Gear hobbing with maching center or turning center

[Tero Kaarlela]

Hi,

Does anyone here do gear hobbing with 4-axis vertical machining center.
Or turning center with live tools? Gear we need to make is 260mm(od)
module 4. Is this possbile to make with equipment above or do we need a
vertical gear hobbing machine?


Tero Kaarlela

[BottleBob]

Post by Tero Kaarlela
Hi,
Does anyone here do gear hobbing with 4-axis vertical machining center.
Or turning center with live tools? Gear we need to make is 260mm(od)
module 4. Is this possbile to make with equipment above or do we need a
vertical gear hobbing machine?

Tero:

260mm? 10"+? Is this a onzie-twozie operation? Will you have to
purchase the hob $$$? Do you have a way of accurately measuring the
final gear form? If the answer to those questions are yes, you might
consider sending it out to a gear hobber that specializes in that sort
of work.

We hobbed some steering racks a couple of months ago, but that was done
on an antique (pre CNC) horizontal milling machine where the hob was
rigidly supported on both ends.

[Tero Kaarlela]

Situation is that we are researching if we could specialize in gear
hobbing. We have several products that need to be hobbed. Now we are
using a sub-contractor to hob these but its quite expensive per year
basis. All parts also require machining with lathe and machining center
this we do in our company. 206mm is a bit over 10"



Tero

Post by BottleBob

Post by Tero Kaarlela
Hi,
Does anyone here do gear hobbing with 4-axis vertical machining center.
Or turning center with live tools? Gear we need to make is 260mm(od)
module 4. Is this possbile to make with equipment above or do we need a
vertical gear hobbing machine?

260mm? 10"+? Is this a onzie-twozie operation? Will you have to
purchase the hob $$$? Do you have a way of accurately measuring the
final gear form? If the answer to those questions are yes, you might
consider sending it out to a gear hobber that specializes in that sort
of work.
We hobbed some steering racks a couple of months ago, but that was done
on an antique (pre CNC) horizontal milling machine where the hob was
rigidly supported on both ends.

[pRecisionmAchiniSt]

Post by Tero Kaarlela
Situation is that we are researching if we could specialize in gear
hobbing. We have several products that need to be hobbed. Now we are
using a sub-contractor to hob these but its quite expensive per year
basis. All parts also require machining with lathe and machining center
this we do in our company. 206mm is a bit over 10"
Tero

Post by BottleBob

Post by Tero Kaarlela
Hi,
Does anyone here do gear hobbing with 4-axis vertical machining center.
Or turning center with live tools? Gear we need to make is 260mm(od)
module 4. Is this possbile to make with equipment above or do we need a
vertical gear hobbing machine?

260mm? 10"+? Is this a onzie-twozie operation? Will you have to
purchase the hob $$$? Do you have a way of accurately measuring the
final gear form? If the answer to those questions are yes, you might
consider sending it out to a gear hobber that specializes in that sort
of work.
We hobbed some steering racks a couple of months ago, but that was done
on an antique (pre CNC) horizontal milling machine where the hob was
rigidly supported on both ends.

Depending on how accurate you need they teeth can probably be milled one at
a time...

But for true hobbing you need the ability of tilting the tool head as well
as have the capability of slaving your rotary table to an exact ratio of the
spindle rpm.

http://class.et.byu.edu/mfg130/processes/descriptions/mechanicalreduction/ge
arhobbing.htm

Tilted tool head can be plainly seen here:

Loading Image...

--

[Why]

Post by BottleBob
We hobbed some steering racks a couple of months ago, but that was done
on an antique (pre CNC) horizontal milling machine where the hob was
rigidly supported on both ends.

BB, the one with the good old sulphur oil?

[BottleBob]

Post by Why

Post by BottleBob
We hobbed some steering racks a couple of months ago, but that was done
on an antique (pre CNC) horizontal milling machine where the hob was
rigidly supported on both ends.

BB, the one with the good old sulphur oil?

Dave:

Yeah, that's the one. It nukes at least a 30 foot area around it when
it's running (which is luckily infrequent). You'd think after all this
time they would have added some deodorant to that stuff when they
formulate it. LOL

[D Murphy]

Post by Tero Kaarlela
Hi,
Does anyone here do gear hobbing with 4-axis vertical machining center.
Or turning center with live tools? Gear we need to make is 260mm(od)
module 4. Is this possbile to make with equipment above or do we need
a vertical gear hobbing machine?

I have hobbed gears on a CNC lathe. The deciding factor is the class gear
(tolerance) that you need to cut the gear to. Unfortunately we don't have
a machine that can handle a part that big. But here is a video of a lathe
cutting a gear:

<http://video.google.com/videoplay?docid=-952907967082928959>

You can also use a tool changer type lathe like this one:

<http://www.tsugami.co.jp/eng/products/auto/turning/tma8.html>

But the tolerance problem becomes even worse as there is no way to
support the end of the hobbing arbor with this type of machine. Run out
of the hob cutter affects the tolerance of the gear being cut. If the hob
arbor is not supported it will tend to deflect under load.

[Tero Kaarlela]

Thanks to everyone who responded. Now I have came to conclusion that I
have to find a "real" gear hobbing machine for us. Biggest problem IMHO
is deflection of tool if it is not supported from other end. This can
make bad quality and slows down process because feed value has to be
slow to avoid deflection.




Tero

Post by Tero Kaarlela
Hi,
Does anyone here do gear hobbing with 4-axis vertical machining
center. Or turning center with live tools? Gear we need to make is
260mm(od) module 4. Is this possbile to make with equipment above or do
we need a vertical gear hobbing machine?
Tero Kaarlela

[Anthony]

Post by Tero Kaarlela
Thanks to everyone who responded. Now I have came to conclusion that I
have to find a "real" gear hobbing machine for us. Biggest problem IMHO
is deflection of tool if it is not supported from other end. This can
make bad quality and slows down process because feed value has to be
slow to avoid deflection.

You are a wise man Tero.