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How would a hobbyist machine gears?

  1. Jan 12, 2009 #1

    DaveC426913

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    I want to play with gears - make my own and such. (They'd be custom, so it's not like I could put in an order for them to be made.) What are my options for getting access to the right machines?
     
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  3. Jan 12, 2009 #2

    Mech_Engineer

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    It will depend greatly on what kind of gears you're wanting to make. The machining process for a "standard" toothed spur gear is not too bad, but a tapered-tooth face gear or helical offset ring & pinion like in a car's differential could be pretty difficult.

    Doing a search for "gear cutting" in Google came up with this interesting article from "The Boy Handbook":
    http://chestofbooks.com/crafts/popu...ings-for-Boys-to-Do/Gear-Cutting-Machine.html

    As for the fact that they're custom gears, there are many machine shops accross the nation that can make any gear you want, as long as you've got a good drawing/ model of it, and money to pay them.
     
    Last edited: Jan 12, 2009
  4. Jan 12, 2009 #3
    You could create a solid model and have them printed on a 3d printing machine...they would be plastic but the cool thing is, once the support structure is dissolved, seperate gears in the assembly are able to move. There are several types of polymers used with different strength profiles (depending on what you may need).

    I am not sure the cost, I have seen several websites that will make parts and send them out. Try Googling it.

    Example of a 3d printed gear assembly:
    http://content.answers.com/main/content/img/CDE/_3DPCOLR.JPG

    One of many companies that specialize in 3d printing
    http://www.3dprintstudio.com/
     
  5. Jan 12, 2009 #4

    Mech_Engineer

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    Depending on the gear application rapid prototyping/manufacturing could be an ok idea. They would have to be pretty substantial in size to be made accurately on a RP machine though, because they usually have trouble making very small features (features smaller than .035 or so, depending on the machine.)

    I wouldn't recommend using an SLA (stereo lithography) machine process, but I've had prototypes and functional parts made on SLS (selective laser sintering) and plastic resin machines that were suprisingly durable.
     
  6. Jan 12, 2009 #5

    FredGarvin

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    It depends on the sizes and loads that you are interested in playing with. There are a few companies out there that have huge selections and are pretty cheap. In most cases, unless you really wanted to figure out how to make your own gears, you'd be better off looking for someone to purchase them from and be done with it, especially if you are looking at something other than a spur gear.

    http://www.rushgears.com/
    http://www.mcmaster.com/
    http://www.emerson-ept.com/eptroot/...m/EPTroot/Public/bnames/browning/Browning.htm
     
  7. Jan 12, 2009 #6

    DaveC426913

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    Inch or two in diameter. They will be almost cosmetic, virtually no load. However, since they may be pretty flimsy, so they'll have to be made of a strong material to avoid binding and distorting, because...

    ...when I say "custom", I mean custom. :wink:
     

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    Last edited: Jan 12, 2009
  8. Jan 12, 2009 #7

    turbo

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    One word.... WHY?
     
  9. Jan 12, 2009 #8

    DaveC426913

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    An art project.

    I want to do things to gears that gears have never conceived of in their worst LSD-induced nightmares being done to them.

    I want people to say "that's impossible".
     
  10. Jan 12, 2009 #9

    turbo

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    Well, that certainly is something I never would have conceived of. This isn't a case of "buy this tool to hob spur gears", for certain.
     
  11. Jan 13, 2009 #10
    If you want this strong and precise, you might get something useful from the stereo sintering mentioned earlier.

    You could do this on a conventional milling machine; I suspect it's fewer than a hundred hours once you get the hang of it.

    Something like a 5-axis mill would be great. The problem is the cost, maybe $250k.

    If it's just a prototype, think about casting it in bronze and doing finish machining.
     
  12. Jan 13, 2009 #11

    Mech_Engineer

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    Yup, those gears look like a perfect candidate for a rapid prototyping process. The gears would be strong enough to be functional, and part complexity has no effect on price. The other nice thing about rapid prototyping is that you can make parts that would be nearly impossible to machine if you want.

    Here are two of the processes I've used before for functional models with good results:

    Selective Laser Sintering (note that it is possible to make "metal" parts with this machine):
    3D Systems Sinterstation® with available materials.

    Printed Polymer:
    Objet Eden with available materials.
     
  13. Jan 13, 2009 #12
    For the purpose you've described, an inexpensive mini-mill will probably be sufficient if you want to machine the gears. Mini-mills can be purchased new from about $600 (U.S.). Tooling can easily equal (or exceed) that, depending on your requirements. Spend some time exploring hobbiest websites and you can find great deals on used machines and equipment. (I've got a pretty extensive bookmark list -- I'll be happy PM or e-mail them to you if you're interested.)

    Here's a great site on making gears from wood:
    http://woodgears.ca/gear_cutting/index.html
    ... including a very slick template generator (Javascript) for tracing the gear profiles:
    http://woodgears.ca/gear_cutting/template.html

    Lindsay Books has a few inexpensive booklets on gear design and machining/manufacturing.
     
  14. Jan 13, 2009 #13

    FredGarvin

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    I'd second the idea about rapid prototype. You can give them your CAD model and they can stereo lithography them or some other process. Those are NOT what I was picturing. Pretty neat looking gears.
     
  15. Jan 13, 2009 #14

    DaveC426913

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    Thanks. This sounds great.

    What is the difference between "mini-milling" and "tooling"?
     
  16. Jan 13, 2009 #15
    A mini-mill just a small (desktop size) milling machine. http://littlemachineshop.com/info/minimill.php

    "Tooling" is a generic term for cutting tools and accessories (end-mills, vises, clamps, etc.)
     
  17. Jan 13, 2009 #16

    DaveC426913

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    So when you say...
    ...you're saying that a mini-mill might set me back ~$600, but all the tools needed to do this "for real" might set me back substantially more. Is that what you meant?
     
  18. Jan 13, 2009 #17
    They would be really pretty coped out of a hardwood bowl.
     
  19. Jan 13, 2009 #18

    DaveC426913

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    Indeed. I like the way you think.
     
  20. Jan 14, 2009 #19
    The key word being "might". The basic tooling to mill some small spur gears could probably be put together for as little as $200-$300. But, like most endeavors, the more serious you get, the bigger the investment.

    You also need to consider your time. For someone who has never operated a machine tool, gear hobbing is pretty advanced work. You're going to need to spend a fair amount of time learning to use the tools.

    Have you looked at what gears are available for retail sale? Brass or stainless steel spur gears are only about $20 to $40 (1" to 2" pitch diameter) from McMaster-Carr. Stock Drive Products is another great source, but they can be a bit expensive.

    You might also try robotic and mechatronic suppliers.
    http://www.google.com/search?q=robot+parts
     
  21. Jan 14, 2009 #20

    Mech_Engineer

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    Let's not forget that the gears you've designed would be very difficult to machine on a manual mill. Sure, it might be possible on a 5-axis CNC machine, but manually machined on a hobbyist bench-top unit, I'm not sure. It would definitely take some rotary stages and pretty fancy clamping, not to mention ball-end bits, etc. etc.

    If you bought the material in a hemispherical shape of the correct thickness, your job would be easier; but clamping will still be an issue.
     
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