Why wont PLA print at the same temperature as my other machine?  

Re: Why wont PLA print at the same temperature as my other machine?

I’m also having to run all filaments 10 - 15 degrees hotter than my other two machines, both of which also use E3Dv6 extruders. I’ve been wondering if the temperature calibration on the Prusa is incorrect and reading high. Certainly my FLIR camera shows the nozzle to be significantly lower temperature than the setting, but I’m aware that the FLIR sees the outside of the nozzle, not the inside.

Re: Why wont PLA print at the same temperature as my other machine?

I’m also having to run all filaments 10 - 15 degrees hotter than my other two machines, both of which also use E3Dv6 extruders. I’ve been wondering if the temperature calibration on the Prusa is incorrect and reading high. Certainly my FLIR camera shows the nozzle to be significantly lower temperature than the setting, but I’m aware that the FLIR sees the outside of the nozzle, not the inside.

I've also noticed that I have a lot more stringing using the same PLA that I use on my other machine. At 190c on my Alunar M508 printer I have no stringing at all, but using the PLA on my MK3 at 210c I have a lot more stringing. I know that there could be other retraction settings that could be the cause of the stringing on the MK3, and I haven't experimented with that as of yet. But this also leads me to believe that the filament is printing at a higher temperature on the MK3.

Re: Why wont PLA print at the same temperature as my other machine?

thermistors are low cost temperature sensors, they may be within tollerance, but incorrectly indicating high or low temperatures.

or other settings such as retraction speed, retraction speed, printing speed. may all be different

my prusa original printers use slightly different temperatures to each other

regards Joan

Re: Why wont PLA print at the same temperature as my other machine?

thermistors are low cost temperature sensors, they may be within tollerance, but incorrectly indicating high or low temperatures.

or other settings such as retraction speed, retraction speed, printing speed. may all be different

my prusa original printers use slightly different temperatures to each other

regards Joan

Thanks Joan, I failed to take that into account. And I'm sure that's the issue I'm having now that you mentioned it.

Guess it's time for me to start experimenting with retraction settings in order to bring down the stringing on my prints a little more. 😀

Re: Why wont PLA print at the same temperature as my other machine?

Certainly my FLIR camera shows the nozzle to be significantly lower temperature than the setting, but I’m aware that the FLIR sees the outside of the nozzle, not the inside.

If you have a FLIR, you can measure this easily.

Remove any filament in the extruder
Unscrew the cover of the extruder until you can view the heatsink of the hotend.
screw on the fan with at least one screw so that it points to the heatsink a bit.
Set the hotend via the menu to about 220 degrees
let the hotend get warm for about 3-4 minutes.
measure the heaterblock with the FLIR, not the nozzle.
measure the heatsink temp also for science.
cooldown
reassemble

the e3d Heaterblock should be within 2-3 degrees of the set target temperature.

Btw, the e3d silver nozzles (copper plated) transfer the heat better to the filament, and from my experience, give a better surface finish because they transfer heat to the plastic more quickly. (side effect is they don't last as long as regular nozzles for me)

Re: Why wont PLA print at the same temperature as my other machine?

Of course if you're using a FLIR camera you'll need to do something to account for the very low emissivity of the bare metal nozzle or heater block otherwise the temperature reading will be low. Kapton tape has an emissivity of around 0.95 so you could stick a piece of that on the metal and then use the FLIR to check its temperature. If the nozzle has a lot of melted plastic on it, this may be a moot point as I'm guessing that the burnt plastic will have a high emissivity already. But I don't know for sure and would use the tape anyway.

Re: Why wont PLA print at the same temperature as my other machine?

Yes, I know about getting the emissivity correct. Did some tests yesterday, I set up the system so I could set the FLIR up looking straight up the nozzle and I’m pleased to say that the temperatures are very accurate. 🙂

I have a new hypothesis. The Mk 3 is my only printer with a metal bed. It seems to me that a metal bed will conduct heat very rapidly away from the first filament layer, and this tallies with my experience. I find that I only need to raise the temperature 10 or 15 degrees for the first layer or two. That gives me a perfect base and then the temperature can be dropped to normal for the rest of the print.

I think what was happening was the first layer was cooling too quickly and giving me a very rough bed. It also had problems adhering. Now I’ve raised the temperature the first layer is flowing correctly, it’s smooth, and adheres to the bed. I’ve found this works with both PLA and PETG.

My other printers both have glass and/or other non heat conducting surfaces, so a lower temperature first layer works fine.

Re: Why wont PLA print at the same temperature as my other machine?

The MK3 requires a higher temperature because it's jamming the filament down the nozzle at a higher speed and with more force than your other printer. The filament needs to be softer in order to accommodate for the increased pressure and speed the MK3 runs at. 190c at 35mm/s is a whole different ball game than 190c at 80mm/s or 200mm/s when printing infill. If the filament isn't soft enough it will jam the nozzle because it can't keep up with the dual bondtech gears shoving it down.