weird bed level issue?

I don't know how this keeps happening but I will level the bed and get amazing prints I printed all day yesterday and got about 4 good solid prints.

Today came home after work decided to print some more so I ran a bed level test to make sure it was still right everything is fine so I go to start a print and come back to it a few min later to find the jhead ripping through the tape on the bed

So I pull the tape off put new tape on let the bed get up to temperature level it and start another print I come back a few min later and my print has skipped a step and is over lapping but print level seems fine.

I put new tape on heat it up walk away and come back to it doing the same thing it did the first time where it is ripping the tape.

has anyone had this kind of gremlin before and know how to fix it?

Sounds more like dropped Z steps when printing, so when you reset for the next print the nozzle is physically lower than your controller thinks it is.

If you are running 2 Z axis motors, one side can drop steps, making it appear the bed is not level when actually Z is tilted to one side.

Dirty Steve Wrote:
-------------------------------------------------------
> Sounds more like dropped Z steps when printing, so
> when you reset for the next print the nozzle is
> physically lower than your controller thinks it
> is.
>
> If you are running 2 Z axis motors, one side can
> drop steps, making it appear the bed is not level
> when actually Z is tilted to one side.


Is there a way to prevent missed steps or is this just something that happens from time to time ?

What is the usual cause ? Loss of interpretation from PC to printer? Or flaw in slicing part ?

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tattooedfish
Is there a way to prevent missed steps or is this just something that happens from time to time ?

There should NEVER be any steps lost when configured properly.

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tattooedfish
What is the usual cause ? Loss of interpretation from PC to printer? Or flaw in slicing part ?

Neither. Probable causes are:
1. Running too fast, for the Z axis try 30mm/m. If you no longer have the problem then you can try 50mm/m or 100mm/m. The unlike the X and Y axis the speed of the Z axis is not that important for fast prints.
2. Stepper driver current set TOO LOW.
3. Stepper driver current set TOO HIGH.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Stupid question where would I adjust the z axis in g code or firmware ?

Not sure which firmware you're using, but with Marlin, I had to reduce default Z steps feed rate in firmware.

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tattooedfish
Stupid question where would I adjust the z axis in g code or firmware ?

BOTH plus in the HOST software e.g. Pronterface.

You can set a maximum speed for X, Y, Z (and E).
Then even if you command the printer via HOST or gcode to go faster it won't.

Better is to also set your HOST and gcode generator (slicer) to this maximum speed.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

I use ReplicatorG, and whenever I start the jog screen that allows you manually move the axis, the software would drive the table back to the origin at max speed. This often causes problem when the table moves and hot end slams into the freshly printed object if I started the jogging screen without resetting the origin. So without setting the max speed in firmware, the Z axis often gets stuck too.

Does pronterface have this problem?