Creating Helical Gears

[KCollins]

We have a need to creat a helical (from an involute profile) gear tooth for the purpose of generating a lathe tool to cut the gear. I'm more proficient with using CAD programs such as Ideas to generate such a solid. Does anyone know how to take a 2-d gear profile and revolve it at the same time as extruding it? Or Translate the profile while performing the revolution?

I'm currently looking into using the helical c-hook to do this but I have no experience with it. If anyone has any Ideas your help would be greatly appreciated.

 

Thanks

Kevin Collins

Valiant Industries, Inc.

 

ps. I'm using version 9 with mill level 3 including the solids package...

[Scott Bond]

I have made Fans,Impellars,Propellars, From V1 and up. Our system will make the sufrace file or parasolid, but it will be more work than;;;;;

quote:

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take a 2-d gear profile and revolve it at the same time as extruding it? Or Translate the profile while performing the revolution?

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I am interested in how the team handles this In Mastercam. I spent years on these shapes,and I am hoping that there is something new (to us) that I don,t know about.

 

[ 07-22-2002, 10:54 AM: Message edited by: Scott Bond ]

[McRae]

KCollins - Please elaborate on the geometry a little more. If I read it correctly, you wnat to cut the gear profile on a lathe and need to know the shape of the contour?? I can see attempting a worm gear in this manner but a spur gear? The Rotation along the helix would require an infinite linear feed rate along the z-axis in order to induce enough shear for the tool to function.

 

For a worm gear, I know pro/e uses a Helical Sweep, I need to look it up in Mastercam to see if it will create it. Otherwise - use the helix c'hook to create successive curves at required diameters, and then make a surface out of these.

[KCollins]

The gear is essentialy an involute tooth with a very high helix angle. The high helix angle creates a tooth profile that looks a lot like a worm gear (or a thread), however the profile of the gear is involute in plane normal to the translation. I've been trying to use the gear tooth chook to create a single tooth geometry and then sweeping it along the helix path. However I've, as of yet, been unsuccessful to generate the desired result. I believe the problem is that I'm trying to sweep a profile that is parallel with the plane of translation...

[KCollins]

I added a mc9 file to the ftp site called involute tooth

ftp://mastercam:[email protected]/Ma..._files/INVOLUTE TOOTH.MC9

 

it shows the tooth profile the helix path and the rotation axis....

 

any further ideas?

[Scott Bond]

Hi

I will look at this file tonight.

[P_Scott]

KCollins,

 

You are very close to the solution by saying that your gear tooth profile is parallel to the sweep path. Close the single tooth geometry and rotate it to a plane where it will be perpendicular to the start point of the helix geometry. Then Create a Sweep solid or surface using the tooth geometry as your cross section profile and the helix as your sweep path. You may want to try it with just the tooth geometry first and then add the base cylinder to the helical gear tooth afterwards. I usually start by drawing the tooth geometry from the Side or Front Cplane and creating the Helix using the new Spiral/Helix entity from the Create menu in V9. HTH

 

Try out this thread topic from the Forum to see if this helps out at all.

Solid threads

The "3_8-16_ThreadV9.zip" file is still in the FTP MC9 folder if you're interested.

[KCollins]

Thanks for the Help....Peter your solution came to me about 2AM last night. However I'm worried that the sweep might not create a truely accurate profile of the teeth.

 

The example I posted is not a true representation of the gear but rather a simplified version (in the effort to figure out what's possible).

 

Given that we plan on using the surface model to create a tool. Does anyone know if the involute profile created by the gear c-hook creates and accurate tooth profile or is it merely a graphical approximation of the tooth?

 

Again thanks to all for the help,

If I do manage to figure out the problem I'll post the solution on this thread for all to ponder...

 

Kevin

 

It's noon somewhere!

[McRae]

Kevin,

 

You are correct, the cross section and orientation of the tool will be normal to the helix angle and inclined to the part. You will not be able to cut this type of a part using a lathe cycle for the following reasons - your pitch is in the order of 6.0" and your diameter of the part is only 3.0".

 

In order to generate the "Thread" you will need to travel 6" in Z for every rotation of the spindle. Example - for a piece of carbide a nice threading sfm would be around 150/200sfm. This translates into G97 S191 - S254. Therefore the linear feed rate requirements for the Z-Axis will be F1146.0 - F1524.0 Inches per minute. If your machine will do this - Please let me know so I can order 3 of them...

 

The machine dynamics for the accelleration and deceleration would also require a design of experiments to determine the lengths needed to get up to speed and to slow down without affecting the pitch geometry of the "Gear"

 

The ways around this are to use a gear hob in a mill/turn machine application. Involute gear hobs are off the shelf items - no sense in doing someone elses work again.

 

I am creating large diameter screw profiles and would be happy to discuss further.

[KCollins]

The part I posted is not an accurate representation of the gear. In tooth profile or in pitch. The actual part has amajor diameter of about 2 inches and an approximate helix angle of 80°. (Not entirely sure as I don't have the gear data on hand.) However, the pitch to diameter is sufficient to be cut on a lathe.

 

We currently have several hobbing machines but are not able to produce such a large helix angle. The part in question was a request from a customer and we would like to see if we can generate the profile on a lathe tool.

 

Again the model I posted to the ftp sit does not reflect the actual gear data but is just a simple senerio that I was using to determine the best possible way to model the gear.

[McRae]

What is the gear data so I can try to model something.

[KCollins]

I've uploaded a better representation of what I'm trying to accomplish (not entirely accurate, but close) including the surface I created with a sweep. The new model is located here

tp://mastercam:[email protected]/Mastercam_forum/MC9_files/INVOLUTE TOOTH 2.MC9

I was able to generate curves on the surface of what should represent the cutter profile. However I have noticed several issues during the sweep. If I try and sweep one full revolution the surface doesn't hold true to the axis (origin) of rotation. The model I created uses only a 45 degree rotation however that should be sufficient for the cutter...I'm concerned that given the errors with the full revolution as opposed to this 1/8 revolution that even though I was able to generate a fairly clean looking surface that it might not be entirely accurate..

 

Again thanks for everyones help,

Kevin

[McRae]

Given the end view - we are trying to develop a Z_X cross section view for a helical sweep. Then in order to design a cutting tool, we need to section normal to the helix in order to generate true shape. I have tried this in mastercam and found it to lack the required tools

[McRae]

Kevin,

 

From the look of your home page, there should be some old gear guy with gray hair and a beard that cut gears for Noah's Arc. He is the guy you want to help find out the profile. think in Z_X rather than the end view. I have a similar application on a twin screw rotary pump element and this is what we had to do to create a successful Pro/E Model.

[KCollins]

It appears from the model that I obtained the neceessary curves to generate a tool but my only real question now is how accurate would the tooth profile be using this method?

 

Our old grey hair gear guy is actually only 40 and hes the one asking me if I can generate the lathe tool....

[McRae]

Kevin,

 

Try making a reverse image of the gear and assemble - or hack, them togeather to see if they fit and are relativly correct.

[McRae]

Kevin,

 

Inclination angle of the insert is important. I tried to use a G32 - Constant Lead Cutting cycle and found that the insert healed along the leading edge as it cut. Also the clearance angle on the insert did not work for a 2.5" pitch. Also the geometry of the holder needs to be inclined in the same direction as the insert.