Rigid Assembly 1

[aer73]

Hello.

I wanted to know if someone I could help with the following.
I have an Assembly to which I added a subassembly and has been rigid.
Can someone tell me how to fix it?
Thank you very much for your help.
Best regards.

 

[JohnRBaker]

OK, what you have to do is at the top level Assembly you need to overide the constraints of the piston/conn-rod sub-Assembly. What this means that the top level assembly will now be in charge of the positions of the Components in the sub-Assembly. You do that by going to the Assembly Navigator and expand the sub-Assembly, select any one of it's Components, press MB3 and select the 'Overide Position' option.

However, there was a problem with your sub-Assembly which I had to fix first. In the sub-Assembly I first added a 'Fix" constraint to the piston (don't worry, this 'Fix' will be overridden at the assembly level). Now this was NOT absolutely necessary, but it's just a good idea that at least one Component in an Assembly be 'Fixed' as this will help when it comes time to test the degrees of freedom in the rest of the assembly. Second I noticed that the split-bushing/bearing was not constrained relative to the conn-rod or the bearing cap. So I added a single axis 'Align' of the centerline of the split-bearing/bush set to the centerline of the bearing cap. Once that was done I saved that Assembly file (I gave it a new name).

I then went to the top-level assembly where the constraints were already OK. All I did there was perform that 'Override' operation as described above.

Now you can rotate the crankshaft and the piston will move as desired. In fact, I went one step further and added a 'Sequence' which causes the crankshaft to rotate 720 degrees.

To see how this works, simply go to...

Assemblies -> Sequence...

...and when the Sequence task toolbar is displayed, select the Red 'Play' icon and the sequence will run. When it ends you have to either run it backwards (select the opposite pointing pointing icon) or hit the 'Rewind' icon (far left of this group of Red 'arrow' icons.

The I saved that assembly. Now the only two files I modified were the sub-Assembly and the top level Assembly. Attached is a zip file of the assembly with my two files replacing your original files.

Anyway, have fun ;-)

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

UG/NX Museum:

http://www.plmworld.org/p/cm/ld/fid=209

To an Engineer, the glass is twice as big as it needs to be.

 

[aer73]

Thanks,Thanks,Thanks,John R. Baker, P.E.
You are one of the best in this forum.
Thanks for making me better understand the functioning of NX.
Tomorrow I say you as me to gone.
Many thanks again for your great help.
Best regards.

 

[JohnRBaker]

Glad I could help.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

UG/NX Museum:

http://www.plmworld.org/p/cm/ld/fid=209

To an Engineer, the glass is twice as big as it needs to be.