Auto feature vs fitting feature

[[Ti...]]

I'm confused why some like to Construct Auto-Features, for example an Auto Cylinder, and then next they apply a Fitting Element to it when you can just just make a fitting cylinder in one step.

What is the benefit to the longer method?  Thanks.

 

Edited June 27, 2022

[[Ax...]]

With the fitting cylinder you can determine which calculation method (Gaussian best-fit, minimum circumscribed - / maximum inscribed element) is used to create it. It is helpful if a geometry in CAD is not 100% geometrically a cylinder.
Here you can apply the referenced construction.

If you use auto-cylinders, you must use the calculation method for the measurement principle. 

[[Ax...]]

With the fitting cylinder, you can also specify dependencies for the cylinder: Axis, direction, etc.
This is helpful if a cylinder cannot be calculated very stably. For example, if there is a very large diameter but only a small height.

 

[[Ch...]]

And as additional note, please be careful about the difference between construction commands and measuring principle. To make the things much more difficult we have booth, a measuring principle called "Fitting element" and a construction command with the same name. 

 

If you start on nominal, even if you use the construction command "fitting element" you have to apply a measuring principle afterwards to create the actual data. And as Axel Hübner mentioned this may either "Fitting element" or "Referenced construction".

 

Please have an look for "Starter Training GOM Inspect" in our training center (training.gom.com) that tells your the basic.

 

Best regards

Christoph Schult

[[Ti...]]

I'm rather confused at the moment, but give me another week to play with the software and I'll come back. I've carefully reviewed the starter training twice, but it doesn't do a good job of teaching you how to construct features and measure them The lady uses only the GDT portion of the menu and it creates a min/max length rather easily. Then she uses the GDT measuring to simply envelope a cylinder instead of going into the construction menu and making cylinder, then using the check feature to measure it.

Using the starter training cad file as a perfect example, here is one of my confusions:

When you open the CAD file and construct an Auto feature cylinder it works, but it in the project guide it tells you to apply a 'measuring principle'.

So then when you go to apply a measuring principle you get the error shown below.

 

If instead you don't use the auto feature cylinder and just start with the fitting cylinder it allows you to apply a measuring principle. So as you can see, I don't understand when you would use Auto feature cylinder, or when you should use fitting cylinder.

 

[[Di...]]

Hi Tim,

regarding the GD&T element creation.

When you use GD&T Quick Creation the software creates the needed elements for you autmatically.

So when you create a cylinder with GD&T Quick Creation the software creates a nominal element, assigns a measuring principle (creates an actual element) and the needed GD&T check automatically.

This works only because of the GD&T ruleset, according to the standards ISO and ASME, is strictly defined and the needed parameters and computations are known. Therefore the software can make use of a high degree of automation for the element creation.

For the manual element creation there's much more freedom to select the needed parameters but also due to the fact that the software does not know what the element will be used for there's also less automation possible.

My suggestion for this case would be: Always use the Auto element as construction command and then assign the measuring principle Fitting-Element.

Personally I would use the construction command Fitting-Element only in specific cases. For example if you need to combine several single points to a circle or cylinder.

 

Regarding the problem above:

I can judge only based on the image as source of information. The error message looks quite unusual for the things that are missing inside of the project.

A full analysis requires the project.

1) There's no actual data inside the project, no mesh

2) There's no alignment set.

In fact this is no real problem for the software as the software is able to plan inspection without meshes and only based on CAD data.

It is absolutely no surprise that the software shows errors in such a case as the base for the computation (the actual data) is missing.

They vanish when you import the actual data and recompute the project.

But the error message does not fit to this workflow. I would expect different error messages.

The source of the problem must be located somewhere else inside the project and is not visible in the image.

Our support can be helpful with an analysis of the project.

Edited June 29, 2022

[[Ti...]]

Your reply explains why I dislike the training and why I think the GOM feature construction is too complicated.

For example, when I create an Auto Cylinder, the software should ask you immediately to define the measuring principle. Why do you need to create a 'Measuring Principle.'?

In what world would you create an Auto Cylinder, but choose to say I don't want to create a measuring principle?

[[Be...]]

Hi Tim,

usually (if you don't use Smart GD&T) the workflow is like:

• Create all nominal cylinders in a row
• Closing the dialog selects all created nominal cylinders
• Apply your measuring principle, e.g. fitting element or measuring by touch probe (which we can't know)

Therefore you have only to chose once your measuring principle for a lot of cylinders and not for each one.

Regards,

Bernd