Workhorse print stops partway through

Print makes some progress, in this case about 200 layers done, then inexplicably stops printing the part. Print head moves up to the top, apparently finished. I check the G-code in cura and it looks like any other part that i’ve printed. All the layers look fine from bottom to top. Third time this has happened and I have no idea what is going on.

So, happened again today. This time right as I was sitting in front of the machine. Nozzle stopped moving in place where it was printing. LCD screen looked like it restarted. Tool head moved to the top of the machine. What is happening here?

Just curious. Does the stop happen at the same z layer?

Have you used any post-processing plug-ins?

Might there be a G28 Z – or even any G28 command other than the one that would be found int he Start G-Code?

no plug-ins used. I can restart the same print and it will not happen in the same place, or at all. Then 2-3 prints down the line on a different print it will happen again unexpectedly. I have updated the firmware on the machine, which I notice may have been out by a few versions. I hope that was it.

The latest firmware is 2.0.9.0.13. You can get it by downloading the latest version of Cura LulzBot Edition (the firmware for all printers is packaged with the download). You do have to check the LulzBot site from time to time to see if there are new versions. Cura LE doesn’t have a way to check for updates on its own.

When the printer stops, do you see any messages or errors displayed on the LCD screen?

not this time. It looked like the software reset, I saw the marlin logo flash before the tool head moved up to the top. The second time this happened there was an error about a power failure - this is a bit odd though as another printer was running at the same time right beside it, plugged into the same power outlet. I know a little about electronics, but not enough to work out if/where there is something strange going on inside the machine. Maybe this is an indication of some electrical connection being loose in some way?

If the printer behaved as if it reset it could be a few things.

First … were you printing via the SD card or were you printing through the USB using a computer (I use a Raspberry Pi running OctoPrint). I have noticed that when the computer establishes a connection with the printer, it results in a reset and the graphic display will show the LulzBot logo when this happens.

If using a computer, I’d try transferring to an SD card and re-run the job to see if it can successfully complete. If it DOES succeed … then possibly there’s an issue with the USB cable or the computer. There could also be a problem on the printers side.

If you do NOT use a computer, then possibly there is a power problem or a problem with a connection. The entire control box assembly is documented here: https://ohai.lulzbot.com/project/control-box-assembly-workhorse/taz-workhorse/

If you own a multi-meter you can check for proper voltage to the RAMBo board (verify the power supply really is supplying the correct voltage, terminals are snug, wire harnesses are snug, etc.)

many thanks. I always use an SD card for printing. I’ll see about inspecting that board when I have a chance.

Well, it happened again today. Gave up about 20 hours into this print.
Screen says 100%


I guess I need to find a few hours to poke around inside this thing.

My Workhorse went from printing excellently to I can’t get the hob gear from chewing up filament and not extruding. Very frustrating. The Taz 5 and 6 (older models) I have continue to work great, but this workhorse has continually been problematic.

The Workhorse is definitely a different printer than the TAZ 5/6 and we see a lot of users treating it like the TAZ 5/6.

The tool head is different and does require a different way thinking when printing with it.

Note if your printer is using the hardened steel nozzles, you may need to make temperature adjustments depending on your filament.

The hardened steel nozzles have much different thermal characteristics than the usual brass/plated copper nozzles. Because of this, it is unable to absorb the heat from the heater block and transfer it to the filament in a quick manner. So this means that even if you have it set to say 210°C, the filament inside may be cooling the nozzle down to around 180°C and that temperature is much too low. This low temperature can cause the filament to strip or grind away.

We have found most filaments will need to be bumped up in temperature by 10-20 degrees or so and sometimes more so the nozzle gets hot enough to melt the plastic for extrusion.

@McLeach, my tests with a temp-tower showed best results on my Workhorse w/0.5 HE head to be about 230°C … a bit warmer than most people would use.

But this printer seems to be randomly resetting … not likely tied to temperature. Something is glitching on it. The O.P. is not using a computer to print so I don’t think it’s a connection reset problem. It doesn’t seem to be throwing any error codes (e.g. not declaring a thermal runaway, etc.). This is what has me suspecting a poor connection somewhere.

My own Workhorse has been extremely well-behaved. I once had an issue where it couldn’t “home” the X-axis and that turned out to be an internal break in the end-stop wire. You can play games like swap the X & Y axis wires … but I put a multimeter probe on the end-stop and another at the board and showed no connectivity with one of the wires. I used a straight-pin and clipped one of the probes to that to “prick” the insulation into the internal wire and found a point where the connection worked … and pricking the same wire 1 cm farther it had no connection at all … so I knew I had found the break. The wire was ultimately replaced (LulzBot covered it under warranty because it happened when the printer was fairly new) … but oddly the wire showed no signs of stress. It wasn’t a pinch point. There didn’t seem to be any strain on it. The outer insulation was in perfect conditions. I can only imagine the wire had a defect in it at time of manufacture. Other than that … my Workhorse has been a champ.

One thing to note is that even if you are printing from an SD card, if you have a computer connected to the USB port it can reset the printer at unexpected times. Sometimes it is obvious, like if you are already printing from SD and you launch Cura and try to connect to the printer. But it can also happen if other apps scan through the serial ports looking for devices or if the OS does something like reset the USB drivers.

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I drew this diagram for another thread. Imagine if you could cut open the heater block to see inside… this is how it needs to be sealed:

Hot End Diagram

The heat-break is a threaded tube that extends from the “cold” side of the extruder to the “hot” side (the heat-block). The nozzle threads up into the bottom of the heat-block and the end of it’s threads must form a seal against the threads of the heat-break to prevent filament from leaking through, into the threads, and ultimately it could leak above and below the extruder.

The left-most diagram is correct.

The middle diagram – showing the gap – is bad.

The right-most diagram is also bad … but this one can trick you into thinking you’ve bottomed out the nozzle against the threads of the heat-break because the nozzle wont tighten anymore. But the reason it wont tighten anymore is because the nozzle bottomed out on the heat-block before it’s threads could reach the heat-break.

The heat-block is aluminum and, being a soft metal, if you are too aggressive with it, it is possible to strip the threads. The good news is that if you do strip the threads, a replacement heat-block is cheap. But swapping it out is a delicate operation to avoid breaking the wires for the heat-cartridge and thermistor.

When you tighten or loosen a nozzle on the heat-block, you need to heat up the heat-block a fair bit… typically about 285°C to expand the metals. Snug it together (snug but not so tight as to risk stripping threads) and as it cools the metals shrink and create a tighter seal.

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Bill,

I have deleted your post with your invoice because it has personal information that is not recommended to be displayed on a public forum.

Do note that this is our public user forum and not a direct contact to LulzBot staff.

It does however look like you will need to replace the heater cartridge with a new one as this is not something that is repairable.

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