# sinusoidal path on a cylinder

#### mmartel

##### New member
How can I write an sinus equation to create a trajectory on a full cylindrical surface with such a shape?

#### eServ

##### New member
I am not 100% sure, but have you tried: Create>Datum Curve>From Equation, select default CSYS, select Cyndrical, enter equation?

#### eServ

##### New member
Or have you tried creating a Formed Datum Curve and then sketch the sinusoidal curve and then write relations for in terms of Theta, r, and z.

#### proed

##### Moderator
There's more about using graphs in features here:

http://www.geocities.com/proehelp/model.htm#gra

Example:

Say you need to add a cut with a sinusoidal profile, or you need a raised profile based on a graph ... how do you model these?

> Use sketch relations or datum graphs to control these features...

Trajpar & graph versions are covered, plus 2 PTC example links.

##### New member
Try this :

Cartesian equation

x = 2 * cos ( t * 360 * 4 )

y = 2 * sin ( t * 360* 4 )

z = t * 3

the number 2 representing the radius off the spiral

the number 3 pitch

the number 4 number off coils

Regards

#### jbuckl

##### New member
Hello MMartel,

There is a difficulty in using the sinusoidal cut on a cylinder:

Detailling it requires that you draw a graph so the part can be manufactured.

We have had parts manufactured from drawings where the model included a graph (also shown in the drawing) The graph is made to fit the cylinder using trajpar.

This modeling technique is in the PTC knowledge base, search under CAM. (the parts made like this worked well)

#### Kloser88

##### New member
I had the same problem! Do it like this:

insert/datum/curve/from equation - done

Select your coordinate system (make sure it points where you want it!)

Select Cartesian coordinates

Equation example:

x = 50 * cos ( t * 360 )

y = 50 * sin ( t * 360 )

z = 25 * sin (t *360 * 4)

Where the number 50 in the x and y equations represent the radius of the circle, 25 in the z equation represents the amplitude of the fluctuation and 4 represents the number of sine waves on the cylinder.

Hope this gets you going!

Kloser88