Video of issue: https://photos.app.goo.gl/XjPAhZUaBp6YwatA9
This machine is 7 or 8 years of frequent use, and has some wear and tear.
It is failing during the leveling process. It doesn’t have a problem with the first two pads, but then when it gets to the third, it appears to make good contact, but then backs off and goes through the noz cleaning process again. Does this three times and then shows a probe failure message.
Anyone seen this before?
My guess is you’re slightly out of level. The nozzle isn’t level relative to the washer. This would happen to me on the 2nd washer. A perfect tap and right back to the wiping pad. My Z axis was slightly misaligned and continues to go out of alignment over time, every now and then I need to re-align them. Yours wasn’t sounding the best either so I suggest adding some lithium dry lube to the z-rods. Your Y axis could also be slightly out of alignment so keep that in mind also.
Like JoeBowler300 said, your bed could be not level. Also, based upon the sound, I would suggest going through the frame straightening process that Lulzbot has on their website and add a little lithium grease to your screw gears. Plus, clean the excess gunk off your hot end.
I am having a similar issue with the probing on my Mini 1. I tried leveling out the Z-axis and have it within 0.5mm. The 4th corner is the one that fails to calibrate, but sometimes it does. I checked the continuity between the nozzle and bed, and once the printer has printed a part, it refuses to calibrate that 4th corner. When I check the continuity, sometimes it isn’t a closed circuit. What do you do in those cases?
Thanks for your help. Do you happen to have the link to Lulzbot’s “frame straightening process?” When I search Lulzbot on “frame straightening” nothing comes up. Thanks.
Instructions for how the frames were put together would be on our OHAI.
Should I look through the Taz 6 assembly information on how to assemble the frames? Or is there some specific maintenance info on frame straightening? Thanks.
Putting a square on it, everything looks perfectly square.
Anyone have any other thoughts?
I think I would perform a manual measurement visually and with some feeler gauges. G28 X Y, G28 Z, and then manually move the nozzle to each corner of the bed. Start with Z = 5mm and then lower it by 1mm at a time after visually inspecting the gap at each corner. If you get to Z = 1mm then you can switch to feeler gauges. I have multiple sets of gauges ranging from 1mm to .05mm (or .035 inches to .002 inches).
If manual measurements look good, then the problem is probably electrical. You can troubleshoot this with a multimeter.
Can you possibly explain the underlying math for me? Do the initial two probe measurements establish a plane such that the third measurement has to be within a certain tolerance such as ±1mm? And therefore the frame has to be level enough so that each measurement falls within a tolerance established by the previous probe measurements?
From a mathematics perspective, it takes 3 points to define a plane.
I’m not aware of any technical descriptions of the Marlin algorithms so one would have to analyze the Marlin code to determine what the 4th point brings to the table.
If you take the time to do the manual measurements, you will have a better understanding of just how flat and how level your bed actually is.
First thing; Test the 4 table bushings, by wiggling the table. If you see play, they need replacing. A machine that heavily used will likely need new bushings regardless.
Second thing; Is the table or platform that the machine is resting on, FLAT? Sometimes, people place the machine on a piece of plywood or a tile top or an uneven surface. Plywood warps from hot & cold cycles.
Third thing; Check wiring to the pad. It can break where the harness flexes and at connector terminals as the bed moves.
Manually clean off your metal nozzle…if it extrudes a trickle of plastic just before arriving above each pad, wipe it off. Sometimes, with switching from a high temp material, the machine will drop the wipe and probe temperatures below the glass temp of that previous material (say 190c) to something like 150c. If you have a tiny piece of jelled high temp plastic left on the tip of the nozzle, it will not make contact.