Bigger printer are more susceptible to structural issues, like bending. Doesn’t seem to be Z wobble. Put your finger on nozzle tip(when cold) and softly push and pull. Check if it moves(it shouldn’t). It can also be extrusion inconsistency, like faulty filament traction or extruder skipping steps. It is not X and Y skipping steps. Can be Z. At what speed are you printing? There is also a lot of ghosting, that increases with extruder weight, belt size, and “soft” structure.
@Daniel_Scheidler we already tried to use some clamps at the top of the lead screw with KFL08 pillow bearing. The results are same. So, I hope it is not due to Z wobbling.
Supply voltage 24V. Heat bed is there, but not using for PLA.
Nozzle and hot end is tight in the mount.
We tried with and without belt tensioners.
We tried to print even with 40mm/s speed.
A4988 for all axis, except Y having external TB6600. Current tried from 1.7A to 2A. Using Nema 17 Motech motor with 8kg, 2A. (We tried to use DRV8825 before also.)
Slack due to Mechanical fault - We almost tried a lot.
What size extrusion are the verticals? On my large format printer I used 20X80 V slot for the verticals so that I would not need to brace it over the large height.
@Tech_World Your bed have a huge mass. Try to reduce Y Jerk and acceleration even more. Check if it is tight and stable. And sorry, but I believe 50mm/s is too much for it. Since you have huge mass on Y you won’t be able to have high accelerations, and that is really bad for bowdens because of the compression/pressure effect bowden tube and nozzle. You can mitigate it using adjusting linear advance on marlin. Try something like 20mm/s speed, Jerk 5 or less, acceleration 500.
@Panayiotis_Savva@Eduardo_Schoenknecht I tried almost all the solutions. None of them worked. Finally I found there is some issue with the temperature. Temperature is fluctuation around +/- 8 deg.
If I set 220deg, it goes from 212 to 228. I tried PID Tuning several times. I changed the thermistor and heater cartridge (Original E3d V6). Updated Marlin, did PID tuning again.
I changed the board also (MKS Gen 1.4)
I am using 24V power supply. Somewhere I read that with 24V, in configuration.h, we have to reduce the PID_MAX. I reduced to 88 (from 255). Still I didnt get any result.
Now, Temperature is raising slowly. But still the fluctuation is between +/- 5 deg.
@Tech_World Are you using a 12V heater cartridge? If yes you should use 1/4 of PID_MAX(63), as relation between voltage and power is quadratic . But this may not solve the problem, as you will have a low resolution output to your PID. I had temperature oscillation problems in the past and the cause was another. In my case I had VCC fluctuations over the micro-controller. I noticed my Rumba board had no big capacitor near the the micro-controller, and 5V Vcc oscillations were transmitted as “noise” to ADC temperature readings. A low resistance 12V heat cartrige, working with a 24V power supply can create too much noise in voltage references, and affect temperature readings. The heated BED is also important. Your bed cannot bed driven directly in a MKS Gen board. It should have an external driver, preferably an AC driver and heater.
Pay attention to your temperature readings. if the oscillation you see behaves like and sine wave it may be a PID problem, but if it oscillates randomly, with “jumps” of more than 3ºC it may electrical noise. Also check NTC sensor wiring and fixation.