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    Quote Originally Posted by michiganbuck View Post
    With knowing the pitch diameter and being able to hold perhaps +- .002 I think a printed gear might work (or a time). First choice the manufacturers gear for perhaps 40 or $60 as a guess.

    ]
    Yes, thanks - forgot to correct a previous post. The stratasys line of 3D printers have an XY accuracy of .002. Z of whatever the print height is, generaly .005 on a printer that can do a high end material. Min wall thickness is going to be .020, but that should be OK, with this print looking at the picture.

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    Would you need to trig out the angle or would the computer do that?

    Knowing the number of layers needed to make height that should not be difficult....? if layers were constant..?

    Stacking would not have the same problem as making (on a conventional machine) as all layers would be the same diameter.

    Still a print or an original part measure might be need to get the root diameter... Is that correct?

    Time seems reasonable for a one up and with walk away after 1/2 hour or so even good.

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    # of teeth, pitch, and pressure angle is all you need. I have this fancy spreadsheet that makes the gear in SW too but its a bit finiky. I like to use gear.dll in mastercam, its so fast. Last time I checked bobcad had one that was pretty good and simple too.

    The concern is the radius at the root might interfere with the mating gear. What I would do is take a 2D scan of the gear then compare it to the drawn gear.

    AG

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    Quote Originally Posted by avongil View Post
    All the hobby printers use 3D printed gears. They are printed mostly out of junky PLA and they work great...
    Not to pile on here but the is no comparison between the mechanical components of a printer and those of a motor home. Delrin is about the strongest engineering plastic there is, and if that failed you had better hob one out of some kind of metal. This reminds me of the belief among college students that carbon fiber is "stronger" than steel. It can be true within a very narrow context, but deviate from that and it instantaneously becomes a piece of rope. It's not impossible that the original design of the mechanism was influenced by the same blind faith in plastics. I hear so much hype about printed plastic that I understand why Dustin Hoffman stayed underwater.*

    *Antedeluvian cinema reference; never mind.

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    http://www.stratasys.com/~/media/Mai...2-13%20Web.pdf

    These are tested in XZ. I estimate 20% stronger in XY. This is what mostly counts on this gear.
    Delrin's tensile strength comes in at 9,000 psi roughly. (there are so many)

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    Why did the original fail?

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    Quote Originally Posted by avongil View Post
    Why so hostile to 3D printing?
    < ...snip... >
    I suggest you try it before bashing the idea.
    Hostile? Hardly. Try it before bashing it? You must not have read my post where I said,
    Quote Originally Posted by Zahnrad Kopf View Post
    I am intimately familiar with SLA and SLS, as well as using both ( and others ) for gears. Don't waste your time. You will not be satisfied with the result.
    Fact is, I use it all the time. Have been actively involved with it for over a decade now. I've been doing this a few days now... I can "bash" it exactly because I have tried. It's called the voice of experience.

    The problem is that you know just enough to spit out some buzz words, without actually having command of the necessities. That's not a big deal in and of itself. We all start somewhere. Where it becomes an issue... where I take issue... is when one starts making assertions that simply are not true, at the expense of someone else's time, money, and aggravation.

    Quote Originally Posted by avongil View Post
    # of teeth, pitch, and pressure angle is all you need.
    It betrays your lack of knowledge of the subject. You need more information for the gear that the OP requested.

    Quote Originally Posted by avongil View Post
    I have this fancy spreadsheet that makes the gear in SW too but its a bit finiky. I like to use gear.dll in mastercam, its so fast. Last time I checked bobcad had one that was pretty good and simple too.
    Hoo boy... I don't even know where to begin with that one... I'm familiar with Mcam's gear.dll and BobCAD's gear function, as well as a number of other ones available. For the sake of discussion, we'll completely disregard the fact that they are unacceptable for this job. So how would you calculate the Addendum Modification Coefficient required with those tools?

    Quote Originally Posted by avongil View Post
    The concern is the radius at the root might interfere with the manufactured/printed gear. What I would do is take a 2D scan of the gear then compare it to the drawn gear.
    AG
    Why? If it is so accurate and made so well, why would there be any concern at all?

