Hi makers! Welcome to my blog. This the continuation post of RenderWrench Gear Series. Today’s blog is a special one because we move from theory to practice. Till now, we have mostly discussed the theory behind gears. But in today’s blog, I will show you how to design a meshing pair of gears in FreeCAD. We will also simulate the motion and render the model in Blender. Bonus—This tutorial is going to bebeginner-friendly and uses only free, open-source tools.

We will use formulas and terms form RenderWrench’s previous blogs (Gear terminology). So, if you’re new to gears, I recommend going through the earlier posts for a better understanding. I’ve linked them below for easy reference. On top of that, I’ve attached a video tutorial below. This is the first time I’m creating a tutorial like this. So if you find this tutorial helpful, please let me know in the comments. The video will be at the end of the post. So with that, let’s start with the tutorial.

Tools & Requirements (Before We Start)

Before we start with the tutorial, let’s list down tools we need for this tutorial. We gonna use 100% Free software. I personally use them for professional work and freelancing. Let’s start with the List –

1. FreeCAD (1.0.1)
2. Blender
3. RenderWrench gear series post. For this tutorial this the overall tools we need.

Understanding the Gear Design Goal

In this tutorial we will design a pair of meshing gear. We will discuss how we will calculate the centre distance of the gear. We will export CAD model and 3D printable model (will available for download). Then we will animate this pair of gear in blender.

Choosing Gear Parameters (Design inputs)

To design gears first we need to choose gear parameters. in this tutorial we will design a Gear and a pinion.
For Gear, let’s take m= 1
Z= 20
pressure angle = 20°
Face width = 6 mm
Gear ratio target = 1:2

For Pinion, let’s take m=1 (same as gear)
Z=10
Pressure angle = 20° (same as gear)
Face width = 6 mm
With that’s it let’s start the tutorial.

Creating the First Spur Gear in FreeCAD

Step-1

Let’s first open a FreeCAD file and make a new body.

Step-2

Then rename the Body as Gear1 and make sure the body is active by Double clicking on it. and the navigate to Part Design menu in Top bar. there you should find Involute Gear. click on it. you should see a gear out line on you work space.

On left side of the screen you should see a task windows. and you can change important gear parameters like module(m), Number of teeth(Z), Pressure angle, can toggle between external gear or internal gear, and more.

Step-3

Now select the involute gear click on the Pad icon in the tool menu. you will see the gear out line is extruded. Then set the face width by changing “Length” value . You will see the Gear’s face width changing accordingly. In the image I’m setting the length value 6mm. then click “OK” to finalize the value.

Now you already created a precise Gear model by all your own. let’s add some details in the gear. lets add a shaft hole in our gear.

Step-4

Now click on cad Sketch icon. then you will see planes in screen. click on “XY” plan. that let you enter in Sketch workbench.
Now select circle tool. and make a circle by centering origin. give it a Diameter you want. in my case I’m giving it 10 mm diameter.

Step-5

After creating the sketch close the Sketch workbench and you will return to part design workbench. There find “pocket” icon in the tool bar. Click on it and set “Length” value in such a way that make a through hole in the gear body. that will create a shaft hole.

Step-6

Now you can repeat the whole process and create the pinion. just make sure in pinion the number of teeth and hole diameter is different. Here I make the pinion with 10 teeth. And the shaft hole 5 mm.

Step-7

Now you see both the gears are at center and overlapping. now lets calculate the Center distance between the gear pinion.

Now let’s calculate the center distance.
For Gear and pinion we know Module and the number of teeth. to calculate Center distance the formula is,

Center distance = {(D₁/2)+(D₂/2)}. [For detailed explanation click here.]

If we calculate the center distance for this gear set, the value will come, 15mm.

So now you know how to make a gear in FreeCAD. If you have any Questions please let me know in comment section. i will happy to answer your questions. lets see a simple Video of the gear pair we made.