There’s a new firmware option for adventurous 3D printer operators: Prunt.
By far most desktop FFF 3D printers use one of either Marlin or Klipper as their firmware. The firmware’s main goal is to control the motion system. For many years Marlin was almost exclusively used, until Klipper appeared. Klipper enables high speed FFF 3D printing through pressure advance and input shaping features.
Prunt is an alternative firmware that provides some very intriguing features.
The main feature is a further advance in motion system control. The biggest problems in motion systems are during acceleration and change of direction. Printheads are heavy, and they carry significant momentum that is hard to overcome. Imagine pushing a heavily loaded shopping cart at the grocery store and then suddenly having to change directions. That’s what your printhead is doing all the time.
Marlin and Klipper’s solution for this involves changing the acceleration. Prunt provides this diagram to explain a typical acceleration scenario:
You can see at the bottom that acceleration is applied, causing the velocity to change at the top. However, the trapezoidal motion generated cannot be done in real life due to the shopping cart problem described above.
Prunt explains how they solve this problem:
“Prunt goes another 2 steps beyond this by making the 4th derivative of acceleration into a rectangular wave, resulting in a 31-phase velocity profile with significantly smoother motion.”
In other words, it looks like this:
Notice how much smoother the velocity curve appears. This is far more achievable in real life, and should result in higher quality prints.
Prunt also performs similar optimizations for directional changes, which have the same — but more complex — problems.
Both of these innovations would make movements smoother, and, theoretically, enable even faster 3D printing. That would be possible only if the extrusion system and material were able to keep up.
Along with the motion optimizations, there are some other interesting features in Prunt. One is that it provides a user interface where various parameters can be edited. This is vastly simpler than the traditional approach of editing firmware files manually.
One feature I’m particularly interested in is the faster homing. Homing is done on all 3D printers, and it’s how the machines figure out where their axes are positioned. The problem is that homing can take considerable time because the machine typically moves quite slowly in its search for the ends of the axes.
Prunt allows a specification of the maximum distance, and the firmware computes a maximum speed for homing movements. In other words, homing happens very rapidly.
Prunt seems to have several very impressive features that are not present in either Marlin or Klipper. However, virtually no 3D printers use Prunt, and I’m not aware of any commercial products that have adopted it. But it’s early days for this software.
Just as Klipper’s innovative features inspired a big change in the 3D print world, it may be that Prunt does the same. Let’s look forward to a Prunt-powered 3D print future.
Via Prunt
