3D Printed Gears

[stephen thomas]

PEI, then, maybe?
Should be stronger than delrin & phenolic.
Less intrinsic lubricity than PEEK, though.

 

[john.k]

Phenolic gears are abrasive against steel or cast iron gears .....the metal gears get worn into ridges by the canvas in the matrix,apparently....there were a few motorbikes that used a phenolic gear in the primary drive ,and as a clutch plate as well.

 

[EmGo]

PEI, then, maybe?

Easier and more relable to just make them out of phenolic. You know it works.

Or an easy thing to try to stop the ringing would be to turn grooves on each side, connect them with thru-holes and fill the grooves with lead. Or depleted uranium, but lead is easier to come by

Failing that, mount a steel ring gear onto a non-ferrous, non-sound-transmitting body of some sort. Lots of work.

I'd just make a lot of phenolics and sell them as replacements.

 

[implmex]

Hi Dan from Oakland:
Yep...that's what I said in the first sentence of post #44.
But if he needs them stronger than what he can make from Delrin, and if he needs plastic then material price may have to take a back seat to those other requirements.

You're perfectly correct...these will not be cheap gears...last time I bought a 6" long 3" diameter PEEK bar I paid 400 bucks for it from McMaster.
A chunk of 7075 aluminum same size from the same source is just over a hundred bucks.

That's why I invited the OP to cost them out before he gets married to the notion.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[???]

I had to make some replacement gears for a surgery table that were phenolic. The original gear was made from phenolic round bar, I replaced it with a gear made from flat sheet which lasted. The layup direction of the fibres has a huge bearing on strength.

 

[stephen thomas]

last time I bought a 6" long 3" diameter PEEK bar I paid 400 bucks for it from McMaster.

I've been buying plastics lately. While i don't have a supplier for PEEK since not using it (yet ) pretty sure there are cheaper options than Mc Master. OTOH, you are correct that it won't be _cheap_ anywhere.

Easier and more relable to just make them out of phenolic. You know it works.

Maybe, maybe not - PEI is tough stuff
But yeah, would need some experimenting to understand how it fails differently than gears made of sheet linen/canvas phenolic

smt

 

[Dan from Oakland]

ST- yes! NEVER make a gear blank out of phenolic rod- the lay of the fabric in a rod has no strength in the tangential direction. Always cut the blanks from sheet stock.

 

[john.k]

Its not cheap ...I have a sheet of phenolic 3ft x 2ft x 1/2 " ,that cost over $1000........it was bought to make vanes for compressors. .........and I might add ,that price was 30 years ago.............The boat guy next to my shop used to sell phenolic boat prop shaft bearings that were $100 each for 6" lengths......It has the important ability to run under load with water or even salt water as a lubricant.

 

[john.k]

The Russians are reported to have made a substitute material from turnips and sugar beet waste..........large blocks are used for bearings in steel rolling mills ,where they run with water as a lube/coolant.

 

[stephen thomas]

Its not cheap ...I have a sheet of phenolic 3ft x 2ft x 1/2 " ,that cost over $1000........it was bought to make vanes for compressors. .........and I might add ,that price was 30 years ago.

I buy largish phenolic, though usually at machine shop auctions.

Must be an Oz factor?
Or was it a low friction or other modified version?

Standard linen price below.
Canvas is about 20 - 25% less.

PHENOLIC SHEET | NATURAL LE - 24x36x0.500

Natural LE Phenolic Sheet.

www.interstateplastics.com

These guys are not even the cheapest - and note that when you go to leave they quickly offer a 30% discount if you sign up for a business account.

 

[???]

Lignum vitae. I've got a stash that came out of the navy yard. Self lubrication and used in ship bearings.

 

[john.k]

Gidgee wood is a good material for gears ...possibly the hardest wood there is.

 

[EmGo]

Lignum vitae. I've got a stash that came out of the navy yard. Self lubrication and used in ship bearings.

Grain goes the wrong way

Possibly try bronze tho. It's worth a shot as a test. OP needs a test stand

 

[???]

Grain goes the wrong way

Possibly try bronze tho. It's worth a shot as a test. OP needs a test stand

I'm trying to offload my stash at an exorbitant price.

