities are endless when it comes to dynamic blocks - it all depends on the industry and purposes for the block in question.


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Tom Gillan has been training AutoCAD 2D to corporate clients in Sydney for seven years. Visit http://www.designworkshopsydney.com.au/autocad-2d-courses/ for more information.