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Adjustable parts for extension springs

I've run into a little issue when using adjustable parts for an extension spring.  I have the spring anchored at one point and the other is attached to a shoulder screw that moves in a radial slot.  The length of the spring accurately tracks the distance between the anchor and the moving shoulder screw, but I cannot constrain the spring so it stays "hooked" on the moving screw. I get an error stating "the requested relationship cannot be placed.  Relationships that position other parts cannot be placed to adjustable parts that act like a spring."  

 

 

 

 

 

 

Kyle

Kyle Joiner
IPA LLC
ST9 MP1
6 REPLIES

Re: Adjustable parts for extension springs

Ajustable parts that adjust like a spring solve last in the ASM and as such cannot drive the position of other parts in the ASM.

 

Not sure of the relationships you have setup in your ASM but I was able to do this
using a measurement variable between the 2 posts to set the spring length.
Also, the red arm part has to be free to slide.

Generally I add the components and make them move correctly and then add the adjustable parts last in the ASM once the components it connects to are positioned and move like a want them to.

 

 

 

Adjust to fit parts solve as part of the main ASM. (Kind of like inter-part) so they can be used to position components as long as solve loops do not occur. These can also be slower because the additional recomputes/solves.

 

Hope this helps.

 

Thanks,

 

Art

 

Re: Adjustable parts for extension springs

Art,

This was not done in ST7! Am I right?

Cool!

BR,
Imi
Imics
http://solidedgest.wordpress.com/

Re: Adjustable parts for extension springs

True, this was done in ST8 but it can be done in ST7 using Automation.

 

Thanks,

 

Art

Re: Adjustable parts for extension springs

Hi Art,

 

The spring in my assembly is the last item in the tree.  The other parts move as desired.  Could there be an issue with measuring the distance between my spring anchors?  

 

Kyle

Kyle Joiner
IPA LLC
ST9 MP1
Solution
Solution
Accepted by dcstaples (Community Manager)
‎08-26-2015 04:32 AM

Re: Adjustable parts for extension springs

[ Edited ]

Aha!!!

 

That could be it. The distance of the spring needs to be measured in a plane.
If you measure from the tops of the pins and the pins tops are not coplanar you will get a little longer value so the spring will not work when you try to relate it back to the pins. (Won't fit)

 

I believe this could be the issue.

 

You could place a PMI dimension between the 2 pins (using between 2 points) oriented to the plane of the base part and use that as the variable to drive the spring.

 

I always forget that you can use PMI dimensions for things like this. (Shame on me)

 

Thanks,

 

Art

Re: Adjustable parts for extension springs

Thanks Art!  That was the problem.  When measuring on the screw heads, I had a Z axis difference of around .150 and this caused my dimension of the spring to be longer than the actual distance between the screws by .001.

 

Thanks again!

 

Kyle

Kyle Joiner
IPA LLC
ST9 MP1