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JDMather
Posts: 26,186
Registered: ‎04-20-2006
Message 1 of 3 (1,221 Views)
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3d sketch equation curve

1221 Views, 2 Replies
03-17-2013 03:02 PM

I'm just starting out with learning equation curves in Inventor.

 

How can I get this curve

r(t)= ti + 4cos tj +9sin tk; where t is greater than or equal to 0

 

I would also like to figure out how to get this VBA as an equation curve

(see attached file)

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GlennChun
Posts: 115
Registered: ‎06-10-2004
Message 2 of 3 (1,181 Views)

Re: 3d sketch equation curve

03-17-2013 11:12 PM in reply to: JDMather

JDMather wrote:

How can I get this curve

r(t)= ti + 4cos tj +9sin tk; where t is greater than or equal to 0


 

Hi JD,

 

I will use five turns for the elliptical helix for illustration purpose.  Enter the following Cartesian coordinates in the Equation Curve command:

 

x(t) = t

y(t) = 4 * cos(t)

z(t) = 9 * sin(t)

 

and you will see this elliptical helix:

 

eq_crv1.png

 

Or a much thinner curve:

 

eq_crv2.png

 

Note that the parameter t is unitless, but the sine and cosine functions can take angles in either radians or degrees.  When rad or deg is not specified inside sin() or cos(), the angle unit from the Document Settings is used.

 

angle_unit.png

The first and second curves above use radians and degrees, respectively.  I believe that the first curve is what you want to create.

 

You can check the Show units option to see all the hidden units.

 

eq_crv3.png

 

eq_crv4.png

 

The following example shows a bad practice in my opinion. Degrees are used in sin() and cos(), and the parameter t is converted from degrees to radians.  It sort of works but could be confusing and misleading.

 

eq_crv5.png

 

I think it's better to specify the angle unit explicitly in sin() and cos().  Simply add 1rad* or 1deg* inside the function.  That will override the angle unit specified in the Document Settings

 

eq_crv6.png

 

Also, beware of equations that imply the number of turns.  Two examples are shown below.

 

eq_crv7.png

 

eq_crv8.png

 

Hope this helps,

 

Glenn

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*Expert Elite*
JDMather
Posts: 26,186
Registered: ‎04-20-2006
Message 3 of 3 (1,134 Views)

Re: 3d sketch equation curve

03-18-2013 07:44 AM in reply to: GlennChun

Thanks, this is great.

 

Pulled out my college Calculus book from 30 years ago and started recalling all these curves we plotted out by hand.

 

Do you guys realize what you have?

I think a lot of facutly still think of Inventor as an electronic drafting board - something beneath their status.

This is a full fledged engineering tool not just a specialized field (MCAD) version of AutoCAD.

Far more interesting than using a graphing calculator and certainly more fun that plotting by hand.

 

I think you guys should find the most popular physics textbook in use and set up all the problems in Dynamic Simulation (or whatever simulation tool needed).

Find the most popular calculus textbook in use and set up all the relevant problems in Inventor.

Make this stuff more interesting.  Make this stuff real for the 21 century.

Somebody is going to do it (a lot of related iPhone apps already appearing).

You could create a comprehensive engineering education tool that would revolutionize the way this stuff is taught.

My daughter went to all electronic books this semester.

You guys could own this (engineering education for the 21 century).

Please mark this response as "Accept as Solution" if it answers your question.
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Autodesk Inventor 2014 Certified Professional
Autodesk AutoCAD 2013 Certified Professional
Certified SolidWorks Professional
Inventor Professional 2015 64-bit
http://www.autodesk.com/edcommunity
http://home.pct.edu/~jmather/content/DSG322/inventor_surface_tutorials.htm

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