Today, I'm swapping out my usual projects to give my lawn a little love—and maybe feed some local birds in the process. My goal is to design and build a 3D-printed seed spreader to tackle the patchy areas in my grass. Sure, I could just buy one, but where’s the fun in that? I’ll design it, print it, and tweak it until I have something that works better than just throwing seeds by hand. Along the way, I’ll show you how to design more organic shapes in Fusion 360 and share a useful free plugin for designing gears.

How Seed Spreaders Work

Seed spreaders generally fall into two categories. The first is a simple drop spreader, which relies on gravity to drop seeds onto the ground. The only real challenge is a mechanism to control the flow rate. The downside is that you have to physically walk the spreader over every single square meter you want to cover.

The second type, and the one I chose to build, uses a spinning fan to fling the seeds out in an arc. This type of spreader can cover a much larger area than the device itself, making it more efficient. That's more my style.

My V1 Seed Spreader Design

My first attempt at a design is a manual spreader with a hopper on top. Seeds fall from the hopper onto a set of spinning paddles, which then chuck them out the front. This spinning action is driven by a series of gears. The main gear is a 1:4 reduction gear that's turned by a manual crank, which in turn drives a set of bevel gears that power the spinning paddle rotor.

A couple of design tips I'd like to share:

• Designing Bevel Gears: Bevel gears are tricky to design from scratch, but a free plugin for Fusion 360 called GF Gear Generator makes it a breeze. It generates various gear types, saving a ton of time. Just a heads-up, once a gear is generated, it acts like an imported model, so you can't easily edit it later.

• Organic Shapes: Sometimes, simple circles and squares aren't enough. For the hopper and handle, I used the Loft function in Fusion 360 to create more organic, sculpted shapes. For the hopper, I lofted a curved rectangle into a circle. For the handle, I used a spline to create a comfortable, ergonomic grip that turned out quite well.

Assembling and Testing

Once all the parts were printed, it was time to assemble what I affectionately call the "particle pinger." The mechanism works just as I designed it: turning the crank handle rotates the bevel gear, which spins the paddle rotor. The seeds should be sent in an arc out of the front.

I took the spreader outside with some grass seed to give it a try. As I walked, turning the handle, the seeds flew out in a nice arc, covering a decent area. It was a huge improvement over a cup, and a lot more fun to use. It's a great feeling to see a design go from an idea to a working tool that helps me fix my patchy lawn.