LuzBot Taz heats to temp - but drops when print starts

Trying to print on a LuzBot Taz. The head will heat to the correct temperature and I can get some plastic to come through the head - using the command in the software. But when I print the head goes everywhere it should but no filament goes out. The temperature of the head drops precipitously as soon as the head starts its printing routine. Help.

Check your print fan speed in the slicer. If it is set at a high %, it may be over cooling the hotend when the print starts.

If you have an E3D based hotend, the silicone sock generally cures this problem.

I did not realize at first that first that there are two fans. A small on that blows directly on the nozzle and a larger one that blows on the plastic being extruded. Tried disabling the small fan with no luck, then finally realized the settings are controlling the large fan. When I first tried printing the smaller fan blowing directly on the nozzle was OFF, allowing the nozzle to reach the desired temperature but after the printer head started traveling to print it immediately came on and cooled the head down. Now the small fam comes on right away and the the print nozzle does not heat up enough. Did not see anythng that controls the small fan.

The small, always on fan is not pointed at the nozzle (or it shouldn’t be), its pointed at the cooling fins on the cold side of the heat break. Without this fan running, you will almost certainly suffer from what is commonly known as “heat creep” which will cause filament jams.

Rather than make us guess at your configuration, please tell us which TAZ, which tool head, what filament, and any other details like the temperatures being used that would help us help you.

OK. I was not entirely accurate in my description. I was being general in my description. I do recall it as being pointed at the cooling fins. Surely if the fan was not needed it would not be there for the purpose you state . . . (naturally) but from the standpoint of somebody with little experience with these bit of technology there appears to be a correlation between the fan and the inability to achieve and maintain operating temperatures.

I can get over to the Makerspace and get the detailed info you need. Any help would be appreciated.

Your comment about the ‘heat creep’ issue with regard to the fan running caught my interest. The other 3D printer (from another manufacturer) is acting up and jamming. We are scratching our head over that. It may be an ‘under active fan’. I have not done so, but will need to pursue this on the appropriate support forum for that printer.


If the printer is properly designed, the “always on” fan will have no effect on the nozzle temperature. The “part cooling” fan is a variable speed fan controlled by commands in the GCode. How much or how little of this fan is needed is primarily determined by the needs of the filament being printed, i.e. PLA wants lots of cooling, ABS very little.

There are some tool heads where the “part cooling” is also “nozzle cooling” and this can cause the issue you are describing. My LuzBot TAZ 6 has this problem with the Aerostruder tool head and the problem is solved by using a silicone sock (its an E3D heater block and nozzle and E3D sells socks for them).

You didn’t mention which TAZ you have or which tool head you are having problems with, so we can’t get any more specific on possible solutions.

OK. Its a Lulzbot Taz 5, 3.0 PLA Filament, Temps 205C/60C, 0.30 Nozzle, Tool head: Single Extruder V1.

I took pics of the setting screen in the CORA software, so if there is anything helpful in that i can send it along as well. We have been messing around with this for months, so if you can arrive at a fix, it would be greatly appreciated.

Lesson learned here! Thanks to the patience of Cody and sometime on the phone it became apparent that the issue was a loose connection on my end. Learned a ton and appreciated the patience of the support team thanks much.

Did you mean to post that here?