Jump to content

Profile with incomplete DRF


---
 Share

Recommended Posts

Hi,
I was hoping someone could help me out with a profile call out (see picture). I have a print that calls out profile of 2 sections of a cylindrical surface. It is called out to a DRF of A, which is the top plane, and B, which is the center ID, with a MMC modifier. It is my understanding from reading through the Calypso user manual that profiles can only be done to either no datums or a complete DRF that locks all 6 degrees of freedom. I also could not find any way to put an MMC on the B datum.

Tom Oakes pointed out to me that free form surface, which I do have, could be solution. The user manual does state that individual datums are allowed. Would a free form surface be able to have a profile callout as shown on the drawing. I can't test at the moment as I don't have CAD for the part yet. Thanks!
2375_8e8232927b97875a0f185d6e39c03933.jpg
Link to comment
Share on other sites

Please sign in to view this quote.

First up all ,this is not an incomplete datum reference frame, Teritory datum is not required for this type of geometry control.

Profile is y 14.5 standards most versatile geometry control.

profile of surface is a three dimensional surface control that is capable of not only maintaining the entire surface within one tolerance zone, but may control size and with addition of appropriate datum feature into the control, may orient and even locate a surface.

Your tolerance zone is a bilateral tolerance zone.
You have three tolerance boundaries,inner boundary defined by minimum size, nominal boundary defined by the basic dimension and outer boundary the maximum size. These three boundary must be perpendicular to datum A, to confirm the produce the surface must reside within or between the boundary of the profile zone

Your secondary dataum controls the location of the feature,it means that the radial distance from the centre of the datum B to any point in the R13 should not deviate plus or minus 0.005 mm for it's nominal value.

it is important to note that the material condition modifier symbols are not allowed next to the feature geometry profile tolerance ,however it is common and often used for datum feature of size used in the feature control frame to be referenced with MMC material condition symbol. MMC symbol does not allow growth in the profile tolerance zone but does allow shifting or movement of the profile zone as a datum feature of size is produced at size other than MMC.

For inspecting CMM curve or free form is better.
Select equal bilateral from definition template, first datum plane A, secondary datum would be better intersection circle of datum A and B.
Link to comment
Share on other sites

That's all well and good, if you have freeform and curve. But if you don't and you don't have 3 datums in the drf, calypso won't give you an actual. I don't have freeform and ran into this problem. I contacted Zeiss and asked them what I should do providing that I don't have freeform or curve available on all my machines. The answer I got back was that all calypso was looking for was a complete drf and all I had to do was enter the secondary datum into the tertiary datum spot also. It won't change the outcome but it will complete the drf for the profile. Does anyone here have a reason that wouldn't work or is the wrong thing to do?
Link to comment
Share on other sites

I am trying to find out from Zeiss (side note: find it funny that "Zeiss" shows up in red as a spelling error on the Zeiss forum) right now!

If adding the same datum to primary, secondary, and tertiary is OK when you have profile to one datum I am hoping that the answer will answer the question about using the secondary datum in the secondary and tertiary spots.

If i get time I will try and play with a plane and a free form surface and see if the profile to one Datum is the same doing it correctly and using the same datum in all 3 spots.
Link to comment
Share on other sites

Yeah, that was part of the discussion I had with them. They told me that in the case of one datum to use that datum in all 3 places. I'm interested in what you come up with in your tests.
Link to comment
Share on other sites

The only unconstrained degree of freedom is rotation around the axis of Datum B.

This degree of freedom should have very little impact on the profile of the two surfaces in the profile callout.

Any rotational feature could be used to stop rotation and have very little impact on the end result.

If you wanted to be exceedingly worried about it being correct, you could use the four sides of the slots in a geometry best fit alignment allowing them to best fit around the B axis, then assign this alignment to a theoretical line that you could then use for your rotational datum.
Link to comment
Share on other sites

Is there any indication on the actual drawing that the four sides of the slots have a callout?
If all they want is the 2 bottoms, then look to Derek's answer.
Link to comment
Share on other sites

Thanks for the help guys. Yeah I figured that adding a rotational datum wouldn't really affect the results much. What about the MMC on B. I remade the radius as a general surface, but I still can't find a way to get an MMC on B. Is there a way to do this?
Link to comment
Share on other sites

 Share

×
×
  • Create New...