【转帖】simultaneous requiremen

yang686526

"simultaneous requirement"?
  i have a customer drawing with some holes controlled with compound true position callouts.  under the true position block is "simultaneous requirement".  what does this mean?
  i understand that both parts of the compound true position are simultaneous requirements, but does this need to be spelled out separately, or is this just a redundancy?
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i have never seen this before. seems redundant to me. redundancy is very common.
chris
systems analyst, i.s.
solidworks/pdmworks 05
autocad 06
  thanks, chris.  that is what i am thinking, but wanted to be sure that i wasn't missing something.
  it sometimes seems that there are as many ways to interpret the standard as there are people using it.
that is true.
you're welcome.
chris
systems analyst, i.s.
solidworks/pdmworks 05
autocad 06
"simutaneous requirement" is understood in asme y14.5m-94 when there would be situation containing various positional tolerances referencing the same datums. this means that there is one (1) checking fixture for all the positional tolerances referencing the same datum in the same mode (mmc)rather than a separate fixture for each positonal tolerance.
i don't believe that many people know this so the designer in this case stipulated it.
the standard also states that if the designer required a separate requirement in one (1) positonal tolerances, then the designer would state "separate req". the one (1) positional tolerance noted must be checked or confirmed separately while the other ones would be checked or confirmed simutaneously.
hope this helps.
dd
thanks again dingy2!
i really appreciate your take on these questions.
so, although it is obviously a "simutaneous requirement", it was listed as clarification for the company.
chris
systems analyst, i.s.
solidworks/pdmworks 05
autocad 06
by y14.5m multiple composite positional tolerance feature control frames (ptcf) by default create separate requirements even if the datums are in the same order.  if there are 'n' ptcfs then there are 'n' separate requirements.  for example, a four-hole pattern of .106 diameter holes controlled with a composite ptfcf utilizing a/b/c in the top line and a in the bottom line.  next, consider if there were another pattern of, say, ten .250 diameter holes in the same part having its own ptfcf where a/b/c is also in the top line and a is in the bottom line.
by default, these two requirements are separate (the note separate is not needed) indicating that the two hole patterns are independant (and probably do not mate to the same part).  if the ptfcfs were not composite but instead possessed a single line then the requirements would be simultaneous by default.
in the composite case, if you don't want the requirements to be separate, then the placement of the note simultaneous under either ptfcf overrides the separate default and makes the requirements simultaneous.
tunalover
tunalover:
your notification the simultaneous requirements are defaulted in groups of composite feature control frames kind of threw me as bit. i check the y14.5m - 94 standard 5.3.6.2 page 93 and you are partially correct.
simultaneous applications do apply to the top section of the composite feature control frames (pltzf) but not the bottom or the (frtzf). if you know of any other section which is more explicit to you thoughts, please let me know.
i learned something myself on this about the bottom sections of composite feature control frames and i have been training in this subject for 18 years.
dd