True Position in 3 axis???

http://www.pcdmisforum.com/showthread.php?t=11367&highlight=True+position+XYZ

Look here

if you can have a center in 3 axis tha means you can do 3d TP. Say if you have gage point in xy and z location thaen you will have a 3d tp. Now a hole is usually is 2d unless The TP is called out in XY and to the perpendicular plane Z.
Hope it helps


The best thing is to show him the formula which will include xy and z.

John,
The part is a square block with a counter bore in the middle of it. The drawing is asking position of the "central point " of the cylinder ( meaning center of x,y,z) of the cylinder to datums, a-b-c. A datum in x, b datum in y , and c datum in z from the bottom of the part. Basically it's a point that has been established within the cylinder with basic dimension to all 3 axis noted as datums. It only makes sense to me that if that centroid point has been given basic dimensions from 3 axis that are labled datums a-b-c-, that you should be able to calculate it as all 3.

Yes, that is correct.
One way to do it is to create a plane at the bottom of the cylinder, another at the top (you probably already have that one), and then create a mid-plane using those 2 planes.
Now intersect your cylinder with the mid-plane. That will give you the centroid of the cylinder
Now dimension with PCD as TP and just pick all 3 axes.
The result will be the 3D radial distance from the perfect centroid as defined by the basics.

Thank you gentleman....................I rest my case.
It's so hard to explain things to people that just don't get the picture. I don't blame them for their ignorance, I do blame them for not at least listening to what is being explained and not trying to understand what is real and what is their personal concept of positioning. Yea, in general, as my boss stated, true position is is 2 axis. I agree, but there is the instance ( be it very uncommon) that position can be measured 3d. Man, cmm concept vs. interpetation of the drawing is everything. I am still learning, but at least I am learning from the best. Thank you guys. It's our working together to teach one another that makes this the best forum out there. I'll say it again..............if it was not for the guys with the high experience helping us new guys, nobody would gain anything. Because the dmis manual is not written like " windows for dummies".
Thanks again,
Patrick

This is my atempt at A formula for Spherical True Position

TP=2(√(c=√x² + Y²)² + Z²

It's been a long time since I did any real math

Try this one.
http://www.pcdmisforum.com/showthread.php?t=10327&referrerid=3010

this is my atempt at a formula for spherical true position

tp=2√ (xdev²+ydev²+zdev²)


it's been a long time since i did any real math

fify

john,
the part is a square block with a counter bore in the middle of it. The drawing is asking position of the "central point " of the cylinder ( meaning center of x,y,z) of the cylinder to datums, a-b-c. A datum in x, b datum in y , and c datum in z from the bottom of the part. Basically it's a point that has been established within the cylinder with basic dimension to all 3 axis noted as datums. It only makes sense to me that if that centroid point has been given basic dimensions from 3 axis that are labled datums a-b-c-, that you should be able to calculate it as all 3.

Is the cylinder normal to the datum axes? If it is at an angle/compound angle then it's not a 3D TP even though it's a 3D basic dim. called out.

PC-DMIS does not support this type of TP, you must report XYZ and IJK direction of cosine for that cylinder separately, for TP you must rotate and translate to theoretical position to that cylinder but measure it as a circle at both ends. With same set of basic dim's also apply to the adjacent surface of that cylinder to control the elevation and angulations of that surface, there should be profile called out for that surface.

tpV=2√(Dev²+Dev²+Dev²)

much simpler thank you

But the spherical TP is only used when there is an Spherical callout otherwise it's just 2d