    How much time does all of this 2D scanning, modeling, figuring, and printing take? How much does all of this cost? Is it then rebated to account for this 80% of acceptability?

    There is much more I could address with your posts in this thread, but I'll decline. I agree that it could be construed that I am coming off against you. I am not. If you have taken it that way, I assure you that it is not my intention. I simply do not wish to see someone so blatantly steered wrongly by someone without a full grasp of what it is they are extolling.

    I'll leave it to others.

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    I actually have a set of gears that were printed on a Fortus 400 and I really don't think it will work in this application.

    The specs Stratasys provides are true in a sense, but you have to remember that the plastic is coming out of a nozzle. They claim 0.02" minimum feature size but that has no real meaning. Text in the Z direction for example always looks garbled.

    Here is a close up of some 3d printed gears that I found on google. The quality looks to be pretty much on par with what you'd get out of a stratasys. The gear is probably 3" in diameter so these teeth are very coarse.


    They look great but the geometry is always off. You can't get a proper involute profile because corners get rounded. I also find that for small curvy paths the process tends to make everything fatter so you generally have to offset the CAD drawing or printed gears won't even fit together.

    Things only get harder as the teeth get smaller.

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    That didn't take long.



    Quote Originally Posted by RyanT View Post
    I actually have a set of gears that were printed on a Fortus 400 and I really don't think it will work in this application.
    The specs Stratasys provides are true in a sense, but you have to remember that the plastic is coming out of a nozzle. They claim 0.02" minimum feature size but that has no real meaning. Text in the Z direction for example always looks garbled.
    Here is a close up of some 3d printed gears that I found on google. The quality looks to be pretty much on par with what you'd get out of a stratasys. The gear is probably 3" in diameter so these teeth are very coarse.

    They look great but the geometry is always off. You can't get a proper involute profile because corners get rounded. I also find that for small curvy paths the process tends to make everything fatter so you generally have to offset the CAD drawing or printed gears won't even fit together.
    Things only get harder as the teeth get smaller.

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    Ryan, would you be so kind as to take a pic or two of the ones you have? I would post some myself, but I simply do not have any around any more as I stopped doing it a while ago because they sucked. Thanks.

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    Those pictured gears work really well belive it or not.
    The Fortus print would look quite a bit better. Unfortunatley I never took any side pics of any gears I printed at .005".

    No need to calc the addendum modification coefficient. I have just modified the profiles so they are undercut. Then when it prints it gets closer to the actual shape or sharp.

    This method produces parts with layers of .005 and XY accuracy of +- .002 Not to mention other inacuracys when at sharp corners.
    This is not some aerospace part that needs to pass cq. Seems resonable considering the application. No need to examine every detail.

    I provided a way to get this done with 3D printing with resonable effort and results considering the application and limited info. The original question was answerd.

    Nit pick all you want, but printed gears work and its a viable option at times.

    I do see your point. It might take two prints for this to work. The test part would probably need to be modified to get the correct profile.

    Quite frankly this problem was resolved when somone posted a link to a $30 gear on ebay that could be modified. That's most likley the best and most cost effective answer.
    The original question was can it be 3D printed. Yeah I think it can be. If you disagree then we agree that we disagree.

    Yes you are hostile.



    AG

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    the .005" accuracy on the 3D print is of no concern in my opinon when dealing with a gear that is half the size it should have been for a delrin part.*
    now, granted that we don't know exactly why it failed, what makes you think it could be replaced with a 3-d printed part?

    i would be more likely caught dead cutting the teeth into an aluminum blank with a hacksaw and a triangular file.

    Quote Originally Posted by avongil View Post
    Those pictured gears work really well belive it or not.
    AG
    yes, for things like the stepper motor driving the printhead of said three-d printer.
    Quote Originally Posted by avongil View Post
    Seems resonable considering the application.
    there are garage door openers that are worm driven at 1750 rpm, 40 or 50:1 with a plastic gear that wears out after exactly 1 year after the warantee is up.
    i notice that in the ebay auction.. the helical part was about the same width as the spur part of half the diameter.... hmmmm.


