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Electronic gearing for gear hobber

- Mechanization of movement of the spindle with the mill along its axis, for uniform wear of the mill. Movement does not occur during cutting.

That's the normal method. What I was talking about is either "minch" or "cash" and involves moving the cutter a miniscule amount during the cut.

The advantage is that the hob wear is uniform across the entire face of the hob. The disadvantage is that it turns a simple spur gear into a non-differential long-lead helical that you have to compensate for.

But it does do a really nice job of keeping the hob uniformly sharp :D

(Both Pfauter and Cleveland have used that method, can find out more from old Pfauter technical manuals. Personally, I think a CNC Cleveland could be a killer conversion. Those things are brutes.)
 
That's the normal method. What I was talking about is either "minch" or "cash" and involves moving the cutter a miniscule amount during the cut.

The advantage is that the hob wear is uniform across the entire face of the hob. The disadvantage is that it turns a simple spur gear into a non-differential long-lead helical that you have to compensate for.

But it does do a really nice job of keeping the hob uniformly sharp :D

(Both Pfauter and Cleveland have used that method, can find out more from old Pfauter technical manuals. Personally, I think a CNC Cleveland could be a killer conversion. Those things are brutes.)
then under a microscope the gear being hobbed is showing that same minuscle amt in that direction-or does hob go back and forth?
 
Played musical iron today. Moved a few dozen tons and made holes for the hobbers arriving tomorrow morning. Once the DB Supreme has landed we can see how shitty it is and make a judgement call on a direction.

My Arduino nut friend is chomping at the bit to kludge together a proof of concept drive system. I told him Carbide Bob says he'll fail, but he wants to try anyway.
 
then under a microscope the gear being hobbed is showing that same minuscle amt in that direction-or does hob go back and forth?

Hob moves a very small amount along its axis as it cuts along the axis of the part. Only moves in one direction. The teeth look exactly the same, they are just a slight helical. A very slight helical, the lead would be in feet, you won't see it visually. Cutting action is the same as normal, just that the cutter advances its way simultaneous with long feed.

This is not normally what you want, so you have to set up the part as an opposite-hand helical of the same amount as the minch, so that your part comes out as a spur gear. And no, you can't get away with just pretending it doesn't exist, gears are too picky for that.

This is sort of the same as cutting a helical without a differential, except that instead of manipulating the feeds you are messing with cutter position. You could probably do helicals this way if you were crazy and had a way to control hob advance (minch and cash-equipped hobbers have a fixed hob advance per revolution.)

Garwood said:
My Arduino nut friend is chomping at the bit to kludge together a proof of concept drive system.

If he's going to do it, don't let him squeak by with a half-ass job. You definitely want two-cut, crowning, taper and maybe hob shift if you're going to bother at all. May as well throw tangential in there in case some day you want to do a worm gear. And don't let him get away with "+/- .010" is good enough." No it's not. It' s gotta be tight, you measure gears in tenths. Even on old clapped-out stuff you're consistently trying to hold +/- .001" over wires which is not exactly a pickanick, Mr Ranger Sir.
 
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Hob moves a very small amount along its axis as it cuts along the axis of the part. Only moves in one direction. The teeth look exactly the same, they are just a slight helical. A very slight helical, the lead would be in feet, you won't see it visually. Cutting action is the same as normal, just that the cutter advances its way simultaneous with long feed.

This is not normally what you want, so you have to set up the part as an opposite-hand helical of the same amount as the minch, so that your part comes out as a spur gear. And no, you can't get away with just pretending it doesn't exist, gears are too picky for that.

This is sort of the same as cutting a helical without a differential, except that instead of manipulating the feeds you are messing with cutter position. You could probably do helicals this way if you were crazy and had a way to control hob advance (minch and cash-equipped hobbers have a fixed hob advance per revolution.)



If he's going to do it, don't let him squeak by with a half-ass job. You definitely want two-cut, crowning, taper and maybe hob shift if you're going to bother at all. May as well throw tangential in there in case some day you want to do a worm gear. And don't let him get away with "+/- .010" is good enough." No it's not. It' s gotta be tight, you measure gears in tenths. Even on old clapped-out stuff you're consistently trying to hold +/- .001" over wires which is not exactly a pickanick, Mr Ranger Sir.
Tenths you say?! Wouldn't that be in the realms of grinding? The spur gears that were made for me from a shitty shop came out more than ten thous undersized when measured over wires.

