Motors? yes/no?

Discussion in 'General Discussion' started by philsta, Mar 14, 2012.

  1. philsta
    philsta New Member
    Just wondering, has anybody printed machines that are designed to have external electronics inserted into them? I would have thought this would have been a pretty popular concept but haven't been able to find similar items on shapeways...

    Is this kind of thing not recommended?

    I'm attempting to build a set of gears that rotate to create a typical video feedback style pattern and would prefer it to be automatic as opposed to a hand cranked machine...
  2. stonysmith
    stonysmith Well-Known Member Moderator
    From an 3d design (virtual) perspective, it's possible. The challenge is making the parts large enough to survive the wear. I personally am designing stuff that is very, very small. Operating gears are only a dream for the future for me.

    Are you wanting to design things that do real functional work, or do you want to design smaller stuff that moves and "looks cool".

    There are design rules that specify a "minimum wall thickness" for each material, but you're going to have to design things considerably thicker if you want them to not break under load.

    An example is FUD.. it can survive printing at a thickness of 0.3mm but pretty much if you breathe on it, it's going to break. However, I've got one FUD model that is nearly 2.0mm thick, and I'd think that it'd support 5 pounds or more of pressure.

    Take a look at this model That's a quarter there in the background. The gears you see are not even 3mm in diameter, and the teeth are at 0.3mm thick. Even though I have the capability of making the gears actually rotate, they first time they encounter ANY pressure, the teeth are going to snap right off.
    Last edited: Mar 14, 2012
  3. philsta
    philsta New Member
    Thanks for the feedback - yeah what I'm making is meant to be fairly large... so it's just a strength issue then?

    I've attached a VERY rough concept render (was just using this to make sure my gear ratios were correct) so basically, it's a set of gears that stand upright connected to a stand, and I was hoping to put a cavity in the base to hold a basic hobby/rc car motor and 9v battery.

    I guess mainly just wanted to make sure it wouldn't catch fire or anything crazy but the strength thing is def something I should consider more hehe

    Attached Files:

  4. stonysmith
    stonysmith Well-Known Member Moderator
    Interesting design. I'd love to see it in operation.

    The question here would be how large of a diameter are you trying for? If the outer disk is larger than say 4" and the inner small gears larger than 1/4 inch, then it just might work if you printed it in WSF.

    The two things you should consider are 1) making the teeth a bit deeper as these may shear off to easily, and 2) keep the whole assembly pretty thick.. 2-3 mm or even thicker if you can afford it.

    Thicker gears are going to have more surface area on the teeth, reducing the overall stress on the faces.

    One thing you might think of is printing just two of the rings first and see how they perform after hours of operation. That way you wouldn't have the extra cost of the whole assembly.

    If there's any other engineers/designers out there.. please feel free to chime in and correct me.
  5. aeron203
    aeron203 New Member
    I know that is just a concept render, but there are some very important theoretical concepts that will have to be respected if this has a chance of success. I like the idea, and I don't want to sound pessimistic, but Stony has it right when he makes the distinction between appearance and function. Functional gearing cannot be modeled by imitating the appearance of a gear. If you are going to have more than two stages, the gearing will either have to be generated by software, or you will have to do some hard core math. That is why you don't see people casually modeling complex gearing systems. Here is some information about gearing concepts you may want to start with.

    Involute gears

    Helical gears

  6. philsta
    philsta New Member
    I was going to make the gear elements around 16cm x 16cm so it's all fairly large. I imagine it will be about the size of a small desk fan... I'm not too fussed about cost but I do like the idea of making a smaller test model first - great idea :D

    I'll post a better model next week for more feedback but the overall concept is each large gear will be suspended by a track on the back of the gear that threads through a verticle arm to hold them in place.

    The whole thing is turned by a gear attached to a motor at the base that moves the most outer set of gears at about 1-4 rpm depending on motor setting.

    oh and I was planning to go with a thickness of 5 mm for the gear elements...
  7. philsta
    philsta New Member
    thanks for those links aeron203 - yeah that model pic is REALLY crap, and only meant to look right when rendering... it was just more about having the correct number of teeth in tha tpic =)

    Thanks for those links though, I was going to go with plain old spur gears, but I'm starting to see why they may not be the best option...

    Ahhh I'll make it work one way or another... I don't mind an odd spot of complex math from time to time hehe
  8. stonysmith
    stonysmith Well-Known Member Moderator
  9. stop4stuff
    stop4stuff Well-Known Member
    Matthias Wandel's downloadable (pay for)Gear template generator can be used to generate a dxf file of the gears for extruding out to 3D gears suitable for printing - that what I used to create a LEGO compatible 24T gear WSF is not so good though as the surface is rough meaning a lot of energy lost due to friction between surfaces - FUD would be smoother but more brittle.
  10. aeron203
    aeron203 New Member
    Sorry for not being more helpful in giving you some direction there. Some good suggestions have already been made, but you can also try the gear generator in the free software from eMachine Shop.

    The best tip I could give from personal experience is that gears with less than ten teeth don't work well. I'd use twelve teeth if possible


  11. philsta
    philsta New Member
    thanks for all the help guys =) it's great to know there's a nice community of people willing to point me in the right direction!

    Hopefully will have something interesting to show off soon...