Printing in the Air - Z Axis

[Cadillac2012 1]

I'm brand new to the 3D world and loving it but need some direction.

 

I have a Longer LK4 and am using Cura on a MacBook Pro to work with models.

I slice and export have tried exporting as .gcode and .stl.

 

Each time I start to print, the Z axis, printer head starts approximately 1.5" or 3.81 cm above the table.

The models that came with the printer have all printed fine.

 

So, I am sure it is my ignorance at this time and could use a pointer on how to make this work correctly as I would would like to start printing face shields for medical and first responders to use.

 

Thanks,

UMS5_eyes shield.gcode

[Guest maht]

Could be an unlevel bed, or it could be that you need to calibrate your z offset from your bed. the z0 point might be a few mm higher than the bed itself.

[Cadillac2012 1]

I appreciate your response!

I releveled the bed and checked the Z axis 0 point.  Those seemed to be in adjustment but didn't hurt to check.

 

I did discover that the Longer LK4 is a rebadged Alphawise U30. So, went into Cura and created a new printer and replaced the model.

That seems to have corrected the Z Axis printing in air issue.

 

The other strange thing is the way it prints models downloaded from the net.  All the files included with the printer printed perfectly. No skipping while printing.

 

I've tried 5 different models downloaded and sliced in Cura and outputted as gcode.  All skip as illustrated in the attached image.

 

AU30a_eyes shield - Revised.gcode

[gr5 2,004]

Those skips in that photo are where the nozzle and bed are too close.  It's normally hard to tell if you are too close or too far but that (95% sure) is too close.  You can verify by pushing up or down on bed/print nozzle with your finger (you only have to move the thickness of a sheet of paper to see a significant difference).

 

So your bed is not flat - not within the thickness of a sheet of paper.  Or maybe your gantry is not flat.  Most likely the bed.  This is okay.  You can just choose a thicker bottom layer.  Or ignore it - in this case - for this print - it's not a problem at all.

 

Why do other sliced jobs not do this?  Well most likely the bottom layer is thicker on the other jobs.  Look at the gcode - search for Z - there are not very many of the letter Z in a gcode file - typically one per layer plus maybe 2 to 5 more.  Look for the first Z just before things really get going (dense amount of moves).  Typically it's around 0.1 to 0.3mm.  Maybe the presliced ones have a thicker first layer to compensate for non-flat print bed.

[gr5 2,004]

Again - for this particular print (PPE mask) - this skip is not even slightly a problem - the next layer will stick really nice.  In fact having it a bit thin makes it so the part will stick extra well to the bed and not come loose during a print.

[Cadillac2012 1]

I wanted to let you know you were correct on the assessment of the issue.

 

I should have known better with a new piece of equipment that things move.

The table was not level.  I think I did not also have enough tension on the springs to help keep it level.

I've leveled twice to make sure and it now prints all the way around.

 

And, the sample files that came with the printer covered a small areas in the center of the table, so I imagine would not be affected by table issues.

 

Thank you for taking the time to give me some guidance!