Many DIY and 3D printer designs offer a variety of controller options, and while sourcing the parts for an upcoming CoreXY build myself, I have been weighing the pros and cons of an 8-bit vs. a 32 bit ARM controller.
While the RAMPS/Arduino combo and the MKS GEN 1.4 boards may be seen as “tried and true”, there are a lot of disadvantages and I would strongly encourage anyone undertaking a new build to look at 32 bit controllers instead. Admittedly, the price (often over $100) is a hard pill to swallow, especially in cheaper builds.
If you’re still on the fence, Ryan Carlyle’s answer is the most convincing argument for a 32-bit ARM controller that I’ve heard yet:
3D printer controllers have to do a lot of stuff very, very fast. Performing kinematics and dynamics calculations while sending many thousands of precisely-synchronized step pulses per second is really, really hard. The 8bit AVR line of microcontrollers used in older 3D printer controllers is basically a late-1990s era Mr Coffee processor. They are completely, utterly maxed out on processor time just executing basic printing functions in simple (eg Cartesian) printers, and adding additional calculation load will bog them down and cause slowdowns, stuttering, pausing, and so on.
The advantages of a 32 bit controller can be summed up as follows:
- Speed – 8-bit controllers slow down the hotend dramatically when calculating curves and arcs.
- Resolution – slicers will compensate for slow and complex calculations by reducing resolution, so as not to introduce overextrusion and zits.
- Acceleration – appropriate centripetal/radial acceleration cannot be appropriately calculated, introducing a multitude of issues on curves and small segments, including a “lowest common denominator” default speed of 40mm/s or less on complex perimeters.
- Print Quality – better motion planning on a higher-speed processor can product better quality prints, faster.
- Reduced noise – the stepper interrupt on 8 bit processors can bottleneck the processor, so firmware will often compensate with step doubling, which causes louder and rougher motor motion.
- Avoiding firmware problems – Many software-based hacks have been created to compensate for the lack of hardware floating point in 8 bit processors. Firmware updates can completely bog down an 8 bit processor if they have not been tested under a variety of conditions.