Drawing circular and non-circular gears for FDM 3d-printing
Contents
Gear profile
Calculating the correct tooth size
Examples included in the PDF
Circular gears with given gear ratio
Internal ring gear
Planetary gearbox
Rectangular/square gear
Rectangular and circular gear
Elliptical gear
Elliptical gear and square gear
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Gear profile
Under normal circumstances, involute gears are the way to go as they offer many advantages when compared to other gear profiles. However, if non-circular gears are required drawing an involute gear profile can become complicated as not all teeth are the same size.
As FDM 3d printed parts are (in general) not as strong as metal parts and therefore torque and transmission efficiency is not as important, we can try to use a different gear profile. If we use circular teeth we ensure that all teeth have the same size regardless of the gear outline.
Figure 1: Circular gear profile
This gear profile is therefore very easy to construct, as you can see in fig. 2 below.
Figure 2: How to construct a circular gear
Calculating the correct tooth size
To calculate the required tooth size \(r\) we have to solve a simple system of equations using a computer algebra program like maple for example.
As the required system of equations is dependant on the gear shape, please take a look at the linked PDF paper for more details on how to assemble it.
Examples included in the PDF
The linked PDF paper contains several detailed examples of how to calculate both circular and non circular gears using the proposed gear profile. Listed below are the results of all included examples:
Circular gears with given gear ratio and centerdistance
Figure 3: Circular gears with given gear ratio and centerdistance
(a) Corners are not teeth(b) Corners are teethFigure 4: Rectangular/square gear with given side length \(r=22/12\)(a) Corners are not teeth(b) Corners are teethFigure 5: Rectangular/square gear with given side length \(r=22/24\)
Rectangular and circular gears with given gear ratio and center-distance
Figure 6: Rectangular and circular gears with given gear ratio and center-distance
Elliptical gear with given size and number of teeth
(a)(b)Figure 7: Elliptical gear with given size and number of teeth
Elliptical gear and square gear that fit together
Figure 8: Elliptical gear and square gear that fit together
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