×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Spring compresion in motion simulation in NX5
3

Spring compresion in motion simulation in NX5

Spring compresion in motion simulation in NX5

(OP)
Hi,

I am trying to simulate the motion of some components in an assembly. The assembly includes a spring as well.
Is it possible to simulate the compression of the spring in motion simulation.

Looking forward to any input in this regard

RE: Spring compresion in motion simulation in NX5

Easily actually! You need a spring defined in such a way that a length parameter will affect its geometry. A simple helix does this. If you want to use the same spring more than once in the same file then you can use deformable parts.

The best way to illustrate is with a simple example. I have attached a file and there is an animation set up inside this so that you can quickly rock the thing back and forth to see the spring length change.

Let us know if there is anything about this that you can't understand from the example.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

(OP)
Thank you Hudson,

I am, however, still not able to succeed in animating the deformation. I can rotate the rocker and move the seat in  your animation set up, but can not deform the spring even though I can see in assembly that you defined the spring as deformable.

Hudson,

Could it be too much to ask whether it is possible for you to tell me step by step what to do in order to animate spring deformation since I am new in motion animation.  

RE: Spring compresion in motion simulation in NX5

Please turn off partial loading and try again it will most likely simply be that the springs are not fully loaded. Make sure for example that you're not loading faceted bodies by default.

If you can get it working it will be better as I undertook to model the thing simply on the basis that it is less time consuming than constructing an explanation. I'd also add that nothing in the explanation I'd give you would make any difference to why it would not be working as delivered.

If on the other hand you've remodelled the spring yourself and don't know how to set up the deformable part then look harder again at mine. What you'll find is that all the features in the model were added to the deformation but the only expression used was the one called "length".

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

Hi Hudson & akrah

This is similar to my question on the torsion spring I posted a few days ago.

I tried the assembly that Hudson sent through but when I clicked to open it all of the constituent parts were left with white square icons and didn't load, even though I saved all the parts in the same folder.

Looks as if the assembly file defaults to the drive where they were created. I loaded them in manually but then nothing was constrained. The deform options are greyed out too so can't be modified.

I did get it to work when I created a brand new & fully constrained assembly.

Is there some good explanation of the deform command somewhere? the five steps to creating the deform are complicated to understand especially on the references (4th step) where its hard to understand what is actually being asked for. If you skip this step completely the command still works OK....

I never managed to get a torsion spring with two bent legs to deform correctly; there is always a small portion of the extrude on one of the legs left behind.

Best regards
 

RE: Spring compresion in motion simulation in NX5

RobLN,

I made the assembly with mating conditions if you want to use constraints in can be done also. Just for reference by the way what version of NX were you running?

 

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

Sorry Hudson, you've lost me there. I don't know how mating constraints work. Are they part of the Motion Simulation program? How do you insert one?

I know that in Solid Edge there was a 'contraint tool' called mate.

My NX is version 5.0.4.1

RE: Spring compresion in motion simulation in NX5

I made a little movie to try and help.
I looked at the constraints and turned one off so I could move part. I also point out the measure expressions that control spring. As far as the deform expression grayed out go ahead and make it constant and you will be able to change they are grayed out because they are both controlled by the expressions I point out. Hope this helps.

Doc
http://www.goodrich.com

RE: Spring compresion in motion simulation in NX5

Thanks for your efforts. Is seems my confusion about mating constraints / Assembly constraints stems from the fact that I don't seem to have access to any of those commands in my version of the NX software.

I did a search on the command finder and got the following results:

1. 'Reposition component': 'This command is not available'
2. 'mate Component'or 'mating conditions': 'This command is not available'

Some of the options for example the Measurements tool seem only to be available in the 'Tolerance stackup Validation application' - whatever that is ;).

If I try to run this from Analysis>Tolerance Stackup Validation I get an error that there is no library for the application. Looks like I don't have that bit of the software. I will be talking to our NX administrator later to see if I can get access to those part of NX.

Best regards.
 