 

[Zahnrad Kopf]

Some pieces I'm looking at pushing towards the printer are gears. Currently we machine some specialized gears from grey iron, mild steel, 4140 and A2, and we purchase more generic gears from the usual sources. There's a few specialized gears we sub out to be made from Phenolic, and prices on those gears has been going up prohibitively. What I'm wondering is if we made a gear from 3D printed Kevlar fiber or carbon fiber (I've been looking at Markforged machines), could we expect the same strength and wear qualities as the phenolic gears of the same dimensions? Or does it really depend on the tooth cross sections, maintained and momentary load, etc.?

These phenolic gears are in open lubricated environments running 500rpm or less. I don't think I've ever seen one worn out, but periodically teeth get broken, so we do sell them as replacements in addition to new builds. With a couple exceptions, most are a long tooth design for variable pitch diameter, and were steel 70+ years ago. Phenolic has been an improvement in the wear properties and operating noise level, but it's not getting any cheaper in the quantities we need. Some of the other tool steel and mild steel gears are also candidates for 3D printing in an effort to decrease noise and improve wear properties, but they are higher load bearing so I'm expecting we would have to do some R&D to see if 3D printings would hold up. I'm curious about the Phenolic replacement though as it could potentially pay for the machine investment, while the steel replacement may or may not pan out.

So in short: What if any 3D printing material is a drop in replacement for Phenolic Resin Gears?

And ...

Again, while making gears on a 4th axis isn't the fastest, it works well for our small batchs. Someday we can get into better conventional methods of making gears, but that's not the problem today qnd not the point of this thread.

With apologies to the OP and his query. The posts that I intermittently responded to seem to have been the result of the typical topic drift and did not help his original query. Thanks to DGFoster for bringing it up to me.

After going back and reading the thread, I did not see any power requirements. Only RPM. Power, Pitch, Tooth Counts, and Face Width would be helpful. Especially in regard to available envelope for Face Width variation toward thicker. Does the mechanism rotate in both directions? Or only ever one?

I ask because if only ever one, and breakage is the most common form of failure ( over wear ), then you might just want to consider an Asymmetric Tooth Form. Not overly common, but not uncommon, and a fantastic way to combat the issues of Strength and Noise, from a gear design standpoint. Also, what kind of breakage? Is it breaking in the Root? Would Root Optimization prevent it? We won't know until more details are available...

If you are limiting to only standard Tooth Forms, then depending on power/strength needs and available Face Width variation, I'd say the recommendations of Phenolic, PEEK, and GFN are all very valid. I would personally stay as far away from 3D printing for a *TON* of reasons, all of which I have written repeatedly about on this and other forums. Between the design side (CAD) and the execution side, they just simply suck. ( that's a technical term ) ESPECIALLY, if you are considering a long tooth variation.

I've machined ( Tooth Space/Form Milled ) and generated ( Hobbed/Shaped ) gears in all three materials, and molded them in both GFN and PEEK. There are pictures of many of them upon our social medias and website, but I'm too busy ( and lazy ) to dig them out specifically. ( it's a lot of pictures to go through ) There is no way to say with any real certainty which will be best for you, without knowing the things that I pointed out, in the beginning of my reply. However, if you can fill in the blanks we can likely get you pointed in the right direction. From the WAG department, I'd wager that any of the three would likely work, and some attention to the actual design side might make them lifelong service. I'd probably try Phenolic first because it's easy, but if there are serious concerns, I'm guessing that cut PEEK gears should be positively fine. Can't really say with any more certainty or numbers without knowing the work envelope and details. Also, you may want to reach out to some other gear making facilities and just simply ask the question, "Can you make this for less than $X.XX?" You might just find that you are making a ton of work for yourself where you do not need to. Dan, EmGo, Peter, and several others gear folk ( as well as myself ) tend to naturally *want* to help someone when they need it.

 

[M.B. Naegle]

And ...



With apologies to the OP and his query. The posts that I intermittently responded to seem to have been the result of the typical topic drift and did not help his original query. Thanks to DGFoster for bringing it up to me.

