making Helical gear with fly cutter

[Sanjaya1]

hello I'm new user of gearotic and really happy to spent 120$ for the great software..
can someone help me
I'm try to create a helical gear with outside diameter 45mm
this gear is copied for the broken gear so i make precise fly cutting tool to fit the old gear teeth
the problem is how can a generate g code for mach3 4 axis cnc ??
I'm try to use the default setting and the cutting always fail in the tangent move.. how can i disable this feature
and how can i create a gear with exact outside diameter with 45mm /19 tooth...
thank you..

[ArtF]

Hi Sanjaya:

  If you select "use involute cutter" in the output menu it wil no longer put out tangent shaving code.
Set a perpass dpeth and your cutter should work.

  To determine what helical you have depends on a few things. There are several ways of making helicals.
Do you know the helical angle? That would help if its designed in the Normal system. If in transverse system and unshifted it should be identical in size to a spur gear. Let me know what you know about it and we'll see if we can come up with what it is.

Thx
Art

[Sanjaya1]

yes i know.. the helical angle is 12 degree

I'll try again to make correct g code

thank you

[Sanjaya1]

how can i over ride the gear diameter in the software ?? than you

[ArtF]

Hi Sanjay:

  A 12 degree helical, using the normal system, with a module of 2.1 , 19 tooth is 44.99mm in
diameter. It may be a module 2 gear with a small profile shift, but I think Id try the above settings
as they should be very close.

Art

[Sanjaya1]

wow that exactly the outside diameter i want how can i figure it out ? my broken gear spec. 19teeth / 12 degre helical angle / 45mm outside diameter / spoke diameter 20mm.

[ArtF]

Sanjaya:

  It can be hard because you never know if its been profile shifted or what method was used to make it, not all gears are made the same, many options exist, but generally, if you make a gear with 19 teeth with module 1, then do a comparison to the size you need, you can figure it out. For example, if a modulel 1 gear is 20mm's in diam, then a mod 2 gear will be 40mm.. so if you use the formula    DesiredGearDiam / MyMod1GearDiam = Mod to use.

  that will get you awful close..
Art

[Sanjaya1]

thanks art after several times for trial and error finally i can get really close to the gear that i want to copy

and i became familiar with the program

thank's a lot for your help

sanjaya

[ArtF]

Sanjay:

  NP, sometimes the best or only way is to use trial and error. :)

Art

[ozzie34231]

Hi Art,
I have been playing with this helical gear and gotten to the point of having all the parameters in GM matching the physical measurements I can measure.
OkaY, cool but I just can't imagine cutting steel with a 0.050" end mill. ( not on my two ton milling machine).
You might know, I hope, that I wrote an article for Digital Machinist explaining how to make a cutter for making diy cutter for an xl timing pulley, using my CNC lathe, along with John Stevenson's cutter scheme.
So, I'm thinking that if I have the correct profile for the cutter, and I tilt my 4th axis to the helical angle, I should be able to cut the gear with this profile cutter.
So, first, is that correct??????
Secondly, if yes, the profile that I might take from an end view of the gear from GM would not be correct. I would need a profile viewed from the helix angle.!
May I request that GT be able to output profiles for making rotary cutters; gears including helical, and timing pulleys, any constant profile project.
Thanks,
Ozzie

[ArtF]

Hi Ozzie:

>>cool but I just can't imagine cutting steel with a 0.050" end mill.

  I can understand that. Thats about a 1.25mm bit, pretty small. Helicals and bevels are both pretty hard to cut in 2d.


>>So, I'm thinking that if I have the correct profile for the cutter, and I tilt my 4th axis to the helical angle,
        I should be able to cut the gear with this profile cutter.


  There are 2 types of helicals, they are called "Normal and Transverse" helicals. Normal helicals are larger than their spur gear equivalent. ( by the cos of the helical angle), and their profile ( as a result of the increased diameter ) is proper for cutting with a normal spur fly cutter. The second type, the transverse helical is the same size as a spur. It increases in size only as a result of any profile shifting. Its profile is not the same as an involute profile and is the hardest type to cut.

  So as long as you generate the first type your spur cutter will cut it. Soon, the program will put out the profiles of a single tooth for any gear except the no-appropriate ones like non-circular. ( where each tooth is different). You'll see it by the end of the beta of GT, which Im hoping wont be all that long. But if your on Normal helicals, you shoudl be able to use a standard cutter with the 4th axis tilted. Its the whole point of the diametric increase in the helical.

Art
   

[ozzie34231]

Just to be clear, it is a profile of the space between teeth that would be useful.
Ozzie

[ArtF]

Ozzie:

  Right click on any gear and select "Tool Wizard", youll see the program already has the tooth shapes stored..

Art

[ozzie34231]

Art,
I see that in GM but I don't see how it helps me.
I want to be able to take the groove profile, open it in my cam program to create G-code enabling my CNC lathe to make a gear cutter; not an end mill, a gear cutter. I can do that now by loading the whole GM gear into the CAM, but I run into the problem of exactly aligning a grove profile with an axis. Then I need to make a mate to the groove and use that to get code.
It would be so much easier if GT would have an output option "Groove profile STL", with a centered axis line.
With that option we could make a cutter, and others might want to make a "D" mill.
Ozzie

[ArtF]

Ozzie:

  Would a dxf of the profile do?

Art