RE: Spring compresion in motion simulation in NX5

Do you hava assemblies turned on?
Click your start and make sure you have a check mark next to assemblies. If you don't you will not have any mate orany of the commands mentioned.

Doc
http://www.goodrich.com

RE: Spring compresion in motion simulation in NX5

'Reposition component' looks like it is being phased out, use 'move component' instead. Likewise 'mating conditions' are being replaced by 'assembly constraints'.

RE: Spring compresion in motion simulation in NX5

By all means try this copy which uses positioning constraints rather than mating conditions.

NX-5 still uses the old reposition component, and the whole mating conditions versus positioning constraints thing seems to remain fairly optional for now.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

RobLN,
Perhaps the commands are not available because of the current role you are using. Try out an advanced role and see if it makes a difference.

RE: Spring compresion in motion simulation in NX5

Your roll dosen't take away or add commands. They control only tool bars and lay out, the commands will still be available you just don't have a tool bar.  

Doc
http://www.goodrich.com

RE: Spring compresion in motion simulation in NX5

Hello,
 Im also having big troubles with springs motion. I know how to define them as deformable geometry so they update in assembly, but I'd like them to animate with the rest of the mechanism in Motion Simulation module. Is it possible?
Best Regards, Koen

RE: Spring compresion in motion simulation in NX5

(OP)
Hi,

As Hudson888 said above, yes it is possible although I am not able to animate the compression of the spring in motion animation despite the fact that Hudson and Doc explained it.

I can deform the spring in the assembly by going to Assembly--component-- deform part, but not the way you showed in the movie, Doc1995.
I attach a simple assembly. Can anybody tell me what I am doing wrong or what I am missing in order to animate the compression of the spring in motion animation?

RE: Spring compresion in motion simulation in NX5

There is a simple animation set up in the file. I assigned some materials and output the video for you.

I can only do so much for you. The deformable parts dialog is kind of a one shot deal since it doesn't allow you to analyse very easily. Do this using my spring. In the first screen you give the deformation a name, in the second you select all the features and move them into the right hand panel, and in the third you select the expression length and move it into the right panel then click finish to complete the task.

When you add the spring to any assembly henceforth it will ask for a value for the length expression. If you have the rest of the assembly set up properly you should be able to set the length to a previously defined length measurement expression. Provided that the spring is located in the base in the assembly articulating the rocker will have the effect of moving the seats (or vice versa) then as the distance expression changes so will the spring length. It simply gives the appearance of being a mechanism because it is now programmed to behave as one.

I suggest to you that as you go you perhaps ought hit the F1 key and read at each stage the documentation associated with steps you may be unfamiliar with. I have made a small model as knowledge rich as I could so that there are by now quite a few techniques used which I really don't think would be better explained at length since there are a largish number of steps involved. If you de-construct my model faithfully you ought get the same result.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

akrah,

I have had a look at your example. What I'm seeing is the the expression L_7 for the deformable length of the spring is locked and you can't edit it to change it to the expression as I did. That seems to be because you selected positioning constraints rather than mating conditions to be used in you customer defaults. Mine works because I started out using mating.

John, if your reading this and I'm correct I suppose it represents an ER for positioning constraints to at least support the same capability that mating could provide. Should I be wrong I'd be overjoyed to know how I might otherwise go about this task.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

Hudson,
Could you share with us your simulation files so we can see how you achieved the result from your last movie? They are stored in a separate subdirectory in the folder with assembly.
Best Regards, Koen

RE: Spring compresion in motion simulation in NX5

Koen11,

No simulation files are involved just positioning constraints or mating conditions, deformable parts and a key frame animation to iterate the default expression FrameNumber. Its all in the files that were posted.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

Thank You for help, I think we are getting closer to the solution :) The last thing is - how to "merge" the motion from motion simulation, with the motion of the spring so that I can record a movie with both motions at the same time? I managed to save the motion simulation as a sequence so now i can view every step (frame) in the Modeling application. Now, is there any way to update spring position (deformation) in every step? Or is there a completely different way to achieve the result that me and akrah are looking for?
Best Regards, Koen

RE: Spring compresion in motion simulation in NX5

You Don't need motion simulation at all it is just done with the expression FrameNumber and a changing distance mating condition.