After going back and reading the thread, I did not see any power requirements. Only RPM. Power, Pitch, Tooth Counts, and Face Width would be helpful. Especially in regard to available envelope for Face Width variation toward thicker. Does the mechanism rotate in both directions? Or only ever one?

I ask because if only ever one, and breakage is the most common form of failure ( over wear ), then you might just want to consider an Asymmetric Tooth Form. Not overly common, but not uncommon, and a fantastic way to combat the issues of Strength and Noise, from a gear design standpoint. Also, what kind of breakage? Is it breaking in the Root? Would Root Optimization prevent it? We won't know until more details are available...

If you are limiting to only standard Tooth Forms, then depending on power/strength needs and available Face Width variation, I'd say the recommendations of Phenolic, PEEK, and GFN are all very valid. I would personally stay as far away from 3D printing for a *TON* of reasons, all of which I have written repeatedly about on this and other forums. Between the design side (CAD) and the execution side, they just simply suck. ( that's a technical term ) ESPECIALLY, if you are considering a long tooth variation.

I've machined ( Tooth Space/Form Milled ) and generated ( Hobbed/Shaped ) gears in all three materials, and molded them in both GFN and PEEK. There are pictures of many of them upon our social medias and website, but I'm too busy ( and lazy ) to dig them out specifically. ( it's a lot of pictures to go through ) There is no way to say with any real certainty which will be best for you, without knowing the things that I pointed out, in the beginning of my reply. However, if you can fill in the blanks we can likely get you pointed in the right direction. From the WAG department, I'd wager that any of the three would likely work, and some attention to the actual design side might make them lifelong service. I'd probably try Phenolic first because it's easy, but if there are serious concerns, I'm guessing that cut PEEK gears should be positively fine. Can't really say with any more certainty or numbers without knowing the work envelope and details. Also, you may want to reach out to some other gear making facilities and just simply ask the question, "Can you make this for less than $X.XX?" You might just find that you are making a ton of work for yourself where you do not need to. Dan, EmGo, Peter, and several others gear folk ( as well as myself ) tend to naturally *want* to help someone when they need it.

Thanks for the insight. I appreciate everyone's patience and hope I'm not adding confusion with the general nature of the query looking at multiple parts.

I'll need to get more of the details, but the phenolic gears are between 5/8 and 3/4 wide. I don’t have data on the specific forces they are seeing, as they were engineered long before my time and all we have are the dimensions, not the data that lead to those dimensions, though I can tell you they are powered by 1/2 to 1 HP motors, and that the motor RPM is reduced via pulleys and gears, and that will of course generate additional torque.

Most of the phenolic gears I've seen fail have been sheared teeth, and again that was due to operators miss using the machine more than a flaw in the gear design. Most of these gears operate in one direction, with reverse only being to back work out of the machine in the event of a problem, but the load on the gears is intermittent and can vary, so I think both sides of the gear profile will see load, but most of it would be on one side.

The steel helical gear that rings is about 1/4" wide, with approximately 45 degree tooth angle (will need to verify that). I've never seen one of those break.

 

[Zahnrad Kopf]

Thanks for the insight. I appreciate everyone's patience and hope I'm not adding confusion with the general nature of the query looking at multiple parts.

I'll need to get more of the details, but the phenolic gears are between 5/8 and 3/4 wide. I don’t have data on the specific forces they are seeing, as they were engineered long before my time and all we have are the dimensions, not the data that lead to those dimensions, though I can tell you they are powered by 1/2 to 1 HP motors, and that the motor RPM is reduced via pulleys and gears, and that will of course generate additional torque.

Most of the phenolic gears I've seen fail have been sheared teeth, and again that was due to operators miss using the machine more than a flaw in the gear design. Most of these gears operate in one direction, with reverse only being to back work out of the machine in the event of a problem, but the load on the gears is intermittent and can vary, so I think both sides of the gear profile will see load, but most of it would be on one side.

The steel helical gear that rings is about 1/4" wide, with approximately 45 degree tooth angle (will need to verify that). I've never seen one of those break.

