Constraining oriented features

[kbotta]

Ok, I've been working on a paper, or file if you will - and would like some feedback. The topic is datum features of size, and how you orient them. I've spent a good deal of time with a friend on editing this, and no it is not perfect, but I believe illustrates my point quite effectively.
I welcome all feedback.
Thanks,
Kevin

[HexagonMarketing]

Cool, the uploading works!

[kbotta]

Thanks for the increase in file size!
Kevin

[kbotta]

Anybody? bueller...bueller...

[Wes Cisco]

some thoughts

Kevin,
I looked over your paper. It should be part of CMM 101. Or maybe even inspection 101 as the ideas apply to surface plate work too. Can I ask why you wrote the paper and what you plan to do with it when you are happy with it?
From what I have seen most experienced CMM programmers understand these concepts fairly well. But how many design engineers do? I often see FCFs that do not list datums in the order I know they should be in to ensure a functional part.
The biggest question is how much data is enough? If you have a hole .5" in dia and 2" deep, how many hits on how many levels are necessary? This is a judgement call on the part of the CMM programmer.
If I think of anything else to say about your paper I will post it here. I am adding your paper to my collection of notes. Thank you for taking the time to write it.
I found one typo on page 7, just below the scenario #2 sketch the word "gas" should be "has". HTH

[John Kingston]

Kevin,
I printed your paper but haven't had time to read it. The little bit I did read made sense. I let you know when I finish reading it.

[craiger_ny]

Matt, would you care to give Kevin some feedback on this please?

[DaddyBluto]

Hi John!!!

[Addison Wood]

Kevin,

Keep in mind that Y14.5 is written specifically for hard set ups on granite. It is not written for CMMs. The reason ASME has not addressed this is that there is no common aggreement on standard algorithms for geometric shapes between CMM software manufacturers. The German PTB (Physikalisch-Technische Bundesanstalt) certification is a step in this direction and will hopefully lead to CMM specific document like Y14.5. You can find more info on at wilcoxassoc.com

[John Kingston]

Hi John!!!

[craiger_ny]

Hook, line, and sinker.............

[tking]

OK Kev, my .02.

#1 is the most often used technique but would not correlate perfectly with a hard gage.

#2 is lazy and just plain incorrect, it is also very often used.

#3 if the cylinder is an OD, would correlate perfectly with a hard gage. As a side note, I'd probably pull the individual points from the feature and project them to the plane rather than the scan. I think it would accomplish the same result. I'm just not that experienced with scanning so I tend to stick with what I know.

Thanks for the food for thought,

TK