Machine a helical gear first nad then a dual helical (CAM)...

[alessiol]

Hello!

I am getting a 4th axis harmonic drive for my CNC. I have a Optimum BF20L (One of the EU version of the Grizzly G0704). The 4th axis will be along the X axis, positioned on the left, classic orientation.

I would like to mill out helical gears first and then move to dual helical which is basically the same, just longer 🙂

I know is possible to machine it from the side with indexer saw but I would like to start with classic milling. The gears are little so it should be still feasible. I will first hobbing the gear on the lathe and only the helical will be done on the 4th axis.

If I understand correctly the wrapping tool path only works for few 2D operations and I could not get a 2D adaptive machine this thing. So I ended up try with a morph strategy and then create a circular pattern. If I check the gcode I see A commands so it should work on the 4th axis. 

I am wondering if there is a better strategy to do it. For instance I could not get the same toolpath showed in this video https://www.youtube.com/watch?v=3FCWysGdUus which looks fairly simple to make in BobCAD-CAM.

I attached the project with the gear and the generated toolpath.

Thanks for the help.

Best,

Alessio

[alessiol]

In case of involute gear cutters that's how I would like to design the tool path, so that the 4th axis takes care of the helix angle, with the saw on the side though.

[seth.madore]

If you want to mill it like in the video, I'd suggest giving the new Feature Flagg "Rotary" tool path. Read about it HERE

If you are looking at doing it with a saw, that's going to be a lot more involved and I don't think Fusion is even up to the task at this stage of development..

[alessiol]

Thank you very much for the reply. I will have a look to the rotary feature. 

With saw I meant the involute gear cutterers normally used. I thought that would be easier to generate the toolpath. Something similar to this https://www.youtube.com/watch?v=L18a_wfaRBE. The guy wrote the gcode so can not be so many lines.

[seth.madore · Accepted solution]

The funny thing about manual code versus computer generated code: Sometimes manual programming is far easier. The CAM system doesn't yet have the tools to synchronize all the axis needed for gear hobbing.

[alessiol]

Understand thank you for the explanation. I was thinking that maybe was possible if you create a sketch where you project the shape of the bottom of the a helical tooth, and then you place it in the middle between two teeth. It could be machine it as a contour following a sort of spline. Probably is not possible to control all the axis at same time. I will try anyway.

I gave a try to the rotary tool. It is awesome. It does exactly what I meant. I see some bugs and missing features, such as. It does not remember the stepover value assigned and moreover there is not multiple depth so I have to work with stock to leave to kinda make multiple passages. For the rest it's really promising and I will use that first to make a helical, takes forever but so be it. Thanks for the help.

[alessiol]

I gave a try to my weird assumption. I have to admit that for a moment I thought is possible. I based the strategy on the video you posted in this thread https://forums.autodesk.com/t5/fusion-360-manufacture/gear-cutting-on-4th-axis/m-p/8144612. I recorded a screencast to show it. Basically I project the helical curve on the surface of the gear. Model a form mill. The problem is when I use the 2D contour I can not get the involute cutter to cut with the tip, but it always goes through the solid. I think that must be possible to solve it, but maybe still the software is not able to compute the all movements.

Well at least I gave it a try 🙂 Let me know what do you think about it. Thx a lot!

[alessiol]

Hi! 

Last video, I swear 🙂 

I think I got pretty close to make it possible with a gear cutter. I leave her ea video with the different strategies that I think will work or are close to that. Maybe is useful for someone.

The first strategy is with the form mill and now it can follow the pattern, but can not make the tool to cut only with the tip, so it will touch other parts too 😞

the other strategy are with normal milling. For metal I see a roughing strategy first (parallel or 3D adaptive) and then a rotary with small step over to get it done. Downside is machining time!

Ciao ciao,

Alessio