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# Deviation Checking and Deviation Gauge

Genius
To my knowledge, Deviation Checking seems to be a simplified version of Deviation Gauge.

Deviation Gauge has "Measurement Definition" allowing specify how the measure the deviation between two objects. The only Measurement Definition method that I can't understand is 3D, for which the official documentation explains: Computes the deviation in 3D space, as for example from a selected object towards a reference object.

Deviation Checking does not have "Measurement Definition", therefore I can only guess how it measures deviation.

Hope to know whether guesses below are correct or not:

1. If the objects to be compared are two curves, two edges or two surfaces, my guess is that, both Deviation Checking and Deviation Gauge (Measurement Definition=3D) would compare two points having equal parameters.

2. If the objects to be compared are a curve and a surface, my guess is that, both Deviation Checking and Deviation Gauge (Measurement Definition=3D) would compare a point on the curve and its projection (normal) point on the surface.

Thanks!
2 REPLIES

# Re: Deviation Checking and Deviation Gauge

Phenom

I'm sorry that nobody answered your question, which is a good one.  You should open an IR for this, asking for a thorough explanation from development about how these commands really works.   It's unfortunate that NX documentation is that cursory about these commands, which are used on a daily basis in surfacing.  We got to know the tools we use !

As for you guess 1) , AFAIK Deviation Checking doesn't use parameters (curves might have different length, and different parameterization), it rather samples points on one curve and then projects them on the other.

Your guess 2) might be correct but, once again, we should know from development how the command actually works.

Some years ago I asked a similar question about the difference between Surf. Cont. Analysis Obj.  and Deviation Checking, I attach the thorough explanation I got, which also sheds some light on your questions about Dev. Checking.

# Re: Deviation Checking and Deviation Gauge

Genius

Hi @Maurizio   Thank you for sharing your knowledge on the topic!

@Maurizio wrote:

As for you guess 1) , AFAIK Deviation Checking doesn't use parameters (curves might have different length, and different parameterization), it rather samples points on one curve and then projects them on the other.

If the deviation is calculated by a projection mechanism, it seems that projecting curve 2 points to curve 1, or projecting curve 1 points to curve 2, would give different results. Of course the difference might be very small. Therefore I think your are basically right and I would adopt it in my current work, and also find time to open an IR.