Thank you

Mac Baker

President

Richmond SWUG

We've got the need to develop an involute curve using real
math. We have found functions to define the curve now we just need
to know how to use them to develop the gear tooth in SolidWorks.
Anyone have a way to do this?

Thank you

Mac Baker

President

Richmond SWUG

Thank you

Mac Baker

President

Richmond SWUG

- Create sketch points in a model based on the equations you described. Connect those points using a fit spline. Or, consider Gear Trax http://www.camnetics.com/GearTrax.htm

- An SW spline does not have the same mathematical DOF's as an involute. If you "connect the dots", there will be some error.

I have made gear tooth profiles using the "unwrapping" method to set up defining points. The involute follows the path of the end of a string being unwrapped from the base diameter (base diameter <> pitch diameter but can be found w/ combination of pitch diameter and pressure angle).

I have a gear model at http://www.esoxrepublic.com/models/ A bit cumbersome, but it worked for its purpose. It uses the unwrap method. Also, the profile is mirrored so the curvature of the resulting spline at the root is not thrown off by spline end conditions. - Error would decrease with the number of points supplied to the fit-spline. As far as quantitatively how many points you would need to get an acceptable error level - I don't know. Any idea Roland?? With the end condition... you could supply involute points past the tip of the tooth and include those in the fit spline. Then you could cut off the spline at the tip of the tooth and that would negate the end condition there... Alot of work. Thats why I mentioned Gear Trax. I'll check out your gear that you did using your method. Curious...
- Has anyone been able to create an involute curve in SolidWorks using the new
*Equation Driven Curve*

When does SolidWorks plan to offer a equivalent of Pro-E's Variable Section Sweep function? This is one area of surface creation I have not yet seen matched by SolidWorks. The VSS is also good for sweeping a draft angle along a split line. In SolidWorks, this requires multiple guide curves for the sweep function.

I have a model of a spur gear in Pro-E that serves as a start part for creating new gears. The involute curve is equation driven (VSS w/ trajpar), and so far I have not been able to recreate this gear in SW.

Regards,

Chris Thompson - Lin and all,

What about an equation that approximates this one? A ploynomial expression that approaches this?

http://www.me.ynu.ac.jp/labora...aekawa/involuteEWC.pdf Peter Yodis wrote:

Lin and all,

What about an equation that approximates this one? A ploynomial expression that approaches this?

http://www.me.ynu.ac.jp/labora...aekawa/involuteEWC.pdf- Sorry Lin... Looks like SolidWorks new curve from equation will not work with parametric equations. Ashame. It seems very handicapped. Maybe its been done on purpose to keep it from encroaching on some add-ins turf - like GearTrax. Or maybe we need to keep paying subscription money to get the eventual working version in 2011 or 2012. New features seem to be teasers of what could be possible if we just kept paying our subscription money. They string us along...
It is sad to see that this question had been asked back in 2008 and yet there is no clear answer to it.

One might needs to make a fully parametric mechanical design including different involute gears in SW, and unfortunately it seems to be impossible at the moment. at least I haven't been able to do that. What I have done so far:

1. tried using "equation deriver curvatures" option with the equation x=r_b*(sin(t)-t*cos(t)) and r_b*(cos(t)+t*sin(t)). apparently I am making some mistake while importing the list of equations and variables from an external file and for that reason it does not work.

2. I tried recording the steps in a macro. but as far as I have understood the visual basic script takes the equations as strings. so one needs to go through a lot of hassle to edit those string to match with value of the base circle diameter.

I put the equations, the visual basic macro and model itself here for others. maybe it can help you, or even you are able to resolve the issue!

P.S. apparently SW forum has removed the option to attach files!!! please find the files here

P.S.1. No Seriously SW team, everybody is going forward and you are going back?! even the open source CAD software FreeCAD now has the option of fully parametric equation curves!

The attached is based on:

Modeling an Equation Driven Involute Spur Gear in Solidworks - YouTube

That should get you enough information to get started. Though in 2014 SW the attached model doesn't work for all cases. It's been a while since I looked at it, but I think it had to do with the base and root circles. The attached gear doesn't work if they switch places.

However, if you are doing this for a production part, you may look into an aftermarket add-on.

thanks for the immediate reply. Meanwhile I tried it again in a new file and it did work!!! as I have explained in other commects I import the list of variables from an external file and the ones imported can't be used!!! but when I define new variables manually they can be used. It is now very confusing because other people have also reported that this feature has been removed!

Look in the Help File, Insert Curve.

Use an Excel spreadsheet to calculate the x, and y points. Then in SolidWorks Insert a Curve based upon the generated data points.

Also, do a Google search on the Add-In software for SolidWorks called GearTrax, an application to generate Gears and Tooth Profiles.