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Block vs. wblock


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You said it, WBLOCK (write block) is just a command that allows you to create a drawing file made of entities from another drawing. There is no such thing as "a WBlock".

 

A Block is an autocad entity whose geometry is made of one or several other entities. You can create a block definition in the drawing by making the block from within the drawing (with the BLOCK command) or by inserting another drawing file into your drawing.

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  • 1 year later...

freeko, what do you mean "best way to clean up a drawing" ?

i'm trying to understand the advantages and disadvantages of blocks in general.

one thing i can see being a problem is the matter of organization (or naming of blocks).

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tzframpton

The definition of a Block is this: "A generic term for one or more objects that are combined to create a single object."

 

Just means that you are combining one or more entities and making it a single entity. If you edit a block, any changes will be distributed to all references (or better understood as all "copies" of the block) within the drawing. You can type BLOCK at the Command Line to create a block.

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Wow, that was a fast reply. thanks.

So, continuing to understand the idea of block vs. wblock...

What's to prevent me from accidentally naming the block that of a name already in use (already in use in current drawing or in library of blocks). Or perhaps the block already exists (exact duplicate of block to be created) and it's not necessary to re-create the block, ie. instead of having redrawn the block from scratch, I could have simply inserted it)

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tzframpton

WBLOCK means to create a block from AutoCAD to the hard drive as it's own DWG file. Think of "exporting to a block". BLOCK means to create a block within the current drawing. You can't overwrite a block accidentally without it prompting you to either overwrite the block, or update the block reference. Either way it's a prompt that can be canceled.

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CyberAngel

You wanted to know about the advantages and disadvantages of blocks. The main advantage is in organization. If you have to draw, say, a cafeteria with tables and chairs, you can make a block for a table and another block for a chair. You only have to draw them once, then it's a matter of placing blocks instead of drawing or copying new tables and chairs. When you're dealing with dozens or hundreds of objects, it saves a lot of time.

 

Another advantage is in modification. If you've placed hundreds of chairs and then someone decides you need a different model of chair, you modify the block definition once and those hundreds of chairs all automatically change.

 

Disadvantages: you have to deal with scales, especially when you recycle old blocks in new drawings. There's no way to change some of the inserted blocks and not others. You have to be careful defining a block because they can do some strange things (you can find some on this forum).

 

As for duplicate names, you can't create a new block with the same name as an existing block. There's a table of block names in the drawing, and AutoCAD checks that table when you add one. If you define a new block that is a duplicate of an existing block, but give it a different name, AutoCAD will let you do that. If you want to use a block from an old drawing in your current drawing, you can cut and paste it.

 

WBLOCK is short for Write BLOCK. It's nothing but a procedure. It doesn't make sense to compare blocks and wblocks.

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If I Wblock a chair, it writes it to file and I can use that block in other drawings. If I change (modify) that chair, will it update it in all drawings that use it?

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No. You would have to insert the block again, to each drawing where it was used, and upon re-insertion, choose to redefine the block.

 

If you want it to automatically update the changes, to all drawings, you would have to xref the chair into each drawing.

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tzframpton
If I Wblock a chair, it writes it to file and I can use that block in other drawings. If I change (modify) that chair, will it update it in all drawings that use it?
No it won't update in all drawings that currently used it. An XREF can do that, but I highly, highly suggest not approaching updating drawings in that manner. Once a block in created, it is dedicated to that single DWG file only.
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Oh, XREF. I heard about that before but didn't give it much thought as block seemed to be my solution at the time.

I'll have to search the forum for XREF info. But isn't xref associated with the idea of Wblock. I mean, isn't it the case that if you wblock, it's for the purpose of xref-ing it into other drawings. (I'm assuming xref is part of block insertion process)

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tzframpton
I mean, isn't it the case that if you wblock, it's for the purpose of xref-ing it into other drawings. (I'm assuming xref is part of block insertion process)
No. An XREF is simple an "external reference". A WBLOCK is a function to "write a block" to it's own DWG. Once you make a block in a drawing, there's no way to save that block into it's own drawing unless you start a new drawing, then copy/paste, then save. It's a hassle so it's better to just WBLOCK it out. It's basically a "Save As" feature for blocks. It's best to not reference it as a WBLOCK, and simply reference it as a BLOCK. WBLOCK is just a command that saves a BLOCK to it's own DWG file - that's it.

