hobbing helical gear

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04 Sep 2020 19:38 #180743 by Aciera
Replied by Aciera on topic hobbing helical gear
I have no idea what kind of gears these are. Information is a bit scant, really.
I just follow my own curiosity here.

Hm, crossed helical gears, there is always something more to look up

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05 Sep 2020 05:41 #180779 by jefsaro
Replied by jefsaro on topic hobbing helical gear
yes it's crossed helical gears 90 degres.

there is a way to catch the head badly with the calculations and the settings of the machine

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06 Sep 2020 17:25 #181042 by CORBETT
Replied by CORBETT on topic hobbing helical gear
@jefsaro
I am assuming you have figured out what to do after henk replied that there is a second gear train for the differential. So basically you need to put a stepper or servo on the second gear train and setup in LCNC.

Andy (andypugh) will be the guy to talk with about setting it up in LCNC. That guy is brilliant, and has been working on this for a really long time.


@Aciera

Yeah at first I thought they were referring to herringbone gears when they said crossed helical, but crossed helical is setup like a worm gear. There would have to be some good mathematics involved to get everything meshed up correctly, especially when one gear is smaller than the other like a worm setup.

I wonder if you get more play in this setup compared to a worm setup? This has peaked my interest.


Robert

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06 Sep 2020 17:57 #181053 by Aciera
Replied by Aciera on topic hobbing helical gear
@CORBETT
I don't really know a lot about gears. I thought maybe I could glean some information by following this project. Alas I have the distinct feeling this is not going to be the busiest of threads. Feels more like milking stones.
Maybe just a language thing though. And he probably gets more stuff done than me. :lol:
Anyway, you seem to have one of those gear hobbers sitting around, maybe you could convert that with all the bells and whistles now?

After all there is no time like the present, is there?
The following user(s) said Thank You: CORBETT

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07 Sep 2020 02:11 #181082 by CORBETT
Replied by CORBETT on topic hobbing helical gear
@Aciera

LOL, I have milked stones...

"After all there is no time like the present, is there?"
Yes I need a good push to get going with it... been trying to reduce some other projects so I can get this one started. Like everyone, way too many irons in the fire, LOL.

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24 Feb 2021 18:31 #200010 by Ravi0000
Replied by Ravi0000 on topic hobbing helical gear
Hello everyone I m Ravi form India patna BIHAR
Making a cnc gear hobbing machine for helical gear cutting

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25 Feb 2021 07:43 #200066 by Aciera
Replied by Aciera on topic hobbing helical gear
Ah, another one.
So are you also refitting an older manual machine?

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28 Feb 2021 22:35 #200473 by andypugh
Replied by andypugh on topic hobbing helical gear

Aciera wrote: I think I'll let Andy figure that out overnight and wait for him to present his solution (including a GUI).


Unfortunately I was not really reading the forum when this was discussed.

I keep meaning to make a helical gear, but have not done so yet.

There are two things to do:
1) Angle the hob to the gear by the normal amount (hob lead angle) and by the helix angle
2) Add in an extra movement of the hob relative to the blank proportional to the distance travelled along the gear shaft axis.

Exactly how the maths works out will depend on the machine. On my mill the X feed direction swings with the table (which sets the hob angle), whereas on a conventional hobber I don't think that it does.

This second part could be done in two ways:
a) By rotating the blank by an extra amount. The problem here is that the extra amount depends on the radius of the cut
b) By shifting the hob along the hob axis. This should work at any radius (but I haven't analysed it, this is just visualising it). It has the advantage of evening the wear on the hob. It has the disadvantage that the hob might not actually be long enough.



b) Would be easy on my my milling-machine hobber, but might not even be an option on a real hobbing machine.

Both are equally easy in HAL. Just another scale and sum. You don't need to worry about the absolute position of the linear axis even, as the starting point will be in the numbers from the start.

If I was to make helical gears there would be a lot of nylon or wax practice parts made first, whilst I checked the maths.

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