Speaking of crowning, how do the kinematics work? Is it just a matter of variable cutting depth as the hob feeds in the Z direction?
 
Hob moves a very small amount along its axis as it cuts along the axis of the part. Only moves in one direction. The teeth look exactly the same, they are just a slight helical. A very slight helical, the lead would be in feet, you won't see it visually. Cutting action is the same as normal, just that the cutter advances its way simultaneous with long feed.

This is not normally what you want, so you have to set up the part as an opposite-hand helical of the same amount as the minch, so that your part comes out as a spur gear. And no, you can't get away with just pretending it doesn't exist, gears are too picky for that.

This is sort of the same as cutting a helical without a differential, except that instead of manipulating the feeds you are messing with cutter position. You could probably do helicals this way if you were crazy and had a way to control hob advance (minch and cash-equipped hobbers have a fixed hob advance per revolution.)



If he's going to do it, don't let him squeak by with a half-ass job. You definitely want two-cut, crowning, taper and maybe hob shift if you're going to bother at all. May as well throw tangential in there in case some day you want to do a worm gear. And don't let him get away with "+/- .010" is good enough." No it's not. It' s gotta be tight, you measure gears in tenths. Even on old clapped-out stuff you're consistently trying to hold +/- .001" over wires which is not exactly a pickanick, Mr Ranger Sir.

First goal- Electronic gearing. If that works, next goal- 2 cut. If that works, well I'm pretty sure I just need to make gears and develop more products with gears.
 
First goal- Electronic gearing. If that works, next goal- 2 cut. If that works, well I'm pretty sure I just need to make gears and develop more products with gears.


I found two links that may be useful to you? Very fascinated by this electronic gearing thing. I have a cnc live tool lathe with fanuc servos and drives which I might just try hobbing with, if the synchronous spindles are up to it that is.
 
It' s gotta be tight, you measure gears in tenths. Even on old clapped-out stuff you're consistently trying to hold +/- .001" over wires which is not exactly a pickanick, Mr Ranger Sir.
I guess it depends on what you are making.
If you want 250,000 to 500,000 mile life you measure in millionths and hold your six-sigma process limits to tenths.
There are many classes of gears and precision. Not sure what the OP wants to do.
Making a gear is sort of easy, making good gears not so easy.
Bob
 
My Arduino nut friend is chomping at the bit to kludge together a proof of concept drive system. I told him Carbide Bob says he'll fail, but he wants to try anyway.
One learns by trying.
It seems logical and straightforward until.....
Built my first before the days of the IBM PC. I was sure it would work just dandy.
I did not know what an electrical or mechanical time constant was. Z domain transfer function? Why is this crap getting in my way?
Torque, velocity, position systems. No..no, go forward on my command. Step response.. that should be easy and we can microstep it if needed.

It is only by doing that we learn so I applaud the effort and 100% understand that it seems that it should be simple and a few weeks of work.
Who as a machinst has not tried stuff that should be golden out of the gate but was not quite right?
Build it and see how it works, patch it and go more....
I am all for trying it, just a warning that it is not as easy as it looks and the devil himself hides in the details.

Bob
(Drink deep, or taste not the Pierian spring : There shallow draughts intoxicate the brain, and drinking largely sobers us again.)
 
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Tenths you say?! Wouldn't that be in the realms of grinding?

Not really ... hobbing is an odd process, the machine does most of the work : if your tools are correct and the machine is tight and the blank is right, a thousandth on runout (for exampe) becomes a tenth on tooth shape, spacing and so on. AGMA 9 and 10 (current automotive general quality level) have tolerances in the tenths on most features. But you don't do that on a Moses Brown :)

The spur gears that were made for me from a shitty shop came out more than ten thous undersized when measured over wires.

Didn't mean to say anything but from the photos, no surprise there.

Speaking of crowning, how do the kinematics work? Is it just a matter of variable cutting depth as the hob feeds in the Z direction?

Same as cutter comp on a mill. A hob is cylindrical with teeth at the outer perimeter, the machine comps the hob radius outside of the crown shape you want to give the part. Used to be done with tracers, now electronic. Taper same. Crowning is usually not very much, mostly to avoid end-loading of the teeth. Sometimes for situations where the gear/shaft will not be wonderfully aligned or held steadily.

Garwood said:
First goal- Electronic gearing. If that works, next goal- 2 cut. If that works, well I'm pretty sure I just need to make gears and develop more products with gears.

