CAD Drafting Tip: Customizing AutoCAD Fields

 

The ‘Field’ is an important tool used in computer drafting.

Have you ever come across text surrounded in grey in an AutoCAD file? (see image at left). It indicates a field object, a time-saver for certain repetitive tasks in AutoCAD.

So what is a field and how is it used?

A field is text in AutoCAD drawings which automatically updates itself (after a ‘regen’ command) whenever there is a change in the values to which the field is connected.

In our opinion, the most common use of fields in computer drafting is to update parameter values in
§    Title blocks
§    Plotting file names along with their paths and
§    Dates

There are of course other interesting and less common uses of fields:

§    One can use fields to update the scale of a viewport automatically whenever the scale of a viewport is modified
§    One can perform simple calculations inside the field and so that the result updates automatically whenever the calculation’s operands change.

But there is yet another use of fields, one that we at TMG employ in our day to day work…

Let us consider this scenario: you have a situation where you need to update multiple instances of text throughout a drawing, including on multiple layout sheets.

Using fields, all those instances, even if they number in the hundreds, can be updated in ONE SHOT.

Of course you could create attributes, convert them into a block, then use the ‘GATTE’ command to update them in one shot … but what if you needed to update only a value or portion of the text inside an MTEXT by doing some simple calculations? This is not possible by the block method, and we will now describe one of the best strategies to get it done.

Look at the image below:

The above ‘X’ values occur individually scattered over several layout sheets. One of the values, ‘Tank volume’, is calculated from the length, width and height listed above it.

The task is to update all the values one time and in one place, then have occurrences in all the layout sheets updated automatically, as well as leave calculation of the tank volume to AutoCAD.

Also please note that a number of different pump models may also need to be used in single computer drafting project, which will result in updating the above a number of times. And, this is a continuous job with different pump and tank configuration.

Enter fields to the rescue! Here are the steps to harness their power:

Step1

Gather all unique data that needs to be updated to a central location as shown in the image below. This is for the convenience of performing changes without moving to various places on the screen or to various screens. Please note that you should use either single line text entities or a table (see image below).

Step2

Copy and paste the expressions for the variable values in each line from the ‘field’ command as shown in the below video (there is no audio in it).

Tips:
Copying and pasting the field expressions directly will allow us to update values across multiple layout sheets.

[SWF]https://themagnumgroup.net/Blog/wp-content/uploads/2012/08/filed-expression.swf, 480, 480[/SWF]

Repeat the above process to insert the field expression for the rest of the field’s data.

Step3

Now all the field data except the tank volume is updated (see above image).  The tank volume requires simple calculation, and we see how to do that in the below video (no audio).

[SWF]https://themagnumgroup.net/Blog/wp-content/uploads/2012/08/calculation.swf, 480, 480[/SWF]

Now we will see the field in action (no audio).
Please don’t forget to do a regen for the fields to update.

[SWF]https://themagnumgroup.net/Blog/wp-content/uploads/2012/08/field-in-action.swf, 480, 480[/SWF]

Finally, since this is a continuous job with different pump and tank configurations, we have created an AutoCAD template file with the above field objects to use as a base file. After completing the drawing, drafters have only to enter the relevant filed data once, as shown in image in Step 1.

Conclusion

By customizing a field, you can save a lot of time in your day to day work and increase your computer drafting productivity.

Let me know in the comments below if you would like anything above explained further. I look forward to hearing from you!