Manufacturing of micro gears

nate8649 · Feb 24, 2017

Hey,
I'm new to the forum and I come to you seeking some guidance. I've been put in charge of figuring out how we are going to manufacture some gears that we will be making in our shop. We have never made gears before so we are new to this. The gears are tiny. One is a 18 tooth spur gear with a 120 pitch and an OD of .1667" and one is a 54 tooth internal ring gear with a 120 pitch and a .4322" ID. Both AGMA class 10. They will be made of 303 stainless and will fit together in a planetary system. We have quite a few machines in our shop that we can use but no dedicated gear machines. We have some swiss lathes that might be able to handle a hobbing attachment. Does anyone have any experience making gears this size? I've done quite a bit of research but cant decide on a direction I should pursue. I've looked into hobbing attachments for our existing machines, dedicated gear hobbers, broaching, and shaping. Production will be moderate so I'm looking for an affordable option. Does Barber Coleman make a machine that would make this size gear? I've also looked into the Mikron 79. Any information or suggestion is much appreciated. Thank you!

Zahnrad Kopf · Feb 24, 2017

Yes. We have made a lot of small gears over the years. So far, the smallest has been 22T 180DP Spur Gears. :eek:

They really kind of sucked to make. And make well. There is a LOT to consider and control when making gears, much less making gears of high quality. This gets even MORE complicated when you add "small" to the equation. Planetaries have their own considerations, as well. Make sure you are not diving head first into the deep end, filled with bricks, here. Moderate and affordable do NOT reconcile each other when one is discussing gear manufacturing. That is a pipe dream, at best. A pitfall of frustration leading to failure, at worst.

If you have any specific questions, feel free to ask.

KilrB · Feb 24, 2017

Zahnrad Kopf said:
Yes. We have made a lot of small gears over the years. So far, the smallest has been 22T 180DP Spur Gears. They really kind of sucked to make. And make well. There is a LOT to consider and control when making gears, much less making gears of high quality. This gets even MORE complicated when you add "small" to the equation. Planetaries have their own considerations, as well. Make sure you are not diving head first into the deep end, filled with bricks, here. Moderate and affordable do NOT reconcile each other when one is discussing gear manufacturing. That is a pipe dream, at best. A pitfall of frustration leading to failure, at worst.

If you have any specific questions, feel free to ask.

How did you make those?

OP doesn't state a thickness but, could something like that be coined?

If so, how well would the teeth take the form and hold up under use?

Conrad Hoffman · Feb 24, 2017

Can they be photo-etched? The watchmaking industry made lots of stuff like that- I'd research that. Big equipment often doesn't lend itself to such things.

DM · Feb 24, 2017

Photo etching would be a good option, probably be cheaper to get them made for you.

The Photo Etching Process | Precision Micro

implmex · Feb 24, 2017

Hi Guys:
I believe these are supposed to be AGMA class 10 gears.
I'm not too confident you can make these by etching especially if they have any thickness.
Etching works best with very thin parts.
And AGMA class 10 gears are fussy to make...they gotta be ACCURATE!! and they have to have the same profile from the front face to the back face.
Etching cannot control the cross sectional profile; it's typically most accurate right next to where the resist was applied and is hourglassed from there (if the resist was applied to both faces; or tapered if the resist was applied to only one face.

The gears also have to have smooth flanks to transmit rolling motion properly and to avoid stress risers.
Acid etching won't deliver that; the surfaces will be pitted.
These sound like precision ground gears to me.
Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com

Zahnrad Kopf · Feb 24, 2017

KilrB said:
OP doesn't state a thickness but, could something like that be coined?

Conrad Hoffman said:
Can they be photo-etched? The watchmaking industry made lots of stuff like that- I'd research that. Big equipment often doesn't lend itself to such things.

DM said:
Photo etching would be a good option, probably be cheaper to get them made for you.

At AGMA Q10? I doubt it.

KilrB said:
How did you make those?

I Hobbed them. Everything about that Planetary absolutely sucked to make. They were for a Surgical Instrument. That's all I can say about the purpose. The workholding alone took a fair amount of effort and time. When you get to gears that small, high quality means a few tenths in every regard. Not only does the Involute Form itself matter, but Tooth to Tooth Errors, Pitch Line Errors, Concentricity, EVERYTHING matters... and one does not get a lot of wiggle room in that envelope.

