Taz Dual Extruder Conductivity issue with one extruder

General LulzBot TAZ
1

I have looked everywhere. I haven’t seen anything posted about a solution to this. I have cleaned the nozzles and the level washers. I know it’s a conductivity issue because I can get it to work if I put a piece of foil across the washer. I believe this works because the foil is connecting extruder 1 and extruder 2. There is only a zero sense wire on extruder 2. I looked at the assembly instructions and don’t see anything about extruder 1 having a zero sense wire.

When running the bed leveling extruder 1 (left extruder) touches the front and back washers on the left side and extruder 2 (right extruder) touches the front and back washers on the right side. I’m not sure if this is how the leveling procedure is supposed to go.

2

Assuming you’re talking about the Dual Extruder v3 here, because that’s the only one with left/right configuration with a single wire.

There should be electrical connectivity between the two nozzles. If not, there could be an improperly installed nozzle. All leveling should be done with the same nozzle. If it’s not, you may have the wrong firmware, or you have homing issues or offset changes that are putting the nozzle in the wrong place.

3

So based on what you’re saying it sound like there might be an alignment problem with the left touch points. If it is always supposed to be the second extruder nozzle touching each washer during leveling mine is not doing that. How do I correct that?

4

Can you post a video of the attempted leveling, and the output from the terminal connection with the printer with an M503 command? It will answer a lot of questions related to what is wrong.

Could be bed in the wrong position, could be a firmware value for offsets for the nozzle, firmware/slicer incompatibility, homing switch not functioning right, etc.

5

Here is a link to the video. 20260706_181155000_iOS.MOV This time it stopped on the back right washer. I ran it again and it stopped on the front right washer. Here is the output from M503:

Send: M503
Recv: echo:  G21    ; (mm)
Recv: echo:  M149 C ; Units in Celsius
Recv: 
Recv: echo:Filament settings: Disabled
Recv: echo:  M200 D3.00
Recv: echo:  M200 T1 D3.00
Recv: echo:  M200 D0
Recv: echo:Steps per unit:
Recv: echo:  M92 X100.50 Y100.50 Z1600.00
Recv: echo:  M92 T0 E760.00
Recv:   M92 T1 E760.00
Recv: echo:Maximum feedrates (units/s):
Recv: echo:  M203 X300.00 Y300.00 Z3.00
Recv: echo:  M203 T0 E25.00
Recv:   M203 T1 E25.00
Recv: echo:Maximum Acceleration (units/s2):
Recv: echo:  M201 X9000 Y9000 Z100
Recv: echo:  M201 T0 E10000
Recv:   M201 T1 E10000
Recv: echo:Acceleration (units/s2): P<print_accel> R<retract_accel> T<travel_accel>
Recv: echo:  M204 P500.00 R3000.00 T500.00
Recv: echo:Advanced: B<min_segment_time_us> S<min_feedrate> T<min_travel_feedrate> X<max_x_jerk> Y<max_y_jerk> Z<max_z_jerk> E<max_e_jerk>
Recv: echo:  M205 B20000 S0.00 T0.00 X8.00 Y8.00 Z0.40 E10.00
Recv: echo:Home offset:
Recv: echo:  M206 X0.00 Y0.00 Z0.00
Recv: echo:Hotend offsets:
Recv: echo:  M218 T1 X0.00 Y0.00
Recv: echo:Auto Bed Leveling:
Recv: echo:  M420 S0
Recv: echo:Material heatup parameters:
Recv: echo:  M145 S0 H200 B70 F0
Recv: echo:  M145 S1 H240 B110 F0
Recv: echo:PID settings:
Recv: echo:  M301 P47.45 I4.83 D116.63
Recv: echo:  M304 P162.00 I17.00 D378.00
Recv: echo:Z-Probe Offset (mm):
Recv: echo:  M851 Z1.31
Recv: echo:Linear Advance:
Recv: echo:  M900 K0.00
Recv: echo:Filament load/unload lengths:
Recv: echo:  M603 T0 L40.00 U80.00
Recv: echo:  M603 T1 L40.00 U80.00
6

The oozing is the obvious problem. Having the temperature too high during homing (wrong filament selected) or wet filament (moisture turns into steam and “pops” more filament out). The major flaw of the Taz 6 is reliance on the electrical connection with a nozzle that’s almost always partially covered in an insulating material.

The way it detects is to get the very rough zero from the button press. That rough zero lets it set the maximum the machine will move down when checking the washers.

From there it goes to the first washer. When zeroing on a washer it will move down until connectivity is registered for the initial zero (or it goes below the maximum detection depth and fails). If it succeeds in getting a measurement for the initial zero, it lifts off the washer before lowering at a reduced speed to get actual zero. After getting that second electrical contact, it will slowly lift (the ticking you hear) until electrical contact is broken. The height that electrical connection was last detected is saved as the zero height for that corner. Rule of thumb, if it ticks more than six times when lifting, it had to push too hard, and your nozzle is dirty.

If it fails to get connectivity before the maximum depth, it will halt the printer. If it gets connectivity too soon, it will halt the printer.

After the first corner is measured, it moves to the second. At this point, there is much less deviation from the zero position accepted (something like 1-2mm, depending on firmware version). Any amount of plastic on the nozzle can electrically insulate the nozzle from the washer. A .01mm thick insulator is still an insulator, and it may require pressing the nozzle down pretty firmly before connectivity is achieved. The rule is that if you visibly see the washer get pressed down AT ALL the measurement is off, and even if bed leveling succeeds, your measurement is off, and failure is likely.

So, in the video, you get the first measurement (nozzle 1 looks fairly clean), but nozzle 2 is visibly oozing the entire time. It usually fails on that second one because it goes down beyond the maximum. It did get a measurement on #2, but not on #3 within the allowable margin and halted.

Additionally, your X axis gantry may not be parallel to the bed, judging strictly on how long it took to lower the nozzle. Hard to tell from the video though, but that can also contribute to failed leveling.