Driver update
A few days ago I learned in the RepRap forum about a new stepper driver from Pololu using the DRV8825 from Texas Instruments. I have read good things about this family of drivers being more robust and higher current than Allegro A4988. Well, thanks to the kind offer from Pololu I've got a few units for testing (at a huge discount) and my first impression is pretty good. This may well be the answer to get a direct drive extruder that does not suck. I have detailed in past posts how I was unable to get a successful direct drive extruder working in my system, as I was needing more current that my electronics were capable of, for my extruder to work reliably at medium speeds. This new driver seems to be able to push 1.5A without the need of active cooling. The manufacturer claims that up to 2.5A per coil are possible with proper cooling. Next stop is to use them for powering a CNC machine with beefier nema23 motors.