Spring Expanding in Motion Analysis 1

[roldy]

I need to be able to show a spring expanding in a motion analysis study. I need motion analysis because I have some parts that have solid body contact with other parts. I want to show the whole mechanism movement in a video. Motion analysis does not allow the deformation of a spring. Is there some way I can show this?

 

[Jboggs]

We're running SW2013 Premium edition and we have springs (compression, extension, and torsion) as one of several available options in Motion Analysis.

 

[roldy]

Jboggs,

Unfortunately, I am running SW2012 Premium.

 

[Eltron]

You can create "live" springs in several ways. I'll try to explain two.

In one instance you can create a sweep of the spring profile within the context of the assembly. The path sketch of the spring should be constrained to the components that are moving relative to each other. In this instance whenever Part A moves relative to Part B the path sketch will change, which will change the sweep path making it appear that the spring is compressing and expanding.

In another instance you can create an assembly of the spring from a series of half-turns of a helical sweep. If you mate the circular face of the sweeps together (coincident) and the axes together the spring will move freely as a spring should.

I can think of a couple of other ways to do this, but these are the first to come to mind. Sorry I can't send over files since I'm not on 2012.

Dan

http://www.eltronresearch.com

Dan's Blog

 

[roldy]

Eltron,

I have tried the first method you suggested but the part did not update in the Motion Analysis simulation. I will try the second method later today.

 

[Updraft]

roldy,

Since you are trying to make video and show the spring dynamically flexing with the motion of the mechanism about the only option that will work is to make a spring assembly consisting of a bunch of half coils similar to Eltron's second suggestion. As you have already discovered, the first suggestion will not work because the solid has to regenerate from a recomputed position of the driving curve, and that cannot be done dynamically in SWX at this time.

Depending on your how good the spring has to look you can make the half coils as simple as a 180 degree revolve of the wire diameter. If you need it to look smoother then the half coils should be 180 degrees of a helical sweep. Both of these techniques generally yield an acceptable appearance.

- - -Updraft

 

[roldy]

Eltron & Updraft,

I have tried splitting the spring into multiple parts but upon doing so I realized that this will not work. The end segments of the spring are to remain parallel to the ground. I have tried just having the coincident mates on the circular faces of the spring segments and a mate for the ends of the spring to be parallel to the ground. Looks like a may have to do some tricky compositing. Composite an animation video with the Motion Analysis video.

 

[Eltron]

You can still do it with the end segments being in a fixed position. Just mate a plane within that component to be parallel or coincident to the ground plane while leaving all other links in the spring free to move.

Dan

http://www.eltronresearch.com

Dan's Blog

 

[EEnd]

Here is an example of what they are describing in SW 2012. I used circular links. Looking at the pitch of your spring, you will likely want to use helical links. If your deformation is large, the kinks at the link may become objectionable. If that happens, you can use more than 2 links per turn. The spacer bar and links in the assembly serve to keep the links evenly spaced.

Eric

 

[Updraft]

Eric (EEnd),

Your model should be a great example to roldy. A star for you and your service to him.

There is, however, a simpler way to mate this and uses fewer elements. I just did the following with your model:
1. Suppressed all the Spacer Bar and Spacer Link parts.
2. Made a parallel mate of the Right Planes of the first and third instances of the Link parts. (This can be a Multiple Mate for more link segments.)
3. On the second instance of Link I made Sketch2 of Sweep1 visible, selected the center point of the circle and the Top Plane of the assembly and mated them coincident. (This, too, can be a Multi-Mate for more links.)
Done.

These changes are included in the attached file, but I am on SWX2014 so you won't be able to open it in earlier versions.

- - -Updraft

 

[EEnd]

Updraft,

I think I follow your mate scheme. Mating the opposite ends of the two links in a turn to the top, keeps their angle symmetric about the joint between them. Making the first links of each turn parallel keeps the pitch of the turns equal. Nice.

Eric

 

[Eltron]

Here's the version that I was suggesting.

Dan

http://www.eltronresearch.com

Dan's Blog

 

[roldy]

I will have to try this again. I will post the file if it does not work for me.