Some Notes on 'Spin Center'

This is both a problem and an answer I found to it, that I wanted to share.

As you know, Pro/E's 3D display comes with a "Spin Center", whose icon looks like a red, green, and blue ball tied together with pins. At our plant, the default is set to "Spin Center" ON, and the Spin Center is set to the Model Center.

With Spin Center ON, when you middle-mouse-button-click and move the mouse around, the model or assembly rotates about the default Spin Center. With Spin Center OFF, when you MMB-rotate, the model rotates around (a) some random location that Pro/E chose, or (b) whatever the last model feature was that you clicked on.

If you want to zero in on a specific part of your assembly for a moment, you can toggle Spin Center OFF using the Spin Center icon (which should be) at the top of your screen. Then click on one of the parts in the area you want to examine, then *click on it again* to select a vertex, edge, etc. Once this vertex, edge, etc is selected, subsequent MMB-rotates will cause the assembly to rotate about this point.

The catch is, as soon as you (often inadvertently) select some other sub-feature elsewhere, the assembly will then rotate around that point instead. So your center of rotation can change on a whim.

I had a problem with a large (physical size) assembly whose Model Center was for some reason way off in space. With Spin Center on, when I MMB-rotated it, it wallowed about in space most awkwardly. But with Spin Center off, while it would "behave itself" for a few moments, the center of rotation wouldn't stay put, and this was also a pain.

Finally I noticed that there was a stray DTM plane way off in space far from the rest of the assembly, and the Spin Center was set halfway between this stray plane and the assembly itself. (It took me this long to notice because normally I turn the display of the DTMs off immediately, else the assembly looks like a big brown hairball and I can't see anything.)

The stray DTM was the "TOP" assembly plane of a subassembly, which for some reason was located 1700 mm away from it, instead of having it lined up on the face of one of its parts, for example. As soon as I moved the subassembly to be right next to all its assembly planes and regenerated it, the Model Center and thus the Spin Center of my main assembly moved to inside the main assembly, and it MMB-rotated much more conveniently with Spin Center 'ON'.

Hope this helps.

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It sounds like something is wrong (or new since WF3) with the way this is working for you when you have the spin center turned off. I almost never have it turned on and when off, it spins around whatever is under the cursor when I press the MMB. Certainly it will occasionally catch the stray datum feature but works the way I want it to 95% of the time or better. If I=92m zoomed in I usually want to spin around the local region I=92m looking at (spin center off functionality) and if I=92m zoomed out then the difference between off and on isn=92t a big deal anyways. This is all in WF3, though the same applied in WF2 and possibly before? I can=92t remember when I first learned about spin center for sure.



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Kyle Altendorf

It's a while since I've even thought about the spin center. Like Kyle, mine is permanently turned off with the configuration option spin_center_display set to no. But, to be complete, it is possible to move it from its default center of model size to something else. Check out TPI 32132 in the Knowledge Base, the stuff that user group meeting are made of. Basically it says to use the Reorient dialogue to select Orient by Preferences where you get to select from several different references like a point or coordinate system to reset the spin center location. This gets it away from the tyranny of the model center which can be thrown off, as was pointed out, by any stray geometry or datums. In case you're curious, Info>Model size will show the bounding box and the length of the diagonal. If you could actually measure it, you'd see that the diagonal runs though the spin center at the mid point of the diagonal.

On the negative side, this move of the spin center isn't permanent, even for the part. It doesn't save with it. Another rationale for letting it slip quietly by the wayside and disappear into the mists, along with turning off Intent Manager in sketcher and other anachronisms.

David Janes

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