john.w60
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Joined: Nov 23, 2018 5:23 am
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X axis slamming extruder into z axis

Dec 05, 2018 3:44 pm

Hello, I just built my mk3 and it printed its first print very well! I was really excited and I went to print something else but ran into an issue. The extruder seems to get stuck in the front right hand corner and then the x axis tries to force it into the right z axis. It makes a horrible sound as the plastic is grinding into each other. I stopped the print and then re did the xyz calibration and had no issues there, but now every print that I have attempted since then fails before starting because the extruder ends up grinding into the z axis. After I canceled the most recent print, I went into settings and tried to move the x axis with the dial on the LCD board, but it thinks that it is at the x coordinate "0" all the way in the right corner, so i can't move it to the left and trying to move it to the right runs into the z axis. This is odd to me considering that the XYZ calibration runs just fine and it says the home point has been located successfully even though for some reason point zero on the x axis is all the way to the right. Any suggestions?

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tim.m30
Posts: 256
Joined: Sep 09, 2018 11:03 pm
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Re: X axis slamming extruder into z axis

Dec 05, 2018 4:12 pm

Sounds unusual... what plastic is hitting?

There are a couple of "calibration steps" where the printer finds the movement extremes by stalling the stepper motors. This is safe and harmless but sounds bad. On power-up the extruder is moved to the top of Z-Axis and hits a few times. Then X and Y homes are found - but these are quieter because the belts buffer the impacts. Each "bump" lasts a couple seconds.

If this isn't what you are hearing,

1) Check that the PINDA probe LED is turning off as the extruder gets near the bed. If set too low, the printer can't know the nozzle is close to hitting.

2) Check X and Y movement: Raise the extruder by pressing the control button a few seconds to pop up the X Move option: put the extruder about half way up. Power off and see if the X and Y axis move freely by hand. Is there any catching, tight spots, or is the movement smooth and continuous?

Does this persist after a power cycle? Have you done a hard firmware reset?

john.w60
Posts: 3
Joined: Nov 23, 2018 5:23 am
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Re: X axis slamming extruder into z axis

Dec 05, 2018 5:41 pm

Thank you for the reply! The plastic that is hitting is just the edge of the extruder casing against the plastic part that connects the x axis to the Z axis. I have done a hard reset, checked the pinda probe, and when it is turned off there is nothing catching the drive belts and it seems to move freely. I have definitely started running out of ideas

john.w60
Posts: 3
Joined: Nov 23, 2018 5:23 am
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Re: X axis slamming extruder into z axis

Dec 05, 2018 9:52 pm

tim.m30 wrote:
Dec 05, 2018 4:12 pm
Sounds unusual... what plastic is hitting?

There are a couple of "calibration steps" where the printer finds the movement extremes by stalling the stepper motors. This is safe and harmless but sounds bad. On power-up the extruder is moved to the top of Z-Axis and hits a few times. Then X and Y homes are found - but these are quieter because the belts buffer the impacts. Each "bump" lasts a couple seconds.

If this isn't what you are hearing,

1) Check that the PINDA probe LED is turning off as the extruder gets near the bed. If set too low, the printer can't know the nozzle is close to hitting.

2) Check X and Y movement: Raise the extruder by pressing the control button a few seconds to pop up the X Move option: put the extruder about half way up. Power off and see if the X and Y axis move freely by hand. Is there any catching, tight spots, or is the movement smooth and continuous?

Does this persist after a power cycle? Have you done a hard firmware reset?

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tim.m30
Posts: 256
Joined: Sep 09, 2018 11:03 pm
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Re: X axis slamming extruder into z axis

Dec 05, 2018 11:23 pm

The X-Axis "homes" or finds "zero" by contacting the extruder to the motor mount. This is normal. It should buzz for about a second. The printer also slides the bed so a bearing hits one of the rod mounts. This all happens on the left side.

These contacts cause the motor to stall and allow an electronic measure of "home" positions for the printer to work with. Once these home positions are found, the printer can count motor steps to accurately position the nozzle in 3D space.

When you power on the printer - it has no idea where the mechanical zero is, and assigns 0,0,0 to wherever the extruder is. It will only move up, right, and 'back' from there.

When you power on the printer, you normally leave the extruder where it is and select a file to print. By selecting the file (or printing from a computer), the gcode has the commands to home the printer, heat things up, and start printing.

Any of this make sense?

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