Live Z Adjust is inconsistent
Hey there!
First of all, I love this Printer, Josef has done a great job there!
I own it for a couple of months now and have gathered quite some experience.
However, I have had quite some trouble getting the Z offset right.
After a lot of PLA printing and continuosly adjusting the Z height, I found the sweetspot of my printer at -650µm. As most of my prints were coming out nicely, I decided to go for ABS which is considered more difficult to print.
So I preheated at 255°C and 100°C for the bed, loaded the filament and selected my gcode. Unfortunately I had to abort the print after just a couple of seconds. The material did not stick to the bed at all. Rather than a nicely squeezed line, like PLA did, I got a completely round line as if the nozzle was way up in the air. So I adjusted the Z Offset by like 20µm and tried again. Print did not stick and I went down another 20µm. Still not attaching, so I stepped down 100µm, which improved the result but was not good enough yet. Well, I ended up at -850µm, which is 0,2mm lower than my usual PLA printing height. To me this seems really weird.
The next day I started printing an object which turned out to be a little too large for its application, so I altered the craft file and created another gcode. But the object was sticking quite well to the bed, however the appearance of the bottom tells me that I was too close to the bed. I went up to -820µm and the print failed instantly, not sticking to the bed at all. So I changed the offset back to -850µm and the result was completely different than my -850µm print from one hour ago. (the edges are ugly because i was not particularly careful cutting the overextrusion with a cutter knife)
At least it sticked till the end, even though it resembles a net with spaces between the lines instead of a solid surface. The second layer is clearly visible through the first layer.
Is it possible that the printer was at cellar temperature before the first print, which is around 20°C, and while the object was printing the Z axis extended a little because the heatbed dissipates hot air to its surroundings? This is the only thing I could imagine other than an issue with the Live Z Adjustment itself.
To further investigate the material/temperature difference I switched back to PLA and ran my calibration process, printing nine tiny circles all over the heat bed, just after printing the second ABS object and letting the heatbed cool down.
As expected, the nozzle was way too close to the bed, resulting in overextrusion. I went to -750µm and repeated the process.
Better but still too low. After all, I put it back to -650µm and printed the planned object.
Am I the only one experiencing this issue?
Thanks a lot for reading this far, and I am looking forward to your thoughts, experiences and opinions! 😉
Greetings,
Stone
Re: Live Z Adjust is inconsistent
I started with the same issue and it has only become worse. I went from ~650, to ~850, to ~1100, to ~1600, and sometimes I'm at ~2100. I figured something was way out of whack, so I re-ran XYZ calibration (this is a pre-built printer), and got the error "XYZ calibration failed. Front calibration points not reachable." So now I guess I need to start adjusting the printer somehow. I wonder if your printer is also marginal in the same way.
Re: Live Z Adjust is inconsistent
PINDA readings depend on the temperature. That's why you are getting different heights when printing with different materials.
Therefore, you should run the Temperature calibration (the latest firmware), which attempts to deal and minimize those differences.
Another thing: when printing ABS you really should make a printing chamber, because ABS is very sensitive to temperature variations. Each breeze when entering or leaving a room with a printer does make a difference, plus, ABS printed objects need to cool down slowly, which is not the case when printing without a chamber. See a full tutorial here: https://www.thingiverse.com/thing:2351938
Re: Live Z Adjust is inconsistent
Oh, the PINDA Probe is affected by temperature. Now it all makes sense.
So, if I just remember the Z-Adjsutment for the different printing temps I should be fine.
But does that mean, that the bed temperature also affects the whole calibration process? Since I am further away from the bed at higher temperatures, it means that the PINDA Probe has a higher sensitivity.
Thats a nice construction you made there! I also thought about designing one, but your solution is so simple and effective.
However, for now my chamberless setup is sufficient.
Re: Live Z Adjust is inconsistent
I think (perhaps one of the senior members should confirm), that once you do the calibration, the printer automatically takes that into account.
Re: Live Z Adjust is inconsistent
I have always had the ever increasing Z adjust problem. "I went from ~650, to ~850, to ~1100, to ~1600, and sometimes I'm at ~2100" Yup, mine is about like that.
The new firmware 3.0.11 was supposed to fix this and seemed to have helped, but I'm not sure it completely fixed it. I have two other 3D printers that just use a sheet of paper and thumb screws its so much easier and once set it rarely needs to be adjusted again.