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# Problem happen when I match two block by surface match instruction

Experimenter

Hi

I found one problem @ ST7 and I try to ask support from tool agent. They using ST10 and also found the same problem. Can I ask your help to check if it is tool issue or not?

I make a simple rectangle as block_1.par and remove a 20mm square at right upper side.

Then I got two surface on original rectangle and I rotate each surface as 10 degree.

I try to using surface match instruction to match block_2.par to block_1.par but problem happen.

If I only rotate one surface to 10 degree, no problem happen.

Video :

Thanks,

Sean Lee

4 REPLIES

# Betreff: Problem happen when I match two block by surface match instruction

Gears Esteemed Contributor

HI @WeiDeh

Look exactly at 32 seconds when You do a measure between the two surfaces.

You will see a real angle between them with 91.73 degrees (in the lower area of the screen with a blue form)

So how shall a rectangular box with exact 90 degrees side angle fit to a 91.73 degrees box surface set?

This can not and this will not be possible even with Solid Edge.

This is a matter of real situation.

Some seconds later You do a angular measurement, but only between the two edges and on a different measurement plane.

This is not the same!

Consider this, and give You Your request, I know, that then You will give Yourself the right answer too, what and how You will achieve

regards
Wolfgang

# Betreff: Problem happen when I match two block by surface match instruction

Experimenter

Hi Wolfgang

I can not uuderstand why these two surface are 91.73 degrees.

Following video shows how I make the block_1.par, my understanding is these two surface should be 90 degree but actually not.

I don't know that is my fault or that is wrong calculation from tool.

Thanks,

Sean Lee

# Betreff: Problem happen when I match two block by surface match instruction

Gears Esteemed Contributor

Hi @WeiDeh

this is no a mater of the tool, or of a wrong calculation, this IMHO simply is a question of fundamental geometric relations.

If there is a mathematician here, he will be able to better explain the rules behind.

But take a simple example shown in my video.

We have a pyramide with four sides.

There only is one corner with angled sides.

What is the angle between them?

This is the core question.

And - as I can remember - the angle between to planes is the angle within their orthogonla plane.

Manually I was able to calculate it via the external vector product from the main plane vectors.

And if You can see, this orthogonal plane must be orthogonal to both sides.

You can see this from the front view and from the side view.

And with a side angle of 10 degrees on both sides You will find a plane angle of 91.73 degrees.

And You must not compare this true angle with the horicontal angle in an horicontal reference plane (shown as extra live section 1)

The two lines (both are witihn each plane) have a linear angle of 90 degrees - right, but this is not the true angle of the two planes.

A very simple example can show this even better.

What will be, if the top face will move towards the base plane.

The both side angles will decrease continously until the finally have reached the base plane and both side planes are horicontal now.

What angle do they have?

Zero degrees.

And what is the angle between them?

Yes, there no longer is any angle between them.

I hope this helps

(view in My Videos)

regards
Wolfgang

# Betreff: Problem happen when I match two block by surface match instruction

Gears Esteemed Contributor

HI @WeiDeh

just to complete my thoughts from the last post.

If You have two planes under an angle, You will be able to measure as many angles between them as You want.

In fact: Infinity

The measurement value depends on the measure plane You use.

See video:

(view in My Videos)

regards
Wolfgang