Issue with touch
Issue with touch
(OP)
So I have a strange problem.
I have a symmetrical part where the constraints work on one side but not the other. Can't think of anything I'm doing differently. The ISA grabber constraints work on one side. On the other they don't work and I also notice that when I "reverse the centerline align constraint it becomes a touch. Is that normal?
I have a symmetrical part where the constraints work on one side but not the other. Can't think of anything I'm doing differently. The ISA grabber constraints work on one side. On the other they don't work and I also notice that when I "reverse the centerline align constraint it becomes a touch. Is that normal?





RE: Issue with touch
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Issue with touch
The RHtwist and ISAgrabber are not solving while the lh twist which was constrained the same way is perfectly fine.
When you change the distance on the handle (expression: handlepos) the left side isagrabber turns as it should.
RE: Issue with touch
When you open the new Assembly, note that there will be one 'Distance' constraint that is suppressed. That's OK for now since I did that so that I could create a Sequence showing how this 'mechanism' works. So to see that, go to...
Assemblies -> Sequence...
...and push the VCR-like button '►' to play the Sequence 'forward' and the '◄' to play it in reverse (you can speed it up or slow it down by changing the 'Playback Speed' setting).
Once you've played around with this awhile, now, leave the Sequence task and look at the Assembly constraints where you will notice a few things. To start with, I used a couple of 'Concentric' constraints simply because they work better for the places I used them rather than a couple of 'Aligns' and 'Touches'. However, the biggest problem with your assembly was that you were creating conflicting constraints when you added the 'Center' constraints on the Blue 'nuts' (or whatever you call them). Now this was not a problem when you did just the first side, but when you got to the other side, when you consider all of the constraints that were being applied in a sort of circle, from the first Blue part to the second, it was just creating conflicts. My approach, was to use a couple of 'Distance' Constraints instead of the 'Center' constraints because that will ONLY define the 'location' WITHOUT trying to also define their 'orientation' of the Blue parts, which is what the 'Center' constraints were doing. Too many 'orientation' type constraints can lead to problems. It's better to sometimes just worry about the 'location' and let something else control the 'orientation', in this case it was the 'Align' constraints relative to the center core holes of the screws.
Anyway, take a look and I think you will see what I'm getting at. And once you're done playing with the Sequence, you can unsuppress that last 'Distance' constraint and then you can move the position of the handle by editing the 'HANDLEpos' expression. Just be careful that you only make small changes to this number and then update, as making a single big change will result in not quite what you're expecting due to what's known as 'Chirality', something that effects how simultaneous equations are solved when there are more than one possible solution, which is very common with constraint systems. For a detailed explanation, go to the following E-Tips entry and scroll down to the second to the last post. Note that while this particular thread was concerning sketch behavior, the solver used for Assembly constraints is just a 3D version of the same solver, which is only doing 2D equations, used in the sketcher:
http://www.eng-tips.com/viewthread.cfm?qid=212859
Basically, you need to sneak-up on the final number using 3 or 4 incremental changes to get there.
Anyway, good luck.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Issue with touch