    *the accuracy of a 3 d printer is dependant on a lot of things.
    first off the diameter of the plastic extrusion.. granted that is constant everywhere.
    second is the backlash in the mechansims.. probably at least .010".
    third is the inaccuracy of the screw.
    suppose one is at +.001"/" and the other is -.001"/inch absolute positioningin.
    combined we have .oo141' position error.
    all of a sudden your gear is an ovel isn't it. after it wears in, it will have the 14 degree pressure angle on one side, and 30 degrees on the other.

    in my opinion 3-d printing gears is good for lost-plastic bronze casting.
    Last edited by johansen; 01-04-2015 at 05:23 AM.

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    One thing not yet mentioned is that if it can not be found perhaps that is because it was a poor design.
    Perhaps the small teeth were not up to the task and the new gear box has a larger tooth gear or a three set to handle the ratio in a different way.
    If that is the case an 80% (printed) gear would be likely fail in half the time..and you might be stuck at the camp site with your thing hanging out.
    With that only a gear as strong or stronger would be the correct answer. (Yes stronger might just wipe out the mating gear faster if it too is plastic or nylon.)
    Perhaps the $300 new box is the way to go.

    Here is an obsolete motor no longer made
    http://www.plccenter.com/buy/VON+WEI...6AH88?reload=1
    http://estore.vonweise.com/v05726ah8...withbrake.aspx

    current
    http://estore.vonweise.com/RVSliders.aspx

    I said:
    I think a printed gear might work (for a time). but with rethinking "for a time" may end up being waste of time so I agree with Zhanrad also..
    Last edited by michiganbuck; 01-04-2015 at 11:15 AM. Reason: added "I said..."

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    Quote Originally Posted by avongil View Post
    Those pictured gears work really well belive it or not.
    The Fortus print would look quite a bit better. Unfortunatley I never took any side pics of any gears I printed at .005".

    No need to calc the addendum modification coefficient. I have just modified the profiles so they are undercut. Then when it prints it gets closer to the actual shape or sharp.

    This method produces parts with layers of .005 and XY accuracy of +- .002 Not to mention other inacuracys when at sharp corners.
    This is not some aerospace part that needs to pass cq. Seems resonable considering the application. No need to examine every detail.

    I provided a way to get this done with 3D printing with resonable effort and results considering the application and limited info. The original question was answerd.

    Nit pick all you want, but printed gears work and its a viable option at times.

    I do see your point. It might take two prints for this to work. The test part would probably need to be modified to get the correct profile.

    Quite frankly this problem was resolved when somone posted a link to a $30 gear on ebay that could be modified. That's most likley the best and most cost effective answer.
    The original question was can it be 3D printed. Yeah I think it can be. If you disagree then we agree that we disagree.

    Yes you are hostile.



    AG

    I agree with Zhanrad, 100%. 3D printing has its merits for producing an item, the right process has to be selected for the task at hand. It is just like anything else.

    This is a great example of: Stop talking, you are making a fool of yourself.

    FDM just is not a good fit for this type of gear. If you were seriously in a pinch, polyjet would be the process to get the resolution you need, if time permitted you could get it plated for some longevity.

    If your going to talk 3D printing in a commercial forum you need to know the different processes and why they are used.

    Tim

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    Quote Originally Posted by behindpropellers View Post
    3D printing has its merits for producing an item, the right process has to be selected for the task at hand. It is just like anything else.
    Exactly.

    Quote Originally Posted by behindpropellers View Post
    This is a great example of: Stop talking, you are making a fool of yourself.

    Yep.


    Quote Originally Posted by behindpropellers View Post
    FDM just is not a good fit for this type of gear. If you were seriously in a pinch, polyjet would be the process to get the resolution you need, if time permitted you could get it plated for some longevity.
    Yep. That, or I would most likely SLA it in a 3DS Viper using Accura25 at fine resolution. One still has to address the construction of a proper model of a helical gear, though. And not just a helical gear. A proper model of that helical gear, with all of its Profile Modification. I'm sure avongil is well versed.

