Major print shifting along x axis

Hello,

I just got my prusa i3 done and printed some nice prints. As they got longer I started getting some x axis shift. It happened a tiny bit with short-ish (20-30min) prints. For long prints about 20min. in the x axis would shift so the next layer would be off by sometimes up to a 5-7mm. I did one 2 hour print where the result was just completely un recognizable and by the end of the print the axis had shifted over 5cm to one direction. I noticed that the steppers were getting quite hot so I turned down the current. I also turned down the current on my y axis because this is something i had not tweaked yet. I turned them down until the motors ran nice and quiet also b/c before the printer was really really loud. I started a print and both axes were completely off so I boosted the current a bit. I got it to a point where at the beginning of a print the axes are fine but then a few minutes in the x axis will shift like crazy. I turned the current up on just that axis but it still shifted a lot. The y axis was running quiet and cool without shifting but the x is shifting a lot. I read that this can happen if you have other things plugged into your power source so I unplugged everything from the outlet the printer is running on and it still happened. The stepper is now cool but shifting. Any help is greatly appreciated. Thank you.

Two things to check. First is the accelleration and speed settings in (marlin? Is that the firmware you're using?) If it's too high this can cause the skipping you're seeing.

Second, check the cog on the X stepper motor is tight and that the belt is tight but not too tight. It should deflect a bit when you press it with your finger, but not too much.

When it skips do you notice any change in sound? This can be a good indication of what the actual problem is.

1. Loose, or too tight belts, or binding on the axis, can cause skipping. Adjust the belts so they give a dull twang when plucked, lubricate your smooth rods.

2. Acceleration, speed, and jerk settings in firmware, can cause skipping (in Marlin the default settings are way too high for many printers).

3. Stepper motor drivers overheating, can cause skipping (they trigger thermal cutout, when they overheat). Reduce current (but see point 4) or fit a cooling fan.

4. Insufficient current from the stepper drivers can cause skipping (not enough torque to handle the speed or acceleration you are asking of them).

Get 1 right first, then set 2 to something conservative., then experiment with 3 and 4 until no skips, finall you may be able to increase 2 a bit ( if you went very conservative).

I am still very new to the world of 3D printing. I had the same problem with my X axis and was advised to lower the values in Config H file

#define default_Max_feedrate
#define default_Max_Acceleration
define default__Acceleration

I have set these values below 500 it made a difference

Hey everyone, thanks for all the help,
my Marlin settings are as follows

#define DEFAULT_MAX_FEEDRATE          {500, 500, 1, 25}    // (mm/sec)
#define DEFAULT_MAX_ACCELERATION      {9000,9000,100,10000}    // 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 retracts
  ...
#define DEFAULT_XYJERK                20.0    // (mm/sec)
#define DEFAULT_ZJERK                 0.4     // (mm/sec)
#define DEFAULT_EJERK                 5.0    // (mm/sec)

Im looking into what my MAX_ACCELERATION should be and based on your comment Edward99 and some other things I have found on the forum I am going to change to
#define DEFAULT_MAX_ACCELERATION {450,450,100,10000} (I will change the #define DEFAULT_ACCELERATION accordingly as well as the retract)
and the
#define DEFAULT_XYJERK 10.0 (instead of 20).

Should I change anything else? And also, will this effect my print speeds at all? Or effect my prints in any way for that matter.

Many thanks.

Hi there Let me share what tweak's I came up with as magic numbers for my I3

#define DEFAULT_AXIS_STEPS_PER_UNIT {78.7402,78.7402,2519.69,544.7} // default steps per unit for Ultimaker
#define DEFAULT_MAX_FEEDRATE {500, 500, 2.5, 16} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {6000,2000,100,10000} // 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 2000 // 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 retracts

The Y axis is slowed down because of the 200 by 300mm heat bed. Hence I have longer smooth rods and over that speed it makes the glass on the heat bed vibrate too much. But the I also had an issue with prints shifting along the x and y-axis, the remedy was changing the 5/16-threaded rods to 3/16 and that changed everything.