Rounding "Problem" on Dims?
Rounding "Problem" on Dims?
(OP)
We have two parts, that are mirrors of each other, that each have dimensions that measure 33.96875. Our standard is 16th fractional dims for these parts - on one drawing the above dimension shows as 34", on the other drawing the equivalent dim shows 33 15/16". When you set each dim to decimal, they are equal - 33.96875. The dim is taken from a model edge to another model edge in each case.
33.96785 is exactly halfway between 33 15/16" and 34" so it seems like SW is using different ways to round the dim on each drawing, though I can't figure out what's driving that.
Has anyone seen anything similar?
Thanks!
33.96785 is exactly halfway between 33 15/16" and 34" so it seems like SW is using different ways to round the dim on each drawing, though I can't figure out what's driving that.
Has anyone seen anything similar?
Thanks!






RE: Rounding "Problem" on Dims?
Rob Rodriguez CSWP
www.axiscadsolutions.com
www.robrodriguez.com
http://designsmarter.typepad.com/rob_rodriguez/
Eastern Region SWUGN Representative www.swugn.org www.nvtswug.com
SW 2007 SP 2.0
RE: Rounding "Problem" on Dims?
If you want the part to be 34", then it would be created as 34.00000, not 33.96785.
If you want the part to be 33-15/16", then create it at 33.93750
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-08-07)
RE: Rounding "Problem" on Dims?
I agree with Chris. Make the part the size it is supposed to be. Why design a part at one size and dimension it as another?
It's one thing to express 33.96875 as an exact fraction (33-31/32), it's quite another to express it as rounded to another denominator (33-15/16 or 34). To make it more extreme, consider 33.5" rounded it to the nearest 1" ... or the nearest foot?
If it's a purchased part, then an exact reference dimension should be used.
SW07-SP3.1
SW06-SP5.1
RE: Rounding "Problem" on Dims?
Long story short these parts are formed sheet metal. We take the flat pattern and use that for laser-cutting - laser cuts to 1/32" tolerance so we usually design parts to "nominal" dimensions whatever those might be. On the drawing we also show the "formed" shape of the sheet metal part, on which the tolerances are 1/16" - which is where the SolidWorks rounding gets involved.
I was just curious as to why SW interprets the same dim 2 different ways on 2 different drawings.
Thanks again!
RE: Rounding "Problem" on Dims?
Rob Rodriguez CSWP
www.axiscadsolutions.com
www.robrodriguez.com
http://designsmarter.typepad.com/rob_rodriguez/
Eastern Region SWUGN Representative www.swugn.org www.nvtswug.com
SW 2007 SP 2.0
RE: Rounding "Problem" on Dims?
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-08-07)
RE: Rounding "Problem" on Dims?
However, in this case the "true" dimension is exactly the same on both drawings, yet SW is displaying them 2 different ways.
What's even more funky...this morning we tried creating a virtual sharp to a corner, rather than measuring off edges (another way of taking the same dimension) and the dim displayed the same way on both drawings: 34" (which I suppose also fits with the odd/even rule).
So when dimensioning to the virtual sharp the display dim is consistent between drawings, however when dimensioning to model edges it is not (at least in this case)...
The plot thickens...
RE: Rounding "Problem" on Dims?
Colin
Macduff![[spin] spin](https://www.tipmaster.com/images/spin.gif)
Colin Fitzpatrick
Mechanical Design Engineer
Solidworks 2007 SP 2.2
Dell 390 XP Pro SP 2
nVida Quadro FX 3450/4000
RE: Rounding "Problem" on Dims?
Our CATIA friends at Dassault were infamous at doing this. It cost my last company thousands of dollars making ECO changes and re-checking of drawings.
Macduff![[spin] spin](https://www.tipmaster.com/images/spin.gif)
Colin Fitzpatrick
Mechanical Design Engineer
Solidworks 2007 SP 2.2
Dell 390 XP Pro SP 2
nVida Quadro FX 3450/4000
RE: Rounding "Problem" on Dims?
This is SolidWorks not ACAD.
SW07-SP3.1
SW06-SP5.1
RE: Rounding "Problem" on Dims?
Our standard back at my old company in Cleveland was draw to nominal no mattter how many decimal places it was. Most of time it was 5 places and show 4 places on the drawing. (The tolerance was a text value/not link to the dimension) Example: .5123+.0003-.0002 with the nominal being .51235. What was happening was the drawing value changed from: .5123 to: .5124 between software releases and was never told by Dassault nor documented. The older release was taking the 5 digit which was the value of 5 and rounded it down. the new release of CATIA was taking the 5 digit which was the value of 5 and rounded it up, bumping the dimension automatically.
Macduff![[spin] spin](https://www.tipmaster.com/images/spin.gif)
Colin Fitzpatrick
Mechanical Design Engineer
Solidworks 2007 SP 2.2
Dell 390 XP Pro SP 2
nVida Quadro FX 3450/4000
RE: Rounding "Problem" on Dims?
Eric
RE: Rounding "Problem" on Dims?
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-08-07)
RE: Rounding "Problem" on Dims?
Thanks for the feedback
RE: Rounding "Problem" on Dims?
"Wildfires are dangerous, hard to control, and economically catastrophic."
Ben Loosli
Sr IS Technologist
L-3 Communications
RE: Rounding "Problem" on Dims?
Chris
SolidWorks 07 3.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-08-07)