Cura frustration - nozzle height vs initial layer height

Hello

I am a PC user but recently i had to buy a Mac for school. I thougt it would be cool to slice on my mac.
I usually use repetier with cura engine for slicing, never had any problems.
But since there is no cura engine in the repetier for mac software and i never made good expirience with slic3r and skeinforge (actually i never used this one) i had to give the Cura standalone a try.

I tried 15.06 first, which i find really confusing. I still cannot find any printbed size settings.
Cura 15.04 is much more clearly laid out in my opinion.

The major problem with both verisons, i cannot find the setting for nozzle/bed distance.
If i set initial layer height to 0.2mm my printer will print the first layer at 0.2mm + 0.2mm (nozzle to bed distance) = 0.4mm which is totally useless.

Do Cura user level their printbed to touch their printnozzle? I really don’t get it.

i added

G92 Z0.2  ; sets current position to 0.200 height without moving anything

at the end of the start gcode. It makes the printer belive it is already at 0.2mm height, so the nozzle doesn’t get liftet extra 0.2mm for the first layer. In case anyone runs into the same issue.

I really wonder how you didn’t run in to this problem or if how you got around it.

I thought about this issue too, but didn’t think about this solution. Very good idea, I will try that too.

Until now I have good results with a nozzle height of 0,1mm and a first layer height of 0,2mm. I’m using a heatbed (PEI-Aluminum) for ABS-prints and have no warping any more, but the parts are a bit too high (~0,1mm, no wonder).
BTW: the PEI-aluminum-bed is great. When cooled down to 50°C there is a “click”, and the parts lay loose on the surface, no more sticking like with the BuildTak.

I added the line to my start code, but changed it to “G92 Z0.1”, as my distance is set to 0,1mm.
Definitely a good thing, great idea!

My first layer allways was a bit thin. Now, after adding the gcode you provided, the first layer is much better filled.
I thought: how can Cura know, what my distance between nozzle and bed is, to calculate the correct amount of material for the first layer. In the GCode the printhead is positioned to 0,2mm, but the real distance is 0,3mm.
No wonder there is not enough material extruded, simply 33% volume missing…

I drink a beer on your health!
Prost! from germany

After some more prints I can say:
this trick has a big influence on the surface of my printed parts. The first printed 3-5mm look much better now, but still not perfect.

So I did some more measurements: when the extruder is heated (210° for ABS), the nozzle is only 0,02-0,03mm from the bed, not 0,1mm as with a cold nozzle. So I changed my values again, with good results. Before the trick I had lots of material, that was pressed out of the surface, but only in the lower layers. The surface was better, when the parts raised.
All my attempts to reduce the flow resulted in new problems: the low layers were better, but then the upper layers became worse.
With the trick “G92 Z0.1” it was much better, but still not perfect.

I also found, that my z-axis has some play, so the layer height is still not correct for the first layers.
I tried to compensate this too with the"G92", and had nearly perfect surfaces!

But now I stepped into another problem:
I now also use the “z-jump” feature (nozzle is lifted when it retracts, no more scratches on printed layers!), but with that feature my “z-axis-play compensation” doesn’t work any more.

  • When the printer is set to the home position the bed is raised.
  • When the printer moves to the first layer the bed is pulled down, and the z-axis play messes the height. I was able to compensate this with a different value for the “G92” command.
  • When the printer does the z-jump and goes back to continue printing, it raises the bed, and the z-axis is back to it’s first position (like after homing). Now I don’t need my “compensation”…

In the software for my diy-milling machine (also driven with stepper motors, software is “Mach3”) I can set a value for “axis-play”, and it works great, and it has a big effect on the accuracy of the parts.

Is there a value in the software or firmware of the K8400, where I can compensate the axis play?