AMS Spring 2023

Meet Nellie, the 3D Printed Weed-Picking Robot


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nellieaniI’ve said it once and I’ll say it again. 3D printing and robotics will continue to converge in the coming years, leading to mass customization of robotic devices which we could have only dreamt of a few years ago. When it comes down to it, 3D printers are actually robots themselves, capable of creating and replicating parts both for themselves and for others. Over the past couple of years, the convergence of 3D printing with traditional robotics has led to DIY creations that have produced some major breakthroughs.

For one author and electrical engineer, Mike Rigsby, 3D printing presented a method of creating a robot that he hopes will one day be able to accomplish one of the world’s most daunting tasks: picking weeds.

As comical as this may sound, in reality, weeds are a huge problem for farmers all around the world, and that problem is only getting worse.

“I read an article in the Wall Street Journal describing super weeds that have developed a resistance to traditional weed killers,” Rigsby tells “Palmer amaranth pigweed can grow 3 inches per day. Currently, soybean farmers are spending around $25 per acre on chemicals to protect their crops. Hand weeding can cost $150 per acre. In the U.S., farmers spent more than 13 billion dollars on chemicals in 2012.”

The evolution of weeds certainly creates a potentially grim scenario for the future of crops around the world. Chemicals work to a certain degree, but are expensive and in many cases harmful to our environment. Rigsby wanted to come up with a solution, and he appears to be well on his way of doing so with a 3D printed robot that he calls Nellie.


This robot is named after his wife Annelle, who is also an author. She recently published a book called WHERE IS EVERYONE?, and provides quite a bit of feedback and help on Mike’s numerous creations. Nellie was designed based on Rigsby’s understanding of the palmer amaranth weed, and the development of the robot was based on trying to provide answers to the following questions:

  • Can the robot visually follow a row?
  • Can the robot detect a plant taller than average?
  • Can the robot arm grab the offending plant?

“I was aware of motorized bases, vision sensors, pincers and the like, but putting them all together in one machine would require custom mounts, brackets and a linear gear arrangement for the pincer,” Rigsby tells us. “Fortunately, these ‘not off the shelf’ pieces are easy to design and create using a 3D printer.”

nellie4All of Rigsby’s custom parts were 3D printed on one of his two MakerBot 3D printers. He used his MakerBot Replicator 2 to print parts in PLA and his original MakerBot Replicator to print additional parts in ABS. Utilizing both printers allowed him to speed up the process quite a bit. The electronics that run Nellie include a $145 Pixy Camera, which feeds data to an Arduino processor that then send commands such as “nothing,” “target left,” “target right,” or “target center” to the motor controller module. The motor controller module is able to receive these commands provided by the Pixy Camera and a Ping/grabber platform. The Arduino processor and the motor shield cause the robot to move in the correct direction or halt to a stop.

“When the Ping ultrasonic detector senses something close, it sends a ‘stop’ command to the motor controller, then it extends the grabber, closes the pincer, releases the pincer at the end of travel, retracts the arm, then releases the ‘stop’ command,” Rigsby explains.

Currently, Nellie only is capable of picking a ‘prototype weed’ which is a weed that Rigsby 3D printed with his own head on top. It does a great job of plucking this weed out of the carpet in his house, but doesn’t yet have the ability to nellie1travel over real-world terrain such as a field. Other additions that it will need in order to function as a legitimate tool in the field would be two cameras: one to follow a row of plants and the other to spot weeds. It will also require some additional torque and another degree of freedom in order to pull real, live weeds out of the ground.

With these changes, could Nellie be mass produced and used by farmers around the world? Perhaps!

As for Rigsby, he is constantly working on interesting 3D printing related projects. He published a book titled A Beginner’s Guide to 3D Printing: 14 Simple Toy Designs to Get You Started and continues to look for new, interesting things to do with his 3D printers.

What do you think about this weed-picking robot? Does it provide some hope to farmers who have begun to see problems with super weeds? Discuss in the Nellie Weed Picking Robot forum thread on Check out the video of Nellie in Action below.



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