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Layer Shift both axis

Posted by jimboh3 
Layer Shift both axis
April 18, 2019 11:33AM
Cubex duo reprap,rumba, 24v, DRV8255s, Marlin 2 bugfix, single extruder stepper, dual y axis steppers on seperate drivers, e3d hot end, all drivers set to around 0.72v.

Recently printed an LCD case for my new MPCNC project and had 2 layer shifts around a cm apart on both X/Y axis at the same time. There are two in the pics, halfway and near the top (RHin pic). I have seen before and sometimes only on one axis but have printed loads of parts with no shifts.
I have read a ton on possible reasons but most causes mentioned would probably only affect one axis. Thought I would see if the experts could help narrow it down before I start pulling things apart.


Edited 3 time(s). Last edit at 04/18/2019 11:36AM by jimboh3.
Re: Layer Shift both axis
April 18, 2019 11:38AM
Layer shifts are usually caused by attempting to accelerate too fast for the motors. What are your printer's jerk and acceleration settings? At what speed were you attempting to print?

The cubeX machines have a lot of moving mass so print speed and acceleration usually have to be kept pretty low. The cantilevered bed tends to bounce a lot of you try to print faster than 30-40 mm/sec.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Layer Shift both axis
April 18, 2019 12:39PM
Thanks for the assistance.
I don't remember why but I enabled JUNCTION_DEVIATION instead of Jerk... i don't really understand either.
These are my config.h settings.

#define DEFAULT_MAX_ACCELERATION { 400, 400, 100, 500 }
#define DEFAULT_ACCELERATION 400 // X, Y, Z and E acceleration for printing moves
#define DEFAULT_RETRACT_ACCELERATION 500 // E acceleration for retracts
#define DEFAULT_TRAVEL_ACCELERATION 400 // X, Y, Z acceleration for travel (non printing) moves

// Use Junction Deviation instead of traditional Jerk Limiting
//
#define JUNCTION_DEVIATION
#if ENABLED(JUNCTION_DEVIATION)
#define JUNCTION_DEVIATION_MM 0.02 // (mm) Distance from real junction edge
#endif

#if DISABLED(JUNCTION_DEVIATION)
#define DEFAULT_XJERK 10.0
#define DEFAULT_YJERK 10.0
#define DEFAULT_ZJERK 0.3
#endif

These are print speeds from .gcode file
travel_speed_mm_per_s = 500
; rim_speed_mm_per_s = 150
; first_layer_speed_mm_per_s = 15
; dmax_per_layer_mm_per_s = 50
; xy_accel_mm_per_s_per_s = 1500
; xy_steps_per_mm = 150
; lo_speed_top_mm_per_s = 10
; lo_speed_perim_mm_per_s = 10
; lo_speed_loops_mm_per_s = 25
; lo_speed_solid_mm_per_s = 20
; lo_speed_sparse_mm_per_s = 40
; hi_speed_top_mm_per_s = 40
; hi_speed_perim_mm_per_s = 25
; hi_speed_loops_mm_per_s = 65
; hi_speed_solid_mm_per_s = 60
; hi_speed_sparse_mm_per_s = 75

Edited 1 time(s). Last edit at 04/18/2019 12:42PM by jimboh3.
Re: Layer Shift both axis
April 18, 2019 12:53PM
It looks like everything is commented out except travel speed at 500 mm/sec which is much too fast for that mechanism.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Layer Shift both axis
April 18, 2019 01:24PM
Sorry mate, they are just the details that kissslicer gives at the top of the gcode file where it reports all used settings. The travel_speed_mm_per_s = 500 would have been commented too but for bad cut and paste.
So what should that be? are the rest ok?
xy_accel_mm_per_s_per_s = 1500 perhaps too high
and should all the rest be below 50?

Those two are both set in kisslicer, guess I never changed them.

Edited 1 time(s). Last edit at 04/18/2019 01:26PM by jimboh3.
Re: Layer Shift both axis
April 18, 2019 04:30PM
In a cubex I think the acceleration numbers should be closer to 500. The 0.02 junction deviation is probably OK. You definitely don't want print speed above 50 mm/sec.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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