Nozzle cools before reaching target

Hi all

Using Marlin, and running gCode from SD card. Prusa i3 all metal hotend e3dv6

When the nozzle is heating, to say 250C, it gets to 250C, then cools to around 242C and then reheats to 250C before starting to print.

Is there a setting in Marin config or a gCode that I can use to reduce or remove the delay ?

Regards

This sounds as if you never did pid tuning. Google that to get a description of what needs to be done.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Quote
Srek
This sounds as if you never did pid tuning. Google that to get a description of what needs to be done.

Thanks Srek

I will go take a look at that. The problem I am having is only during the initial heat-up before printing starts.

OK. Have done the PID tuning.

Values were not far off what was in the configuration file already. I have updated the config file and uploaded from IDE to Arduino.

It has not affected the behavior.

When initially heating the nozzle before print starts, I set :

M109 S250

The temp increases to 250, then drops back down to 240 - 242 ( display on the graphic LCD ), and then increases again to 250 and then the print starts.

I do not have any issues with holding the temp steady during printing.

So why does the print not start the first time it reaches 250 ?

That is a security mechanism of the firmware. The target temperature must be stable for a short time before printing starts.

---

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Quote
Srek
That is a security mechanism of the firmware. The target temperature must be stable for a short time before printing starts.

Is the time or the amount of temperature drop adjustable in the config ?

In config.h check for TEMP_RESIDENCY_TIME
Default is 10 seconds. I would not change this below 5 though, especially in your case 10 or more degrees less than expected can clog your hotend right from the beginning.

---

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

You might want to give repetier-firmware a try. For the most part the two firmwares are fairly similar, but I think repetier has the edge for thermal control.