Machining Bevels.

For discussions of the various methods of Bevel Machining.
Damo
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Re: Machining Bevels.

Post by Damo »

I think all the calculations for a stanard involute are correct, just have to do one more function to them. Imagine a spur gear and the flat plane on the side of the spur gear, now all of a sudden that flat plane is spherical? Image the teeth. They are still an involute, just the world they live in is now a sphere. Now imagine 2 spur gears working together on parallel shafts, no imagine the flat plane on the side has become a sphere and the 2 shafts are now at right angles. Gives more meaning to me now of the work spherical involute. :-)
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ArtF
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Re: Machining Bevels.

Post by ArtF »

Damo:

  To the first question:  I cant imagine that piece of paper, though Im sure you can. Its the problem with such dicusions, their very hard
to describe in words. To the second comment.. exactly, I think when you take that spur tooth and fold it into a sphere you create a spherical
involute whos pattern of contact is then an octiod if its done correctly. Are mine? Christ only knows. I know they mesh very well, but if they pattern
on a figure 8... beats me.
  When I do finish the non-circ's in GT, I will visit the Gcode generator to add bevels. Since we're speaking only of using a ground cutter for these
the GCode will work fine no matter if we're rigth or wrong..the entire issue will be the cutter shape.. so we'll see.. :)

  Ill have the Gcode put out so that the blank will have to be tilted to root angle..

Art
Damo
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Re: Machining Bevels.

Post by Damo »

Hi Art, I tried to draw what I meant. Sort of looks like a potato chip. The line passes through 2 sets of axes at the same angle. From the side it looks like a figure 8. Imagine the rack going around the circumference and 2 opposite tooth flanks are on the surface.
Cheers Damo

Not sure if this will work, am attaching 2 images
Attachments
octoid-2.jpg
octoid-1.jpg
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ArtF
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Re: Machining Bevels.

Post by ArtF »

I see what you mean, it is a figure 8 on profile..  Im just not sure how that helps me in terms of getting the rigth profile..

Its interesting to note that the specification for the calculation of the bevel toothform produces a very bad looking curve in the
axial plane..its only once you fold that to spherical that the curve looks correct as a semi-evolute..

Art
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ArtF
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Re: Machining Bevels.

Post by ArtF »

Damo:

Just found this out there..

>>While gear manufacturing is well developed, with precision gears cut under
tight tolerances and producing smooth motions, the geometry of gear meshing
is not yet fully exploited in the industry. For example, bevel gears are
still designed using Tredgold?s approximation, under which the tooth profile
is designed so as to yield a projection onto the tangent plane of the back cone
that matches the profile of an equivalent involute spur gear.


  This IS what Im doing. The tooth form IS created to be correct as a typical spur when viewed from the
tangent plane on the back face..

  This link explains how to make the correct  (if thats the correct word) method..
http://www.geometrie.tuwien.ac.at/stach ... g_Proc.pdf


  As you can see, its not something Ill jump into lightly. :)

Art
Damo
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Re: Machining Bevels.

Post by Damo »

Out of those 5 theorems, they lost me at the first.  :D
Cheers Damo

Damo
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Re: Machining Bevels.

Post by Damo »

Actually, i'm just happy i understand the word "octoid" now.
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ArtF
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Re: Machining Bevels.

Post by ArtF »

Words just dont work..do they. :)

Art
John S
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Re: Machining Bevels.

Post by John S »

Yes but will it cook the turkey on Gas MK 5 ?
John S.
Nottingham, England
CMcDaniel
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Re: Machining Bevels.

Post by CMcDaniel »

Hey Art, Anything new with the bevels or are You busy working on other things?
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ArtF
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Re: Machining Bevels.

Post by ArtF »

Hi:

  Bevels will be dealt with in a waterline engraving module, but probably not till next fall.

Art
Chuck
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Re: Machining Bevels.

Post by Chuck »

Art,

Here is another paper on spiral bevel gear generation and inspection.

http://gear-net.com/report/rep-03.html

Also Klingelnberg method is in a spread sheet with macros that create tooth form for Solid Works IGES inport.

https://www.youtube.com/watch?v=k-WdPTxinZk

Chuck in Wyoming

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Re: Machining Bevels.

Post by Nate »

ArtF wrote: Hi:

  Bevels will be dealt with in a waterline engraving module, but probably not till next fall.
...
Naively, it seems like the easiest way to cut bevel gears on a 3-axis CNC machine would be to generate a gear profile numerically, and then profile cut with a ball nose end mill, but I haven't seen any discussion of that in the thread.  Is there some compelling reason not to take that approach?
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ArtF
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Re: Machining Bevels.

Post by ArtF »

Nate:

Thats the plan. Its not easy to cut bevels, but for beverls less than 45 degrees, the workbench shoudl be
able to profile them, for more than 45 degrees, he 4th axis shoudl eb able to profile them..

Art
Nate
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Re: Machining Bevels.

Post by Nate »

ArtF wrote: That's the plan. Its not easy to cut bevels, but for bevels less than 45 degrees, the workbench should be
able to profile them, for more than 45 degrees, he 4th axis should be able to profile them..
A bevel gear with lots of helicity, a small pressure angle, and large teeth can have both radial and axial overhangs.  (That is to say, require a 'tilt' or 5th axis set up.)  I'm not sure whether gears like that have any practical application.

This is a section of a decorative bevel gear I  modeled.  If the pitch cone angle were larger, you can see that there would be a 'double undercut'.
Image
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