Sweep loses relationship to line

[christianbaileypaulsen1]

Ive been using the sweep command and lines to give the illusion of dynamic 3d objects for awhile now. I started a new project to try and simplify something at work but am running into an issue. As soon as i stretch this block in one direction it loses association in the other direction. Ive tried using both stretch actions and move actions to move the surfaces on the top and right side but have had no luck. 

Any ideas how to achieve a block that can be stretched in both directions and still give a 3d look?

Ive attached my block for reference.

[j.palmeL29YX]

Try the attached suggestion. (Your Geometry I have hidden on the frozen _Old Layer. ) . 

[christianbaileypaulsen1]

This seems to work but im trying to understand why. What does putting the old geometry do to make it work? Why are there so many new polylines and multiple kinds of surfaces for each object?

[christianbaileypaulsen1]

Also extruding it this way make the two long faces see through on each piece since those are the hollow part of the surface.

[christianbaileypaulsen1]

Here is my iteration of the new way that you suggested. Closer but still not giving the correct 3d look.

[j.palmeL29YX]

The main problem, why your first attempt didn't work properly is, because Dyn. Blocks are for 2D-Geometry only. 

With a small "trick" (workaround) you can also give simple, very limited 3D-models a dynamic behavior. The base idea for solution: Create 2DPolylines (or lines or circles or ...) parallel to the XY-plane which can modified as usual with dynamic actions. Additional create assoziative surfaces based on the 2D-Geometry. (Do not include the surfaces in the selection set of the actions)

(>>Some hints to 3D modelling<<)

Your last posted model: 

You still need to add a lid and a bottom. I'd suggest to use the surfpatch command as shown in the video. There are two possibilities: either you use the Chain option and select the upper and the lower edge of the extruded surface or you use the Curves option and select a top and a bottom polyline. In my example above I decided for the second method. Although you need additional polylines for this, this method seems for me to be more stable while modifying the dimensions (but I can not prove that).
The U-shapes must be a combination of three boxes. Each of them based on a horizontal (parallel to the XY-plane) rectangle. (see attached image).
In the stretch action(s) include only the planar polylines. If the surfaces are assoziative to the source they will follow if the polylines are changed (stretched).