Getting a datum or reference that actually aligns with the original object?

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GrantRobertson
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Re: Getting a datum or reference that actually aligns with the original object?

Postby GrantRobertson » Sat Aug 18, 2018 12:01 am

chrisb wrote:
Fri Aug 17, 2018 1:51 pm
Can you please upload your model so we can have a look at it? I'm pretty sure that you did not create the ShapeBinder from the body, but from something inside.
Chris,

I cannot tell if you are talking to me or to freedman. I did upload my original file with my original post. However, I have created a new, bare-bones file to illustrate what I am talking about. Here are the exact steps of how I created this file, and the result:

1. Create a brand new file.
2. Click the "Create a new body and make it active" button. (Resulting in an empty body (except for the origin, of course), named "Body.")
3. Rename that body to "Body1," just so we don't get confused.
4. Create a new sketch for Body1 and create a simple pad.
4.1 With Body1 active, click the "Create a new sketch" button. (Geez, these buttons have long names.)
4.2 Select the XY_Plane and click OK.
4.3 Draw a small rectangle with one point locked on the origin. (I did not bother to constrain the dimensions of the rectangle because that doesn't matter for this discussion.)
4.4 Click the "Close" button.
4.5 Turn on the global Axis Cross to verify that the sketch is at the origin.
4.6 Click the "Set to axonometric view (0)" button to see the sketch lying flat in the XY plane.
4.7 Click the "Pad a selected sketch" button, leave all the settings and options unchanged and click "OK."
4.8 See that we now have a pad in Body1 and said pad is sitting right at the origin with edges aligned with each of the X, Y, & Z axes.
5. Reposition Body1.
5.1 Select Body1 in the Model Tree.
5.2 On the Data tab, click the arrow/triangle next to "Placement" then next to "Position" to expose the fields for the x, y, and z position.
5.3 Set each of the x, y, & z values to 1 (inches or centimeters doesn't matter).
5.4 Verify that Body1 is now positioned away from the global origin.
6. Create a new body and name it Body2. (It is now the active body.)
7. Rotate the view such that you can see the face of Body1 that is in the YZ plane, which is closest to the global origin.
8. Create a Shape Binder from that face in Body1 (which will end up in Body2 because that is the active body).
8.1 Select the above-mentioned face on Body1. (It should now be green.)
8.2 Click the "Create a new shape binder" button.
8.3 The "Datum shape parameters" pane will open on the left. (The "Object" field will say "Pad" because we didn't rename that pad. The large (unlabeled) box will contain the word "Face4.")
8.4 Click "OK."
9. Notice that the Shape Binder created in Body2 lies at the origin rather than aligned with the face that was selected in Step 8.1.
10. Click the shape binder named "ShapeBinder" in the Model Tree and look at the data tab. Notice that there is no "Placement"or "Position" field, so this shape binder cannot be moved.
11. Realize that you have just wasted your time because that shape binder is useless for aligning things in Body2 with Body1.

Think a little bit about the wording of Chris's question...

12. Create a third body and name it "Body3." (This will now be the active body.)
13. Select Body1 in the Model Tree rather than any individual face in Body1.
14. Click the "Create a new shape binder" button.
15. Say, "Holy Shit! That worked!"


I have attached this FreeCAD file, exactly as it appears after finishing with Step 15.

I gotta say, the steps described up through Step 10 are the types of steps that are described in absolutely ALL of the documentation I have been able to find. Including the Shape Binder documentation in the Wiki. All this documentation says to select faces within the body. The last line of the Wiki does say, "The shape binder will adopt the same internal coordinates as the copied body," but that is vague, not totally accurate, and ignores the most important implication of that statement. The fact that the program behaves differently depending on whether one has followed all the instructions in all the documentation or one has selected the entire body in the Model Tree (which is not mentioned in any of the documentation), is a serious bug, in my opinion.
Attachments
006 - Repositioning Body leaves Shape Binder behind.FCStd
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