When you set up the animation tick on "update expressions" all it does and in capable of doing is to increment the expression called FrameNumber by 1 for each successive frame of the animation.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

Yes you are right in this case, but the actual question was related to engine assembly which has got some more complex relations impossible to create with assembly constraints/mating conditions so motion of main parts (all excluding springs) have to be "imported" somehow from motion simulation application.
Best Regards, Koen

RE: Spring compresion in motion simulation in NX5

Take a look at the videos page of my website. The engine there is also reasonably complex. The motion is nevertheless achieved by the use of mating conditions and expressions. The only trick involved is to articulate it by rotating the flywheel or crankshaft. If you try to do it by reciprocating the pistons they always get stuck at top dead centre (i.e. either end of the stroke).  

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

Hello Hudson 888,

I have taken apart your example, and can recreate everything. Accept this last expression... I have attached a screenshot of the item in question.
I am running NX5, and the screenshot is in assemblies.

this expression should be the last piece to the puzzle,
any help would be greatly appreciated  

RE: Spring compresion in motion simulation in NX5

Page3,

Please take a look at my post above dated 11 Mar 09 19:20 since I found after much going back and forth with the other posters that it is likely that what works with mating conditions in this instance will not operate correctly when you employ positioning constraints instead. I have yet to hear anything from other posters to indicate that if done differently it can be yet be achieved.

My example works when I use mating conditions. Then when I change the customer default settings in NX-5 and allow it to automatically convert the mating conditions it still works. However when I try to construct the same example from scratch then it will not allow me to build the expression that links the length of the deformed spring with the measurement between the two ends.

You appear to have hit the same hurdle my earlier posted example (8 Mar 09 20:00) using mating conditions may be better suited to your needs if you're not already heavily vested in positioning constraints. Sorry if you feel you were mislead it appears that I had assumed that the functionality would be equivalent and indeed I was surprised when I discovered what appeared to be a deficiency.

I have suggested that if this is the case then I would obviously request that this functionality be catered for and a fix or an enhancement to bring the level of positioning constraints capability into line with what I'm able to do with mating conditions. I can only suggest that I would be more than happy to welcome anybody who proves me wrong on this. Maybe it is I who am using positioning constraints wrongly? Thus far all is quiet.

P.S You're better to attach Jpegs to your posts in the future since the bitmap format is larger and therefore less efficient.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

Hudson,

I just found the mystery expression, If you right click the spring and select 'deform' a window pops up and you can select the deformable part created when first defining the spring. then attach it to the distance measurement.

Now that I can deform the spring, I can apply it to the big  project :P

I have attached the assembly I made while following along with yours. It is very very simple, just to show the springs deformation.


thank you Hudson for responding so quickly, and for providing such a solid example to use in the first place

 

RE: Spring compresion in motion simulation in NX5

Page3,

Yes I'd very much expect that example to work despite what I said earlier. I hope we get to the bottom of that other thing but for what you're doing I can see it working quite easily.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

(OP)
Hello Hudson,

I used positioning constraint in my assembly and it works perfectly. The problem I had regarding not being able to deform the spring during the animation was that I defined the spring to be deformed in a specific range in the third step of defining the deformable part.
Thanks to you for your help in this regard.
By the way, I am still not able to animate the deformation in motion simulation. Is there any further help on the way smile

RE: Spring compresion in motion simulation in NX5

akrah,

I don't know whether motion simulation actually has any other means by which it would be better to deviate the spring. In other words you might constrain all the rest of the assembly with the motion solver for whatever reason, and yet still employ a measurement between the elements at either end of the spring to drive the deformation.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

I think its not possible in motion simulation module from the simple reason - expressions from basic assembly (like spring height or measurments) are not being updated in motion solver.

