Hello,
I have had the K2 Plus for about a month now. For the most part it has been an excellent printer. I did have some issues with z banding on tall parts, and found that loose rail screws were causing that.
THis printer has delivered a trouble free experience with printing PLA. Yet recently I started doing mainly ASA parts for some projects. Since then I have been having 1st layer issues with printing ASA. THe 1st layer is always too close and I have to watch the 1st layer going down and adjust it manually from the screen to get it right.
This is quite annoying, and I have talked with creality about it and have followed their suggestions with no improvement. Their suggestion was to raise the bed temp to printing temp and allow it to sit for 10 minutes, then run the bed leveling. It didn’t change anything.
After thinking about it some I noticed that the bed leveling procedure runs with the nozzle temp at 140C. But ASA prints at 260C. I was curious if maybe the nozzle is expanding when heated to print temp causing the 1st layer to compress.
I ran several tests on this idea. I heated the bed to printing temp of 90C and let it sit for 15 minutes. I then set the nozzle temp to 140C, let it sit for 5 minutes, cleaned it thoroughly and home the printer. After that I jumped into Fluidd and set the nozzle height to .2mm. I used metal feeler gauges and sure enough it was perfect at .2mm height from the bed.
Then without moving anything I heated the nozzle to 260C, which is the printing temp for asa. I let that sit for 5 minutes and then used the feeler gauges to check the clearance. I could not get the same .2mm gauge to fit. So I went down in gauge sizes incrementally until one would fit the same as before, which ended up being a .10mm.
I ran this test several times thinking maybe filament was oozing throwing off the results. To elimante that I changed out the nozzle to a new one and still got the same results. I tested this 6 times with all showing that the nozzle was expanding anywhere from .075 to .125mm when going from 140C to 260C.
So as far as my brain works this would explain why high temps filaments have first layer compression issues. The printer probes the bed and sets z height at a nozzle temp 140C. And when the nozzle temp goes up to 260C the 1st layer is too close.
I am amazed that the nozzle seems to be expanding this much, but it is very long. Maybe is is the hotend body itself expanding, I’m not sure. I’m pretty sure that you shouldn’t probe the bed with the nozzle at 260C because it would probably damage the bed.
So I started setting a .1mm positive z offset (which was the average expansion number I got from my testing) in my slicer for High temp filament prints. This sounds crazy but the printer seems to like it and all the prints I have done since have worked perfectly.
I would like to see if anyone else could test this to verify my results.
Thanks