Using Generic Features In PC-DMIS

Published by CMMXYZ on March 23, 2022

PC-DMIS Tech Tip:

This video demonstrates one example of how to use a generic feature in PC-DMIS. Measured data from a pin gauge check is combined with a location check to create a hybrid-type feature for greater accuracy.

In this video, I wanted to show you just one example of how to use a generic feature in PC-DMIS. So what is a generic feature? Generic features are constructed custom features that allow you to use attributes from other features like measured X or Y values and also let you use variables and expressions. Let's take a look at a drawing here in one dimension in particular. Let's focus on the 10-millimeter bore and the position column for that particular feature. Recently I was working with a programmer in a tech support case where he wasn't happy with the measured result for his bore, his diameter. He was using a portable rumor arm where the accuracy is a little less than what you would get from a CMM. He asked me if he could use a pin gauge to check the size and still use the measured Z and X, in this case, from his actual measurement of that circle. What I suggested was that he use a generic feature and also a keyed-in dimension.

Let's go to my PC-DMIS program and I'll show you what I did. Here we are in PC-DMIS. You can see I have my datums A, B, C, and I've measured the front bore as a circle, called it circle 1, but that front bore ID, that is actually a generic feature. The first step was I needed to actually measure the circle 1 first. After that, since I won't be using the measured diameter from that feature, what I did was I created this key-in dimension here. You can see mine is already filled in, as per the drawing, a nominal 10 millimeters plus 0.25, minus 0.15, and the actual is just something I keyed in when I was prompted. That will take care of all our measured data. The next step is really the trick here. What I've done is created a generic feature and the beauty of a generic feature is it's a custom feature so I can enter any information I want in all of the field.

The syntax here is nominal XYZ is first. These values here, I don't want to be a variable. I want that to be static and I'm drawing those from circle 1, theoretical X, Y, and Z. In this case, Y doesn't really apply but we'll just fill it in anyway. When we report the measured Y and Z, what we're doing is drawing on the measured circle values and plugging them in to this generic feature. You can see the code there, the name of the feature circle1.x is the extension. The .x is the measured X and then 0 for Y because we're not really concerned with that. Measured Z, circle 1.z. And for diameter, I just typed in the nominal is 10 for that hole. Now we're using the actual keyed in dimension for the measured so the code is pin.m is the axis and .measured is the result. The whole point of all of this was to actually dimension position using one feature only but that feature has properties of two different features. Actually, one is a dimension and one is a feature.

The rest is pretty simple. We go to position, and this front bore is actually my generic feature. You can see it there. Now that's a valid feature that I can do position on. Apply MMC. That's where the size would come into play and then you just fill in the rest, plus 0.25, minus 0.15. That's important to calculate bonus and then the datum reference frame BAC, I think it was. Yeah, BAC, and that's it. On a report, it doesn't look anything different than a normal report. Even though this is a generic feature, it's not gonna be flagged saying this is just a construction. That's how you use a generic feature, one of many examples. I just had it top of mind because I did it a couple weeks ago. Well, I hope you found that useful. Thanks for joining me and we'll see you next time.

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