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CANT TOGGLE ON MMC FOR TRUE POSITION CHARACTERISTIC


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Are you taking about how the engineer defines the tolerance on the print?
Tolerance and GD&T callouts are always drive by function of the feature in the assemble process.
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I'm addressing this^^^... and contend that evaluating the position of an elongated hole, that has been derived with the Slot feature, as implemented with Calypso, is incorrect to either standard.

I could be wrong regarding the ISO 1101 standard which is why I'm asking, but I can say that it is incorrect to the Y14.5
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Are you taking calling it as position to a slot?
Slot are called out all the time but they should be a callout for the width and a callout for the length.
That isn't incorrect to ISO or Y14.5 if called out this way.
If I am understanding your question.

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The drawing you posted is correct to ASME, and all that is needed to verify conformance of the position control is ensuring that no portion of the slot violates the virtual condition boundary. Using the slot feature with a position characteristic would be incorrect.
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Glad we were able to clear that up. Would hate for someone coming in here looking for information and get the wrong idea. That's how rumors get started.... 🙂
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  • 2 weeks later...

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I create theoretical Circles or Cylinders.
From there you can use modifiers. I do this because many do not understand the formulas and or why its done that way.
It provides answers and minimal if any questions.
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Calypso doesn't let you select MMC on a Slot Feature. Look at other posts it is explained per ASME Y 14.5
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I'm not talking about a slot feature. I'm talking about using a symmetry plane, which allows MMC and can be used to measure the width and position of a slot.
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Yes, the symmetry plane feature would be appropriate when evaluating the position of an open-end slot as depicted in Fig. 7-31 of the 2009 standard. Calypso allows for the MMC / LMC modifier to be applied within the position characteristic.

However, the standard only supports the "boundary concept" for a position control applied to an elongated hole as shown in Fig 7-34. Anything done to the contrary could be subject to scrutiny.
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The Problem is when it determines the distance of two planes is the Dim perpendicularity/Parallel to the primary Datum or to the Feature? Also is it using the LSQ or the Minimum feature?
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I believe it's completely different than what you are thinking. It isn't two planes, it is one feature itself. Think of it as the same principle as measuring two circles, and recalling the feature points into a Cylinder. You wind up with one feature with one axis line that is created from all of the measurement points.
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As I am thinking about it more then likely doesn't matter in todays world of CNC controlled machines.
The difference would more then likely be negligible. It was more of a Question of how Calypso determines the distance. I know if you use a point to point it is to the base alignment.
What one of the 4 does it use? This is where things get hard in the CMM and GD&T

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All of them... Calypso passes the measured points through an algorithm where they get mixed with a blend of 11 herbs and spices that produces the desired result. You have the option to select the type of fit you need.

Side note...
The LSQ & Tangential distance result within Calypso matches the values calculated by another commercially available fitting software.
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Phillip that is great

😃 😃 😃 😃

But I thought only 2 employees at KFC knows the spices. How did Zeiss figure it out?
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