Subtract command act like union

[kavgreenleas]

I'm using the creation of a 3D model of a workbench to learn 3D modelling. The legs of the bench have rails fitted using a tenon on the end of the rail and a mortice slot in the leg. I created the rail using the Box command and then two tenon tusks which I attached to the end of the rail using Union. I know there are other ways of doing this, but I thought I would use a copied version of the rail to create the mortice slot in the leg. I put the rail into position and then used the Subtract command. All I got was a combined solid consisting of the leg and the rail. As if I had used Union. Using a separate Box to subtract from the leg worked fine. Any ideas?

[maxim_k]

Hi,

Are you sure, that you are using SUBTRACT command in right way?

After you call SUBTRACT - first select object(s) to subtract from, then hit Return and select objects you want to subtract.

Maxim

[kavgreenleas]

Yes, absolutely certain. When I use a box to subtract with without any additions, the command works fine. It's only when I use a solid made up from boxes merged using the "Union" command that this problem happens. 

[maxim_k]

Please check also the state of Solid history- maybe you see not the result, but original solids.
Could you post here your DWG?

Maxim

[kavgreenleas]

I've attached the drawing. As you look at it, the right leg at the rear has been sliced to make sure the subtract command has worked. The leg fwd of that and the rail are the result of the problem subtract command.

Regards, Mike

[maxim_k · Accepted solution]

Hi Mike,

I was right, when I wrote in previous post:

"Please check also the state of Solid history- maybe you see not the result, but original solids."

If you select the leg and go to Properties palette, you will see "Record history" and "Show history" option checked:

So when you subtract the rail, it actually get subtracted, but as "Show history" is checked you see "history". If you uncheck "Show history", then you will see the result (the mortise slot in the leg).

You are confused also because when you use Wireframe (or 2D Wireframe, or Sketchy) visual style the history of the solid shows the same way as resulting solid itself. If you will switch to Realistic Visual style (or Shaded) you will see the difference.

You can read more about solid history feature in On-line Help:

http://docs.autodesk.com/ACDMAC/2013/ENU/filesAUGMac/GUID-F68B5226-E29C-4100-A493-38E411B8654F.htm#W...

HTH

Maxim

[kavgreenleas]

That's great Maxim and explains a lot about the history checkboxes which I did not understand. Thanks for your time reviewing this issue.

Regards Mike