That brings up another question that the OP will have to consider. How will they be inspecting them? And at what frequency? Things can go sideways QUICKLY when you only get a few tenths either side. :angry:

wheels17 · Feb 24, 2017

Grob, Inc. makes gear stock in the form of long rods. They don't go down to the size you need, but perhaps the fixturing issues could be helped by making a long gear shaped rod and dicing it into individual gears. Would anybody be able to make a broach that is accurate enough for the ring gear?

Peter Colman · Feb 24, 2017

The Mikron will make the spur gear but not the internal gear. I would certainly hob the spurs and consider broaching the internals, as bot are used together, you have control of the fit so can adjust the spurs to suit the internal.
You could consider hobbing the broach on the Mikron or buy the broach and adjust the spurs to fit.
Peter

nate8649 · Feb 24, 2017

Zahnrad Kopf said:
Yes. We have made a lot of small gears over the years. So far, the smallest has been 22T 180DP Spur Gears. They really kind of sucked to make. And make well. There is a LOT to consider and control when making gears, much less making gears of high quality. This gets even MORE complicated when you add "small" to the equation. Planetaries have their own considerations, as well. Make sure you are not diving head first into the deep end, filled with bricks, here. Moderate and affordable do NOT reconcile each other when one is discussing gear manufacturing. That is a pipe dream, at best. A pitfall of frustration leading to failure, at worst.

If you have any specific questions, feel free to ask.

I guess my specific question is the same as KilrB's. How did you make those? I know its not going to be easy, especially with us not having any experience. There are some pretty cool machines out there but I doubt they will be in our price range. Affolter makes some pretty cool gear cutting machines for stuff like this.

KilrB said:
How did you make those?

OP doesn't state a thickness but, could something like that be coined?

If so, how well would the teeth take the form and hold up under use?

The thickness is .133" on the spur gear and .125" on the ring gear.

Conrad Hoffman said:
Can they be photo-etched? The watchmaking industry made lots of stuff like that- I'd research that. Big equipment often doesn't lend itself to such things.

I just looked into photo etching, more like wizard machining. That's pretty cool, unfortunately it wont work for this application as the gears are too thick.

I'm thinking we will be trying to go fairly cheap to start with this project as we need the machines to make and inspect these things. Is there such thing as a mini shaping machine? Gear shaping seems like a decent solution because we could theoretically make both gears on the same machine. Most gear shapers are huge and expensive though. I've looked into broaching the internal gears and there seems to be semi-reasonable options there (minibroach makes some cool machines) but then I need to figure out the external gear. I was looking at Mikron 79 machines or maybe one of the barber colemans. What is the smallest barber coleman they made? Anyone have any experience on either one of these machines?
Thanks

nate8649 · Feb 24, 2017

Zahnrad Kopf said:
At AGMA Q10? I doubt it.

I Hobbed them. Everything about that Planetary absolutely sucked to make. They were for a Surgical Instrument. That's all I can say about the purpose. The workholding alone took a fair amount of effort and time. When you get to gears that small, high quality means a few tenths in every regard. Not only does the Involute Form itself matter, but Tooth to Tooth Errors, Pitch Line Errors, Concentricity, EVERYTHING matters... and one does not get a lot of wiggle room in that envelope.

That brings up another question that the OP will have to consider. How will they be inspecting them? And at what frequency? Things can go sideways QUICKLY when you only get a few tenths either side.

I looked into inspection briefly. A roll checker will be necessary. We also have an optical comparator and a OGP quest 250 that may be able to do some of the inspections optically. It seems measuring tooth thickness over pins is a common practice. I think I was typing the response asking about the Mikron 79 as you were posting. Did you guys use the Mikron 79? They are cheap and I'm thinking that might be an option. Is it hard to find parts for them? These gears will be used for medical equipment as well.