Hudson,

Nice website, I wish I had such job after I graduate :)
Anyway back on topic, I managed to animate all gears in my assembly using angular constraints and framenumber expression, but I have a problem with cam followers touching cam ring (see attachment). Its not a problem in motion simulation (Im using curve on curve constraint) but in assembly, I can't set a constrain betweet cam follower surface and cam ring surface, because I can select only one face on cam ring, and it consists of 2 faces. Do you have any advices how do to this?

Best Regards, Koen

RE: Spring compresion in motion simulation in NX5

Disclaimer: I have never applied constraints to a cam and follower(s). If the problem is that the cam consists of 2 faces, here is what I would try: you have 2 tracks on the cam, can you split that into 2 cams so that each side has its own track? If so, you are still left with the problem that each track will be made of multiple faces. To minimize this you can remodel the outside shape of your cam track with spline(s) (or use join curves on the geometry you have - essentially the same idea) so that it is only 1 face.

RE: Spring compresion in motion simulation in NX5

cowski,
 Your solution works perfectly! I extracted the edge of my cam, joined curves, extruded new shape and moved to reference set. I dont know how to thank you guys (hudson888 and cowski), you were really helpful :)
I'll post a link to the movie when I put everything together.

Best Regards, Koen

RE: Spring compresion in motion simulation in NX5

I would have suggested the same. For an animation you'd create a piece of construction geometry for mating (constraining) the CAM contact and hide it out of view on another layer and/or with reference sets so that you get around that single face requirement.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

Hi all,

I read this thread accurately. I experienced the same problems with springs both with animation or as deformable part in the assembly. Everything started when i had to design switch with torsion spring. To create torsion spring is very easy even with nx2 (now we are on nx4 and preparing to move on nx6). The main problem is to position and assemble it to the assembly. Note, that in most cases in the assembly spring must be compresd, and this compresion depends on your assembly. So if your spring is defined as deformable part, before defining assembly constraints for the spring you must have a certain value as parameter for deformation (e.g. measurment value, or already existing positioning value).
Then you must define, how realistic will your spring be. Then the spring compress, it tries to roll around its axis, so torsion ends will became shorter/longer. This can be easily calculated.
But then you combine both deformable part and physics of the spring, simple torsion spring becomes to a bunch of curves, expressions and of course errors :)
I have some discusions with mr John R. Baker about deformable parts (not here, but in bbs.notes forum). And its clear, that deformable components (especialy springs) is one of the most complex parts of the nx.
How to create torsion spring it is another story. Because i had lot of problems with tangency of the curves (e.g. it is quite complex to add tangent line to the one of the end of the helix curve. It is quite difficult to describe it here, but if you try to create smth like in the attached picture, you will see).

 

RE: Spring compresion in motion simulation in NX5

Oh boy have you got some stuff to look forward to if you thing that's complex! There's plenty more where that came from .

They can be a little tricky though I don't think that there is much doubt about it. The fact is that most people approximate in one way or another when they undertake to create such a spring and the subtle changes as it deforms are frequently overlooked. We could spend time arguing as to whether the axis of the coils ought to be aligned with the axis of the shaft, or whether the arms at either end lie on parallel planes or tend to twist as the spring flexes. The differences are small and nobody much notices until that is you need to construct a CAD model and you can't quite hit on the best thing to do first time around.

The fact remains it usually only has to look relatively correct and support a drawing, while for deformations in an assembly you can approximate. Mathematically it would indeed be awkward, but if you can model the spring with deformable parameters that duplicate the boundary conditions in your assembly then you can deform it. If on the other hand the boundary conditions can vary from one application to the next then you can't guarantee that the deformation will be identical.

There are however a lot of constructional tricks that you could use to develop associative sections that might work with a certain amount of fuss and linked geometry in order to arrive at measured expressions that you could get quite close to working. I suspect it is a lot of trouble to go to for one of these springs but it ought to be possible.

I think this example looks doable but time consuming.  

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

RE: Spring compresion in motion simulation in NX5

Hi Eex23

I saw your post regarding the torsion spring and I am still having problems with elements of the torsion spring not updating when using the deform command. Would it be possible to see the .prt file of the torsion spring to see how it's done?

Regards

 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources