true position question

[john d]

How do I know what workplane to use in pc dmis when dimensioning a true position feature. If I use a x workplane, the true position dimensions a y and z and diameter. If I use a y workplane, the true position dimensions a x and z and a diameter. If I use a z workplane, the true position dimensions a x and y and a diameter. When I use the y workplane, there is no red dimensions, however, when I use the x and z, there is red. What is the secret???

[Robert Davis]

Generally your workplane is normal to the feature your measuring for TP. You select the workplane based upon the direction you want to dimension the part from, and that depends on your callout on the print.

[Wes Cisco]

The ole quarter image

John, You have to learn to think about how the software "sees" your part/alignment. The idea I use to isllustrate this is think of a quarter laying on you cmm table. If you are looking down on it, or up at it from the table (z +/-) then you see a circle. But if you get down eye level to it, you see a line (x or y +/-). When you designate a workplane you are telling the software a "perspective".
Try placing a 1-2-3 block on your table. Make lines of the sides and measure some of the holes on two or three of the surfaces. Now use distance to dimension from line to line, hole to hole, and hole to line. Change workplanes a couple times while doing the dimensioning. That exercise should help you understand which workplane you need to be in for the task at hand.
Remember that if you do not choose a workplane Z+ is default. HTH

[cmmguy]

Good answer Wes

[craiger_ny]

I'm telling John on you.

[Matthew D. Hoedeman]

Easiest way (assuming you are using AUTO FEATURES and you are using SURFACE SAMPLE HITS) is to dimension TP with all 3 axis and mark PERP TO CENTER LINE. This will give you the TP of the hole, in the 'plane' of the surace the hole is in and it will remove the surface deviation, just like a stab pin on a fixture.

[cmmguy]

http://www.combat-fishing.com/poprc.gif

[craiger_ny]

OK you got one.

[cmmguy]

yea, it was a big one too...

[Wes Cisco]

tsk tsk, boys, boys, boys. (Shakes head in pretend despair). What should we do with you? (sarcastic rhetorical). Does it make you feel all powerful to revive the dead?

[JamesMannes]

tsk tsk, boys, boys, boys. (Shakes head in pretend despair). What should we do with you? (sarcastic rhetorical). Does it make you feel all powerful to revive the dead?

Yeah they so funny. They funny like clown...
http://www.christmas-treasures.com/d...e/American.jpg

Find more emoticons too while you at it wide eye!!

[cmmguy]

Yeah they so funny. They funny like clown...
http://www.christmas-treasures.com/d...e/American.jpg

Find more emoticons too while you at it wide eye!!

Yea, yea... give me something worth replying to. Looks like you have been shopping on eBay. http://floridasportsman.com/art/fish.gif

[Rob_K]

If you use Datum Definition, PCDMIS creates REF due to selected features(i.e. if Datum -A- is a plane, rotated 3D in Origin REF, it's Normal Vector creates Z+ axis, if -B- ...). So, all TP axes are constrained to new REF.
No need to worry about workplane.

[John Kingston]

bobber.jpg