Small unit+high tolerance or vice versa?

doubleprecision

(Miguel Villegas Ballesta) #1

I’ve done ma time of research around the concepts of tolerances and I think I understand them.

I’m working on architectural models intended for construction, so our precision needs lay around milimeter (1-5). So my question lies on which approach is better, to use lets say milimeters as unit with a tolerance of 1 or to use meters (that’s our firm convention, with a tolerance of 0.001).

The result should be the same (I think) but the floating point difference makes me intuitively think, there might be a processing difference between the two. Am I wrong?


#2

I would have a tendency to work in cm with a tolerance of .01, that usually works fine for architectural stuff here… There is no need for the tolerance of your drawings/model to match that of what is actually built, in general it should be better (smaller) than that by at least an order of magnitude.

Working in mm with a tolerance of 1 is not a good idea IMO; plus for building sized objects you will have lots of numbers to the left of the decimal. Working in meters to .001 is OK, but you will again be expressing your sizes with a lot of fractional values, which are hard to read. That’s why I find cm a good compromise for readability.

–Mitch


(Miguel Villegas Ballesta) #3

The point of readability is right, but wanders from my question. It can be easliy solved with a correct dimensioning style.
Furthermore, I find working in mm really comfortable as you don’t have to type the decimal separator, which I find really annoying to have to do.


(Miguel Villegas Ballesta) #4

The point of readability is right, but wanders from my question. It can be
easliy solved with a correct dimensioning style.
Furthermore, I find working in mm really comfortable as you don’t have to
type the decimal separator, which I find really annoying to have to do.

Lourdes Bueno y Miguel Villegas


#5

OK, no problem working in mm if you are used to it, I would keep the file tolerances at 0.1 minimum though, 0.01 even better. You can set your dimension styles to not show anything smaller than 1 mm (i.e. 0 decimal places).

–Mitch


(Miguel Villegas Ballesta) #6

Thanks, though my question is still open as my concerns regards on the computing process of tolerances.
Is it better for the computer to adjust with no floating points or to be able to use them, or does it always use them anyway?


(Pascal Golay) #7

Yeah - the bigger brains here say that Rhino is most comfortable in the .01 - .000001 range.

-Pascal


(Wim Dekeyser) #8

Perhaps that simple fact could / should be communicated to the user when one sets the tolerance outside of this range? Not necessarily prevent people from doing so if they absolutely want to - just a reminder of the facts of life…


(Pascal Golay) #9

Yeah, not a bad idea… it could be on the Units page, perhaps as a tooltip sort of thing. My only concern, off the top of my head, is that I would not want users to infer that if they keep things in that range everything will always work…

-Pascal


(Wim Dekeyser) #10

:expressionless: Perhaps a lawyer should take a look at the wording… :wink:


(David Cockey) #11

Just a message such as “Recommended tolerance is 0.01 to 0.000001” or “Tolerance is set out recommended range of 0.01 to 0.000001.”


#12

hmm… i wouldn’t try to match my rhino tolerances to my construction tolerances…

try to make the rhino model perfect… when you’re building, there’s a different set of tolerances that come into play (human skill, machine tolerances, etc)…

if you set rhino tolerance to match the construction tolerances then you’ll likely compound the error at some point (say rhino is +/- .125" and construction is +/- .125"… there’s a chance you’ll be out .25" in some places which is twice your allowance).

idk, i have rhino set to .001 inch and i seriously never change it… in the shop, i’m typically aiming for .03" (1/32)… sometimes .015" (1/64)… if framing then it’s more like +/- .125"…

but, rhino is always at a much tighter tolerance (.001) regardless of the final construction.