Evaluation Constraints

[[K...]]

May I know the application of Evaluation Constraints , When and how to apply this tool.

Thank you

[[Pa...]]

It is something you really should understand because it can be helpful or it can be misleading.

When you tick one of those boxes (x,y,z, normal vector etc) and navigate back out to the feature definition template, you will find that your actual value for whichever box you tick is precisely the nominal value for that feature.

This can be helpful for picking up a small segment of a radius, where a very tiny probing error can make a big difference in results.  If you're evaluating the radius for size, you can constrain for 2 axes.  If you're evaluating the radius for location, you have the option of constraining the size of the radius.

Basically it's like you're telling Calypso: "Regardless of what it might look like, just trust me.  The constrained features are perfect.  Any variation you find must be coming from other sources".

As you can see, this can have the opposite effect.  A great example would be that you would never want to constrain the normal vector in an evaluation of perpendicularity.  You would be misleading the software to consider a nominal vector as opposed to the actual.

Where a cylinder and a cone are turned concentric in one operation and I need to pick up the transition, I will often constrain the cone for normal vector.

It's a powerful tool worth using properly.

[[Je...]]

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, this is the most thorough and useful explanation of Evaluation Constraints that I've encountered.  Screenshot and saved to folder.  Thanks.

You should rewrite the entire Calypso manual using this same tone.

[[K...]]

Thank you Pat for useful explanation of Evaluation Constraints. 

Assume, I have to report 1.5mm radius, at z plain (0,0,1), so I supposed to contraints X, & Y.

Please correct me if I m wrong, as I never use this tool.

Thank you,

[[An...]]

Pat did a great job explaining the function of constraints. Typically I've used constraints for small radii that you cannot do more than 180 degrees of scanning anything less you will get repeatability issues in both the radius size and center location of the circle. 

The software has to juggle those two factors (size and location) when making a circle based off the actual points. If you are able to prove/have absolute confidence one of those factors are precise to nominal. E.g. you use some other tool to determine size or center location like a gauge. You can then constrain one of those options, thus making it significantly easier for the software to calculate the other portion. 

DO NOT just check one of these options on if the part is not perfect in those constraints because you are telling the software to disregard deviations and assume nominal. 

[[An...]]

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In this regards yes. If you lock the X and Y, you are saying the center of your circle is perfect and just calculate the radius accordingly. 

[[K...]]

Thank you very much

[[Lu...]]

I often use the constraints when dealing with a small arc on a radius. For the size characteristic I would usually constrain the x, y, and z. This means it will go from the nominal center of the radius, and tell me the distance from the nominal center to the points i have picked up.

For the position of the radius, i usually constrain the size of the radius. this basically means it will take a perfect circle of the radius, and try to fit it to the points I have picked up. This usually gives me a much more accurate number than trying to calculate the size and the position from the points at the same time.