Stuttering

Hi everybody,

I’ve been having an issue with honing that started recently. When the nozzle comes down for the second verification it stutters before going back up, this happens on all four corners. Usually it’s Less than half a second. At first I thought it was the washers so I cleaned the, then I cleaned the nozzle, still nothing. Then I took the tool head of and noticed one of the purple wires, that goes to the end stop switch, was routed poorly and had melted from the hotend. Also the red wire to the thermistor had failed to keep contact. I bought and SE tool head hoping that would alleviate the issue but it did not. I’m asking for help because I believe the honing issue is why my prints fail after 45%, the tool continues in its path but nothing is extruding. Is there something I’ve over looked??

When the guys at LulzBot change their firmware, often times they change the style in which the nozzle taps the washers. For instance, in earlier versions the nozzle would make a hard tap in order to clean any filament out of the way and then softly touch the washer. In later versions there is kind of a rapid “dot,dot,dot…” sound. This would be normal. The nozzle has to make a 5V connection with the washers in order to set the z-offset. Filament will act as an insulator and inhibit this process. I’m thinking that this is normal for the firmware you have.

I see, I did count the “dots” at each washer and it seems to be 4 every time. I think it may have something to do with the orientation of my design. I scaled it up to 135%, I’m still not sure what’s going on.

I believe the stuttering you are referring to is the backlash compensation.

If there is that much backlash I wonder if the motors for the Z axis need to be replaced. See how this problem came out of nowhere I would think so, that and the fact that my taz6 is a refurb

No, each “dot” is the sound of a single step of the Z motors. The printer is checking for a break in the electrical connection between each step. Did you update the firmware at some point? The backlash exists in the interface between the lead screw and the nut. It has nothing to do with the motor itself. The TAZ 6 has a Z resolution of 0.000625mm per step, so 4 steps is 0.0025mm (or 0.0000984") which is essentially undetectable. The reason it does this is because it probes the washers to calculate the Z offset transformation needed to keep the nozzle equidistant from the bed at any point of XY motion (auto bed leveling). This requires raising and lowering the Z constantly between layers to compensate for the tilt within a layer at the given XY location. The backlash values (in your case 4 steps per washer) are factored into the number of steps needed to adjust the Z axis every time the direction changes to compensate for that lost motion. Again, it is very small. 4 steps is very good. It indicates that you have very little backlash and that the nozzle was very clean when probing. Sometimes if there is plastic on the nozzle, it takes more force to press on the washer before an electrical connection is made. This pushed the bed corner down and once connection is detected, requires many backlash steps to break the connection (like 10-20+). This is a sign that the nozzle was not prepared properly. Your machine sounds like it is operating great.