Ok so I got my mb today and finally I have the bloody awesome thing printing however first attempt the extruder motor wouldn’t drive the large gear it stopped after a layer… so I’ve cranked voltage up to .65v… is this safe to run at?
Set the voltage to 0.55V and sure not above 0.6V
If the extruder has problems, check that the there is not too much friction between the small and the big gears.
Anything above 0.6 may over heat the stepper driver.
Check the gears make sure they are not to close together also check the nut for the large gear make sure it’s not to tight.
Pololu specifies the current per coil at 2.5 Amperes per Volt times the reference voltage, and states that the A4988 can run up to 1A per coil without an additional heatsink or active cooling. Since the K8200 kit doesn’t contain any heatsinks for its stepper drivers, you should keep the reference voltage as low as possible. Even the .425V specified in the assembly instructions results in a current sink above the manufacturer guidelines (.425 * 2.5 = 1.0625). The upper limit with active cooling is 2A per coil.
Make absolutely certain that your carriage geometry is square. Use light machine oil on your bearings and rails (NO white lithium or silicone). Attach small aluminum heatsinks to the 5mmx5mm BGA chip on each of the driver boards. Position a small fan to draw air through the chimney that runs under the driver boards. This is a nice, light weight solution for cooling: thingiverse.com/thing:1013388. I’ve remixed a case with 40mm fan that I’ll be adding to Thingiverse this weekend. My cooling fan is wired to the backside of the coax power jack with an appropriate dropper resistor.
Raising the reference from .42V to .52V makes a significant difference. Just make sure that you get some cooling on those modules. Also keep in mind that the stock power supply only has 6.5A available for all steppers, heated bed, and hot end capsule.
PS. Reduce the spring tension on your extruder and make sure that the gears aren’t meshed too closely - they must turn freely.
BGA? Ball grid array?
Most are HTSSOP so where did you get those BGA chip versions?
The DRV8825 can co up to 2A 2,5V if heatsinks used and active cooling.
The A4988 is older design stepper driver