During previous prints I noticed my hotend moved a couple of mm in the Y-axis direction (and this messes up the Z-leveling). The hotend was seated directly into the extruder and secured with a mounting plate. Now I've placed some fancy washers in the 16mm extruder hole (orange arrow below) and the E3D hotend. Now the hotend is firmly secured and not moving at all in any direction = better prints!
To make the heatbed heat up even faster I added 2 layers of PE-thermal insulation(95% heat reflection) under the heatbed.
MK2a heatbed @ 110° + E3D hotend @ 240°C + powering the Sanguinololu = ATX power source wires melting!
So I decided to solder thicker wires that feed the Sanguinololu directly to the ATX printed circuit board(PCB). Results are good, the wires get a bit hot but don't melt anymore. I also added new spacers to the bottom of the ATX to be able to mount them to the Pusa's frame.
Next issue: the MK2a heatbed takes 30 minutes to heatup to > 100°C
So I took care of these 2 things: "create direct current paths" to spare the Sanguinololu PCB and "Balance the ATX power supply"...
1. Create Direct Current paths on Sanguinololu PCB
The pads and traces on the Sanguinololu board are not robust enough to handle the high current involved when controlling the heated bed with the dedicated mosfet. If left as is, the board will heat up in this area, could be damaged and the plastic connectors discolored.
To fix, simply add a direct current path by way of (preferably insulated) wire:
from the 12v input to the 12v pins on the Heated Bed (HB) connector;
from the center pin of the HB mosfet to the two ground pins on the HB connector;
from the ground pin on the mosfet to the ground input of the board (probably the ground side of the 12v connector)
I get these results (for now) that I need to configure in my Marlin firmware:
(In "Configuration.h" the variable: DEFAULT_AXIS_STEPS_PER_UNIT {80,80,2560,674.6521728} )
Edit: I have 5mm threaded rods for my Z-axis so there are 4000 E steps for 1mm (and not 2560!)
Wiring done for all three axis and the extruder stepper motors. Also the connections to both thermistors and the extruder heater and heatbed are ok. Still need to connect the fans to the ATX power source. (I connected the extruder fan to a free header on the Sanguinololu but I read this is a bad idea)
Setting the Vref to match my stepper-motor-driver configuration. My calculations don't match my measurements (calculated 2.24Volts and measured max 0.74Volts so my sense resistor value must be way off). But hey, the motors are working fine after some manual tweaking while listening to the motors' sound. I'll check what went wrong with the calculations later to fine tune the driver current...
This video shows the X & Z axis move during a test with Pronterface (the Z-axis moves really slow, this is normal).
Another milestone in the building process: To test the extruder I heated up the hotend gradually to 290°C and meanwhile extruded some blue PLA using Pronterface.
Open issues that need to be looked at:
Z-axis & Extruder inversion
The Z axis goes UP while going to the home position in Pronterface. Also the exdruder retracts while it's supposed to extrude and vice versa. So I need to reverse my stepper wiring from ABCD to DCBA or change the inversion setting in Configuration.h in the Marlin firmware and upload it to the Sanguinololu again.
Whoooops, I think I might have fried the Sanguinololu board :/
While fine tuning the driver current for the Y-axis i made a short circuit with my multimeter. Now my Y-axis won't move properly. Just when everything was going so good. Stupid me!
