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# Parametric Curve Extrude.

ethan_ofondo
Member Posts:

**3**✭
Hi,

I have been using the Parametric Curve Feature Script, but I can't seem to use the curves for anything useful in my model.

For example, I cannot extrude a plane from the curve, or use multiple curves to define an area to extrude on an existing surface.

Below is a screenshot of what I am trying to do. I have two equation-driven curves that have been defined in the x-y plane, where the z coordinate matches that of the extruded surface that is visible. I am now trying to remove material between the two curves. Any suggestions?

I have been using the Parametric Curve Feature Script, but I can't seem to use the curves for anything useful in my model.

For example, I cannot extrude a plane from the curve, or use multiple curves to define an area to extrude on an existing surface.

Below is a screenshot of what I am trying to do. I have two equation-driven curves that have been defined in the x-y plane, where the z coordinate matches that of the extruded surface that is visible. I am now trying to remove material between the two curves. Any suggestions?

0

## Comments

8723✭7PROI'm trying to do the cartesian equation for a cycloid curve. I originally had two parameters, but now am typing in the Radius of the generating circle (248mm) and keeping it to one param.

248mm*(acos(1-#y/248mm))/deg*pi/180-sqrt(2*248mm*#y-#y^2)

I feel like such a noob.

Here is the equation:

Anyone feel like attaching the electrodes of knowledge on me?

Mike Everman

7PRO7PROBest regards,

Mike

1,110I think the trouble you're experiencing is probably that you need an independent variable that represents the parameterization of the curve.

In this case lets pick an arbitrary variable "t", and say that "t" moves from 0 to 2R (it seems that this is the domain of this function).

Then we need to define x, y, and z in terms of "t".

z is easy. It seems like you're trying to plot this in 2d, so we can just say that z is 0.

Since y appears to be the driving factor in your equation, we can say that y is t.

Now, we can set x to R*acos(1-t/R) - sqrt(2 * R * y - y^2).

Due to the fact that t should be a unitless parameter, I will divide t by some arbitrary unit (here I am choosing inch) for the definition of the range of t, and multiply by the same arbitrary unit everywhere I decide to use t. So the parameters will actually look like:

t is 0 to (2R / inch)

X is R*acos(1- (t * inch)/R) - sqrt(2*R*(t*inch) - (t*inch)^2)

in Onshape syntax: #R*(acos(1-(#t*inch)/#R)/radian) - sqrt(2*#R*(#t*inch)-(#t*inch)^2)

Y is t * inch

Here it is an a part studio:

https://cad.onshape.com/documents/223a8b97a2f7f469664b4bd5/w/d48f2b3f6a952d52981f6990/e/ff814e7f9f5409604eceff8d

Hopefully this curve looks similar to what you were looking for?

7PRO7PRO409