Calypso MMC

[[Ja...]]

 

I am trying to check a Perpendicularity and position using MMC. As I understand MMC, it allows extra tolerance when the diameter is larger than nominal size. In the example above the actual diameter is smaller than nominal yet the MMC position is almost .004 under the actual position. How is this possible, what have I done wrong?

[[Ma...]]

As replied in another thread - in this table where is (M) it's calculated statistical value just for SPC purposes - real value is without (M) but your tolerance is increased.

(M) value can be "ZERO" when you have allout as "0 (M)" because of formula ( can be found in forum ) - in that formula is final step a multiplying of base tolerance.

[[Pa...]]

Be careful.  Nominal size is never a factor in MMC / LMC.  Only maximum and minimum sizes matter.

First, I assume the FOS is an EXTERNAL cylinder.  If so, it goes like this:

If your external cylinder is at its very smallest size allowed by the tolerance, the design can tolerate greater deviations to position.  MMC gives a "bonus" tolerance calculated by subtracting the actual size from the maximum allowable size and adding that value directly to the position tolerance given in your FCF.

If your cylinder is an INTERNAL FOS:

If your internal cylinder is at its very largest size allowed by the tolerance, the design can tolerate greater deviations to position.  MMC gives a "bonus" tolerance calculated by subtracting the minimum allowable size from the actual size and adding that value directly to the position tolerance given in your FCF.

Looking at the two red lines in your report, the top one contains the value you need to report.  This is the position fully resolved including all bonus tolerance.  The second line is something that should default to excluded but doesn't.  It's a useless value to you.  Search the forums; there are ways to remove this line with a snippet of code in your report template.

[[Ca...]]

Here is a direct link for how to hide the .(M) value on the report if desired: https://portal.zeiss.com/knowledge-base?id=458620

[[Ri...]]

https://portal.zeiss.com/my-voice/own-activities/software/metrology/product/066cc67a-e50f-470f-9884-a3ec3253c37c/request/f2cd665d-6c94-494a-a434-ba6c86bfcd77

 

Please please please Zeiss, implement this. 

[[Je...]]

Please sign in to view this username.

, what

Please sign in to view this username.

 mentioned is spot on.

When the (M) material modifier is used in a position characteristic, additional deviation is allowed as the feature of size departs from maximum material condition.  An internal feature of size such as a hole departs from maximum material condition (and gets bonus tolerance) as the hole gets larger, and an external feature of size such as a post departs from MMC as it gets smaller.

Although that's an important clarification, it doesn't appear to account for the .0036 difference of your characteristic between the (M) result to the unmodified result.

Please sign in to view this username.

 seems to be on the right track.  There's a lot of feedback from programmers about the confusing way that PiWeb reports this characteristic, even if there was an SPC-related reason for it during development.  It feels messy and unfinished.