Blob on start.. of layer..

Hi..

Im using a Prusa i3 with Repetier/Marlin..

Im getting a tiny blob when starting layers..

Im not sure if its a Jerk issue... or that I need to Extrude slower..

Here are my settings for Marlin

#define DEFAULT_AXIS_STEPS_PER_UNIT   {80,80,4000,97.68}  // default steps per unit for Prusa was set to 700
#define DEFAULT_MAX_FEEDRATE          {300, 300, 3, 35}    // (mm/sec) DERATED FOR PRUSA FROM 500, 500, 5, 45 
   
#define DEFAULT_MAX_ACCELERATION      {1000,1000,50,500}    // X, Y, Z, E maximum start speed for accelerated moves. // DERATED FOR PRUSA FROM DEFAULTS 9000,9000,100,10000. E default values are good for skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION          1000    // X, Y, Z and E max acceleration in mm/s^2 for printing moves DERATED FOR PRUSA FROM 3000
 
#define DEFAULT_RETRACT_ACCELERATION  1000   // X, Y, Z and E max acceleration in mm/s^2 for r retracts DERATED FOR PRUSA FROM 3000


// 
#define DEFAULT_XYJERK                20.0    // (mm/sec)
#define DEFAULT_ZJERK                 0.4     // (mm/sec)
#define DEFAULT_EJERK                 5.0    // (mm/sec)

I'm running Retraction at -3mm would increasing the retraction help?(or does Slicer compensate and add say this 3mm back?)

Im using a direct drive Bowden extruder.... with PTFE tube, so not sure if its Hysterisis, and by retracting more..might help

So many questions ;-)

whats your thoughts?

Edited 2 time(s). Last edit at 04/23/2013 10:05AM by mrfunk.

mrfunk Wrote:
-------------------------------------------------------
> I'm running Retraction at -3mm would increasing
> the retraction help?(or does Slicer compensate and
> add say this 3mm back?)

The retraction setting should be a positive number, at least in my version of slic3r. Not sure how it handles a negative one, worst case it pushes out that amount of filament every time instead of retracting it.
And yes, slic3r compensates this and adds the distance again every time it starts extracting again.

There also is a setting called "Extra length on restart", try setting that to a small negative number, start with -0.1 and increase if necessary. That distance gets added when extraction is restarted. So with a retraction distance of 3mm and -0.1mm extra slic3r will retract 3mm when it stops extracting and extract 2.9mm when it restarts.