How to disable 'Err: MINTEMP'  

RE: How to disable 'Err: MINTEMP'

fit a 100 K ohm resistor in place of the thermistor, and it will read about 25C instead of mintemp!

regards Joan

RE: How to disable 'Err: MINTEMP'

Thanks Joan, I'm looking to disable at a firmware level.

RE: How to disable 'Err: MINTEMP'

Hi Jamie, 
I understand, however if nobody else steps forward, you have an alternative

And you also know that there is a minimum temperature to permit extrusion that also   needs attention, 

Best of luck, 

Joan

RE: How to disable 'Err: MINTEMP'

There are two MinTemp constants declared in the firmware (nozzel and bed) you can set them to any temp, recompile and burn.

None of my business but are you sure you want to do that to a E800 printer? Maybe consider and Ender or something. Where is the mechanism (that will apply pressure to the clay) going to sit?

RE: How to disable 'Err: MINTEMP'

Posted by: @towlerg

There are two MinTemp constants declared in the firmware (nozzel and bed) you can set them to any temp, recompile and burn.

None of my business but are you sure you want to do that to a E800 printer? Maybe consider and Ender or something. Where is the mechanism (that will apply pressure to the clay) going to sit?

or just leave the thermistor attached, and use M302 to bypass cold extrusion. No firmware alterations required.

RE: How to disable 'Err: MINTEMP'

@towlerg

Thank you (and everyone else) for your responses! Do you know if there is a location in the firmware where the process that checks for the error can be overridden?

Our clay will be pressurized on a system separate from the print platform and delivered to the print head via a tube.

RE: How to disable 'Err: MINTEMP'

This err: MINTEMP is doing my head in!

My Prusa is located in a cold garage which suits it fine and I get good results.  However whenever I start it up or leave it for more than a few minutes,  the temp drops below the MINTEMP threshold and I get the error.   I therefore have to get the hot air gun out each time I want to run it.   Once the nozzle heater is active it's not a problem.

I can understand that the temp needs to be above a minimum value but why does it lock up my machine?  Surely it would be enough to block printing until the temp is above a certain value and there is a perfectly good nozzle heater which could be used to heat it up.

It seems a pointless restriction

Peter

RE: How to disable 'Err: MINTEMP'

@drpeej

Hi Peter, it's a safety feature intended to protect against problems with thermistors
YOU could alter the firmware if you are confident that it will not cause safety issues, 
or you could put your case / suggestions on the Prusa Github page for the printer. stating what your preferred low temperature would be,

Prusa have looked at this situation a number of times, and they have erred on the side of safety. there are limits on the granularity of A to D samples at very high thermistor resistances, 

How long is it safe to heat a hot end if the thermistor is faulty? in the hopes of overcoming a cold start situation... 

I believe that on the Mk3 printer there are 4 thermistors, Heatbed, Hotend, Pinda and Einsy, perhaps you could scan all 4 thermistors and see if they concur, as it is unlikely that all four  are simultaneously faulty.  and use this as the basis for a decision tree before declaring Mintemp error... 
but I guess there could be reasons where this would also fail. e.g. if the printer has been switched on but inactive for a while, it is unlikely that the Einsy thermistor will show the same temperature as the other three... 

Is there sufficient free memory to make changes on the Einsy?

regards Joan

RE: How to disable 'Err: MINTEMP'

@joantabb

I do realise this but I cant believe there isnt a solution.   How about doing a short, timed heat burst (say 15-30 seconds) to warm it up if there is a MINTEMP error and then check the thermistor reading again and only lock us out if the second reading fails.   

Peter

RE: How to disable 'Err: MINTEMP'

@jamiefthompson

I would not deactivate the process but rather reduce the value for the Mintemp variable, e.g. to 10degC.

RE: How to disable 'Err: MINTEMP'

@drpeej

There are options, as I suggested above, 
there is also the 'Redneck' option

Take a mug of hot coffee or tea out to the Garage with you, rest it on   the heatbed, over the thermistor, near the hot end for a short while, then remove the mug, install the build plate and start your print.

I suspect there is a rather small number of folk having this issue, and suspect that prusa would rather develop other features using the remaining free memory space.

As Karl and I suggest there is nothing stopping you from modifying the firmware to suit yourself.!

regards Joan 

RE: How to disable 'Err: MINTEMP'

I'll look at modifying the firmware, I think.   I see that MINTEMP is already set at 10 degrees!  My garage is certainly cold!

I am using the Bondtech geared mosquito HT thermistor version of the firmware.

Thanks for the advice

Peter

RE: How to disable 'Err: MINTEMP'

@drpeej

Good Luck. 
regards Joan

RE: How to disable 'Err: MINTEMP'

@joantabb

I fully understand - thanks

Peter

RE: How to disable 'Err: MINTEMP'

I wouldn't be too quick to disable MINTEMP as it is a safety check. If the thermistor is reading low due to a fault, you do not want the printer pumping current to the heater. The cup of tea approach works and adds a bit of class to the process. You might also consider an enclosure for a cold printer as the entire printer benefits from being warmed up. If you do reduce it, don't disable it completely!

RE: How to disable 'Err: MINTEMP'

I too have this problem, my garage is sitting at 4 degC this morning, frustration i cant just put the bed on for 5 mins to warm the enclosure up

RE: How to disable 'Err: MINTEMP'

@shalo

I've changed all the firmware MINTEMP values to 5 degrees which seems to have fixed the problem.

I agree that a solution would be to heat for a short time before checking for MINTEMP

Peter

RE: How to disable 'Err: MINTEMP'

@drpeej

Thanks Pete, dumb question how do you edit the firmware, done it on my old mendle, not done anything on the Prusa yet

RE: How to disable 'Err: MINTEMP'

@drpeej

@shalo    

when you change the firmware to lower the mintemp, it is a good idea to check that Mintemp alarm still triggers  when you unplug the thermistor
if this does not work,  for you, then the safety function is failing... 

regards Joan.