Derek Smalls · Feb 24, 2017

If it's any help to you, I have a couple of roll checkers I would sell for a reasonable price. I don't know much about them, they came as part of a large package of inspection equipment I bought from a small screw machine/gear shop a few years ago when the owner was retiring. He included them in my package because someone else had already bought all his master gears, but did not want the machines themselves.

triumph406 · Feb 24, 2017

I generally try and keep everything I can in house, but gears I'd vend out, too much to learn. Making gears might be a steep learning curve. What are your quantities? If you were to vend it out I'd go with Gearles in Costa Mesa CA

nate8649 · Feb 24, 2017

triumph406 said:
I generally try and keep everything I can in house, but gears I'd vend out, too much to learn. Making gears might be a steep learning curve. What are your quantities? If you were to vend it out I'd go with Gearles in Costa Mesa CA

Probably somewhere around 2,500 ring gears and 10,000 spur gears per year.

Milland · Feb 24, 2017

Nate, you want a specialist to make those gears, it's not a trivial project. Also, if these are to have a significant life you may want to rethink using 303ss, as I'd question its fatigue life/strength (it is made purposely contaminated with soft inclusions to facilitate machining).

Is this for a medical tool? There are existing companies that make such gear sets, and much as it's nice to keep everything in-house, I'd not try it.

adama · Feb 24, 2017

Im in the send em out camp too, its one of thoes things to some one already tooled its more or less a programme setup and hit the green button type job. to setup tooling and inspection alone is going to cost you what you can probably buy several thousand finished pieces for.

nate8649 · Feb 24, 2017

Milland said:
Nate, you want a specialist to make those gears, it's not a trivial project. Also, if these are to have a significant life you may want to rethink using 303ss, as I'd question its fatigue life/strength (it is made purposely contaminated with soft inclusions to facilitate machining).

Is this for a medical tool? There are existing companies that make such gear sets, and much as it's nice to keep everything in-house, I'd not try it.

Yes, its for a medical device. We have looked into having them made elsewhere but they are quite expensive. I think the 303 stainless was chosen because it may be subject to water or other fluids. I wasn't around for the material decision making.

Zahnrad Kopf · Feb 24, 2017

nate8649 said:
Probably somewhere around 2,500 ring gears and 10,000 spur gears per year.

Nate, is this an engineered gear box? Or, rather is this a crunching of numbers and ratios, done by an engineer? There's a bit of an important difference, and it might behoove you to examine exactly what it is that you will actually need from the Planetary to deliver desirable results. I'm happy to help with either path if you should decide to go that route, having some experience with your field and our own.

implmex · Feb 24, 2017

Hi nate8649:
Why do they need to be AGMA class 10?
is there a timing requirement?
Is there a precision motion requirement?
Is there a low backlash, low rolling resistance high load factor, long lifespan or what that forces this somewhat ambitious requirement ??
Is it possible the engineer's gone batshit crazy just because it's medical? (I deal with this a LOT, so it's a legitimate question)

Also were you aware that an AGMA class 10 gear in 303 stainless ain't gonna be AGMA class 10 for very long if it sees any load or speed.
If you wish to preserve the precision for any length of time under any sort of load, they really should be hardened (or at least harder and more wear resistant than 303 SS)

Also, just for shits and giggles, are we talking about AGMA 2000-A88 standards here or are we talking about ANSI/AGMA 2015-1-A01?
The old AGMA standard designates class 10 gears as a quite precise specification while the new standard is just the opposite.
Under the new ANSI/AGMA standard a class 10 gear is a loose tolerance gear; one step up from what you'd find on a backyard cement mixer.

Last, are you SURE you want to get into this as deeply as it's gonna take to certify to the standard you're hoping to meet?
I'd give these to Zahnrad Kopf in a heartbeat and let him break his head making this all happen as it should, since guys like him know the turf really really well compared to you and me.
Otherwise, judging from the lack of gear experience demonstrated by your questions, I predict some pain before you get in the groove.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
www.vancouverwireedm.com

triumph406 · Feb 24, 2017

nate8649 said:
Probably somewhere around 2,500 ring gears and 10,000 spur gears per year.

If you were to do it house, I would suggest you hire somebody who has run machines that can make internal/external gears, and could advise you on the best machines to get.
I would try and calculate the cost of machines+mat'l+labour, and compare with quotes your getting from outside vendors before I committed to doing this in house. You could calculate a break even to see whetether it's cost effective to bring in house. My thinking (seems to be general consensus) is it's better to vend out. Those are pretty respectable quantities to get a decent price I would think.

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