Hi-Temp PLA printing ?

Hey guys,

Is it normal for some printers to print PLA at around 230-250c( jumps all around the place) at 20mm/s ? mine hangs around this temp when its set to 250c, it hardly ever see's 250c tho... it has always jumped around...

I have attached a fan blowing on the hotend tube, teflon tube, some air does pass the hot end,
my printer also has never been to maintain temp easily, is this kinda normal for gen 6 board and a j-head mk3 style hotend?

im going to attach a pic of my printer and prints to get the idea of what kinda results im having, my printers hotend does seem to be the weakest link on my machine

Edited 1 time(s). Last edit at 07/21/2013 05:56AM by nechaus.

Doesn't sound at all normal.

I start off with 220 max for my pla and drop it to 210 after first layer.

Ben

the only reason to print pla at higher temp is that the pla flows so quickly it never reaches that temp . if the print were to pause even for 10 seconds the pla would likely crystallize, and jam the nozzle. so care should be taken to ensure that the print stays flowing. Also printers that run this way often have large diameter nozzles such as 0.6mm and 0.8mm

Have you ran the Auto PID command? This might make your temperature more steady.

Take a look at step number 2. PID Auto Tune in this blog. Auto PID. You could just start off with m303 which will run the hotend up to the default temperature 150 C. But, I would try a lower temperature to start off with instead of 250 C just in case that's to hot for the hotend.

-Cameron

hey guys,

I have not tried the Auto PID command,

The reason why i got it up this hi is because i dont get good flow,

its hard to hand feed unless its on 230c + ( on the packet of PLA it sez 190-240c)
It takes about 10 mins to print a small extruder gear

iv got a j-head mk3 gen 6 board, 3dstuffmaker, 200mm x 200mm x 200mm


It could be a firmware or heater issue, the bugger of a thing has never been able to keep a consistent temp.
its more jumpy than i would expect something like this to be...

are you using the correct configuration for the thermistor? if so is your thermistor located right along side the hot end nozzle?

there can be a 30 deg C variance in temp from the bottom of the heat block to the top of the heat block. you want the temp at the nozzle hole. insulation of heated block will allow a better temp equilibrium, and improve accuracy.

thanks for getting back to me,

I am not to sure how to get access to the firmware, the printers from 3dstuffmaker, I have tested the thermistor is around 6.8 Ohms at room temp...

I would assume they have the correct calibration for the hotend, but prob not, How much does your hotend readings jump around ?
im talking every single second, its around +/- 30c , it would not be bad if it was just a few degrees... but this seem odd


Which would be the best method of taking temp readings externally ? like a non contact temp thermo?

This could be a hardware issue, short circuit or a bad connection. You shouldn't have temperature readings that jumps +/- 30 degrees.

Does it matter if the hotend is turned on or off, as in, if you heat the hotend up and turn it off, does the readings stabilize?

Hey Ralf, thanks for your reply


My thoughts exactly, But 3dstuffmaker support advise me this is normal...



I have checked with 5 hotends, also rewired them, do you think it could be my gen 6 board or the firmware ?...
I also have checked when the hot end is cool, the temp does go down, it is actually responding, but in the past it has been shorted, from what i can remember this issues has always been happening, so i have just lived with it,

living with inconsistent prints to,, BUT NO MORE!!! i need to iron these issues out or buy a new printer.

Strange.. it isn't physically possible to have that large of a temperature swing, but judging from the number of hotend's tested it could indicate a deffective AD input on the processor.

You could try to move the hotend thermistor and heater to the heatbed input/output, and see if that works better. The firmware probably won't let you go to more than 150 degrees, but it should be enough to see if you get a stable reading.

Ralf Wrote:
.
>
> You could try to move the hotend thermistor and
> heater to the heatbed input/output, and see if
> that works better. The firmware probably won't let
> you go to more than 150 degrees, but it should be
> enough to see if you get a stable reading.


Thanks again ralf,

This basic gen 6 board has no Heat bed, so i do not believe there is any spare spots left on the board anyway...

So your thinking its the motherboard?

what reading do you get when its idle? i just actually blew my ramps the arduino just reads 25c on the bed and 130c on the hot end, with or without the thermistors, and i checked the arduino its fine i think, its just the ramps itself i think something got shorted out. so try testing the components on the board to see if its all good.

That would be my best guess. One way to be sure would be to disconnect the hotend alltogether, and substitute the thermistor with a resistor, with a value between 220 - 1000 ohm, this is roughly equal to what the EPOCS 100K NTC outputs between 170-250 degrees. But that requires that you have a spare resistor laying around.

This should give a stable reading, if it doesn't something is definitely wrong with the electronics.

Yes i get this on idle and when printing, its all over the place..
I can make a youtube video on this if im not explaining it the best..

its not the same issue tho.. i have tested everything except the actual gen6



Last night i started a print on 260c .. it goes down to about 230c, goes up and down.. its just a mental printer,
But it never reaches 260c , maybe 250, but hoovers around 230 - 240c..


iv got 3.0mm filament