3D Printing Gets a Brain: What Is Klipper?

3D Printing & Imaging Computers & Mobile Digital Fabrication Electronics

I wrote Klipper to do something different from what other 3D printer firmware does. Much of the existing software is designed to work within the limits of the tiny computer on the printer’s mainboard — typically referred to as a microcontroller. The software works, but it tends to put as much emphasis on getting things to work on a tiny computer as it does on manufacturing excellent quality objects. 

My goal was to model some interesting physics in software, so as to improve the quality of the final printed object. Getting the physics model correct is itself a large challenge — getting it to also run on a tiny computer would be a nightmare. Others have run into these limits as well, but past solutions basically involved replacing a “very tiny” computer with a “mostly tiny” computer. I took a different route, and Klipper was born.

WHY KLIPPER RIPS

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• Bigger brain, faster motion control: Klipper models the motion physics on a real computer, so all the printer’s microcontroller has to do is rip through scheduled motor movements with microsecond timing.

• Resonance compensation: Like noise-canceling headphones, Klipper detects your printer’s vibrations, and adjusts its motion to erase them.

• Smooth pressure advance: Predicts molten filament pressure to reduce ooze during non-print moves and blobbing at corners. 

LET’S GET PHYSICAL

On Klipper the software starts with the physical models. We process those models in Python (and a little C) on a real, general purpose computer, typically a low-cost Raspberry Pi. The software then determines the best robot actions needed to follow the desired physics; those actions are arranged in a schedule of events, compressed into a small stream of data, and sent to the microcontroller. All the microcontroller has to do is rip through the events using the timing described in the schedule.

RATTLE AND HUM: Klipper detects your printer’s unwanted vibrations and cancels them out.

Because Klipper starts with the physics and uses a real computer, it is able to implement some advanced transformations that improve the quality of resulting objects. For example, the
input shaper can model the machine’s vibration (caused by rapid movements) and produce resonance compensation movements that minimize its impact (less “ringing” artifacts in printed objects). Input shaping has a rich history in CNC machines, but Klipper is the first to deploy it widely in 3D printers. Klipper’s unique smooth pressure advance models the fluid pressure of plastic in the hot-end and can reduce ooze that causes blobbing and stringing artifacts on objects. These transformations can enable faster print times while maintaining excellent quality.

It’s worth pointing out that Klipper does do things differently. If you have a printer that is working well for you, it’s unlikely that Klipper will revolutionize it. Klipper has been most successful as a tool to “push the envelope.” It has helped facilitate machines with many motors (for example, the Voron 2.4 machine with seven motors) and high-speed movements (for example, 300mm/sec and faster). The hardware in some of these machines was designed to take advantage of Klipper’s capabilities, just as Klipper has evolved to drive these machines.

That said, Klipper will run on a large number of existing machines, both homemade and out of the box. If you’re interested in tinkering, or just want to try a different approach to 3D printing, then feel free to download the software and try!  Klipper is Free Software (free as in freedom). 

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Kevin O'Connor

original author and current maintainer of Klipper (klipper3d.org). You can support this open source project at ko-fi.com/koconnor or patreon.com/koconnor.

View more articles by Kevin O'Connor

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