
Re: driven dims + sketch relations + equation = quandary
Alin Vargatu Sep 11, 2012 1:01 PM (in response to Andrew Thompson)Is this a duplicate of this thread?
https://forum.solidworks.com/message/314224#314224
Please attach the fileset.

Re: driven dims + sketch relations + equation = quandary
Todd Sutherland Sep 11, 2012 1:17 PM (in response to Andrew Thompson)Submitting file for Andrew above....

umbrella_setup.SLDASM.zip 63.2 KB


Re: driven dims + sketch relations + equation = quandary
David Suelflow Sep 11, 2012 3:51 PM (in response to Andrew Thompson)Don’t the outer endpoints of Line A and Line C lie on a circle as they do on the inside (by the pole)?

Re: driven dims + sketch relations + equation = quandary
Andrew Thompson Sep 11, 2012 4:23 PM (in response to David Suelflow)Unfortunately they do not.
The canopy is basically a square pyramid, and the pivot point locations that satisfy the equal length provision do not lay on the same plane or circular or square path. I say basically, because a strict pyramid would have a square shaped pivot ring at the top, not a circle.
FYI: I managed to find the correct length manually by "cheating SW with driven dims used in an equation, but SW throws flags about circular references for obvious reasons. And since it only finds the correct pivot location if C and D are driven, you cannot set one or the other to driving, because then the equation will not work unless you have already entered in the correct value, which is what I want SW to find for me on the fly.
By the way, the values are C= 619.51787472mm, or D = 697.48212528mm. These satisfy SW's 8 decimal place precision.
Hope that makes sense.

Re: driven dims + sketch relations + equation = quandary
David Suelflow Sep 12, 2012 11:46 AM (in response to Andrew Thompson)It would seem to me that you would have to certainly define the lengths of A & B (or the horizontal offset from the pole) as well as either C or D. I don’t see how A+B=C+D defines the relationship between C & D. Lets say that A + B = 10, C + D could equal 9 + 1 or 8 + 2 or 7 + 3 and still satisfy A+B=C+D.
This is how I might approach it (w/ equations)...

Umbrella 01.SLDPRT.zip 51.8 KB

Re: driven dims + sketch relations + equation = quandary
Andrew Thompson Sep 12, 2012 12:39 PM (in response to David Suelflow)I agree. The equation A+B = C+D while necessary, is not sufficient to determine the design intent. That's where sketch relations come in. In the context of the existing sketch relations, there is only one value of C and one value of D such that A+B = C+D.
I just want SW to find it for me. That way I can enter various A, B or canopy dimensions and have SW find C and D, and down the line, rebuild the parts and assembly such that the umbrella will open and close without binding.
I created a jpeg and clearer assembly setup that hopefully illustrates this issue more clearly.
I had trouble uploading attachments yesterday. Hopefully it goes better today.

umbrella_setup.JPG 195.0 KB

umbrella_setup.SLDASM.zip 60.2 KB



