Using Union in 2D

[magwea]

I'm trying to use region and union to get the silhouette or outline of the screwdriver, i know the tool is intended for 3D but is it possible to use it like this at all.

 

AC is making regions that are smaller then the entire outline, is there a way to fix this.

 

I was thinking that union would be ideal for getting silhouette in 2D drawings that have more complex details were trimming would be tiresome and time consuming. Is it used like this at all.

 

Thanks in advance.

screwdriver union.dwg

[ReMark]

Sorry...union is for solids.

[Geordie]

"Sorry...union is for solids." .wrong

Union subtract & intersect can also be used on closed Regions

[Tankman]

I did open your file in vs. 07.

 

I'm sure you could measure the screwdriver and adjust the sale, the save.

[magwea]

Indeed, you can use the union command in 2D but in a limited fashion, could be a great tool though if it worked correctly.

 

From what i can tell, i'm still very green at AC, its the fact the when i use region on the screwdriver the entire outline is not selected: eg. some lines form regions with just themselves while some circles and arcs make one region.

 

Is there anyway to jig the region command to get it to do what i want.

 

Attachment shows how handy it can be occasionally.

screwdriver union example.dwg

[Cad64]

In order to create a 'Region', you need to first have closed geometry to work with. For example, the handle of the screwdriver has a closed circular shape at the top, a small closed rectangular shape and two open arcs connecting them. Try using the BOUNDARY command and click in the area between the two arcs. This will create a closed shape that the 'Region' command will be able to work with.

[magwea]

Well, it almost did it, using boundary does give better results results but is still a bit tiresome. Is there no way to just select the outline of the screwdriver and make that one boundary or region and then inverse and delete the inside lines. Seems like a lot of work just to get the silhouette.

 

Attachment: my attempt.

screwdriver union with boundary.dwg

[Cad64]

If you just want the silhouette, why don't you just use TRIM and ERASE to eliminate the internal lines?

[magwea]

Sure, it would work fine for this drawing but i would have imagined that that would be really tiresome for more complicated drawings like screwdriver union example.dwg which i uploaded earlier.

 

Union would seem to be the one to use right?

[Cad64]

For that other drawing, Union worked because all of your shapes were already closed, so it was a simple process to make them all Regions and then Union them. There were no open line segments. if you had open lines and arcs in there, you would not have achieved that result.

 

There is a procedure you have to follow to get the results you're looking for, and that procedure is "Boundary, Region, Union". There is no automatic way that I know of? Maybe with a custom lisp routine?

[magwea]

I don't think i'm ready to start making custom lisp routines, heck, i haven't even used 3D AC yet.

 

Still, its strange though that there is no easy and quick way to get the silhouette of a drawing, something that i would have imagined would be needed frequently.

 

Thanks for the help Cad64, seems "Boundary, Region, Union" is the only way atm.

[ReMark]

"Sorry...union is for solids." .wrong

Union subtract & intersect can also be used on closed Regions

 

You are right. I stand corrected. Thank you.

[rkent]

you can quickly draw a rectangle around the screwdriver, invoke the BPOLY command, pick a point outside the screwdriver, done.

[magwea]

Rkent, genius exactly what i was looking to do: quick, easy and simple. Thanks a million for your help

 

And cheers CAdtutor as a whole for your diligent to my problems