unsolved problems
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Unsolved Problems. Generator lines Straightness. section line of section plane. Generator Line. Staightness. ISO 2692 CZ common zone SZ separate zones. Acc. To Principle of independency. CZ superfluous. CZ superfluous. CZ ?. b). sz. sz. When a group of toleranced features - PowerPoint PPT PresentationTRANSCRIPT
Unsolved Problems
Generator lines
Straightness
Generator LineStaightness
section lineof section plane
ISO 2692CZ common zone SZ separate zones
Acc. To
Principle of independency
CZ superfluous
CZ superfluous
CZ ?
szb)
sz
When a group of toleranced features
is related to a datum or datum system
containing a modifier M or L
it is questionable whether
CZ common zone (e.g. simultaneous gauging) or
SZ separate zones (e.g. separate gauging)
applies.
Therefore in the future
CZ or SZ
shall always be indicated in these cases,
see examples …
Alternative rule for ISO 2692:
CZ applies (without indication of CZ) when positional tolerances are applied together with the maximum material requirement or the least material requirement, unless otherwise specified, e.g. by the symbol SZ.
Advantages:
Coincides with most functionsCoincides with former practiceCoinsides with ASME 14.5
Disadvantages:
Violating the (fundamental) rule of Prindiple of independency
Whatever the rule is,
there is a need for an additional symbol
SZ (= separate zones)
ISO 1660
Limitation of Steps
Profile tol. 0,003 / 3in order to avoidsteps and chatter marks
What is the length 3 ?
a) Length of a straight line(width of the window)
b) Stretched length
Proposal: a) = reference length(width of the window)
Form of tol. zone limits =equidistant to theor. exact form0,0015 apart (width = 0,003)
location arbitrary
ISO 1660
Best Fit Reference