Translation modifier questions 4

[sendithard]

I didn't understand the translation modifier until I simply watched Don Day's tec ease video on it recently:

https://www.youtube.com/watch?v=fYbu-lPSTlk

Makes sense that a datum fixed by a basic dimension could not be properly located to the actual feature location so shit could not be stable.

My question is b/c you are placing this modifier after its own Datum Symbol if the Datum location was spelled out with Basic dimensions in both X and Y locations(and not a centerline like Don's video), I assume this could translate in both directions...and AS much as possible, potentially not adhering to an engineers idea when they place a basic in two directions. Either my idea of how wrong this could go is indeed wrong...or the engineer understands what they are doing with this modifier...this is a modifier I'd be happy to not ever use....unless I could tolerance the modifier itself, which is quite odd.

Just looking for some discourse on this odd section in the standard, thanks as always.

 

[3DDave]

The following was a suggested valid callout from Multi Metrics about the 2009 custom datum reference frames. (not a necessarily a practical one, just valid)

The part is a rectangular plate with datum feature A using the front face, datum feature B the bottom face, datum feature C is a spherical growth on the face used as datum feature A, and the other two datum features are holes perpendicular to datum feature A.

I don't see how the translation modifier can manage this.

Also, rather than just repeating datum references in composite tolerances, there is a suggestion to add the exact degrees of freedom to make explicit that they limit only orientation.

Isn't Multi Metrics Bill Tandler's company? Yes, yes it is.

The file was GDT_2009_review.pdf titled "The New Y14.5 2009 Standard" 240 pages. Presented via Quality Magazine

 

[Burunduk]

"I don't see how the translation modifier can manage this"

It's not supposed to, and not vice-versa either. These are different concepts for different purposes.

 

[axym]

3DDave,

That's quite an interesting example. I can imagine the part - it's probably Bill's blue Geo-Fact demonstration model. At first glance, the customized DRF looks valid - I don't see anything that doesn't work.

I agree that the translation modifier couldn't duplicate this customized DRF, and I agree with Burunduk that it doesn't need to. A customized DRF allows the simulator to translate or rotate away from basic in a particular direction, and the translation modifier allows the simulator to translate in a less well-defined way. In some cases (such as the plane-hole-slot case discussed earlier in the thread) the same DRF can be achieved using either tool but this is not true in the majority of cases.

Regarding composite FCF's, that's a whole other topic. I know that Bill (and many other GD&T experts) believe that composite lower segments could be duplicated using customized DRF's. I happen to disagree, and I believe this has been discussed several times on this forum.

I'm not sure what you're getting at with the emphasis that Multi Metrics is Bill Tandler's company.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[3DDave]

axym -

Yes - the translation modifier doesn't need to duplicate it, and that's not the point. The point is that customized datum reference frames are a proper superset of which the translation modifier is a tiny part. That there is no function available via the translation modifier that is not contained within the customized datum reference frame capability. That the control of acceptable variation by the more capable approach is identical to the more limited approach with the correct syntax.

I considered leaving off mentioning Tandler, but I don't want to play "gotchha" with Burunduk. His retort was limited to a tautology, an incomplete one. There is a difference. One requires placing a Coordinate system symbol on the drawing and the other doesn't. The purpose for the two is different - the translation modifier is a shortcut for the customized datum reference frame.

Maybe in 2035 when the next release is made the committee that does so will repairing it to make that clear.

 

[Burunduk]

The point is that customized datum reference frames are a proper superset of which the translation modifier is a tiny part. That there is no function available via the translation modifier that is not contained within the customized datum reference frame capability. That the control of acceptable variation by the more capable approach is identical to the more limited approach with the correct syntax.

As you should have understood by now, that is completely false argumentation.
These concepts differ in both their purposes and the way they work.

The purpose is different because while the customized DRF, as it was standardized, is a tool to override the default constraints of degrees of freedom by each datum feature and simulator as implied by the datum precedence order in the feature control frame, the translation modifier is intended to grant the secondary or tertiary datum feature simulator mobility relative to the preceding datum feature simulators, in cases where such mobility is not otherwise allowed by Y14.5 requirements.

The way they work is different too. Basic location between datum feature simulators is not necessarily overridden by the customized DRF. Where it appears to be (Fig. 7-56 in the latest edition) mutual location fixed by the basic dimensions is not feasible anyway and some level of mobility is already required by portions of Y14.5 that are unrelated to the customized DRF.

 

[3DDave]

"the way they work" to produce the identical results by allowing mobility.

The translation modifier overrides default degrees of freedom.
The custom datum reference frame overrides default degrees of freedom.

 

[Burunduk]

And to support "That there is no function available via the translation modifier that is not contained within the customized datum reference frame capability",
Explain how the customized datum reference frame would resolve the 1" bore primary 0.1" press fit hole secondary case I described in this thread earlier.

 

[3DDave]

Must I explain everything to you? Start a new thread if you need help with a problem at your work. Include a photo of what you are trying to make.

 

[Burunduk]

I am not the one needing the explanation. You need to attempt it - to either support your argumentation or finally realize where you are wrong. Not surprising that you refuse.

 

[3DDave]

Not refusing - put up a separate discussion with a drawing and an example application. This is an engineering blog and you might want to ask an engineering question.

"Explain how" is a request for an explanation. Literally.

 

[Burunduk]

Fair enough. You will be given a chance to legitimize your statements in a separate thread with an example drawing that will be started soon, addressed to all forum members who will be interested to discuss it.