Ringing problem?

Hi guys!

Currently I'm really happy how my mini Kossel prints. Only problem I see left are these tiny ribs on the side of my print. I doubt it's mechanical ringing problem because I don't see or feel any noticeable movement of the frame while it prints. Also, I have vibration dumpers on my steppers.


However, I have noticed that my extruder makes little twitches while running in a long straight line.
Tell me, do I expect too much from my basic machine, or is this something that could be solved?

I'm running on ArduinoMega+RAMPS with DRW8825 stepper drivers.
max x,z,e jerk 15.00 mm/s
min segment time 20000 ms
max acc x,y,z,e 600 mm/s2
x,y,z resolution 200 steps/mm
e resolution 6 steps/mm

Here's also a screenshot of my EEPROM settings in Repetier:


Thanks!

The main culprit is probably the DRV8825 drivers. See [forums.reprap.org].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Is it a typo or do you really print with 6 e-steps/mm?
Do you run it in full step mode? That would explain the pulsing....

Quote
o_lampe
Is it a typo or do you really print with 6 e-steps/mm?
Do you run it in full step mode? That would explain the pulsing....

An excellent point, I should have spotted that before I replied.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
o_lampe
Is it a typo or do you really print with 6 e-steps/mm?
Do you run it in full step mode? That would explain the pulsing....

I'm not 100% sure what you mean by full step mode?
I have re-calibrated my extruder and I get the correct extrusion lenght with 5.95 steps/mm.

Did some quick sums and if its 1.75mm filament at 6 steps per mm then 1 step is about 3.2mm extrusion from a 0.4mm nozzle.
Since steppers just move between steps you only extrude when moving then just get leakage when it stops. So if the number of steps is low you could get extrusion as pulses instead of a smooth flow.
Speed also has an influence, but I would think you want enough steps and a good enough speed to try and get the moving time longer than the stopped time. Increasing the print speed should help. What is your print speed?
Bowdens are probably less affected as there is some damping due to the filament length.

I have been printing at 30mm/s. Doubling the speed solved the problem.


Thanks guys!

Quote
Andres_Mikkelson

Quote
o_lampe
Is it a typo or do you really print with 6 e-steps/mm?
Do you run it in full step mode? That would explain the pulsing....

I'm not 100% sure what you mean by full step mode?
I have re-calibrated my extruder and I get the correct extrusion lenght with 5.95 steps/mm.

Full step is the opposite of microstep. Usually with 1/16 microstepping your steps/mm are around 90-100.
Either your drive gear diameter is very huge or you haven't set the microstepping jumpers correctly.

Printing faster just blends the problems into one big problem