constraints puzzle

[Werner.D]

Hi all,


I am trying to sketch a simple shape with equal angles. I have achieved this up to apoint with relations. The sketch is locked inwith equal angles where I have set them, as well as the other constraint locking the apices to the horizontal guide lines.The two end lines however are locked to both thehorizontal and vertical guide lines.


View attachment 3149


I can move the arrangement within the remaining degree of freedom to the left and to the right with the"related" angles remaining equal. However if I try to lockdown the remaining degree of freedom of the variable angles "A", (dimensioningone side only) it tells me I am overdefining the sketch.





View attachment 3150


I was under the impression that you can only move items within their degrees of freedom, if so then why can't I dimension this to lock it down?


Any thoughts?

 

[jeff4136]

You're showing / telling an incomplete story.


I don't see any weak dims so you shouldn't be able to drag anything.


In the pic below the weak dims correspond to your angles. Once those
are locked it's a fully constrained sketch.


Maybe if you can post that or duplicate it and post ...


View attachment 3151

 

[AHA-D]

With all lines parallel (and why on earth don't you set one angle and apply parallel relations ? ) and fixed connection points horizontally and fixed endpoints, the only way I can makethis sketch move is by leaving the angle free. Only then you get a solution where the lines move together within their confined space. The moment you set the angle between 2 lines the construction is frozen in one state.


Alex


PS


Try to minimize parameters and constrain sketches with geometric constraints and/or construction geometry as much as possible. It saves you the trouble and risk of making parameters equal to eachother.

 

[mcgowanp]

that last dim your trying to add is not needed, the 36.06mm dim.


Your sketch if fully defined without it. The remaining degree of fredom that you think you have to define is not actually needed.


AHA-D is talking incredible sense, relations are powerfull and convienent, so why not use them. it will get rid of dims that can easily confuse.


what are you trying to sketch/modle.

 

[Werner.D]

Thank you all for your response. I have now been able to upload the sketch so you can see things the way I have them. The main angles are constrained with relations, but the sketch can still be moved as I am unable to place a dimension at either end. I also tried constraining the various lines parallel, butthen I would still need to calculate one of the end angles. I wastrying to use relations to make either end angleequal to halfof the other angles. That way I could modify this more easily in future.


2007-02-14_175848_wire.sec.rar

 

[jeff4136]

You'd have to give it a dof.


Any help ...


2007-02-14_191616_wire_02-wf2.sec.zip


?

 

[Werner.D]

Looks good jeff4136,


I don't think Icould have come up with that solution myself. (I'm just a poor machinist

).


I have learnt a lot though, in the past year.


Thanks for your help.

 

[jeff4136]

Super deal. Glad it helped.


I probably wouldn't have thought of it either if Alex hadn't
mentioned parallel lines. `;^)

 

[AHA-D]

ProE often leads you the wrong way. I find myself deleting more dimensions than I keep. Take for instance that you have a disk and want to cut out a 60