Hypocycloid & Epicycloid 1

[IvanNX]

what is right NX expression for
hypocycloid
i tried with:
xt=(r*(k-1)*cos(2*pi*t))+(r*cos((k-1)*(2*pi*t)))
yt=(r*(k-1)*sin(2*pi*t))-(r*sin((k-1)*(2*pi*t)))

where t is automatic NX variable from 0 to 1, r is small radius, k is predefined integer and pi=3.141592653589793238462643383279

& Epicycloid
i tried with:
xt=(r*(k+1)*cos(2*pi*t))-(r*cos((k+1)*(2*pi*t)))
yt=(r*(k+1)*sin(2*pi*t))-(r*sin((k+1)*(2*pi*t)))

 

[JohnRBaker]

What version of NX are you running?

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
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To an Engineer, the glass is twice as big as it needs to be.

 

[IvanNX]

NX 8.5

 

[JohnRBaker]

BTW, you do not need to create your own expression for Pi, simple enter the function 'pi()' and you'll get Pi to the system tolerance.

Are you simply trying to create curves or a 3D body? I ask because there is no direct function, that I'm aware of, to create a body using 'laws' (formulas).

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[IvanNX]

I need only curves. i will use them for linking to other parts where i will make solids.

 

[JohnRBaker]

Have you looked at the various Law Curves available in the Reuse Library's folder labeled 'Reusable Object Library'? They might have something there which will get you started in the right direction.

But if you're goal is actually something a bit more complex, look at the attached visual basic program, 'BlobDialog.vb' (which you can execute as a Journal). This program will create a 'hemispherical' sheet body using conic profiles. If you enter a Rho value of less than 0.500, the profile curve used will be an Ellipse, if the Rho value is greater than 0.500, the curve will be a Hyperbola, and if it's exactly 0.500 than it will be a Parabola.

After downloading the file, change the extension from .zipper to .zip before extracting the visual basic program.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[IvanNX]

actually i need hypocycloid and epicycloid for this...
can you find errors in my formulas as i do not know what i did wrong, but i do not get curves that i need...

i am not sure if i am allowed to post link to wikipedia where you can find math formulas for these curves, so you can compare it with my equations?

 

[JohnRBaker]

I've never seen anyone object to links to Wiki items as long as they're not patently incorrect or misleading.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[loki3000]

you are allowed to post link to wiki/ etc. also post the part file itself, JBaker works @siemens, he might be able to help you out.

 

[JohnRBaker]

OK, the problem is that the 'trig' functions in NX, such as SINE and COSINE, use degrees and NOT radians. Simply replace '2*PI' with '360' and you should be good to go.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[IvanNX]

ok... i am idiot! thank you John!

 

[JohnRBaker]

No, you're not an idiot. When we first implemented the Trig functions there was a debate as to whether we should use Radians or Degrees. I was one of the people who voted for 'Degrees' since that's what we used when you entered an Angle in modeling so I felt we should be consistent, besides, many people are just not all that used to using Radians. But is you really need to, there are functions that convert Degrees to Radians as well support for both Radians and Degrees when you're creating expressions with Angle units.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.