projection angles

[[Gr...]]

Could somebody explain what projection angles are actually reporting?
They have the worst descriptions I have ever seen. Like, angle from what? Which way is positive?
Also, why do cmm people hate using correct mathematical convention so much?

[[Cl...]]

Projection Angle One Size Characteristics Determines the first projected angle of a certain feature based on the part alignment. In a spatial system of coordinates, the axial direction can be defined by two projected angles. A projected angle is an angle on a workpiece plane viewed from the third axis. Projected angle No. 1 is based on the reference axis (the axis common to the two planes of projection) of the feature.
Feature axis
X
Y
Z Angle 1
Y/X
Z/Y
X/Z
Projection Angle Two Size Characteristics Determines the second projected angle of a certain feature based on the part alignment. In a spatial system of coordinates, the axial direction can be defined by two projected angles. A projected angle is an angle on a workpiece plane viewed from the third axis. Projected angle No. 2 is based on the reference axis (the axis common to the two planes of projection) of the feature.
Feature axis
X
Y
Z Angle 2
Z/X
X/Y
Y/Z

[[Gr...]]

That is word for word the description that I said I already read.

[[Ja...]]

I figured it out when I took the training but I still have to refer back to this attachment once in a while.

20180522091531779.pdf

[[Cl...]]

Sorry about that Gregory. I wasn't paying close attention.

[[Aa...]]

For me, the confusing bit is the "Reference Axis (the axis common to the two planes of projection)". So...how does one know, for example, if the reference axis is the +Z or -Z? (Technically, +Z and -Z are not two different axes, but this explanation and the graphic .pdf treat them as if they were.)

[[No...]]

They are not different axes, but the angles can count from different "ends" of an axis (+/-).

[[Aa...]]

Right, but how does one know from which "end" of the axis the angle counts?

[[De...]]

The Space Axis is the vector of the feature. This will also be the second vector shown in A1/A2 angles.

The positive angle will be from the feature vector to the first vector shown in each.

So if you have a cylinder with a +Z vector, A1 will show X/Z and A2 will show Y/Z.

A1 will show the tilt of the vector with respect to the ZX Plane. A positive angle will show deviation from Z towards the positive X direction.

A2 will show the tilt of the vector with respect to the YZ Plane. A positive angle will show deviation from Z towards the positive Y direction.

The positive direction will always be from the second vector shown (also space axis) to the first vector shown.
If the space axis is a negative vector, the positive direction will be counted from the negative vector towards the secondary direction.

[[Ke...]]

If you really need to see what is going on: Take 4 individual points, and recall those into a plane. Then, you can correlate the angle with the point deviations

[[Gr...]]

So far there is not an answer.
Could somebody explain what projection angles are actually reporting?
Be REALLY PRECISE. Define everything. If possible, use actual correct math language, then translate it into incorrect cmm language.

[[Me...]]

I don't consider myself a Calypso whiz, but this is what I think of when I think of projection angles, (Not very math adept either, sorry), lemme know if you need any other info. The negative direction is because it is the direction it is rotating around the controlled axis (X), I.E if i flipped my alignment 180 degrees it would show positive I believe? Sorry if it seems small, right click and go to view image and you can blow it up a bit, and I scribbled in the center of the part to conceal it, so ignore the scribbles.

angle.jpg

[[Ri...]]

Starting from the left, reading to right, you have the empty box. If you check this, you will create a Projection Angle Characteristic. The next bit is important. "A1 X/Z" This is Calypso telling you which working plane to look at the measured plane in. So I'm going to stand at the front of my CMM, put my nose on the plate and look at the measured plane in two degrees only. Essentially looking this plane as if it were a line. I have a nominal of 0 degrees and a actual value of 0.018. This telling me in the ZX working plane, the measured plane has about 1 minute of angle and since the deviation from nominal is a positive value, this tells me the vector of the actual plane is tilting toward the position X. The next line is the same "A2 Y/Z". I walk over to the side of the machine, put my nose on the plate and look straight on at the measured plane. Deviation from nominal in the YZ working plane and if the measured value is negative then the vector of the measured plane is tilting toward the -Y from the nominal vector.

[[Pe...]]

I whipped this up over lunch. It's just based on my experience with Calypso, not on any specific documentation, and may be wrong. But probably not completely. Hope it helps.

ProjectionAngles.pdf

[[To...]]

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Can we get a pic?

[[Gr...]]

So far the only person that had an answer that wasn’t unintelligible gobbledygook and was helpful in any way was Peter (thanks Pete!).

However, I still have some questions.

First off, what is a –Z axis? There is no such thing. There is also no such thing as a +Z axis. There is only THE Z axis. It is an infinite line. (I understand what they are in calypso world, but I just wanted to highlight the need for nomenclatural precision when explaining arbitrary things.)

What even IS a space axis? It seems to have absolutely nothing to do with the feature’s direction (for example, the space axis does not have to be a vector perpendicular to a plane). Does it move with the actual data or is it a theoretical thing? It also seems to have nothing to do with the projection angles (the thing it actually uses is the reference axis from the button next to the A1 in the Feature window). As far as I can tell, it isn’t used for anything at all.

When referring to axes, planes, or directions, please define which system you are talking about (like are we talking about the base alignment, feature alignment, cmm alignment, or…?)

What does the projected angle go to? How are we supposed to know? What is it measuring on a circle? On a plane? Nobody mentioned anything about this.

What alignment is the projected angle in? Getting some conflicting answers here.