Can they have a 1.0" Face Width? 1.25"? What is possible? Also, this sounds like a great opportunity for Asymmetrical Tooth Forms. Think helicopter rotor gear boxes... It's not necessary, as I think we can likely figure out a solution for you, but I would definitely remain open to considering it as a very possible solution.

Also, have you ever considered simply attaching dampening material to the face of the metal gears? (assuming that there is room)

For the purpose of simplicity, you should be able to have a properly designed gear of otherwise typical form, though. I really do not see any reason that you shouldn't. This could really be as simple as a Face Width as wide as the envelope allows and an Optimized Root Trochoid Geometry to relieve stress risers.

For those others as self abusive as I am that have spare time and interest, more on Asymmetric Tooth Forms and their applications can be read about to some extent, here - Alex Kapelevich on Harnessing Direct Gear Design for asymmetric gears results in low weight-to-output torque ratio and reduced levels of noise and vibration

 

[M.B. Naegle]

Can they have a 1.0" Face Width? 1.25"? What is possible? Also, this sounds like a great opportunity for Asymmetrical Tooth Forms. Think helicopter rotor gear boxes... It's not necessary, as I think we can likely figure out a solution for you, but I would definitely remain open to considering it as a very possible solution.

Also, have you ever considered simply attaching dampening material to the face of the metal gears? (assuming that there is room)

For the purpose of simplicity, you should be able to have a properly designed gear of otherwise typical form, though. I really do not see any reason that you shouldn't. This could really be as simple as a Face Width as wide as the envelope allows and an Optimized Root Trochoid Geometry to relieve stress risers.

For those others as self abusive as I am that have spare time and interest, more on Asymmetric Tooth Forms and their applications can be read about to some extent, here - Alex Kapelevich on Harnessing Direct Gear Design for asymmetric gears results in low weight-to-output torque ratio and reduced levels of noise and vibration

Wider might be possible. There's room in the gearboxs, but I'll have to look at clearance with the surrounding parts.

With the phenolic gears, failure as they are currently made isn't really an issue. When they fail, it's typically just one gear and that's the only one replaced, so ideally we would want to make new gears that still assemble and mesh with old ones, though having a new design and stocking a few old style gears for support is a possibiliy too. The only reason I would want to improve the design is if having a better profile or wider gear would enable a slightly more inferior material to perform the same or better than the old way, using better material with a more inferior design.

I was looking at the 3D printing aspect as a way to simplify manufacturing, provided the gears would perform the same. If we're going to stick with conventional gear making though, I'd just stick with phenolic since it's already proven itself. I'll get a print for the next phenolic gear we need and put up an RFQ here. Maybe it's just about finding the right gear shop.

Now the steel gear is another story because of the ringing issue. If there was a synthetic that held up as good or better than the steel, we'd use it, but It dosn't have any room to change tooth profile or width, and I think other than some cutting edge stuff (why I'm asking), phenolic and other more common plastics would break too easily. If 3D printed carbon fiber isn't the ticket, I think keeping it steel would be in order and we'll recess some O-rings into the sides to dampen it.

 

[michiganbuck]

I think printed gears for a hobby guy would be good. Likely quieter and long enough lasting for a lower price.
Printed phenolic with 50% metal might be good, for one-ups or few-ups likely very good.
I once made a special gear of hard wood out of sections so the grain gave the most srength, it did not last very long.

 

[Zahnrad Kopf]

Wider might be possible. There's room in the gearboxs, but I'll have to look at clearance with the surrounding parts.

With the phenolic gears, failure as they are currently made isn't really an issue. When they fail, it's typically just one gear and that's the only one replaced, so ideally we would want to make new gears that still assemble and mesh with old ones, though having a new design and stocking a few old style gears for support is a possibiliy too. The only reason I would want to improve the design is if having a better profile or wider gear would enable a slightly more inferior material to perform the same or better than the old way, using better material with a more inferior design.

That's what I'm thinking. Specifically, if you determine that it *is* a Root Stress issue it's nearly certain that simply adding Face Width and optimizing the Root Trochoid will eliminate the issue as well as remain backwards compatible. ( with all other things being equal )