coil spring equation

[megaladon]

i down loaded the coil spring form the archive here and am trying to change the size ofthe inner and outer overall diameters and maybe number of coils etc...not to familiar with the equation form in pro-e here is what it says





x = ((DIA_INNER / 2 + PITCH * NO_REVOLUTIONS * t) * cos ((NO_REVOLUTIONS * t) * 360))
y = ((DIA_INNER / 2 + PITCH * NO_REVOLUTIONS * t) * sin ((NO_REVOLUTIONS * t) * 360))
z = 0


note when i changed the 2 to 1 it got bigger.


1 last thing when i redefine the csys type i am unsure which type it is


i tried to recreate this part first by copying the above formula with all 3 types of csys and none work.
Edited by: megaladon

 

[megaladon]

just wanted to add something. if anyonehas a web site bookmarked on where to get information from pro-e to writing equations or has any could you please post a link to them im sure i just need look on the inside cover of some of my books for them but need to know if pro-e gets picky about how they are written.


thanks again

 

[dr_gallup]

This part obviously has some parameters defined that you are supposed to use to control the size. Change the values of parameters DIA_INNER, PITCH and NO_REVOLUTIONS to control the part, leave the relations alone for now. There is probably another parameter for wire diameter, maybe some others.

Csys are all 3 types at once, you don't specify the type in the csys, only in the features that use the csys. So you can use one csys and use it to make 3 datum curves by equation that use all 3 different csys types.

There is something wierd in your equations, Z=0. Normally this would be a function of t. Post your part or a link to the download so we can take a look at it. Since the introduction of the helical sweep that has become the standard way to make most springs.

 

[megaladon]

[url]http://www.mcadcentral.com/proe/files/gallery.asp?action=bro wse&categoryid=49&whichpage=5 [/url]


View attachment 1362


"Csys are all 3 types at once, you don't specify the type in the csys, only in the features that use the csys. So you can use one csys and use it to make 3 datum curves by equation that use all 3 different csys types. "


how can they be all 3 at once might need to explain that 1 a little more to me. i was assuming they would have used cartesion bc its not growing in the z direction

 

[dr_gallup]

OK, it is a flat coil like a watch spring, not a compression or extension spring. That explains the Z=0 part of the equation and why helical sweep was not used.

The csys just defines the location and orientation, the coordinate type is defined in the curve by equation feature.

Select the curve_spring feature and right click, pick edit definition. Select Csys Type and pick define. You will see that you can use the Csys as either Cartesian, Cylindrical or Spherical. The current equations are written for Cartesian coordinates which use x, y & z variables. If you change the csys type to Cylindrical, you will have to rewrite the equations in terms of r, theta and z. Changing to Spherical will require new equations in terms of rho, theta and phi.

The equations you have are obviously valid for a cartesian csys so I don't know why it did not work for you. Make sure you copied them exactly, no missing ), etc.

 

[megaladon]

that answered almost all of my questions


the one last question i have is do i need to change it to modify the size of it


this is exactly the part i need but dimensionally off a bit

 

[dr_gallup]

Some things can be changed in tools/parameters. You can change the inner diameter, pitch and number of turns there. The rectangular cross section is changed by picking the COIL feature and editing it. The start & stop ends can be changed by editing the CURVE_SPRING_ENDS feature.

I don't see any need to change the equations but you can if you want to explore how it works. It is a simple thing to rewrite the equations for cylindrical coordinates just as a learning experience.

r = dia_inner / 2 + pitch * no_revolutions * t
theta = t * 360 * no_revolutions
z = 0

 

[megaladon]

thanks gallup


this is what i ened up doing. made an assembly bc not sure if i could make another feature in same model using parameters unless i renamed thing s like inner dia... etc


View attachment 1370

 

[Zaki]

Hy Megaladon
In your fist question, the csys is Cartesian and u must make dia_inner, pitch and no_revolutions perameter (real number type)
Then u can control the sizes with parameters and it is working properly. If u wanna check u can!!!
Zaki ur Rehman<?:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" />