REPRAP:

The printer that prints itself (*): https://reprap.org/wiki/RepRap
TIP: get familiar with 3D printing terms, this is not included in this training.
Focus on the names of the different reprap parts: heatbed, extruder, heatbreak, heaterblock, ...

I have two original Prusa printers (MK2S and MK3 upgraded to MK3S later), those are reprap printers.
Since Stargate, I am fascinated with replicators, which matches my early fascination as kid with Battelestar Galactica. I printed and painted one (several parts glued together) for old times sake (see attached image).

Basically Prusa uses an Atmega processor (Arduino) and specific boards. The open source community uses other boards. I use the Arduino mega with the RAMPS v1.4 board but not for those two original Prusa printers.

I started somewhere in 2017 with 3D printing and since then I encountered shitloads of issues. Longs tory for another time :-).
The issue I have with Prusa:

• One board, if one chip fails you need to be a solder iron superhero to fix it. Usually better to just buy a new one. So, I like the RAMPS board that has the drivers for stepper motors. Stepper motors need specific dirver chips that apply the current to "step" in one or the other direction.
• Arduino means sequential execution, hardware like FPGA can do true parallel.
• Firmware builds from Prusa are end of life for MK2S. And I always have issues recreating the hex file to load into the board because it uses specific Arduino IDE versions and needs to resolve a library name issue. This kind of issue that repeats is something that I loath.
• Firmware builds need to fit into the memory on the board, algorithms need to be short to make sure the sequential execution of the motor control isn't delayed.
• Protection mechanism used stop the printer. They don't remember the position so if I was printing 10 parts in one go and the printer aborts after 5 hours, I cannot continue. The MK2S extruder filament feed gets stuck sometimes and a bondtech gear (double gear), see picture on https://www.bertverrycken.com/mk3, solves this. There are by now thousands of 3D printed extruder bodies to fix one or another thing. It is chaos in my opinion. Anyway, I upgraded the MK2S with a MK3(S) bondtech extruder and used a wider fan but with the MK2S original firmware. I get a temperature runaway abort, all parts lost after 5 hours of printing. Most likely because the software assumes the MK2S fan and it is a slightly different fan. I need to be creative when something fails or needs replacement, I use what I have lying around. I want to make sure I am in control when something happens.
• In MK3, the extruder was improved and I thought I was forever free of the "ticking" problem of the MK2(S). Not. If you ever want to reliable operate 3D printers (every day printing), the extruder must be your main priority. Detecting issues and the right way to react, needs to be under my control.

Hence, my idea to do the FPGA to replace the pure software based Marlin firmware (Arduino) and Klipper (RPi).

(*) Electronics, wires, nuts, bolts, heaters, thermistors, endstops, rods, motors, ... are not printed (yet). They refer to the plastic parts in the design.