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# Offset CSYS by rotation

Genius
The angles for rotating a CSYS seems to be difficult to understand. Do you have a good illustation? Thanks!

8 REPLIES 8

# Re: Offset CSYS by rotation

Solution Partner Phenom

did you check the help?

https://docs.plm.automation.siemens.com/tdoc/nx/11.0.2/nx_help#uid:xid1128416:index_coord_sys_datums...

Ruud van den Brand
cards PLM Solutions

# Re: Offset CSYS by rotation

Genius

Hi @ruud_vandenbrand  Thank you! The help doc is too brief. I wonder how the rotation is done with the three angles.

If I understand it with the Orientation Tool, the rotation is always done by the axes of the new CSYS, but not by the axes of the reference CSYS. If this is correct, it means that rotating first by X or by Y or by Z does not make any difference.

Is there any problem with my understanding?

# Re: Offset CSYS by rotation

Solution Partner Genius

@surfactant

I just created CSYS and I can tell you following:

1. Offset Csys xrot 20°, yrot 30°, zrot 40°

2.1 Offset Csys xrot 0°, yrot 0°, zrot 40° (reference: origin CSYS)

2.2 Offset Csys xrot 0°, yrot 30°, zrot 0° (reference: 2.1 CSYS)

2.3 Offset Csys xrot 20°, yrot 0°, zrot 0° (reference: 2.2 CSYS)

Result: 1. Offset Csys equal 2.3 Offset Csys

Is this what you are asking?

Image legend:

Orange: Csys 1 and 2.3

Green: origin Csys

Mangenta: Csys 2.1 and 2.2

# Re: Offset CSYS by rotation

Genius

Hi @WinnCh   Thank you for sharing your experiment!

Your 2.1/2/3 is in fact: zrot 40° > yrot 30° > xrot 20°

I wonder whether all the six combinations always give the same result.

zrot 40° > xrot 20° > yrot 30°

zrot 40° > yrot 30° > xrot 20°

yrot 30° > zrot 40° > xrot 20°

yrot 30° > xrot 20° > zrot 40°

xrot 20° > zrot 40° > yrot 30°

xrot 20° > yrot 30° > zrot 40°

# Re: Offset CSYS by rotation

Solution Partner Genius

@surfactant

zrot 40° > xrot 20° > yrot 30° not the same

zrot 40° > yrot 30° > xrot 20° the same

yrot 30° > zrot 40° > xrot 20° not the same

yrot 30° > xrot 20° > zrot 40° not the same

xrot 20° > zrot 40° > yrot 30° not the same

xrot 20° > yrot 30° > zrot 40° not the same

https://en.wikipedia.org/wiki/Euler_angles#Conventions

# Re: Offset CSYS by rotation

Genius

Hi @WinnCh   Thank you for your experiments and reference!

# Re: Offset CSYS by rotation

Siemens Genius

Typically: you get different results depending on the the order of how the angles are additive (and what they reference)

One seemingly long-winded way (especially for angles is to do this by feature: one-at-a-time)

Create a Csys: Rotate say x=30

Create the next Csys say y=20 referencing the required previous Csys.

One frequent issue is best explained by example:  a Die Angle definition.

In 2D it is easily defined by 2 ortho views     say 2 degrees in the XY view and 4 degrees in the YZ view

3D: the correct way to represent BOTH these angles:  2 * Csys to be defined from  the Origin Csys and the Die vector to be a "combination" of both.

Its a good use of: "Combined Curve Projection" to get the required... (you need the curves to project though..)

- Neil

Genius