Block Parametric From Center

If you use the block function, you'll see that when you resize it the anchor is the bottom left corner (Block grows in pos x,y,z). I had a very large need for a start-out block that grew from center that I could use for everything from cavity blocks to inserts. To do this, start a new part. Then put all 3 datum planes in by going to datum plane, fixed methods & placing all 3 planes. Now enter sketch mode - it will go to X-Y plane by default - & sketch a 2-point rectangle. Inthe Xdirection put both a half & overall dimension on your box with the half dim coming off of the corresponding plane shown on edge. Now, you'll see each dimension has a value as well as a name like p0, p1.Edit the overall X dimension & where it says p0 or p1 name this to X. Double click on the half-dim & change the numeric value to X/2. This will ensure that the half dim will always truly be half. Do the same for the Y direction naming that overall Y. You will have a total of 4 dims, with the overalls being named X & Y. These overalls will be the only dimensions you will need to edit & the block will now always resize from center. Now, extrude this in Neg Z &you're done. You can also name this Z value as Z so that the named values you see when doing a <CTRL>+E will be X Y & Z. Save this block in your UG stuff folder as 'generic block' or something & you can always snag it later & copy it to your work folder as a cavity or whatever & resize it as needed.
Edited by: bugfanatic

If you create the Datums after your block feature and select opposite
faces of the block as your references you will get 3 mid planes. This
would be a good solution as long as you don't need your block centered
on the WCS. Using the method I've described below you can get the
same result as long as you create the block with the bloack started
from the origin.



You can also create a Block XYZ and do 3 move region comands selecting
one surface and no bounding surfaces and group these and give the
movement dimensions as -X/2, -Y/2 and -Z/2 you'll
get a beter result than the fixed datum method you
described. Also as you create a block you can type

X=10

Y=10

Z=30

and the parameters will automatically be created as X, Y and Z instead
of p1, p2 and p3 since your saving the part this is no real time saver
since you're saving the part but you can enter a parameter name for any
value as you create it which will really help on large parts with many
dimension.



Michael

Bug,


I much prefer Michael's way (since I've learned how to do the same thing in Pro/E and now Solidworks) it is much simpler to create the block first and then add center datums. This way all modeling afterward would/could be based on those center datums.


Michael points out a greate feature that only UG has (to my knowledge) and that is the ability to create expressions on the fly by typing them.

OK, I've tried both ways & given them a fair chance. Either datums, sketch,& extrude or block, datums, & move. Both work good but I'll have to stick with doing the datums first. Same number of steps making the datums, but this way the block is always on center from the start & it makes a great generic starter file for any kind of insert that you want controlled from center. I guess it really just boils down to I don't want a move command controlling anything, I want to start at the beginning from the center.