Extruder doesn't work right

Hello everybody,

I am currently in the process of assembling a printer based on the i3. So far I have been able to solve the problems that arise myself.
Unfortunately, I'm not getting any further at the moment. I can't get the extruder running properly.
First I want to calibrate the extruder. For this I use cold extrusion and wanted to adjust the flow rate of the filament.
I have the following data for DEFAULT_AXIS_STEPS_PER_UNIT in the Marlin firmware (version 2.0.x): {4.98, 4.99, 250, 400}
I was able to adjust the X and Y axes using the principle of remeasuring between the actual and target value. With the Z-axis, however, the motor no longer runs with the calculated value (approx. 50). The motor for the extruder only runs reasonably with values ​​between about 300 and 500.
However, far too much filament is being conveyed with these values.
Can someone help me, why this is or whether I can carry out the calibration in another way? For example, changing the print flow (in Pronterface) also reduces the conveyed length. If I change this to 20% it actually moves for the expected vale.

I also tried the extruder when it was heated (230-250 ° C for ABS). Even with the settings that are actually too high, the filament does not come out of the nozzle and clogs the hotend. Do you have any tips to prevent this?

Another strange note is the control of the extruder in general. I use Pronterface. Regardless of whether I control the extruder via the Extrude and Reverse buttons or via G-Code commands, the direction of rotation of the motor is not always the same. Above all, the motor rotates in the same direction on the extrude and reverse buttons.

Thank you very much for your support in my project.
I'm new here and don't know what are some basic printer information are necessary. So if you need further information let it me know.

greetings

You've left out some useful details, however generally to calibrate your extruder you first have to ensure your steps/mm is calibrated properly. So when you command 100mm of filament to be pushed through, 100mm of filament actually gets moved. You do this with a pair of digital calipers (if you don't have this already, get one). Measure out roughly 120mm of filament from where it enters your extruder and back. Now, without the extruder being connected to your hotend, command 100mm of filament to extrude, and measure how much of your 120mm is left sticking out of the extruder. In a perfect world, this will be exactly 20mm. If you have 16mm of filament sticking out instead then you moved 104mm of filament instead of 100mm. You can now calculate a correction to your extruder steps. 100/104 = 0.9615. So 400 * 0.9615 = 385. Set your firmware to this and repeat test until it moves a perfect 100mm.

Flow rate is used to fine tune flow when tuning a slicer profile for specific filaments.

Regarding your motor issues, it is hard to say, it sounds like either a wiring problem or interference and that can be difficult to troubleshoot remotely like this. Try checking google, I'm sure someone has had a similar problem before.

For your nozzle clogging, make sure you have your thermistor settings correctly defined. After that, set a nozzle temp for ABS, then take a small piece of filament and press it up against the nozzle to make sure it melts easily to make sure that its at least getting properly hot before troubleshooting further, if its a cheap knockoff hotend it could easily just get clogged and replacing the nozzle might fix that problem.

Edited 1 time(s). Last edit at 05/26/2021 09:22AM by obelisk79.

Thank you for your fast reply.
Coming to the first point. This is the step I tried to do. The problem is, that if I use the calculated value, my stepper motor doesn't work properly and doesn't drill any filament.

Then I'll check weather the thermistor shows me the correct temperature.