Involute gear and profile correction?

[Vezku-]

Hi!

I

 

[Miko]

Hi Vezku I worked on the Willson planetary gear-box earlier but I really dont know about abilities of this kind in Wildfire. For what exactly do you need something like that? If you need this for motion analyses than it is not important (I think those corrections). When I worked on gears in my assembly, I used curve definied by equation as profile curve. For mechanism connections I didnt use any corrections and I dont know about some equation with correction, but of course in hand made calculations I used it exactly.
Hope this help you.
Edited by: Miko

 

[Miko]

And maybe these links will be useful for you.

here you can see my animation of Wankel engine:

http://mcadcentral.com/proe/forum/forum_posts.asp?TID=30539& PN=1

and here is the animation of Willson gearbox:

http://mcadcentral.com/proe/forum/forum_posts.asp?TID=24917& PN=2&TPN=4

http://mcadcentral.com/proe/forum/forum_posts.asp?TID=24917& PN=2&TPN=3

 

[Vezku-]

That part would be manufactured with lasercutter, so the shape of that gear should be 100% correct.

Looks like that i have to scan that gear to get the right shape.

 

[JRay]

Vezku,read the article in the attached link. Hope it helps.


http://www.profilesmagazine.com/p33/marsalek.html

 

[brchapman]

Most gears are modified from there standard values to improve there performance. The bending strength can be greatly improved by "Thickening" the gear tooth. When a tooth is modified, the profile correction factor "k" is defined as follows.


K= (tP-pi/2)/(2Tan(phi)) where


t= tooth thickness at the standard pitch diameter.


P= diametral pitch


phi = Standard pressure angle.


The standard or unmodified tooth thickness = pi/2*P. As you can see from the equation, this case leads to K = 0,when the tooth is not modified. As "k" increases, so does the tooth thickness. Remember that the O.D. of the gear, and the Center Distance of the operating gear pairalso changes. The O.D. of the gear should be the standard O.D. + (2*k)/P.


The center distance should be the standard center distance + [(K1/P)+(K2/P)]


(K1 being k of gear1 etc.)


When you model the gears, calculate your tooth thickness and diameters first. Then model the gear accordingly. You will model it just as you would a standard gear, but make the tooth thicker by the amount you calculate.


If you are working in modules instead of DP, remember that m=25.4/DP


I hope this helps you out.

 

[Miko]

Thank you for info brchapman.
wezku> does your gear have less than 17 teeth? If does then use correction if doesnt than your correction is useless. Or, do you need this correction for better performance and properties of gear or why? < Just for my info.

 

[brchapman]

Miko,


You are welcome. You are also correct to have concern for external spur gears with a small number of teeth. The problem comes from the cutter geometry, which will start to undercut the root of the tooth when the number of teeth gets small. There are many factors to consider when designing a gear, but, as a rule of thumb, undercut wont be a problem when you have 14 or more teeth and are using a standard cutter that is cutting a standard or enlarged addendum gear. If the cutter (Hob, shaper etc.) has an enlarged addendum, or your gear has less than 14 teeththen the exit point of the hob tip should be compared to the path of contact to ensure no involute profile is removed. "Pulling" the cutter (Using a positive correction factor) will usually help reduce the undercut. Just make sure you don't pull your cutter so far that the teeth become pointed! Also remember that you will be increasing your operating Pressure Angle as you enlarge your gears. Another thing that really helps the bending strength of your gear, whether it has a high or low number of teeth, is to use a full fillet cutter (2.335/DP for 20 deg. P.A.). This will greatly reduce the bending stress of your gears and increase there life.

 

[Miko]

brchapman

I am a student at university - faculty of special technologies and engineering. I know some things about this issue, but I have to say that I really appreciate your offer. I please do not forget at the PITTING check of gears.

 

[pubi2cv]

Hi!


I have made an involute gear with correction some time ago with proe 2001, but normally it work in wf2 with no problem too. There is no teeth number limit and correction works perfect. The involute profil is made with the equation and everything works parametric, so there is no need to change anything except the desirred input data (like modul, no. of teeth and the profile correction). I've spent quite a time doing that....but I'm satisfied with the result. I can get an involute head gear of any size in few secunds

The only thing I heaven't done is undercut in case of small nr. of teeth, but there is no problem to add it to the model now when it's done.


There is an example with 15 teeth and correction factor x=0,3

Edited by: pubi2cv

 

[Zaki]

HY PUBI2CV


WOULD U LIKE TO POST UR PART HERE?? IT SHOULD USEFULL FOR ALL

 

[Vezku-]

Great work Pubi2Cv, but would you like to post the equation that makes profilecorrection possible in involute gear?

 

[pubi2cv]

No problem, i can do that. I hope that You will not have to many problems with the following language....I bealive You guys don't speak Slovene

There it is:


2006-05-12_075209_zobnik_celni_ravni.prt.zip

 

[jake_mci]

There is another thing to watch for if you are planning to lasercut this part. Some lasercutting software uses .dxf format to importthe geometry. If you are cutting gears that are quite large, you can run into a problem with how Pro/E exports the involute curves and end up with a rough / faceted edge. The tooth profile is no longer a smooth curve and is made up of a finite number of points.

 

[RyanHarris]

Involute gear cutters are a type of form tool and are used to generate gears in hobbing machines. Involute gear cuttersalso differ in types, size and shape. Since, gears have to work a lot of in tandem with each other, a lot of friction happens and heat is generated. What come in handy at this time are involute gear cutters, which help create gears that have with their high level of precision and efficiency.Involute gears power the most powerful brakes of the airplanes and at the same time achieve efficiency by reduction on amount of heat produced.


Fore more information please visit capital-tool.com/milling-cutters

Edited by: RyanHarris

 

[SRINIVASANIYER1]

I didn't find time to read the earlier replies. So excuse
me if I am repeating

Gear corrections are either S0
or S1. Either way the involute profile is a function of
the base circle which remains constant. It is only the OD
that change. In case of S0 correction, the pinion (smaller
gear) undergoes a Positive correction; meaning larger OD
than normal and the Larger gear undergoes an EQUAL
negative correction. The whole depth remains the same.
Corrections are done for various purposes, e.g to prevent
undercutting, to increase contact ratio etc.

 

[ME-BAC]

Hi!


I have made an involute gear with correction some time ago with proe 2001, but normally it work in wf2 with no problem too. There is no teeth number limit and correction works perfect. The involute profil is made with the equation and everything works parametric, so there is no need to change anything except the desirred input data (like modul, no. of teeth and the profile correction). I've spent quite a time doing that....but I'm satisfied with the result. I can get an involute head gear of any size in few secunds

The only thing I heaven't done is undercut in case of small nr. of teeth, but there is no problem to add it to the model now when it's done.


There is an example with 15 teeth and correction factor x=0,3

Edited by: pubi2cv

If you want to do some experiments with correction of gears, go to Mechanical software and web applications | ME-BAC, there is a web app to create corrected spur gears.

 

[dross]

Spam!!
Take it elsewhere!!!

 

[ME-BAC]

Spam!!
Take it elsewhere!!!

Dear Dross, my application is not spam, it's a free web application to create standard and corrected spur gears, to download the dxf profile of the gear and to study the involute profile of the gears. Useful for cad designers, students and researchers.

B.R.