Ha. You're kidding yourself. Get interested in gears and next thing you need a cylindrical grinder for the shafts, an id grinder for bores, then a rolling tester, then a lead tester then an involute tester then a bigger hobber then a shaper for internals then a pointer then a redin then a bunch more measuring equipment then your own heat treating then I dunno, how about a tooth grinder ?

It's worse than most of metalworking :D

Carbide Bob said:
I guess it depends on what you are making.
If you want 250,000 to 500,000 mile life you measure in millionths and hold your six-sigma process limits to tenths.

Ja, anyone who goes into automotive is certifiable, no doubt about it. Nuttier than a fruitcake, as grandma would say !

Gar should be safe for the time being tho. New Departure probably doesn't envy his 1946 David Brown :D
 
Ha. You're kidding yourself. Get interested in gears and next thing you need a cylindrical grinder for the shafts, an id grinder for bores, then a rolling tester, then a lead tester then an involute tester then a bigger hobber then a shaper for internals then a pointer then a redin then a bunch more measuring equipment then your own heat treating then I dunno, how about a tooth grinder ?

It's worse than most of metalworking :D

I was just joking about this yesterday with a friend helping me move machines around- Now I need an optical comparator and a Fellows to compliment my hobbers then what else? It's almost a certainty if I have any success making gears there will be more heavy shit to track down and move in.
 
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I was just joking about this yesterday with a friend helping me move machines around- Now I need an optical comparator and a Fellows to compliment my hobbers then what else? It's almost a certainty if I have any success making gears there will be more heavy shit to track down and move in.
I hope you like cutting oil- the real stuff, not the stuff you mix into water, cuz that's where you are headed.
One good thing though- your hands never get dried out.
 
Ha. You're kidding yourself. Get interested in gears and next thing you need a cylindrical grinder for the shafts, an id grinder for bores, then a rolling tester, then a lead tester then an involute tester then a bigger hobber then a shaper for internals then a pointer then a redin then a bunch more measuring equipment then your own heat treating then I dunno, how about a tooth grinder ?

It's worse than most of metalworking :D

You forgot the bit about staring at the ceiling while everyone else sleeps, waiting for the less insane hour to arrive, so that it's only just barely outside of acceptable, so that you can pester every friend you've ever had about helping you clear the hurdle of making your own tooling to be able to make that stupid tooth form that someone theorized about the efficiency of...

Beware of battling monsters.
 
First goal- Electronic gearing. If that works, next goal- 2 cut.
From an electronics point of view, this is a fairly simple task. Not even the coolest PLC can do this.
Another question is how are you going to implement it mechanically? In what condition is the worm gearbox of the table?
 
You forgot the bit about staring at the ceiling while everyone else sleeps, waiting for the less insane hour to arrive, so that it's only just barely outside of acceptable, so that you can pester every friend you've ever had about helping you clear the hurdle of making your own tooling to be able to make that stupid tooth form that someone theorized about the efficiency of...

Well see, if you weren't such a cheapskate you'd buy a bigger building and fill it with machines good for one-offs ! Maag for big parts, ITW generator for fine pitch and maybe a Fellow straight-line generator for small productin jobs. With your wire edm you'd be all set for weirdos !

One nice thing with gearing, you can find new strange stuff to buy until you're too old to even dodder into the shop :D
 
The Eagles have landed. The DB doesn't look terrible now that it's landed in the shop. Jesus the Overton is a hefty girl! The book says 8800. The crane said 11k. The Hyster H80C pulled off a Thanksgiving miracle and didn't snap her 60" forks off lifting the Overton at a 48" load center with an extra ton of counterweight.

Once they're nestled in I can inspect the DB in depth.
 
The Eagles have landed.

Photos !

Overton was a shop that cut gears, then decided to bring in a (don't quote me here) Polish or other east european Pfauter lookalike and put their name on them. They had a decent reputation.

You might consider setting Mr Brown aside for a while while you concentrate on the runner, ya know. Or are you set on living those James Bond fantasies ? :D
 
Yes, its an Overton FD320 made by Automatica Romania. 1979. Looks nice. Sounded good. Truckload of gears, hob arbors, books and parts. No real clue what I am looking at though.

When I first saw a picture my first thought was it looks like a Pfauter.

20221123_115106.jpg20221123_131701.jpg

No unloading pics. It was dark time we got to the shop.
 
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