Basic Bevel Gear - Milling a valley for gear teeth

I am trying to make a bevel gear using a 60 deg. cone shaped end mill. I have a flat (1D) drawing which looks like a spoked wheel with each line representing the valley of a gear tooth. I have not done any work with 2D or 3D design so my challenge to is come up with the G-Code to make the valley for gear teeth.

If you can imagine a gear, the valley will be deepest at the OD and end at the ID. The Max depth of the valley will be .25" at the OD with a linear incline to 0" (top of material) at the ID. For testing purposes I will used some round aluminum stock which will be machined at 90 deg. Once I have mastered the setup the final gear configuration will have a pressure angle of 20 deg. so it may resemble an actual bevel gear.

I know what I am doing is not a real or legitimate method of producing a gear, my application will apply very little pressure so therefore it should be sufficient.

Are there special G codes for this sort of machining or do I need to move to a 2 or 3D CAD/CAM setup? If this easy code that someone could share with me it would be greatly appreciated. I am using MACH2 s/w with TAIG CNC mill.

Thanks

Norman

Hi Norman,

I would imagine what you would need is a 3d modelling system. Since all features of the tooth and the toothspace converge to a point, you could simply scale down your basic "1d" profile ;) and translate it. Then use cross sectional surface to create the surface. This is then readily machined in a 3d cadcam such as OneCNC.

Actually, you will not be much ahead with the 60 degree endmill. You would be better off using a small ball mill to cut the profile.

Here is a quick view of what I mean. This is the toolpath preview from OneCNC. I did not take the time to make a custom toolpath which would create converging tool lines, but that would be possible also.

Thanks for the feedback HuFlungDung.

I am not sure if I am over simplifying here but I am looking for G-Code to control the up and down travel of the Z axis while making the straight passes to create the valleys. I am relying on the 60 Deg. cone shaped end mill to shape the teeth with consistency, by creating equally spaced valleys I will then produce the teeth of the gear.

What would G-Code look like if I were to mill a 1" long straight line in a flat piece of stock, width equal to OD of cutter and a linear change in depth from -.25" to 0" from left to right? Multiple passes of 1/16" would be preferred.

Norman

Norman,
Is this what your looking for?
Bill

{dakcnc3.0}
test
{program start}
G90
G0Z1.1000
G0 X-0.3125 Y0.0000
/M3
G1 Z1.0000F10.0
G1 X-0.3125 Y0.0000 Z0.0000
G1 X0.6875 Y0.0000
G1 X0.6875 Y0.0000 Z-0.0620
G1 X-0.3125 Y0.0000
G1 X-0.3125 Y0.0000 Z-0.1240
G1 X0.6875 Y0.0000
G1 X0.6875 Y0.0000 Z-0.1860
G1 X-0.3125 Y0.0000
G1 X-0.3125 Y0.0000 Z-0.2500
G1 X0.9375 Y0.0000
G1 X0.9375 Y0.0000 Z1.0000
G0Z1.1000
M5
{program end}

Thanks for your help Bill but I think your code will mill a flat slot rather than one with a linear incline.

I have attached a side view of my requirement.

Norman

I think I see now, but milling that slope with a flat bottom end mill will leave you with a "cupped" shape for the bottom. Is that what you want?
Bill

The tip of your endmill is also a fixed width, but the root of the toothspace is of varying width. Real life practicality says that the cutter's tip is going to be an extremely small diameter to fit through the narrow end, small enough that the cutting action is lousy because sufficient flute depth does not exist.

You can overcome this hurdle somewhat by roughing the tooth out first, but you still have much the same problem with the roughing cutter. 3d software would help you a lot to make the roughing easier to figure out.

Other than that, your assumption that a 60 degree cutter will even make the correct shape of space is in error. A real gear tooth (in interchangeable gearing) is an involute shape. Unless your gear is very large in diameter, and the tooth is not very wide in propertion to the diameter, there will be significant interference caused near the top inner edges of the tooth tip. With a proper gear tooth model, and a ball mill, you can get the right shape and not have to fiddle with a bunch of handwork later on, so that the gears will mesh smoothly.

I've cut bevel gears on a horizontal mill (not the ideal machine for it), so I know how ornery these teeth can be to shape :)

Bill, I am looking for sample G-Code for now so I am not concerned about the end mill or the shape of the slot.

Hu, thanks for your additional comments.

Ok, here is code for a sloped slot. Milling thru the center.


G0Z1.1000
G0 X-0.1582 Y0.0000
G1 Z1.0000F10.0
G1 X-0.1582 Y0.0000 Z-0.2896
G1 X1.2000 Y0.0000 Z0.0500
G1 X0.9526 Y0.0000 Z0.0500
G1 X-0.0582 Y0.0000 Z-0.2027
G1 X-0.0582 Y0.0000 Z-0.1409
G1 X0.7052 Y0.0000 Z0.0500
G1 X0.4578 Y0.0000
G1 X-0.0582 Y0.0000 Z-0.0790
G1 X-0.0582 Y0.0000 Z-0.0172
G1 X0.2105 Y0.0000 Z0.0500
G1 X0.2105 Y0.0000 Z1.0000
G0Z1.1000
M5

Hi Bill, when I imported the code into MACH2 it did not appear correct. Can you please forward me the DXF file so I can try it again with MACH2?

good morning friends
I need a software to design the profile of the tooth with real surround Pinons hypoid, Zerol tooth ring gear, bevel helical spiroid, etc.. for machining 4 axis cnc machines

I appreciate your cooperation.
thanks