Fixing the Biggest Problem with Robot Mowers
Why I Love Robot Mowers
Robot mowers are one of the few household robots that actually deliver on the sci-fi promises we were raised on. We’re still waiting on a robot that folds laundry, but mowing the lawn? That’s sorted.
I’m not a lawn guy. Never have been. So when I saw autonomous mowers like the Mammotion Luba Mini, I was immediately intrigued. Imagine reclaiming a couple of hours every fortnight, without compromising on your lawn? Sold.
So I reached out to Mammotion to see if they'd be up for a collaboration. To my surprise, they were already fans of the channel and sent over a Luba Mini for me to test out. (Don’t tell them, but I already had one in my cart ready to go.)
And honestly? It’s brilliant. If you're time-poor or just not into lawn maintenance, a robot mower is an absolute game-changer.
The Problem
There was one catch. My house has both a front and back lawn, separated by a side gate. The mower handles the backyard beautifully, but every couple of weeks I had to go outside, open the gate, and let it through to the front yard.
It’s not hard, but it breaks the illusion of total automation. Some people solve this by buying a second mower just for the front lawn... but that felt a bit silly. The Luba can already handle large areas, so I wanted a more elegant (read: overcomplicated) solution.
The Solution
My first thought was to make a simple flap the mower could push through—basically a doggy door. But then I remembered Polly (our cavoodle) would definitely see that as an invitation to go on self-guided adventures.
So I landed on the idea of a robotic airlock—a pass-through tunnel that only opens on one side at a time. That way, the mower gets through, but the dog stays put.
After ruling out mini roller doors (too big, too fiddly), I stumbled on a better idea: a tambour door. Yep, like the old-school appliance garages from 1980s kitchens. A flexible, slatted door that slides along curved tracks.
If I could motorise a single tambour-style door that covers either end of the tunnel—but never both—it’d be secure and smart. And kind of cool-looking.
The Build
I grabbed some outdoor-rated bullnose profiles from Hammerbarn (Bunnings) to use as slats, then designed 3D printable tracks in Fusion 360. For motion, I used geared stepper motors on each side, driven by a fantastic little all-in-one controller called the PD Stepper. It’s ESP32-based, has built-in power delivery, and mounts directly to the motor—highly recommended.
I used PETG for mechanical parts like the cogs and drive teeth (those little tabs that move the slats), and UV-stable ASA for the external components. After printing and testing a mini prototype, I cut the full-sized slats, glued outdoor canvas to the back, and assembled the full tambour mechanism.
Once the tunnel was assembled and tested, I built a simple frame against the fence and finally cut the hole (laser-leveled, of course). I wired up the motors, installed my electronics, and connected everything to Home Assistant using some custom ESPHome code.
The Luba was then trained to use this “channel” as a link between the back and front yards—just like you’d record a zone route in the app.
To make it work smoothly, I used the Home Assistant integration to:
Disable obstacle avoidance when approaching the airlock (so it doesn’t freak out about the tunnel),
Slow down the mower to give the door time to actuate, and
Only open the door when the mower is nearby and working.
It’s a bit hacky, but it works beautifully.
Final Thoughts
Is this overkill? Absolutely.
But I now have a fully automated lawncare setup where the mower handles both yards without any manual input—and that’s something I’m weirdly proud of.
It’s been running reliably, it looks great, and Polly hasn’t escaped once. The door itself is weather-resistant, modular, and easily removable if we decide to redo the fence in future. (Which we will.)
So, would I recommend this exact approach? Maybe not. But if you're looking for an excuse to blend robotics, 3D printing, and a bit of Home Assistant automation—go for it. You’ll never look at your fence the same way again.
If you want to see the build in action, check out the full video on The Stock Pot YouTube channel. And if you’re into projects like this, our smart greenhouse build is probably right up your alley too.
Thanks for reading!