Z Homing Movement very jerky

Okay guys, im trying to troubleshoot an issue i have with my Smartcore. When printing and moving (by manual control) the printer moves fine, X & Y homing works fine also, but when it tries to home Z, the movement of the X & Y axes to the centre of the bed is very jerky. See my video attached.

Smartcore Z Home Movement

Anyone have any advice regarding this?

Thanks

Edited 1 time(s). Last edit at 01/18/2016 04:57PM by ixlix.

What's the problem as you see it. To me it looks good :-) First x and y is moved to their home positions then the height of your buildplate is measured at 4 or five spots. Then printhead is moved to buildplate 0.0 and printing begins.
You have to calibrate your z-autolevel so the printhead is at the right distance from the buildplate. several descriptions and videos can be found via the search
engines.

You should adjust this

#define XY_TRAVEL_SPEED 5000 // X and Y axis travel speed between probes, in mm/min

then lower the acceleration settings and see what happens.

Does your x carriage slide smoothly along the smooth rods? Are they well lubricated? Are your belts too tight? Do you have enough motor current on x and y motors? Is the power supply up to the job as it seems to happen when z is in motion and I presume all your heaters are on, so maybe it's just short of enough power.

I'm specifically talking about the movement between 0:14-0:18 in the video, the movement from X0Y0 to the center of the bed before the bed moves upwards. It's a brand new 33a psu, stepper drivers are getting plenty of voltage. As I said, it prints fine, the axes move smoothly, belts are good.

Was making the move smoothly until I replaced the ramps board.
I will try the acceleration settings.

Ok thanks s0me, I had to lower the accelleration settings down to 700 for it to move smoothly. Now everything is working great!

Yeah the default acceleration settings and homing speeds/travel speeds and jerk settings for z, in the default 1.0.0 marlin firmware are all very high given that the amount of movement required in this axis is very small, unless you have a massively uneven bed. Its worth leaving the homing feedrate a little higher to reduce the time taken to get the bed up from its rest position to the print head but everything else can be quite low. I've got mine setup with these settings (using 1.1.0 rc3) and it moves really nicely.

#define DEFAULT_AXIS_STEPS_PER_UNIT   {80,80,80,132} // default steps per unit for Ultimaker
#define DEFAULT_MAX_FEEDRATE          {500, 500, 50, 100}    // (mm/sec)
#define DEFAULT_MAX_ACCELERATION      {6000,6000,500,10000}    // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for Skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION          1000    // X, Y, Z and E acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION  3000    // E acceleration in mm/s^2 for retracts
#define DEFAULT_TRAVEL_ACCELERATION   3000    // X, Y, Z acceleration in mm/s^2 for travel (non printing) moves

// The speed change that does not require acceleration (i.e. the software might assume it can be done instantaneously)
#define DEFAULT_XYJERK                16.00    // (mm/sec)
#define DEFAULT_ZJERK                 1      // (mm/sec)
#define DEFAULT_EJERK                 5.0    // (mm/sec)

Quote
s0me
You should adjust this

#define XY_TRAVEL_SPEED 5000 // X and Y axis travel speed between probes, in mm/min

then lower the acceleration settings and see what happens.

I found this high travel speed was causing poor first layer adhesion, any small perimeters in the first layer were getting pulled off the bed. The nozzle was moving away so fast they didn't have time to stick, and the nozzle supplied is way too sharp. I Lowered travel speed to 2000. Whilst you can lower the first layer print speed it's a shame there isn't a way to lower first layer travel speed in slic3r (might be possible in more expensive slicers) as it's not a problem to have high speed travel on any other layers.

That is the travel speed while probing.

You can only modify the travel speed (non printing moves speed) trough the slicer program or manually by editing the gcode file.

Your adhesion problem is caused by the Z offset of the probe. Nozzle needs to be closer to the bed.

Yeah that's an issue sure but I use babystepping on the first layer skirt to optimise the nozzle to bed distance. I've got two other printers and with those I've had a fair share of z offset related problems which I've solved.

I just observed small delicate areas on the first layer being pulled away with the nozzle as it moved rapidly to the next printing coordinate. Reducing the travel speed has helped. Sure it's at the cost of some printing speed but I can live with that. I also filed the nozzle a little as it was incredibly sharp. Should just swap it for a decent one.