Undimensioned loft drawings- tolerances
Undimensioned loft drawings- tolerances
(OP)
I'm wondering what methods are used out there for tolerances on traditional undimensioned loft drawings on mylar/film.
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Undimensioned loft drawings- tolerances
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RE: Undimensioned loft drawings- tolerances
Chris
SolidWorks 09 SP5.0
ctopher's home
SolidWorks Legion
RE: Undimensioned loft drawings- tolerances
You can apply profile tolerances with respect to the model or drawing. I cannot think of anything else.
RE: Undimensioned loft drawings- tolerances
Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion
&
RE: Undimensioned loft drawings- tolerances
There should be some sort of tolerance specified, whether it is in the drawing notes or in a related company spec. An allowable tolerance has to be applied somewhere.
"Good to know you got shoes to wear when you find the floor." - Robert Hunter
RE: Undimensioned loft drawings- tolerances
I'm not sure what the OP means by "loft drawing", though.
Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion
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RE: Undimensioned loft drawings- tolerances
A "loft drawing" in my understanding is a series of sections of profiles, i.e. wings, and were often done in ink on linen or mylar at full scale without any dimensioning other than butt-line, water-line and/or fuselage station locators.
"Good to know you got shoes to wear when you find the floor." - Robert Hunter
RE: Undimensioned loft drawings- tolerances
My case is for small run production parts where, frankly, GD&T paper gaging and that sort of thing is way over any reasonable need from the inspection department.
EWH suggested a company standard or a block on the drawing. Those were also in my mind. I have heard 0.030" over the length of the part for one OEM standard but I'm unable to confirm.
I have suggested to perhaps control the tolerance on our printed lofts by controlling the lineweight so that the part passes inspection if the inked line can be positioned on the full contour of the part. Has anyone heard of this sort of control used? It would certainly make the gaging easy for the inspector and allow flexibility in tolerancing.
RE: Undimensioned loft drawings- tolerances
If relying on plotted prints, be sure to include dimensioned vertical and horizontal lines to verify plotter accuracy.
"Good to know you got shoes to wear when you find the floor." - Robert Hunter
RE: Undimensioned loft drawings- tolerances
In these cases you can potentially do inspection at the places where the sections are. Either CMM or 2D profile go & no go gauges.
(It's called 'lofting' because it originated in ship yards where it was done 1:1 on big rolls of paper, in the 'loft' above the construction shed - so I've been told.)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Undimensioned loft drawings- tolerances
They were not however always hard dimensioned as that could require a s**tload of dimensioned points to properly define an irregular profile (at least for aircraft lofts).
"Good to know you got shoes to wear when you find the floor." - Robert Hunter
RE: Undimensioned loft drawings- tolerances
While I never got to play with them 1:1 drawings on large rolls of paper tens of feet long were still in use not that long ago, I know some aircraft still in operation used them.
Anyway, that's why I said in some cases. The parts I'm thinking of were fairly small from 'aircraft accessories' shall we say.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Undimensioned loft drawings- tolerances
RE: Undimensioned loft drawings- tolerances
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Undimensioned loft drawings- tolerances
Not every company has CMM capability. If you don't have a computer measuring device, you cannot inspect an undimensioned profile without a plot. I don't believe our inspectors even have email.
RE: Undimensioned loft drawings- tolerances
Depending how the loft was defined I suggested one 'manual' inspection method above.
I'm well aware that MBD doesn't work for everyone all the time.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?