From 3D printed gears to functional mechanism

Posted By on Jun 21, 2017 | 0 comments


In our previous blogposts, we explained how to create your own spur gear thanks to Sculpteo laser cutting service and to our 3D printing service. We now explain how to choose wisely between both technologies and how to succeed with each one.

I. How to drive a Gear

There are two ways of transmitting the movement from one gear to another.

A.Meshing gears

When thinking about gears, the first image that comes to mind is two meshing gears. The Gears are driven by the torque transmitted by the teeth. In order to have the right distance between the two gears, their pitch surfaces have to be held in contact. For a spur gear the pitch surface is the cylinder generated by the pitch circle. For a bevel gear, it is the cone generated by the pitch circle and the contact angle.


For spur Gears distance between axes is Modulus x (Number_of_teeth_1 + Number_of_teeth_2)/2

B.concentric Gears

The other way to bond multiples gears is through the axis. In traditional manufacturing a key inserted in a keyway or a splined shaft are often used. Digital manufacturing allows you to override the standards and use any geometry for your fixations. In a 3D printed object you can directly join the gears in your model.
With this type of joint you can easily modify the modulus of the gear train or change the transition mechanism for the next part (Belt, crank, Geneva Drive…)
Our best material for gear design using laser cutting is POM, a technical polymer. Discover all of our materials available for laser cutting.

II. Gear trains

Gears reveal their full potential in complex mechanisms. An assembly of gears is called a gear train. As mentioned  in our previous article on laser cutted gears, the angular ratio for gears is the following:

 

 

By using both meshing and axes links you can greatly modify the ratio between input and output of the gear train. In the video above, the ratio is calculated as follows :

Z1=35
Z2-1=13
Z2-2=35
Z3-1=13
Z3-2=40
Z4=35
Z5=35

 

We get a total reducing ratio of 0.121.

TIP: Don’t forget that another aspect to take into account with laser cutting is the heat dissipation. When the laser hits the surface, the material is heated even aside the laser’s impact point, especially when the amount of details is high. The material cannot dissipate the heat fast enough and the material might deteriorate. For 5m thick POM, do not use a modulus below 2 mm.
If you need a really thick and small gear, for a better heat dissipation choose a wide pressure angle:

smallest gear 5mm black pom 35

 

35° Pressure angle VS 20° Pressure angle, 5mm Thick POM

III. 3D modeling

Laser cutting can be used for custom, precise, resistant – and still affordable – pieces. However for more complex shapes, 3D Printing is more profitable. Thanks to 3D printing you can design any type of gears. Create yours with your favorite CAD software or download it from a 3D design marketplace. Many software have integrated plug-ins allowing you to 3D build custom gears.

Here is a nutation gear we created, it allows in a restricted space a high gear ratio and minimizes the backlash. It has an immobile crown and two nutating bevel gears driving the last crown.

Designing it is not an easy task, but once you’re done the printing process can be executed in one step versus a dozen with traditional manufacturing techniques. And there is no assembly step!
We recently made available a new material called glass filled Nylon, which is perfect for 3D printed Gears. It has a better wear resistance than our classic Nylon and is resistant to environmental constraints.

Upload your file and 3D print your first Gears !

 

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