 

Let me try and give you an example of XREF vs BLOCK.

 

If you XREF one drawing into ten drawings, when you make changes to the XREF it updates in all ten drawings. If you use the INSERT command to import the same BLOCK into ten drawings, you can only make changes to the BLOCK in each individual ten drawings, and the changes that are made are specific to each drawing only - they are not referenced in any way. So, making changes to the original BLOCK does nothing unless you re-import it into each of the ten drawings.

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ijon tichy

In the old days WBLOCK meant WORLD BLOCK.

A BLOCK was only available for insertion in the drawing it was created in.

A WORLD BLOCK was available for insertion in any ACAD drawing.

Has this changed.

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Yah, world block makes more sense then write block.

wblock (write block) is more like a Save Selection As feature ie. save selection as dwg or dxf. really nothing to do with block at all.

 

I was thinking, the process (automatically if you will) of copying a block from one drawing to another (providing the second drawing does not have that block in it yet) would be that the cad program would automatically convert the block being copied into a world block. Then modifying that block in either drawing would update in both drawings.

Edited by opreese
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oh, in ref to the autodesk link above:

the wblock dlg box has option to set base point when creating wblock.

so instead of just being a save selection as feature. it's more like, save selection as a blank drawing with and only with a single copy of a block.

i'm unable to verify this as i don't have autocad (note: i'm just going from memories using r12 or r13 back in 1993)

so, when you wblock and then open that drawing does autocad report it as such.

if someone has a chance can u email a simple sample of a file created using wblock. pls send it in dxf r13 format so i can read it with note pad. 2d only please and perhaps just few entities (ie a couple lines and circles), thanks in advance.

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WBLOCK creates a single .dwg - exactly the same as if you started a blank drawing and drew the item from scratch. One advantage WBLOCK gives you is that it purges the drawing on the way. ONLY the entities (text style, layers etc.) that are needed go across.

 

The biggest problem you have with creating a BLOCK is people don't set the base point sensibly, they just leave the base at 0,0. This WILL bite you big time in the future as you start using blocks in more than one drawing.

Edited by dbroada
changed WBLOCK to BLOCK in final paragraph
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Block base point of block vs wblock:

3 dxf files for discussion purposes:

http://htwif.com/owen/fbcadcam/wblock_test/initial_drawing.dxf

http://htwif.com/owen/fbcadcam/wblock_test/wblock1.dxf

http://htwif.com/owen/fbcadcam/wblock_test/initial_drawing_wblock.dxf

First off, these dxf files were created via my cad program (a hobby project... see profile). I hope they are compatible.

initial drawing has line (100,100)-(200,100) and circle (100,100) with radius 100. file saved as initial_drawing.dxf.

i then select the two entities and wblock using block name "wblock1" with base point set @ (100,100)

my wblock function does two things, 1. creates wblock1.dxf & 2. converts selected entities into a block with block name "wblock1"

Note: my drawing (initial_drawing.dxf) has changed (ie. two entities converted to block) so i Save As initial_drawing_wblock.dxf.

 

inspecting wblock1.dxf and comparing it to initial_drawing.dxf:

both files do not have any blocks.

both files have two entities (a line and a circle)

entity positions are the only difference

line (100,100)-(200,100) and circle (100,100) with radius 100 ... (initial_drawing.dxf)

line (0,0)-(100,0) and circle (0,0) with radius 100 ... (wblock1.dxf)

 

inserting the wblock1.dxf into a new drawing:

since this dxf is not a block it has no base point. so the default base point is the lower left corner of the extents of the entities with in.

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