What is the best way of getting the COM location in a part into a usable dimension? I know how to create a COMR point from the COM point, but I'm having trouble getting usable dimensions from it.
I'm embarrassed to say that I did this once before but now cannot figure out how. I have a COM point and a child COMR point in the Feature Manager for this part. (The COMR feature is below all other mass-modifying features in the part.) Following the COMR feature I have a sketch point whose location is set by an equation such that its distance from the part origin equals "RD1@Annotations". This seems to work and allows me to define a plane through the COMR point -- my ultimate goal -- but I can't reconstruct how I found that dimension, and in any case this seems an awkward way of going about it. Isn't there a more straightforward way?
Related Question -- In the part describe above, the COM and COMR points don't seem to be in **exactly** the same location. I've used the Measure Tool to locate them both individually and relatively to "high" accuracy, and they disagree by around 0.1%, even after a rebuild. The COMR point seems to agree with the Mass Properties output, while the COM point does not. I've even deleted the COM feature, but the COMR feature remains and continues to track the true COM of the part. (I'm using SW Premium 2014 SP5.0)
Possibly relevant: I don't understand the meaning of SW Help ("Example: Changing Model Geometry in Parts Containing COM and COMR Points"). In particular, what are "tab features?"
-- John Willett
I think I finally stumbled on an answer again. First create a new global variable in Manage Equations and select Measure for the RHS. Then there seem to be two options. Either
1) Show the COMR point and the part origin, Select Other the COMR point in the graphical window, then Select Other the part origin in the same way, and finally click somewhere in the graphical window to produce the dimension both on the screen and in the RHS of the global-variable definition, or
2) Click the COMR feature in the feature manager, then CTRL-click the part origin in the same place, and finally click somewhere in the graphic window to produce the dimension both on the screen and in the RHS of the global variable.
Either of these methods produces both an entry, "RD#@Annotations" (where # is a sequential integer), in the RHS entry box and a visible driven-dimension measurement of the same name in the graphical window. The visible dimensions that I just created seem to survive closing Manage Equations and the part and then re-opening them, but the Manage Equations window has to be open to see them in the graphical window.
I still have no idea why I still cannot see the original "RD1@Annotations" mentioned above, even when the Manage Equations window is open...
Is this about right, or is there a refinement I should know about?
And is there any way to reveal the original disappeared dimension, "RD1@Annotations", which still appears to be working in the equation where it is used? -- John Willett