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# planar align offset

PLM World Member Valued Contributor

When I create a planar align offset, what dictates the side of the offset, + or - value?

Thank You,

Marc

7 REPLIES

# Re: planar align offset

Phenom

it depends on the + vector of the 2 faces selected.

I believe that

Mate = Surf A with +Vector  -to-  Surf B with +Vector

or

Mate = Surf A with -Vector  -to-  Surf B with -Vector

where as

Plainar align = Surf A with +Vector  -to-  Surf B with -Vector

or

Plainar align = Surf A with -Vector  -to-  Surf B with +Vector

Assuming this is correct

Then

Mates with a positive offset value result in a "gap" between the faces

planar align differs in that a positive offset value results in the B face being "inboard" (A-) of the A face, and a negative offset value moves the B face "outboard" (A+) of the A Face

???

maybe some else has a better way to describe this or pictorially display it?

I just toggle and invert as needed...

# Re: planar align offset

Honored Contributor

This would be more initiative if the origin arrows were in the direction of the planes "+ normal direction" X and Z are, but Y is negative relative to the arrow. The real trick is getting the offset to be + so that the math is easier in variables.

# Re: planar align offset

Phenom

never really thought of this before, but you are correct...

I have just always known to establish origin via the X axis marker on the plane and thus normal is coming out of the screen at me...

# Re: planar align offset

Phenom

It took me a many years of frustration before I finally realised how this works, and its not easy to explain in words.

The distance is measured along the surface mormal of the part being positioned, starting from the surface.

So, assuming your surface is a face of a solid, positive is away from the solid, negative is 'into' the solid.

HP Z420 16GB RAM
ST10 MP6 on Windows 10 Pro 64.

# Re: planar align offset

PLM World Member Valued Contributor
Your rule is true only if you select first the part being positioned. If you do not know or you do not have a fixed part the direction depends of what part is select first. A little bit confusing...

# Re: planar align offset

Honored Contributor

My guess as to why things are this way is the differance between drafting conventions in the USA vs. the rest of the world.

USA:

starts in lower left corner

3rd angle projection

right hand rule

REST OF THE WORLD

starts in center

1st angle projection

left hand rule

The reason this is important, w/ left hand rule, the XYZ axis are set up as theya re in SE. This (the Y axis) is backwards for people in the USA.

# Re: planar align offset

Solution Partner Phenom

Hi,

since with the alignment relation both normals point in the same direction, there are 2 solutions to solve a distance.

In Solid Edge the alignment offset is defined relative to the normal of the first face.

So if it is positive, then the second face is "in front" of the first.

If it is negative, then the second face is "behind" of the first.

When you look at this scenario from the second face, then in front or behind changes.

You can compare this to a car race: the first car is in front of the second (seen from the second car= positive offset), but seen from the first car, the second is behind (= negative offset)

The problem is, when you edit the relation, it is not obvious which planes is the first. But when you define a new relation, then it is clear which is the first and the second face.

There is no difference, if the other part is fixed or has other restrictions.

This has nothing to do with right/left hand rule, any coordinate system or the projection method (only in 2D)

Hope this was not too complicated ;-)

regards

Jürgen

regards

JB
SE ST10