Frequency/Level of Tol analysis
Frequency/Level of Tol analysis
(OP)
Out of interest, how frequently do people do tolerance analysis (all drawings, only for precision/complex parts etc) and how thorough are they.
I've been getting a lot of parts/drawings to check with interferences at worst case (typically a long way before worst case) and am wondering what most people do with tolerance analysis.
I admit I don't do a full analysis on every interface of every part but I at least make sure hole patterns match etc.
I've been getting a lot of parts/drawings to check with interferences at worst case (typically a long way before worst case) and am wondering what most people do with tolerance analysis.
I admit I don't do a full analysis on every interface of every part but I at least make sure hole patterns match etc.
KENAT, probably the least qualified checker you'll ever meet...





RE: Frequency/Level of Tol analysis
Features critical to proper safe performance should always be analyzed for interferences or stackups.
If the component/assembly is sub-contracted out and becomes a procured item, it should be analyzed. This can save tremendous headaches down the road in the event of quality issues.
If you have confidence in manufacturing's capabilities to do certain processes with accuracy and repeatability then you might consider letting your diligence "slide" a bit. Here you start gambling with the odds of something going wrong.
Please keep in mind that it is less expensive to discover errors at the drawing level than when you have a fabricated part on hand that you now need to diposition.
Regards,
RE: Frequency/Level of Tol analysis
Heckler
Sr. Mechanical Engineer
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RE: Frequency/Level of Tol analysis
Back to the original post:
I do it for all female, male interfaces. Problem is when someone pulls the tolerance off old prints, or vice versa forgets to they don't know what they are applying. I am sure to look for interferences when I build the asssembly model. anything close I analyze. If it is to complicated for stackups, I sometimes build the max/min models and assemble them for a quick visual check of interference.
RE: Frequency/Level of Tol analysis
Lots of times, I get dumped off the turnip truck into a swamp of stuff that has reccurent manufacturing problems, needs hammers or big wrenches at assembly, or fails in strange ways. Usually I find that no one has _ever_ done a detailed tolerance analysis, or designs have been adjusted in a direction that minimizes the screaming, without consideration of side effects. That's when I start measuring things, myself. I usually find stuff like blind threaded holes that are too short for the screws, o-rings crammed into a cavity that's too small, stuff like that.
A lengthy revision list is often a clue that there's a problem that goes beyond the extant part.
Mike Halloran
Pembroke Pines, FL, USA
RE: Frequency/Level of Tol analysis
Someone gave me a print on Wednesday pm that was a very slight modification of an existing part that they wanted checked fairly quickly. Given it was based on an existing drawing I knew that if I wanted to change much they'd say 'well we've been making to the existing drawing with not trouble' so was fairly careful on it.
The moment I looked at it I saw what appeared to be implied coaxiality and asked a few pertinent questions.
I looked more closely at one of the parts it mated with and discovered the the CSK holes matching threaded holes in the other part had a massive potential fastener interference.
Also that two of the diameters I'd already spotted not only had coaxiality issues but at max tol had a greater diameter than the mating female feature on the other part.
I've seen similar problems on a number of other prints and was starting to wonder if expecting a basic worst case tol check on simple/obviously close features was too much to ask.
KENAT, probably the least qualified checker you'll ever meet...