    Quote Originally Posted by behindpropellers View Post
    If your going to talk 3D printing in a commercial forum you need to know the different processes and why they are used.
    Yep. Last night I recalled the words of Shaw - "I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it." Not saying avongil is a pig. Only that I realized it was a futile effort because he is not willing to listen to people with more experience and knowledge of the subject.

    Can it be done? Absolutely. Will it work? Possibly marginally. Is it the best option? Not as long as there are any number of other options available.


    EDIT - changed material from Accura 60 to Accura 25 because of mistake while typing. ( I always confuse the two names ). /EDIT
    Last edited by Zahnrad Kopf; 01-04-2015 at 11:43 AM. Reason: material correction

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    Tim, polyjet is not the right process for this. Its completly wrong. It will fail instantly. It is also very dimensionaly unstable.

    I drew the aproximate gear up last night (straight) and ran it through catalyst at .007" and the gear teeth filled pretty well. Nylon 12 will work. Tweaking the toolpaths in insight would make a pretty darn solid gear. Marginally... Don't think so, a bit better. I stand by my initial post of 80% of a solid nylon gear. Quite frankly, I doubt anyone has seen printed nylon 12. It came out last year. Except for Zahnrad - he has infinite knowledge on the subject.

    NO its not the best option. If it failed out of solid delrin, then its probably not strong enough from the factory. Cutting it would be. I also did some research and these gearboxes have shear pins, so Id get it cut out of metal.

    Found this dudes web site while trying to find the gear specs, he has done them before and advertises them on the web site so perhaps try giving him a call. Perhaps he has some ready to roll.
    Any Gear Made Quickly Inexpensively & Perfectly Al Meekins GearsMade.com. --Delrin gears Plastic gears Bevel gears Worm gears Spur gears Helical gears Phenolic gears Stainless steel gears Cast iron gears Machine gears Steel gears Metric gears Bronze

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    Quote Originally Posted by Zahnrad Kopf View Post
    As proof of concepts, yes. As anything else but a curiosity, no. I'll point out that .005" of _anything_ on a gear is unacceptable for a replacement of an actual working gear. For the money that such a part would cost I would rather buy the appropriate Involute Mill and mill them. It would be more acceptably accurate. In your BEST case scenario, let us assume an actual perfect Involute, with the result being as you say above, even though there is no way in hell that a FDM printer will create an actual perfect Involute, as neither the machines nor the materials are capable of that kind of accuracy. This will mean a gear that will have high spots and low spots on its teeth, varying by .005". Given the size range of the gears being discussed as applicable to be printed, this represents all of the typical backlash. So, if working to a fixed center distance once has just completely blown the backlash spec at best and caused a bind, at worst. I am willing to be wrong on this, but years of running and maintaining 3D printers and running an actual gear producing shop tell me otherwise. Let me know when you start finding FDM gears in mass produced consumer goods requiring good function and durability.

    EDIT -

    I'm wondering how you can say it's accurate when you earlier state -



    /EDIT


    2nd Edit -

    Never mind. I just realized that you're a reseller and salesman for FDM printing services.

    /EDIT
    Actually he mentioned .005" THICK layers, might want to learn what you are reading before you go off on someone. The accuracy of the print itself has the potential to be much better depending on the printer. Thin layers would be required here due to the angle of the teeth so you can get a good finish, tips would be radiused due to the extrusion being round. I can print with a .35mm tip which I would say at worst case would leave about a .020" radius on the tips.

    Attached is a picture of a print I did this week on my $700 printer.

    Horizontal features such as the holes leave a lot to be desired since I do not use support material and layer height can affect where the hole is sliced leaving a flat top but vertical features come out very nice. There is an 8mm hole on the top side of this that printed at 8.04mm when measured with a caliper and an 8mm rod fits nicely.

