CMM_Best Fit_Group of pins as datum 1

[roberto1brazil]

Hello everybody !
Please, could someone help me with this following issue?

At my job we have a part to be inspected applying best fit to the datum. Below I describe the machine caracteristics and the sequence of the process. Our doubt is how to apply the function best fit on the pins using the software of the machine. Our operator is not familiar with this command, Would be possible to give us an idea of how and where to input the data? I have attached a drawing in order to clarify the question.
Thanks to all.

CMM MACHINE MODEL – DEA 07-10-07
CMM Software – PC DMIS 4.3 MR2

Aim : To obtain the offset (out of position) of the three diameters A, B and C in relation to the Datum D
Datum D : Is defined by the six pins on plane X.
Do not consider any perpendicular’s geometric offset

Steps (described in the process):
Creation of measurement reference K (marker K)
Main reference: Probe the X plane at 12 points evenly distributed over the indicated face.
Secondary reference: Probe circle DB at 12 points evenly distributed over the diameter in the half of height H.
Tertiary reference: Probe circle DA at 12 points evenly distributed over the diameter in the half of height H.

Optimization of Marker K

-Create theoretical points PT1 to PT6 in the plane X.
-Probe circles PP1 to PP6 at 4 points evenly distributed on the pins circular surface.
-Perform a “Best Fit” on points PT1 to PT6 of marker K with respect to the center of circles PP1 to PP6.

Measurement:

-Probe DC at 12 points evenly distributed over the diameter in the half of height H.

Post processing:
-Create theoretical points DTB, DTA and DTC in plane X.
-Determine the distance from DTB to the center of circle DB.
-Determine the distance from DTA to the center of circle DA
-Determine the distance from DTC to the center of circle DC.

 

[Valek]

Hello Roberto1Brazil,welcome to the forum.
Try this,

http://www.pcdmisforum.com

 

[roberto1brazil]

Thanks Valek. I will try your information and I will check the site calledout.
Best regards.

 

[powerhound]

Depending upon the use of MMC modifiers, this could be a great job for a hard gage.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[RXMetrology]

Hello, Roberto:

This task should be very easy to do in pc-dmis. The alignment routine that you described in your post is correct as a start up alignment. Then after you measure those 6 pins, when you use the best-fit function you need to define if it's "rotation and translation" or just "rotation"/"translation" only to establish datum -D- from 6 pins. If you really have tough time to make it work in pc-dmis please contact me, I currently support a few customers remotely through gotomeeting or skype.

Good luck,

Ray Xing
GDTP S-0605
CGP Certified
CMM Application Specialist
RX Metrology Solutions

http://www.rxmetrology.ca

 

[roberto1brazil]

Dear Ray.

Once again I am back. This issue is very interesting and important to us. I have read your suggestion and other opinions about and for sure there are different points of view of how to resolve the problem. I have attached a sketch. Enclosed I have tried to explain with more details my understanding about. You can disagree with my suppositions but after analyzing all alternatives, this was my closing understanding of the case. Please, if you or someone else could give us more details about the case, we would appreciate so much your feedback.

Clarifying some aspects:

-Of course the part displayed is to be assembled in another one with holes to fit the pins. The external boundary is not so important because the pins and their correspondent’s holes of the other part will determine the correct location. The purpose is to have the big holes of one part aligned with the big holes of the other part oriented by the pins and holes.

-Our drawing does not mention GD&T to locate the pins. In fact we have no access of designing details of mating parts. The manufacturer assures that they fit and that is all. Perhaps the original blue print has some information about, but we do not have access.

-There is a not "M" modifier at D datum. In this case the assembly between the two parts was not well established if GD&T was not applied conveniently. Without modifiers the assembled between parts has a low probability of fitting accordingly, but as I said before, these information are not available.

If our suppositions were right, would it be possible to give us an example (*) of how the set of holes (PT1 o PT6) can be adjusted when passing from phase 1 to phase 2 according to our sketch?

(*) What functions should be activated in the screen of the software – In another words- when performing the translation and rotation of the marker K- doing the best fit properly saying. NOTE: I have tried to explain our operators about the idea described but, I was not succeeded.

Thanks so much.
Roberto

 

[RXMetrology]

Roberto:

If you look for particular function in pc-dmis, it's under Alignment Utilities and click the Best Fit button. Please find my attachment.

Ray Xing
GDTP S-0605
CGP Certified
CMM Application Specialist
RX Metrology Solutions
www.rxmetrology.ca

 

[roberto1brazil]

Hello Ray.

Your tips and information were very useful. I guess that now we are able to follow the main site requirements. All the best for you and all people that had contributed for the solution of this issue. This site is really very good. Thanks so much.
Roberto