Screw Bolt Animation

My guess would be that the software doesn't "know" that the bolt is engaging the nut, and thus the nut doesn't pull the bolt in. One way to fix this would be make the bolt advance itself by one thread pitch per turn (or one thread lead in the case of multiple threads).

Here is a fun little exercise: See if you can find a common consumer product that uses a 7-multiple thread, and guess why.

This may be a good guess. Your idea of full travel in a turn or less is right on, but I don't know if any cameras do it this way.

The instance I know of is milk bottle caps. The plastic is rather thin, but fairly fine multiple threads make it possible to twist the lid off in about half a turn or so.

Well clearly your code does not include the tensile strength of the threads of your bolt or nut in your calculations.

On a less obnoxious level, getting an animation to react similarly if not identically to how things actually work in the real world, as you have just found out, quickly becomes a very complicated task. If you assume that your threads are incapable of cross threading or in other words that thread alignment works flawlessly every time then for every turn either the nut or the bolt must move a certain distance closer to each other each and every complete cycle of a nut versus bolt rotation. You should include some reference piece of information on what the gap between nut and bolt head (or other surface) that will be reduced during tightening until that value reaches zero. This should give you a reasonable graphic (visual) image of the macroscopic things that happen during assembly.

As you might guess, this will be an excellent level of animation control for any high schooler and many of the visual arts. But predicting stress load deformations, torque load expectations or the anticipated bolt length stretching that will happen only when an assembly gets properly torqued will require much more considerations.

what software are you using?? as Tornado said you could use timing and a simple transition of the nut along the path of the bolt, you could use a script the tells the nut to move a set distance per revolution, you could use a spline and constraints.... it all really depends on what software you are using.... there will be more than one way to do it .........

Welcome to CR4 cosmiccolonel. (if you are new here)

I agree. what software??

Chris

Yes, if we know the software being used, we could guide better.

With the present software, you are able to rotate the nut or bolt. You could be using a tool or code/script to do this, right? In the same application, look around for the tool or script to move the object. Precisely or by trial and error, move the the nut or bolt by one 'pitch distance' per rotation and keep moving until you want. Now there are two options:

Either you rotate the nut (or bolt) and make the bolt (or nut) to move.

Or, keep the bolt (or nut) fixed and rotate and move the nut (or bolt).

If you require, I can do this for you and keep it here as animated GIF images.

My grandaughter is a senior in an animation curriculum. She uses 3DS Max program for this kind of animation. Still, it is not easy. Here are her comments:

I'm presuming he's working in 3D? I'm still new enough at this to be
unable to say for certain, but it's unlikely there's any sort of control
that can do this for him. The big problem is that even though your models
look solid, the program doesn't treat them that way, and objects slide
through one another far too easily. Thus, the program doesn't recognize
anything special about the threads relative to the nut. As far as I know,
the best way is to zoom in and be completely anal about setting your keys.
Oh, and I recommend doing this in set key mode rather than
autokey--getting superfluous keys like you're likely to get in autokey is
a recipe for frustration.

Nice work... I've added that to my favourites list. I used to work for Johnson Controls, and would have appreciated all that valve tech (as JCI is a valve mfgr)

ga

Chris

Spin the nut backwards for a couple of revolutions, as the beginning of the thread on the nut passes the beginning of the bolt thread the nut will seat itself (drop into it's lowest point in the backwards rotation.)

Now that you've determined the low point of the backward rotation you can use that as the starting point of screwing the two together.

Guest in absentia,

here is what I would do. (assuming 3ds max, but the process is similar for others)

I would count the number of threads per inch on the parts I was modelling. The nut and bolt must have the same TPI.

I choose how long the animation is to last in real world time. (ie. 30 seconds)

I choose an frame rate appropriate to the hardware it will be shown on, so that the animation will look reasonable.

I calculate the number of frames I need, based on the frame rate and duration.

I know that there will be a few frames at the beginning and end, where motion is stopped. so I subtract those numbers from my calculation for 'actual nut animation'

I determine how far the nut must travel in the animation. The nut only has to turn axially while engaging the bolt. The other part of the animation it doesn't need to turn. so you can subtract those frames, and create a simpler animation for that portion of the animation.

Now, I know exactly how many frames i have to turn the nut, so I will find out on the nut, exactly the axial distance the nut will be travelling on the bolt.

Because I know the 'Threads Per Inch" of the bolt, I can calculate the number of rotations the nut must turn axially, in order to travel the length of thread it needs to. (and how many frames i have to do it in.)

Now I can create three animations...

• part one, just the translation of the nut coming up to the bolt (for x frames).
• part two, just the rotation of the nut (for x frames), and this will be simultaneous with;
• part three, the translation of the rotating nut on the threads of the bolt (for x frames).

here is an interesting sample work (not by me)

Chris

If its Pro-desktop I may be able to help.