Mini won't start printing


My mini was printing just fine when it suddenly stopped working. I can connect to printer, but when it’s heating up for nozzle wipe, it just stops before doing the nozzle wipe.

I am running the latest version of Cura 3.6.2, have the latest version of firmware on the printer and the only change I’ve done to the GCode is to reflect that I am using a 0.6 nozzle. I’ve also changed the USB cable and port on my computer to rule out any comms issues.

No error message, it just says “printing” but it’s stalled and doesn’t begin to wipe nozzle.

Any help would be appreciated.

Normally when processing g-codes, the printer continues to execute the g-codes as they are received (well… as fast as it can physically process them). However… there are a couple of codes that tell the printer to “wait” and not proceed until some condition is true.

For example…

M104 says to “set” the nozzle temperature… but this code sets the temperature without waiting.
M109, on the other hand, says to “wait” for the temperature … the printer will not continue until the temperature is within acceptable range of the target temperature. This can cause a printer to just stop.

Similarly, M140 and M190 do the same thing except they set or wait for the bed temperature.

Once you connect with Cura, go to the “Monitor” panel, make sure you are connect (you can click the “connect” button) and then open the “Console” window.

In the console window try a couple of g-codes (manually type them). AFTER typing each of these test g-codes, press ‘enter’ to send them to the printer (it wont do anything until you press enter).

For example, try to ‘home’ the printer in all axes by typing:


Does it ‘home’ the printer on X, Y, and Z axes?

If yes, try a basic move command… enter:

G0 X100 Y100 Z100 F1500

This will move the print-head to the X=100mm Y=100mm Z=100mm at a speed of 1500mm/minute (25mm/sec). BTW, the printer also has an “E” axis. That’s the extruder motor. It advances or retracts filament. But we wont insert an E move on this line because your hot-end isn’t heated and we don’t want to try to force cold filament through the nozzle or it’ll just end up grinding filament.

Does the printhead move on all three axes?

Try setting some temperatures.

Set the bed temperature to 40°C (I’ll use a low-ish temperature here just so you don’t have to wait a long time for the bed to heat up) type:

M140 S40

Watch the LCD display to see it shows the bed has a target temperature of 40°C and also watch the actual temperature to see if it is actually heating the bed (is the temperature climbing toward 40°C?)

If the bed heater is working as expected, go ahead and turn it off (just set the temperature back to 0) using:

M140 S0

Test the hot-end. Let’s set it to 180°C by typing:

M104 S180

Again… watch the LCD panel on the printer to confirm that the nozzle’s target temperature has been set to 180 and that it actually is heating to that temperature. 180°C isn’t particularly hot for a nozzle so it shouldn’t take too long to reach that temperature. Sometimes a thermistor can go bad and doesn’t accurately report the temperature while the hot-end is actually heating. If the hot-end is heating but the thermistor doesn’t think it has heated enough, it can result in a thermal runaway condition (you may see an error message on the LCD and/or alarm.)

Monitor as the extruder heats … because if you do have a bad thermistor you might see the temperature jump around rather than heating up as expected. Defective thermistors can report erratic readings … instead of the temperature climbing a few degrees at a time… it might fail to climb … then suddenly report a huge jump in temperature… then a few moments later report a cooler temperature, etc. You should get a fairly consistent heating trend without the temperature jumping around.

If you DO see it jump around, you likely have a defective thermistor. Switch off the printer (it isn’t going to work correctly and frankly isn’t safe to operate … defective thermistors can over-heat to the point of causing a fire. Your printer does have thermal run-away detection (the board realizes it has been supply far too much power for too long for the hot-end not to have reached the desired temperature over some period of time and suspects the thermistor is broken … and will typically display an error message and/or sound an alarm).

If the nozzle is working as expected, go ahead and turn it off (set it to 0°C) by typing: M104 S0

You can look up g-codes here:

If there is an issue with the printer itself, then my guess is that one or more of those commands wont work as expected.

However, if everything works as expected, there may be something wrong with the start g-code. You mentioned it doesn’t even do a nozzle wipe… and the only the reason that would happen is either (a) it hasn’t reached the desired temperature or (b) you’ve inadvertently editing your ‘start’ g-code and there’s something invalid in it. But if that’s the case, you can just restore the correct start g-code and you should be good again.

