Help homing/calibrating axis!

Hey guys, was wondering if anyone would be able identify a solution to a problem I am having.

I have never successfully printed on this printer. As you can see in the pictures attached, the printer will print a few layers but will then lose its place and start a layer a few cm to the left of the layer before it.

It is my best guess that this problem is connected to the fact that I have never "homed" the axes. That is, they are calibrated to move the right distance, but the printer does not know where the ends and center of the axes are. How would you suggest I proceed?


I am running a SeeMeCNC H-1 with RAMPS 1.4. Firmware is Marlin, using Slicer and Pronterface on my mac. Let me know if I can provide any further information!


Thank you very much for any help in advance!

Not a homing problem, you're skipping steps on x axis. You might be able to fix it with a little more current to that motor, or there might be a mechanical problem to fix.

Your flow rate may be too high, lower it by 30% and post results. also you can change 1st layer height to be up past 0.4mm this should compensate for slightly uneven bed, and still allow for proper adhesion to the tap.
If the above does not fix your issue, there are still more things to try.

Hi Andrew-

I have tried upping the current by turning the x pot to the right, but any more current than what I have it set as starts making the motor pause every second (because of too much power?).

I have considered that friction or over extrusion may be the cause, but the print still moves to the left when printing dry, cold, and when z axis is lifted far above the bed... Any other ideas?

The motor is not making any unordinary sound when it moves the print to the left, and it is not as though it is randomly skipping. It moves over at the same interval, same time, every time. It seems now that it is consistently moving over once every layer.


My axis homing & endstops are all set up now, so that is out of the way.

James-

Thanks for the reply. I will try those things, however the problem of the motor stepping to the left every layer happens even when printing dry, cold, and when the z axis is lifted far above the bed.

Any other ideas as to what could be causing the x axis to skip steps?

Thanks!

In Marlin, can anyone tell me what

#define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000}

is and what the values reflect? I changed the x value from the default 9000 to lower increments and the problem got progressively better. When x max acceleration is zero, the problem is, to my best knowledge, nonexistent. What does this mean?

Thank you!

it means that your motor accelerates slower. probably because the driver can not pull the mass that fast. also lower jerk settings to 15 for x/y if they are set higher.




look for loose belts, and if they are reasonably tight the issue may be the driver setting, or a motor on x axis that has too low of torque. you may want to order a 48oz/in motor or equivalent if this is the case. have you posted your configuration.h file? that would held us to know your settings.

also add 3-1 oil to the x rods, wipe the entire rod down with it, it will reduce friction

Edited 1 time(s). Last edit at 03/08/2013 05:19PM by jamesdanielv.

Thanks for all the help so far.

configuration.h file is attached. If you have ever seen a SeeMeCNC H-1, the thing is basically a piece of crap. The build plate is warped by at least 2 cm, the axes wobble at least a cm in each direction, etc. I think the stepping problem is a combination of the many design flaws of the printer.

I have begun to make a new build plate, and I bought some linear bearings to get rid of the play in the axes, I think this will allow me to bring my acceleration back up a little. Also oiled the rods.

Questions concerning the config file:

- Is the flow rate connected to the "max feed rate" that is seen in the config file? How do I extrude less, as it seems I am over extruding? Is this setting in slic3r, or Marlin?
- Where is the actual print speed defined? Would it be beneficial if I tried slowing down the actual speed, not just the acceleration?

you can change settings by altering the lines in your configuration.h

btw your x and y settings sizes are to a different scale #define DEFAULT_AXIS_STEPS_PER_UNIT {126,127,550,836}
is this on purpose?

Also your z settings may be different and your extruder flow is currently set to 836, if your extruder flows too much you can change that value to say 720 or something like that axis are in order from x,y,z,e



//// MOVEMENT SETTINGS
#define NUM_AXIS 4 // The axis order in all axis related arrays is X, Y, Z, E
#define HOMING_FEEDRATE {50*60, 50*60, 4*60, 0} // set the homing speeds (mm/min)

// default settings

#define DEFAULT_AXIS_STEPS_PER_UNIT {126,127,550,836}
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 45} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {0,9000,100,10000} // 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 3000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for r retracts


change max feedrate from:

#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 45} // (mm/sec)

to this
#define DEFAULT_MAX_FEEDRATE {50, 50, 2, 15} // (mm/sec)

change this:
#define DEFAULT_MAX_ACCELERATION {0,9000,100,10000} // X, Y, Z, E maximum start speed for

to this:

#define DEFAULT_MAX_ACCELERATION {5000,5000,100,1000} // X, Y, Z, E maximum start speed for

and if x and y are the same scale then change this:
#define DEFAULT_AXIS_STEPS_PER_UNIT {126,127,550,836}

to this:
#define DEFAULT_AXIS_STEPS_PER_UNIT {126,126,550,836}



it looks like maybe your Z may axis was not raising because it was likely going to fast. z axis is usually directly controlled by firmware. after changing the above line then go back and work on the extruder flow rate. also if you are using slicer, look under printer tab and speed settings.

It looks to me like you are probably losing steps in 'X' and 'Y' because the acceleration parameters (and possible max feedrate depending on what speed you are printing at) are probably not optimal. Try changing the X and Y parameter to 1000 for acceleration and just giving that a try to see if that solves your problem before bumping the values up.

Chelsea - QU-BD

Edited 1 time(s). Last edit at 03/09/2013 09:32PM by Chelsea - QU-BD.