So a few months ago I traded in my Mini for a Mini 2, which I was so grateful that LulzBot offered. However, I have finally started to get my Mini 2 up and running with its intended goal to run the SL head permanently (no more swapping it out on my Taz 6 and all the steps that takes).
However, as I have started to print with it, I’ve started to see some growing concerns of mine, that I am no longer brushing off as “normal” or “my fault”. While I was told the noisy steppers (they make a loud static like sound when not moving, but not disabled) is normal, I feel these other two aren’t.
X-Axis Dropping
Originally I thought this was a normal issue. If I turn off the printer, or if the steppers are disabled, the left side of the x-axis drops down, making it no longer leveled. As I mentioned, I thought this was normal, but, as I started to read about another issue on the forums, I’m quickly realizing it’s not. Can someone offer some advice on this? Am I right to be concerned this is indeed wrong?
First Layer Uneven
The first level for me is very crucial when it comes to printing, and I will spend what feels like hours dialing in my settings to get that perfect smooth first layer (sadly this has become almost impossible with the changes to auto-leveling doing a double tap, still haven’t gotten my Taz 6 the same since). Well yesterday I started to calibrate my printer, getting it all lined up to use the SL head (e-steps and all), and realized that on my first print, the first layer was nice and smooshed on the left side, but on the right side it wasn’t. I could see the print lines.
Thinking this was just an issue with the auto-leveling being inconsistent (as I mentioned above it seems to be now), I did another print, only to see the EXACT same effect. Now I know this isn’t the leveling just being off. I have read posts about this being an issue but they date back, and I’m unsure if it’s even been fixed. Note I am running CURA 3.6.20, so it’s rather new, and I make sure I clean my components between every print. With the bed and washers getting wiped down with isopropyl alcohol as well as the nozzle being cleaned BEFORE it’s scrubbed (heat it up, wide it down with a paper towel, same process I’ve used for year).
I could really use some help with this too as it’s rather frustrating. I would love to hear “oh that was fixed in later versions of CURA”, but, I haven’t found anything to support it.
To be honest if I learn these are still on going problems, it’s really making me question LulzBot and their designs. I used to praise them, but lately I’ve growing annoyed. With stories I hear about the Taz Pro, or what I have listed here with the Mini 2. Shoot CURA even gets annoying now with it magically forgetting settings I changed when reopened (or reverting an unsaved one … sometimes), or just switching profiles when I open it (or the fact it crashes if you load too large of a model).
When powering off the printer, the x-axis tends to droop on the left side of the printer. This is in fact fairly common and usually resolves itself once the printer homes before each print. If it is really far out of level and the homing procedure does not resolve the levelness, you can run a level x-axis via the movement menu on your printers LCD.
This process does sound aggressive as it is pushing the x-axis into the 3d printer motor mounts, but again, this is normal. Try this and run another test print to see if that resolves your issue.
As for the levelness of the bed, this can be caused by the aforementioned issue. I would first perform the level x-axis function and see if that helps in bed levelness. If it does not, sometimes the jam nut that is behind the smooth leftmost smooth rod of the y-axis may need to be loosened up just a little bit. If it is too tight, it can push the left side of the bed up a very small amount and cause it to be higher than the right side.
My Mini2 also drops when powering off. Even worse, when Octoprint connects, the steppers shut off for a few seconds and one side of the X axis drops. As to whether that is normal or not, I don’t know, it is for me. I always do a “Level X Axis” from the menu right before printing and that seems to avoid issues.
Make sure your nozzle is getting clean for the auto-level sequence. I had issues when I first got mine that if the nozzle was not perfectly clean, it would push on the bed too much during auto leveling - I could actually see the bed moving until it finally pushed hard enough to make contact. For this, I just try to keep the nozzle clean and watch the auto level. If the bed moves at all, I will cancel and start over.
Those 2 items have made most of my prints clean now. Like you, I was chasing these 2 problems, constantly adjusting Z Offset, etc which was just making it worse. I never have to adjust Z Offset now.
You have to disable the steppers and manually move the x-axis all the way down to the plate before you level the x-axis on the LCD panel. Otherwise, you run the chance of breaking the brackets at the top of the machine that hold the z-axis rails and belt pulleys in place. Auto leveling the x-axis without doing this step will result in an incredible cracking noise and you will actually see the z-axis brackets flex from the force of the head going up at an angle. Even with doing this and auto leveling, the z-offset will need to be examined on EVERY print. You got lucky ControlsFreak that your z-offset doesn’t need to be adjusted.
I actually know why it drops, because, when you connect with OctoPrint (I use OctoPi, why I know this), it reconnects your printer. The equivalent of turning it off pretty much and back on. Great way to see this, tell you printer to warm up certain temp, then connect OctoPrint, all of sudden it forgot you told it that.
I can confirm my nozzle is clean (I do pre-cleaning of my printers), the leveling itself works as it should, nice tap and raise. From what I have read and what not, it’s almost like the Marlin code had an update, and it can’t handle the decimal places correctly or something (some precision decimal issue that can be annoying … looking at you C#). That’s my guess.
I am going to try McLeach’s fix, since everything I have been doing SHOULD work (I use these same steps with my Taz 6, and it prints smooth … thankfully FINALLY got it dialed in, I had to refasten the washers).
I don’t think I’ve seen it that bad, not going to lie. Course I will admit I am not a fan of it either. Not sure why they stopped using switched for detection (I have already dropped my bump sense down to ‘3’), since there are times that voltage change isn’t detected (one time having my printer halt and force a reset).
By the way, you mention you have to do the auto leveling each time, let me ask you, a few questions.
Do you clean your washers off before each print? Good old rubbing alcohol on a cotton ball approach
How tight are your washers? One trick I learned back with the Taz 6 is if they are too tight, it does effect auto leveling. In fact a week or two ago I refastened all of mine on my Taz 6 (literally taking them off), and all of a sudden my auto leveling is almost back to where it was before the firmware update like a year or two ago. My rule of thumb, use one finger on the Allen Wrench, and the second you get resistance, stop.
I don’t bed-level my mini 2 very often (although I use a spring steel sheet which is hugely helpful in keeping the bed tilt constant across prints). But I do level the x axis before everything. There’s so much inherent play in the x gantry design that the moment the steppers lose power or momentarily exceed their torque threshold the x gantry is no longer horizontally level. Along with @McLeach ’s points, a few things I have done to try and ameliorate this:
Bumped up z stepper driver current a bit. (Also added a heat sink to the driver, just in case). Since the steppers are the only thing truly keeping the x gantry level, it’s important that they don’t miss a step.
disabled stealthchop on the tmc2209s. I did not try this in marlin builds, but it has helped in Klipper.
When I do bed level, I do probing extra-slow. This seems to help with getting the best level possible with the lulzbot conductive sensing in particular. The conductive probe tends to drive the nozzle physically into the washer unless everything works perfectly on every corner. Even a little too aggressive of probing on a corner can throw the 2 out of level. Since I don’t level very often this slower probing is not annoying for me.
there is a tiny belt clip that is used to hold the free end of the x axis drive belt where it is clamped on the back of the x carriage. If the clip closest to the x stepper (left side looking from the front of the printer) is even slightly too far out from the edge of the carriage it will hit and drive under an angled portion of the x stepper mount assembly/z assembly when the x axis homes to the left. This is a hugely frustrating design flaw, as it slightly pushes down the left side of the gantry as the printer is homing — meaning that if you level the x axis, but then home again before printing you can actually end up tilting the x gantry down on the left side.