Mounting part on setup tooling

2011 MR1, Romer 7525

I have been programming offline, using only the part model "floating in space", and creating a local coordinate system on the part. I want to bring models of knee blocks, 1-2-3 blocks, and other setup equipment in so I can program around real-world setups, allowing me to simulate datums, etc. I am finding the instructions in the Help screen very vague.

Can anybody give me (or point me to) a step-by-step tutorial on resting a part on a knee block in my Graphics Display Window?

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Wes Cisco over 12 years ago

Example: -A- is the back surface of a part. -B- is one edge, -C- is another. The part must be secured to a plate, making -A- inaccessible. I must use the plate to establish -A-.

I see 2 possibilities:
1) When creating the program, bring in my model mounted on a surface that I can probe instead of probing the actual part surface, or,
2) Program using the part model surface, then, when measuring the actual part, probe the plate and manipulate the alignment.

I seem to be getting responses wondering why I want to do this; isn't this a common scenario? I well know that I cannot just arbitrarily ignore the designed datum/feature relationships and controls, and it is not a matter of convenience.

mcultice & Collin, you are both exhibiting a great ignorance of GD&T. Because I am basically a pretty good guy, (Don't Tell Anyone!!!), I am going to try to teach you a little bit.

GD&T is a black art. Many of weak character dabble about generally doing far more harm than good. Those brave and stout enough of mind to strive for comprehension often fear there is a direct ratio that raises their insanity and anguish tat for tit with their growing knowledge. In short this is dangerous stuff best left to paid professionals.

Yeah, that means us. So let's start with a few definitions:

Datum = theorhetical entity of perfect geometric form that does NOT exist in physical reality.

Datum Feature = surface(s) of an actual part from which the Datum is derived.

Datum Feature Simulator = A imperfect fixture made precisely enough it's imperfections are ignored and it can be used to help derive the Datum from the Datum Feature. (examples of this would be a surface plate, or a gage pin, or a co-ordinate measuring machine.)

If you have not studied these ideas you should. I will not try to teach all of this complex abstract stuff in minute detail for free via the innerwebz.

You can secure the part to the plate, provided the plate is sufficiently flat to be a Datum Feature Simulator, and then probe the plate around the part to create the Datum. That is how it is supposed to be done. However I do not think you can pick points from the Datum Feature on the CAD to write the program offline. You will have to create vector points that appear to be in space in your graphics window offline, but that will probe the plate when actually executing the program. From those points create your Datum [A] plane that you will use in your alignment exactly the same as you would if you had taken the plane on the actual Datum Feature of the part.

Which is NOT the same as what I thought you were saying previously, that you secure the Datum Feature to the plate and then probe the OPPOSITE side of the part from the Datum Feature and use CAD nominals to Offset that to create the Datum. That is WRONG.
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Wes Cisco over 12 years ago

Example: -A- is the back surface of a part. -B- is one edge, -C- is another. The part must be secured to a plate, making -A- inaccessible. I must use the plate to establish -A-.

I see 2 possibilities:
1) When creating the program, bring in my model mounted on a surface that I can probe instead of probing the actual part surface, or,
2) Program using the part model surface, then, when measuring the actual part, probe the plate and manipulate the alignment.

I seem to be getting responses wondering why I want to do this; isn't this a common scenario? I well know that I cannot just arbitrarily ignore the designed datum/feature relationships and controls, and it is not a matter of convenience.

mcultice & Collin, you are both exhibiting a great ignorance of GD&T. Because I am basically a pretty good guy, (Don't Tell Anyone!!!), I am going to try to teach you a little bit.

GD&T is a black art. Many of weak character dabble about generally doing far more harm than good. Those brave and stout enough of mind to strive for comprehension often fear there is a direct ratio that raises their insanity and anguish tat for tit with their growing knowledge. In short this is dangerous stuff best left to paid professionals.

Yeah, that means us. So let's start with a few definitions:

Datum = theorhetical entity of perfect geometric form that does NOT exist in physical reality.

Datum Feature = surface(s) of an actual part from which the Datum is derived.

Datum Feature Simulator = A imperfect fixture made precisely enough it's imperfections are ignored and it can be used to help derive the Datum from the Datum Feature. (examples of this would be a surface plate, or a gage pin, or a co-ordinate measuring machine.)

If you have not studied these ideas you should. I will not try to teach all of this complex abstract stuff in minute detail for free via the innerwebz.

You can secure the part to the plate, provided the plate is sufficiently flat to be a Datum Feature Simulator, and then probe the plate around the part to create the Datum. That is how it is supposed to be done. However I do not think you can pick points from the Datum Feature on the CAD to write the program offline. You will have to create vector points that appear to be in space in your graphics window offline, but that will probe the plate when actually executing the program. From those points create your Datum [A] plane that you will use in your alignment exactly the same as you would if you had taken the plane on the actual Datum Feature of the part.

Which is NOT the same as what I thought you were saying previously, that you secure the Datum Feature to the plate and then probe the OPPOSITE side of the part from the Datum Feature and use CAD nominals to Offset that to create the Datum. That is WRONG.
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