    .5mm nozzle, .18mm layers, PLA material
    Attached Thumbnails Attached Thumbnails sample.jpg  

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    Quote Originally Posted by tjb1 View Post
    Actually he mentioned .005" THICK layers, might want to learn what you are reading before you go off on someone. The accuracy of the print itself has the potential to be much better depending on the printer. Thin layers would be required here due to the angle of the teeth so you can get a good finish, tips would be radiused due to the extrusion being round. I can print with a .35mm tip which I would say at worst case would leave about a .020" radius on the tips.
    Attached is a picture of a print I did this week on my $700 printer.
    Horizontal features such as the holes leave a lot to be desired since I do not use support material and layer height can affect where the hole is sliced leaving a flat top but vertical features come out very nice. There is an 8mm hole on the top side of this that printed at 8.04mm when measured with a caliper and an 8mm rod fits nicely.
    .5mm nozzle, .18mm layers, PLA material
    I really have no interest in a debate of semantics with you. The Shaw Rule applies, still. I stand by my statement taken within its context. Let me know the last time you have put a SLA, SLS, FDM ( or any gear for that matter ) on a Vari-Roller, Gleason, or M&M inspection machine and what those results were. I have. So until you can actually give me numbers that equate to an actual, acceptable replacement for a gear in a consumer product that functions with accuracy and longevity from any of these methods I'll continue to stand by the knowledge and experience I have gained by doing so for myself and studying the subject at length with others in the field. I do have to admit to finding good humor in the fact that you seem to think that you can print an accurate Involute when you cannot even hold true roundness or size of a diameter.

    In fact...

    Here's an offer for any of the knuckleheads that just refuse to listen to reason, fact, and experience. Wanna waste your time and money as well as the OP's time and efort? Put your money where your mouth is.

    Make your gear. Send it to the OP. If it works as original and lasts, I will come back and declare your superiority and my own stupidity. If it does not work as original and with longevity, you will eat all costs related to it, as well as pay the OP for his time for removal of gear box, installation of yours, and removal again once it has failed, as well as purchase of an actual, suitable replacement. We will assign a typical average shop rate of $75 per hour to the tasks and put a cap on it at $1000.00 USD. And it ALL counts. Every minute of your time doing calculations and modeling and set up and printing and clean up. And as long as you're doing that, send me another one and I will put it on one of the above mentioned machines and film a video of its inspection for all to see so you know that I am not fudging the numbers. Longevity will be defined as a similar number of usage cycles equivalent to the number it took for the original to fail. So, if OP had it for 10 years, and used it 10 times a year, your gear must cycle 100 times to pass.

    Is that fair enough for you? Let's go. I'm willing to do it. Are you? I'll say it again - Put your money where your mouth is. Hobbyists need not apply.

    Until that time, every single word you write or speak regarding the subject is simply empty rhetoric.

    Let's see who's willing to piss away up to $1000.00 USD...

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    I am very excited about the development of additive manufacturing processes (though I still hate the term 3D Printing) and have no dismal pessimistic attitude toward the subject in general like many often display when this forum section is on the 'recent posts' list.

    But to bastardize a Vader quote: "I find your lack of objectivity... disturbing."

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    Quote Originally Posted by JNieman View Post
    I am very excited about the development of additive manufacturing processes (though I still hate the term 3D Printing) and have no dismal pessimistic attitude toward the subject in general like many often display when this forum section is on the 'recent posts' list. But to bastardize a Vader quote: "I find your lack of objectivity... disturbing."
    JNieman, It is not clear if you are referring to my post. It seems to be, so I will reply in kind -

    I _think_ I am very objective about it. I _love_ what Additive Manufacturing can do. In case you missed it, I'll quote my own message -
    Quote Originally Posted by Zahnrad Kopf View Post
    Fact is, I use it all the time. Have been actively involved with it for over a decade now. I've been doing this a few days now... I can "bash" it exactly because I have tried. It's called the voice of experience.
    This is where I'll quote my own message again -
    Quote Originally Posted by Zahnrad Kopf View Post
    Where it becomes an issue... where I take issue... is when one starts making assertions that simply are not true, at the expense of someone else's time, money, and aggravation.
    I'm not bashing Additive Manufacturing. I love AM. I use it all the time. I do however take issue with people that so obviously don't have clue recommending things to others that will cost that other person time, money, and aggravation. ( in this specific case - recommending an inferior product as acceptable ) So I am suggesting that if they truly believe what they say, then put some skin in the game. It is really that basic.

    EDIT - added clarifying in parens at end /EDIT


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