IJK, angle conversion?

[MrComment]

I have the following, IJK values from a CAD model that PCDMIS spit out at me.

I would like to know the angles relative to the current coordinate system for this feature though.

There are so many ****ed options for the angle dimension I have no idea which one is what I want.

Is there a easy whay to figure this out?

I=-.914856
J=.3778484
K=.1423694

Thanks again

[Ceeph]

I think your I and J is about a 66 degree angle.

Do the sine and cosine of 66 degrees and see if it is close to your I and J vector readings.

[JamesMannes]

Try this....

http://www.box.net/public/39xjrv1i3g

It is multiple pages so look at it all.

[phil george]

Is it just me or is the 3d vector calculation in that spreadsheet wrong? You can't have 3 vectors of .707 - at least not in pc-dmis - if you type that in it changes them to 0.5773503. Someone once showed me a method for converting 3d vectors to angles and vice versa - unfortunately I don't remember what it was, but im sure it was more complicated than using the sine and cosine. I'm thinking that at least one of the very knowledgable people on this board must know it.

Anyway, maybe you could create a point offset along that vector, then construct a 3d line from point to point and dimension the angle.

[MrComment]

Thanks

[Stuart]

Vectors I, J and K are the cosine of the angles to the X, Y and Z axes respectively.

Cos(X angle) = I
Cos(Y angle) = J
Cos(Z angle) = K

To find the angle from the vector, just perform an inverse cosine of each (I, J and K).

Stu

[cmmguy]

I think that only works when the k component is equal to 0

ijk are based on a unit of one(1) and when the k component is added it shortens the unit vector and changes the ij components. I will check this more, and if I am wrong or it is different than earlier stated then I will report that.

All examples that I can find right now(including Richard Clarks) always represent k(Z) as zero.

[dwade]

Another question on topic.

Can you use a variable assigned to the IJK values for trig functions? Such as COS or TAN x V2. What would be the proper format for using this to calculate angles if you wanted to use the IJK values for this?

[than_357]

Per the help file: "PC-DMIS will normalize the vector, making its length one unit. This vector is used for probe compensation."

Hence the 3x by 45 degrees turning into a solid row of .577's instead of .707's.

Amazing how 45 and 60 deg cosines are now engraved into memory.....

Tom H>

[cmmguy]

Another question on topic.

Can you use a variable assigned to the IJK values for trig functions? Such as COS or TAN x V2. What would be the proper format for using this to calculate angles if you wanted to use the IJK values for this?

yes

[Lee Johnson]

A little off the question but when I run into a problem where I need all three vector directions I just rotate the part so the one direction' vector is zero. I just make a rotate align. I then calculate the sine / cosine plug them in the right location. You can then remove the rotation and PCDMIS will do all the nice math for you. just say yes to update when you remove the alignment.