Wire edm helical gear

Can anyone wire cut a shallow helical gear profile? Reading it can be done on a wire with independant axis wire guides, but need to find someone who has done this before.

claya said:

Reading it can be done on a wire with independant axis wire guides, but need to find someone who has done this before.

Click to expand...

I would like to see an explanation of this. The helix is a curve, as far as I know wires have to be tensioned in a straight line ?

Maybe if you ROTATED the part in relation to the wire

Akin to helical milling set up on Universal mill

But no, wrong shaped "cutter" to do anything useful

See Post #17

Helical Lead? 30T drive gear K&T

Another handy place to see a HELIX is look at an empty paper towel core tube

Hi Clay:
I have faked a set of mold inserts for a helical gear on the wire EDM but the application was super crude and made an acceptable part (The helical was used as a worm wheel in a display shelf leveling mechanism).

Emanuel Goldstein has nailed the problem in his comment about the helix being a curve and the wire being straight.
However, helicals have been faked on the vertical milling machine with a set of shaped saws and the blank tilted up on an angle, and rotated in small increments as the cutter stack is moved up and down to keep it in mesh.
Those are all linear cutter paths but so far as I know they make a pretty shitty, lumpy fake which kind of defeats the purpose of helical teeth in the first place.

Now there may also be another way to fake it on the wire other than what I did, and probably the best guy I can think of to answer that question would be Zahnrad Kopf.
He knows both gears and wire EDM really well...so if you're lurking ZK, I'm dying to know too!

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Claya,

A TRUE Helical Gear cannot be produced by a Wire EDM, but you can come close depending on the geometry, thickness, and helix angle. This a complex issue that is all about geometry, and this does confuse many people. Most Wire EDM machines can perform 4-Axis machining, meaning that the wire can be tilted at different angle, but the wire itself will always remain in a straight line as it machines thru the work piece.

I did an article in EDM Today a few years ago (2017 Summer Issue - link below - marked Pages 66~68) that discusses Gear Machining on a Wire EDM in detail. The issue with Wire EDM machining helical gears is that the wire itself cannot produce or be bent to follow the proper radial rotational form. Even when machining with a 4-Axis program, the wire path can only produce the proper geometry at the very Top and Bottom of the helical gear. This means that the central radial geometry is overcut (too much material is removed)since the angled wire is producing a straight linear blend between the Upper and Lower geometry profile. As the work piece thickness and/or radial helix amount increase, so does the amount to overcut that will result by Wire EDM.

- Brian

2017 Summer EDM Today Magazine

2017 Summer EDM Today Magazine

claya said:

Can anyone wire cut a shallow helical gear profile? Reading it can be done on a wire with independant axis wire guides, but need to find someone who has done this before.

Click to expand...

"Because the upper and lower wire support arms move independently, this process approximates some three dimensional shapes, including crowned tooth surfaces, low helix angle helical gears, and bevel gears"

Above from a 2000 article found here: EDM speeds cutting of precision gears | Machine Design

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claya said:

"Because the upper and lower wire support arms move independently, this process approximates some three dimensional shapes, including crowned tooth surfaces, low helix angle helical gears, and [straight tooth] bevel gears"

Click to expand...

He should have added "narrow face width" to that list. And one thing is entirely wrong, no way in hell to do crowned teeth. Tip and root relief on a spur but definitely not crowned.

In other words, you can fake it for a part that doesn't care, and isn't too far off from a normal spur. With a narrow face width

Hi again claya:
Yeah, the operative word here is "approximates"
Of course, if your microscope is discriminating enough that is true of all processes that make gears, but there is a fundamental disconnect between what a true helical gear tooth space must be, and what a wire EDM can make.
So a helical fake is possible, but a helical gear is not.
If you can get away with what a wire can produce that's fine, but that comment in the article the OP referenced is a badly misleading shill piece for wire EDM as some sort of magic process for something it clearly cannot do, and frankly, I am surprised that Roderick Kleiss (whose company does gear design and analysis) would sign his name to such a basic misrepresentation of the truth.
The other co-author appears to sell EDM machines...I can understand fully why he would write a puff piece like this...he'll sell more machines that way.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

PS
Hey Brian:
While I'm thinking of it, thank you for that reference to your article; I really enjoyed reading it.
MC