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Dude, you the man! Not only did you teach me a new language but I think I know what the issue is. Every command works except heating the bed. It sets the temp to 40, but bed does not heat. Same when I try to print, bed doesnt heat up. I dont know how I didn’t see that before!

From my untrained eye, it looks like it sends the command and when it fails to heat the bed, the printer just stops responding. Does that makes sense? I get the below:

[11:54:46] M140 S40

< [11:55:48] Error:Heating failed, system stopped! Heater_ID: bed

< [11:55:48] Error:Printer halted. kill() called!

< [11:55:50] Requesting temperature auto-update

< [11:55:56] Requesting temperature auto-update

< [11:56:02] Requesting temperature auto-update

I looked at all the bed cables and all seem to be properly connected. How do I troubleshoot this? (i.e. if it’s the heater at fault, not sending power?).


The printer has a few fuses on the logic board … only one of these fuses is a 15amp fuse. That’s the heater-bed fuse. The other fuses control the extruder, motors, etc. but those are 5amp fuses.

You may want to take a look at that 15amp bed-heater fuse and make sure it hasn’t blown.

I don’t own a Mini or Mini 2 so I’ve never opened one of these. It looks like there are 6 screws (3 in front and 3 in back) that let you into the electronics cabinet. Just be careful as you open it to avoid pulling on wires that are attached to the side of the cabinet that pulls away from the printer.

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Fuse good and checked voltage, it is sending 24V to bed. It’s just not heating up.

I guess it’s time to replace the heated bed? Strange that it shouldn’t work, its a heating element, seems simple enough to not break down…

The only other thing that I can think of is if the wiring itself were to be damaged. Did you check end-to-end continuity on the bed-heater wires to make sure it isn’t just a damaged wire? If the wires are good, then yeah… sounds like the heater failed on the bed.

If this is a Mini 1 it looks like LulzBot is out of stock on the original bed but they sell the new style bed used in the Mini 2 (and it fits the Mini 1 because the power, connectors and size are all the same).

If you want the original Mini 1 heater, “IT Works 3D” shows them in stock (they do LulzBot sales & service including selling service parts). You can get a “new” heater or you can get a “blemished” (factory seconds) version for around half the price of new.

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Upon further inspection it looks like there may be some tricky business with the wiring. I am getting a solid 24V at the beginning of the wire (RAMBO connection), but I cant say the same at the end of the end of the purple wire. I can’t see how the wire would get damaged? it seems like it’s protected all the way and seems like quite a task removing and putting it back so neatly in place.

I’m going to also see if I can connect the bed directly to the RAMBO 24V to see if it heats up, if it does then it’s the wiring… ugh…

It is the purple cable that goes from RAMBO to connect to heating bed.

Was able to directly connect bed to RAMBO 24V source and bed heated up. Good news, I dont need to buy a new bed, bad news replacing that purple cable will be a nightmare. It seems very well and neatly routed from the RAMBO to the bed…

I strangely enough am having the same issue with my Mini Gen1. Does anyone have any info on where to get the connectors that connect to the heated bed? I would prefer to not splice them if I can help it.

I am having the exact same issue. Before anyone takes theirs apart: I have already done so and it does not fix the issue. I have been printing with no problem at all whatsoever, and everything is heating up exactly as expected. However, whenever I execute “Print” it will stall and never actually heat up enough to print. It will seemingly begin, but never execute it. It says “printing” and nothing ever happens. LULZBOT said it was my heater cartridge, but I have installed and ordered a brand new one from LULZBOT, and it is STILL happening. I have not heard back yet for what the problem could be. All wires, everything is in pristine condition. I wanted to contribute since this issue has been driving me wild for the last two weeks and I cannot figure out what could possibly be happening. This leads me to believe this is not internal, but a communicate issue with CURA 3.6.20 and the Lulzbot Mini first generation. I have tried newer versions of CURA, and can sometimes get a print if I clear out the Cache from local apps on the computer. If anyone else can think of a fix, let me know.