TheSwamp
CAD Forums => CAD General => Topic started by: SDETERS on August 17, 2006, 03:18:15 PM
-
I did not know where to put this so please move this to the appropriate place if need be
What method or software and or work flow do you use for tolerances stacks? Just wondering if there is a better way out there than the way I am doing it at this time. I am doing it long hand and it really time consuming.
Thanks
Shane
-
If I'm reading this correctly (which may be highly unlikely as it has been one of those days where my brain stayed home),If you have access to AutoCAD or anything autoCAD based there's a tab in the dimension style that will tack on the information.
-
OK that is not what I am looking for
What I am looking for is when one has an assembly with say 5 to 10 different parts in the assembly I want to make sure these parts go together at worst case condition.
Say the parts will go together in nominal case but I want to make sure when all the parts are at maximum material condition the parts will go together.
-
ACAD Dimension styles generally handle 2 levels of information either tacked on the to the end of a dimension or a limits style
To actually calculate them I think Inventor or Mechanical Desktop have a built in option.
-
Here is a possible tolerance stack to give an example. I have 3 parts that I am bolting together. I want to make sure the bolt will go into the holes when everything is at its worst case condition. One has the tolerances of the holes tolerance of the location of the holes back to the datums and the tolerance of the major diameter of the screw. This a simple one but I do really complex ones which take a long time to calculate by hand. Just wondering if there is an easier way of doing things. Thanks If you are doing a 2D drawing how do you know that the parts will go togther when they are manufactured? How do you know what tolerance to put on the print?
-
Well, I don't allow for tolerances ... it is either what I tell them to cut/drill/bend/break etc or they do it again.
I understand your concern I think ... are you speaking for example, part A has a bolt hole that must be within 1/32, the bolt diameter must be within 1/32 and the alignment of the bolt holes from part A to part B must be within 1/32 .. thus if they are all off by the maximum tolerance will they still fit together ... i.e. will a bolt that is 1/32 too large, fit in a hole that is 1/32 too small, that is out of alignment on the parts by 1/32 ... the only way I know of doing that would be to actually create the thing at max tolerance, then check it at min. tolerance.
-
Insert Quote
Well, I don't allow for tolerances ... it is either what I tell them to cut/drill/bend/break etc or they do it again.
Wow I would hate to work with ya on this? A drill even had a tolerance nothing is ever dead nuts on! I am talking about dimension with tolerances of +/-.01 or so adding up
We do high volume manufacturing and parts come in all over the map.
I will draw an example up later and show everyone what I am talking about.
Thanks
Shane
edit I can not figure out how do a quote yet
-
To create a quote, you will need to utilize the quote tags at the beginning and end of the section you wish to quote. i.e.
[ quote ] (minus the spaces) and
[ /quote ]
-
Thanks keith for quote I will try it later
anyways I have an example of a Tolerance stack that I am talking about. This is a real simple one. My goal out of this thread was to get a more efficient way of doing these things.
Part 1 and part 2 is bolted together and part 3 is put in this small assembly before the two parts get bolted together. Part 1 and part 2 is a die casting of some sort and part 3 is a turned machined part. The pourpose of this tolerance stack is to make sure the two die casting parts can be bolted together with part 3 in place. If the tolerance of part3 is to big the parts will not bolt together. So the following is how I do this.
I write out the equation
A-B-G+C=0
then I solve for G
A-B-+C=G
Then I put dimensions to the letters per the 2D drawing
A=.024+/-.020
B=1.279+/-.010
C=1.377+/-.020
Then I put these values into the forum la
(.024+/-.020)-(1.279+/-.010)+(1.377+/-.020)=g
then I do the math I add all the +/- tolerances and do the regular math on the dimensions.
g=.122+/-.05
Since G has a range of .172 to .072 these parts will always go together if the parts are to print.
I hope this helps maybe this is a good way of doing things I do not know but was just wondering if anybody had a better way of doing things
Thanks for your time and help
-
Ok so why not write a simple formula in a spreadsheet or a function in lisp or vba to do the math for you, you just supply the values.
-
DUH
I never thought about doing this in EXCEL crude we ususally have like 100 gaps and
use some of the same dimensions over and over again. This way I type it in once and forget about it. I will link dimensions across the the sheets to do the different gaps. SO if I change one dimension all the other will update
I will set up an EXCEL work sheet and try it from there.