Helical Gear

[Erincook112]

Guys, I’m having a hard time finding help with a gear I need to mill for a project. This is a MOD 0.5 40 tooth helical gear. There is a concave surface at the top face of the teeth and also at the bottom of the pocket between the teeth. This gear will mate with a worm gear.

Here is a link to the gear in F360.

https://a360.co/2UHyurH

I will be using a converted mini mill with a 4th axis. Material will be Delrin and possibly aluminum.

Thanks in advance for any help!

Dan

[seth.madore]

Were you thinking you would 3D Mill them or sidemill them with a gear saw?

3D Milling is going to be an insane amount of time, fwiw

A saw would be the quickest, although will require a bit of sketch and CAM work on your end. Further, due to the geometry, you would have to get your 4th axis kicked up at a slight angle so as to match your gear profile

[Erincook112]

Thanks for the response, Seth. I’m currently making the gears by hobbing, but milling these gears using my 4th axis is something I’d like to figure out. If I could load some roughed stock in the machine, and let it do the work, I’d be happy.

I found a tapered end mill with the 20 degree angle and 0.5mm tip that seems like it would be perfect to make the cuts... just need to learn how to use this side of F360.

[seth.madore]

What sort of setup do you have for the hobbing, can you share links to tools or pics of the setup?

The issue with using an endmill to do this is the complex geometry of the gear profile. There is a constant arc on the teeth, so your endmill would either:

A) Have that correct profile ground into it

B) Result in a **** ton of 3d surfacing

If the endmill DOES have the correct form ground into it, then yes, this will be possible. Let me know and I can work up an example

[Erincook112]

I'm hobbing the gears using my lathe... I made a tap from a lead screw and
3D printed a mount that bolts onto the Y axis which holds the gear blank...
I slowly spin the lathe and move the blank into the tap until the threads
are cut to the correct depth.



The end mill I was thinking of using is a 20° tapered bit with a 0.5mm tip,
but if I could find one that has the correct shape for a MOD 0.5 gear, it
would be awesome!


[image: mill bit.jpg]



The pressure angle is 20° and the helix angle of the gear is 2.5° Worst
case, I could angle the 4th axis for the helix, but is this something that
the CAM program can do along the XY axis and cut from the top? Could that
concave arc around the perimeter of the gear be roughed in with a ball tip
end mill and then use indexed slotting for the teeth?



I haven't seen any tutorials on something like this... maybe because it's
not the best method for making a gear like this. There are plenty of
tutorials for basic spur gears.



By the way... I checked out your website (where you spend most of your
time)... unfortunately, I didn't get into 3D printing, milling, and now CNC
machining until my early forties, so I'm basically stuck with my civil
engineering line of work. I'm sure the milling industry can be stressful on
the professional level, but as a hobby, this stuff is very satisfying.
Congratulations on your success in the business!



Thanks again!



Dan Cook

[Anonymous]

For some reason I'm having trouble replying in the thread... worked fine from my email...

Here's that image:

[Erincook112]

Seth,

I found another video of yours for creating a tool profile for a spur gear... I'm still a little confused when it comes to tilting the gear at the 2.5° for the helix angle and orienting the tool/model. If you have time to work out an example, it would really help!

I ordered an involute gear cutter, so I will be cutting from the side instead of the top. The tool has a 32mm outside diameter... M0.5 / 20° Pressure Angle

Thanks again!

Dan

[seth.madore]

Let's talk about your machine and 4th axis. Can you share a bit more info as to what you have to work with. This SHOULD be possible to do, although it's not a 100% guarantee

[Erincook112]

Seth,

I have an X2 Mini Mill converted to CNC using the Heavy Metal Conversion kit... 4th Axis is mounted to the left side of the X axis with the chuck facing the right side (typical setup)... 4th axis is homemade, built from a harmonic drive to eliminate as much backlash as possible...

I was hoping I could us a small endmill or tapered endmill and mill from the top of the gear, but I have an involute gear cutter coming across the pond soon... so milling from the side is another option, which means I have to angle my 4th axis for the 2.5° helical angle the gear's teeth.

I've been working with it in F360 all weekend... but can't quite get it right. Trying to create a form mill and get the software to cooperate has been quite difficult.

Let me know if you need anymore specifics... and here's a link to what I've been working with: 

https://a360.co/2IazUcT

Thanks!

Dan

[Anonymous]

OK... I think I've figured out how to do this using the small tapered end mill... 3D Morph seems to do the trick without having to tilt the 4th axis (A) for the helical of the teeth... it's all done from above... yep, slow, and probably impossible for aluminum, but it'll be satisfying to watch the machine whittle these gears out of Delrin in this fashion at least.

I'd still like to figure out how to make them with the involute gear cutter, so please share if you have something in mind.

Thanks!

[seth.madore]

I"m sorry for abandoning this thread. Things have been quite busy in the shop. I will try to get something together before long...

[Erincook112]

Seth,

No worries... I haven't finished my CNC conversion yet... just wanted to get a head start on learning CAM before it's ready. Hopefully it'll be ready in the next couple of weeks.

Here's a quick and dirty Screencast:

Thanks,

Dan