1st and 2nd Layer Temperature Change - Option to Keep Printi

[Garry Bartsch]

Maybe I'm not doing something right, but if I set the first layer temp to 200C and the main temp to 190C, the extruder parks when the first layer is done until it has dropped to the main temp layer; then starts moving again. This is fine for big parts but with tiny delicate parts the extruder just sits there and melts the area around the nozzle. When the nozzle starts moving again it drags that blob of plastic that has globed onto it possibly destroying the part.

I'd like to see the option wherein the print would carry on after the first layer has completed with the temp dropping while the print continues. This is how Slic3r works and it seems fine. Now I have to set 1st and 2nd layer the same in KS and then send G-code manually to drop the temp once the first layer is done.

Again, I'd like to see this as an option so people could choose.

[PenskeGuy]

Well, evidently, it depends upon the hardware/firmware. On a 3DT when a temp change is commanded, the head doesn't stay on the part, it goes back to the wipe box until the temp has been reached and then resumes the path. So, in this instance, not a problem.

[Garry Bartsch]

I am using a Mendel90 with Marlin.

[Mikk36]

In the Printer G-code Select Extruder section, change the M109 to M104, if you want it to continue printing before the temperature has been reached.

[Garry Bartsch]

Thank you. That did work to keep printing while temperature dropped but something unexpected happened.

I have this start gcode:

Code: Select all

G28 ; home all axes
G1 X0 Y98 F9000 ; place extruder to middle of the front of the build plate
G1 Z0.0 F9000 ; place nozzle 0.0mm from glass
M140 S<BED> ; heated bed control

This code lowers the nozzle to the front on the glass where it sits till the heater stabilizes. When temp has been reached the nozzle moves rapidly to the center of the glass and starts making the part.

After changing the extruder gcode to this:

Code: Select all

T<EXT+0> ; select new extruder
M104 S<TEMP> ; warm it up, and start printing right away

the printer drops the nozzle to the front center of the glass as before, but rather than wait there, as soon as the nozzle hits the 0.0 height it starts making the part. The first time I tested it Protefrace gave a message "cold extrusion prevented" but the extruder was actually extruding.

I wish KISSlicer would natively build in the ability to have the print temperature drop without the user doing manual overrides.

[Mikk36]

That's how Kisslicer works, each temperaturechange is the same as selecting new extruder.
That's odd though, since in default Marlin shouldn't wait until it reaches a lower temperature. It should however wait, if you give it an R parameter instead.

Let's say that current temp is 190C
M109 S180 should set the temp and continue immediately, since the temp is above 180.
M109 R180 should set the temp and wait until it's 180 at most.
It's also possible to combine the two, for example M109 S180 R185, that way it will wait until the temp is from between 180 and 185.
There is some talk on the net about Cooldownnowait variable, but I couldn't really pinpoint where in the source code that should be. Last time I used Marlin, however, it behaved as I described.

Edit: Found the cooldownnowait variable, but it's quite an old bit of code, it isn't there any more in the current code. I guess it got removed when they added the R parameter.
So either recompile the firmware with that variable set to true (if you even have that option, not even sure how old your firmware is) or update your firmware.

[Garry Bartsch]

Thank you for explaining. I haven't had a chance to try this yet and am just dropping the temp manually which works fine for now.