difficulties in torsion spring

[vinoth]

hi

how can i make the leg of the torsion spring is flexible to the assembly? please note am nat asking about dynamics mechanism. in a standard assembly i need to fix the torsion spring in a practical method, i mean by deflecting the two legs. how it has to be done in an assembly?

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[Dale_Rosema]

Unless you have an answer already, you may have accidentally marked you discussion as having an assumed answer.

The way I have done this before is to have two instances, the free state, and as assembled.

Thanks,

Dale Rosema

[vinoth]

hi Dale rosema

i think thats not a right way to do that.

[BrianMartin]

Hi Vinoth...

You can set your torsion spring to be a Flexible Component. As a part, the spring can appear in it's relaxed/unsprung state. At the assembly it can appear under tension to mimic the actual installed state. Check out Flexible Components in the help files.

There are several ways to go about setting a flexible component. You can flex it by measurement, by modifying a dimension, by suppressing a feature, by varying a parameter, etc. Depending upon what you're trying to achieve, you may want to use one of these techniques over the others.

If you need a quick tutorial, I may be able to whip one up. Take a look at the help files and let us know if you need additional assistance.

Thanks!

-Brian

[TomD.inPDX]

Found this... might help.

http://www.ptc.com/appserver/wcms/standards/textmultitextimg.jsp?&im_dbkey=13764&icg_dbkey=382

[vinoth]

Hi brian

thanks for ur reply..

S i found some help files, to make a flexible in torsion spring the deflection angle of the leg must be controlled, if i make a spring using helical sweep or variable section sweep (with trajpar relation). i cant able to control leg angle. i want to control it without any loss of no of coils, how did u do that ?

Thanks,

vinoth

[BrianMartin]

Hi Vinoth...

I think the answer is all in the modeling of the spring. You have to model the spring in such a way that you've incorporated the leg control angle. If there's no dimension controlling that leg angle, you can't make the angle "vary" using Flexible Components.

When you say you want to control the leg angle with no loss of coils, what do you mean? You're going to get a little "uncoiling" of the spring as the leg angle changes. I'm assuming you're okay with that, right? This is a normal characteristic of a torsion spring. What I'd be worried about is total length. You want the spring to coil and uncoil as the leg angle varies without total length of the spring changing.

There are various ways we can achieve this... it all depends on how you model the spring. For example, you could model it in such a way that as the spring "uncoils", the coil diameter increases a bit. You can also keep the coil diameter absolutely fixed and allow the leg to grow ever-so-slightly in length as the spring uncoils.

It really does depend upon the spring model itself and the behavior you're trying to capture. I'd always try to mimic the real world characteristics as closely as possible. I don't have a torsion spring handy to see exactly what happens when the spring is flexed. Assuming you do have one, I'd carefully examine how it moves and flexes and develop a model to mimic this behavior.

Can you make a simple picture showing which leg angle you want to vary... including any other pertinent dimensions. For example... if you have a spring diameter, spring wire size (OD of the wire itself), leg length, number of coils, etc. please include those things. With that information, I can probably make the model you need and send it back to you so you have an example to work from.

Also... what version of Wildfire or Creo are you using?

Thanks!

-Brian

[vinoth]

once again thanks brain

am using wildfire 5.0

here the parameters of the spring

wire dia : 1mm

no of active coils : 4

leg length : 35mm

OD:10mm

at free state it should be in 90deg

deflection angle: 35deg

[SylvainA.]

Hello Vinoth,

if I had to do this kind of spring, I would have done it this way:

1. helical sweep to model coils

2. protrusions on both ends of helical sweep to model legs

3. adding a relation between legs angle, length of coiled section and diameter:

Assuming that legs length=constant, pitch=cstt, wire Ø=cstt, no space between coils, length is growing, diameter is decreasing.

(See: http://www.mitcalc.com/doc/springs/help/en/springs.htm , §Helical cylindrical torsion springs )

Dl=D*n/(n+alpha/360)

Ll=Lk+d*alpha/360

Dl: Ø loaded

😧 Ø unloaded

n: number of active coils

Ll: Length loaded

Lk: length unloaded

d: wire Ø

alpha= angular deflexion (your driving parameter)

Your helical sweep profile have to use Dl, Ll and d (pitch=d).

Hope this will help (and that I've made no mistake ).

[vinoth]

Thanks Arjona

i will try this one , this sounds good

[SylvainA.]

You're welcome.

PS: My first name is Sylvain

[vinoth]

oh! sorry sylvain

[vinoth]

hey sylvain

i tried that one, i can't able to give this relations i found some errors.

will u please help me. am i did that in a right way ? i dont know. here i shared the screen shot

[SylvainA.]

You have to create all used parameters first. (in Tools>Parameters>+)

Then you have to set the driving parameters (n, Lk, d, spring_d, alpha and so on...) in the parameters window.

I also see inconsistencies in your relations:

First, you have to know that relations are read from top to bottom.

Thus when you write Dl=(d8*n)...... and in the last but one line Dl=d8-d5 , the first relation becomes useless.

The relation Lk=d0 has to be deleted. Lk parameter's value has to be set in the parameter window.

When you write d=d5 you are assigning the value of the dimension d5 to the parameter d. Don't you want to do the opposite?

If you want the dimension d5 to be equal to the parameter d, you must write d5=d.

You can get rid of some parameters if you write d0=Lk+d5*..... (if d0 is the length of the helical sweep and d5 its pitch) and d8=spring_d*n/..... (if d8 is the diameter of the helical sweep)

Have a look at all of your relations and it should work.

[BrianMartin]

Hi Vinoth...

Sylvain's method is very close to the one I was going to use to model the spring. I think we're both thinking about approaching the problem in the same way. I'll write back when I have a model to share.

Thanks!

-Brian

[vinoth]

s ur right brian

Thanks for ur support!

-vinoth