New TAZ challenges

Working through a hand full of issues with a new TAZ. Got most of the undercontrol. Now down to the last big one…

It seems that when I try to heat my Bed, that it doesn’t heat correctly. Now let me be more specific.

if I set it for 110C for ABS, it will heat to 85C and then it will start to cool, and never return to 85, it will then moderate to a around 65.

But there’s more. I first thought it was a power supply issue, so I hooked up an external thermocouple to the bed and watched what it was doing. In fact, it’s heating way hotter than 85 or 65.

Now I don’t know which the issue is. Is there a problem with the Rambo not detecting the bed thermocouple correctly (wrong component on the board somehow), or is it a bad thermocouple on the bed? If that later, I have no idea how to replace that as there is a mat that is attached to the bottom of the glass and the thermo couple is embedded in red RTV in that mat.

Also note, that with an IR temp gun, the bed is indeed hotter than the the Bed thermo thinks it is… At the moment, I’m suspecting the thermo in the bed as the likely hood of the Rambo being bad is pretty remote.

I wonder is there any way to plug the thermo into one of the other inputs on the Rambo just to verify that part? The nozzle works just great, but I’m having to play games with the bed at the moment to make things work…

Any thoughts from anyone?


Thanks for verifying the bed temperature with the thermocouple. We’ll need to check the resistance of the thermistor, it should read approximately 100k ±10 at room temp. It would help to see where the thermistor reading starts deviating from the thermocouple reading. If the thermistor is bad we’ll be able to replace the bed. Replacing the bed is as easy as powering down the printer, rotating the bed fingers off the bed and uncoupling the connectors for the heated bed.

I just posted about this exact issue with my TAZ a few days ago as well:

I’m at a loss as to what to do to identify the real problem here. In that thread, jebba pointed out that TAZ shouldn’t need to be over 80-85C to print ABS even though the manual says to use 110C. I’m still concerned that my bed stops heating at a certain point though. I tested again last night - it only got to a reading of 75C after 45 minutes of heating whereas it got to 110C within 13 minutes when used the TAZ the first week. My IR temp reading indicates that my bed is much hotter than the reported temp as well, but I don’t have a thermocouple to get a more accurate reading.

  • Adam

We are using the heated bed at 85C in the fleet for printing with ABS, with the ABS+acetone solution. People are reporting that bed temps as low as 65 are still adhering well. One reason why the thermistor reading is not matching the Fluke reading is the positioning of the thermistor in relation to the heatbed hot spots. The heater tends to be hotter in the center of the bed.

Been working with Orias during the day today… Still have some more testing to do, not specific answer yet… If anyone has any doubt, these guys at Lulz are AWESOME… Glad we could use some electronic forms of communication so we didn’t have to burn up telephone lines, but so far, nothing but major kudos… And they continue to reaffirm that they will get it sorted out for me… I don’t mind providing the input to them. After all things happen where it’s a bad component, lot, or something else…

I just needed to make sure everyone understood how good they guys have been to work with… Jebba and Orias!!

Thanks both!