Assembly3 - DOF

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Medestrac
Posts: 21
Joined: Fri May 04, 2018 5:27 pm

Assembly3 - DOF

Post by Medestrac »

Hello,

Is there any tutorial on DOF and how to not over-constrain an assembly?
With two "square parts" I usually use "Same orientation" + "Point coincident" to remove the 6 DOF without over-constraining...but with more parts or round parts I don't know.
Here is an example: two cylinders with a 2mm hole, two flat bar with two 2mm holes at each end.
CTEX.FCStd
(147.23 KiB) Downloaded 6 times
The first flat bar is locked
I use "Plane coincident" on the hole edge of the bar and the hole edge of the cylinders -> 5 DOF out, the last one (Rz) doesn't matter
Idem for the second cylinder.
And now the last bar... I can use the same method but it will over-constrain. Shall I constrain the second bar with only one cylinder? Use both? Try to constrain with the first bar? What is good practice, what is the way of reasoning?
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Shalmeneser
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Re: Assembly3 - DOF

Post by Shalmeneser »

(BTW, Sketch004 is horrific.)
Attachments
CTEX_SHALM.FCStd
(110.79 KiB) Downloaded 2 times
Capture d’écran 2022-07-07 114130.jpg
Capture d’écran 2022-07-07 114130.jpg (77.69 KiB) Viewed 190 times
Capture d’écran 2022-07-07 114245.jpg
Capture d’écran 2022-07-07 114245.jpg (158.28 KiB) Viewed 190 times
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FBXL5
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Re: Assembly3 - DOF

Post by FBXL5 »

Medestrac wrote: Thu Jul 07, 2022 8:46 am
"Plane coincident" leaves one DOF unconstrained: The rotation arund the z axis. This can be fixed/locked by setting the property "Lock Angle" of this constraint to true.
Medestrac
Posts: 21
Joined: Fri May 04, 2018 5:27 pm

Re: Assembly3 - DOF

Post by Medestrac »

Shalmeneser:
Sketch004 is horrific
True, but it's not the topic, and it's not really constructive...any hint how to improve this sketch?

FBXL5: Thanks, I didn't know about this "Lock Angle" property

More than a solution for this specific topic, I'm more looking for a "Good practices" advice that I can apply generally.
adrianinsaval
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Re: Assembly3 - DOF

Post by adrianinsaval »

I would make just one circle then use a PD multi-transform, make another sketch and re-pad the sections where there shouldn't be holes (center and corners), looking at his tree it seems that's what shalmeneser did too.
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Shalmeneser
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Re: Assembly3 - DOF

Post by Shalmeneser »

The file is in my 1st message above the image.
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