A few weeks ago I decided to upgrade my belt driven extruder (upgraded with an E3D hot-end) by the direct drive extruder as offered in the Velleman K8203 kit. I did not install the included hot-end but modified the angular mount to fit the E3D hot-end.
In the past I printed magnificent pieces and since the upgrade the quality of the printed parts went heavily backwards. It looks like the extruder steppermotor was missing steps and has not enough torque to turn smoothly. As a result the extrusion looks like a cobblestone path.
The force required to push 1.75mm PLA through a 0.35mm hotend at 190° Celsius is between 15 N = 1.5 kg (slow) or 25 N = 2.5 kg (fast). The Nema17 steppermotor is able to produce 30 N, so there should be something else wrong.
I’ve spent at least 3 nights browsing the web to find a solution and another 3 nights with trial and error:
[ul]- steppermotor driver set to 0,75 - 0,80 - 0,85 - 0,90 volt
- multiple adjustments to align the filament pulley
- PLA extrusion temperature set to 170° - 175° - 180° - 185° - 190° - 195° - 200° - 205° - 210° - 215° - 220° - 225° - 230°[/ul]
Nothing helped !
After some more sleepless nights, I noted the following facts:
First of all it feels the driver spring is way too strong and pushed the filament too hard between the bearing and the filament pulley. I could barely push the filament by hand. As a result the Nema 17 steppermotor floats betweens microsteps and nervy skips.
This issue was easily handled: I grinded off one resolution of the spring.
After reading an in depth description how steppermotors works, I concluded the 1/32 step modus as default set on the high power DRV8824 driver wil not do the job. As test I replaced the DRV8824 driver by the original A4988 board with default 1/16 step modus and guess what: the extrusion was as soft as a baby’s skin !
Of course the A4988 driver is not able to deliver enough current as needed in direct drive modus for a long time without getting extremely hot, so this solution was only a temporary one for test purposes. Next I cutted the M1 and M2 traces on the backside of the controller board and inserted the high power DRV8824 driver over again. Cutting M1 and M2 forces the DRV8824 in 1/16 step modus with the same extrusion result as with the A4988 board, but now able to work for a longer time.
Sorry for the double post, but perhaps this is also useful for you…