Simple Extrude Problem?

[Anonymous]

HI

I've been looking at this problem for too long so perhaps someone else can shed some light. I've attached a simple drawing, fully constrained consisting of 3 circles. The smaller circle is further constrained with tangent constraints with the larger two. I've also attached an image showing the area I wish to extrude into 3d. Now if if trim the drawing then the extrude is quite simple, however I want to keep the circles in place so that I can alter their dimensions at will and therefore automatically adjust the dimensions of the extrude at will....any ideas how this can be done?

Thanks in advance

Roger

[Anonymous]

Might be a simpler way, but make your sketch lines construction and then put 3 circles back over erach one conctraining them to each other (no dimensions) By draging the circle until it touches the other it goes on top of. Then trim those lines. This way you still have the original skecth.

Although if you trim them properly in the right order you will still have your dimensions and it will be editiable.

[Anonymous]

Thanks for that, though if possible I want to avoid trimming or any other manual operations. The end goal is to be able to parameterise the dimensions so I simply type in the parameties and the 3d part is created ready for dynamic simulation (I need to run hundreds of simulations with different sized extrudes)

Roger

[Anonymous]

Object resizes fine in both examples by simply changing diemnsion values.

[Anonymous]

oh, I misunderstood you, let me try this and I'll report back...

[sam_m · Accepted solution]

Inventor is "seeing" 3 separate closed profiles and doesn't realized you're trying to link them together.  You can do this by using the "point" tool in the sketch (not a work point but the drawing "point" - button left of Text).  While in the sketch click "point" and then click on the 3 joints - the 2 tangents and the cross-over.  Now try extrude 😉

no need to redraw arcs over the top or trim your sketch away to something less easy to relate to. 

[Curtis_Waguespack]

Hi Roger456,

sam_m beat me to the punch, but here is a link that illustrates his suggestion:

http://inthemachine-autodesk.typepad.com/blog/2009/03/no-need-to-trim.html

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[Anonymous]

Thanks for both of these, I won't be able to try either of them until I get home tonight. One question about the 'point' solution though - as I said I want to be able to alter the dimensions of the circles - in which case will the points at the intersentions automatically and corrently move as I do so as I'm looking at it and have the horrible feeling that they won't?

Roger

[Curtis_Waguespack]

Hi Roger456,

The sketch points are constrained to the intersection of the circles, so as the intersections shift, the points do to. So it should work very well for you.

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[Anonymous]

I'll try that at soon as I get home then....

[Anonymous]

Hi

Yes the 'point' trick worked very well! A much underestimated tip I imagine. Thanks to everyone who took time to respond

Roger