Flow rate not able to be set to zero on second extruder used for marking pen

[FredFish 4]

Flow rate not able to be set to zero, when setting up Cura to use marking pen as second extruder using Cura 5.3

 

 I can make a custom printer profile (although i am using Ender3), and filament type with temperature setting at zero for the Ink pen,

but must make retraction setting greater than zero.  

And under the profile setting the flow rate must also be greater than zero.  

The box turns red indicating a known issue when set to zero. 

I am using the Ink pen to include images inside transparent layers, the offset and tool change can be set up under additional extruders g-code setting, 

Is there a setting to not use the extruder motor on on selected materials?

[GregValiant 1,240]

I'm not 100% sure I understand but...

If you have the pen added as a second extruder and the temperature of that extruder is set below the setting in the M302 register in the printer (or as set in the StartUp Gcode with an M302 line) then when the printer sees a line like "G1 F2100 E90" then nothing should happen.  The firmware prevents the extruder from actually moving and so there shouldn't be a problem.  You can set the "pen extruder" temperature to your ambient temperature and set the retraction and other numbers as needed to allow Cura to slice.  You would need to lower the material standby temperature to a low number as even the default 175° (for most materials) might be above the M302 setting of the printer.

 

The default M302 in my Ender 3 Pro is "M302 S170".  If the set temperature for the "pen extruder" is M104 S25 then the printer processor simply won't allow the extruder movement.  There will be a message sent to a print server (if you are using one) that would be something like "echo: cold extrusion prevented" and there might be a lot of them, but it would only be a problem if you are printing other than via an SD card.  I don't know how Octoprint would react to the flood of error messages.

[FredFish 4]

Thanks for the reply, please allow me to clarify, when adding the second Ink tool type with the temperature set to zero, the minimum retraction is preset to 0.01, and the minimum flow rate at 0.001.  

 

Using Cura on laptop, connected directly to USB port, in my case.

 

It will set the temperature to zero at the tool change as expected, the extruder will cool down, but the E value within the code for that tool will continue to rise.

 

is there a way to have it just not include the E code, or at lease keep it at E0?

[FredFish 4]

I think I may see an issue in translation, I do not see the M302 in my saved code,

it may be because the ender3 profile only allows one extruder.

 

In order to provide additional extruders I have used Custom FFF printer, this setup allows for multiple extruders, and also allows the tool change to include additional setting to load and unload the additional tools (in my case pickup pen from holder, and return it when done). It does not include M302 command so I am not seeing any error message for that.

 

thanks for your help, your insight did cause me to lookup relevant M codes, and may need to experiment more along these lines,

 

do you know if the ender3 pro with latest merlin accepts the M17/M18 start and stop extruder codes? And if so will this cause errors with Cura settings?

[GregValiant 1,240]

M302 is not a setting that would typically be accessible to a user.  It (should) exist within the printer to prevent cold extrusions.  I can change the setting by sending an M302 S0.  That's what I do when I calibrate the E-steps as I don't have to heat the hot end to get it done.  M302 automatically resets when the printer is turned off.

 

Although the E values are increasing in the Gcode, there really shouldn't be a problem with the actual print.  You could pull the filament out of that extruder/hot end since you aren't using it anyway.  Then if the extruder was ordered to spin it could spin to it's hearts content and it wouldn't effect anything.

 

M17 and M18 (M18 and M84 are identical) should be understood by the printer.  You would see in your ending gcode "M84 X Y E" to turn off all the motors except for the Z (to prevent the Z from drifting down).

You can try putting "M18 E0" (or "M84 E0") into your startup gcode.  The MarlinFW site notes that M18 will accept an extruder number (E0) but it didn't say anything in that regard to M84 which Cura and Creality routinely use.

 

Playing with my printer it seems like entering an E0 disables the extruder.  You will need to experiment.

 

 

[FredFish 4]

I had limited success with the M84 E0, although it worked as M84 E, I could not turn it back on.

 

I did however find an appropriate work around, the override of merlin can compute 0% of feed rate as no movement,

 

 I used the command M221 S0 to turn extruder off, and M221 S100 to turn it on, this seems to work.

 

I have added the line M221 S0 to the INK PEN tool, extruder start G-code. And added the line M221 S100 to the extruder end g-code, along with the temperature set to zero, the minimum retraction set to 0.01, and the minimum flow rate at 0.001 for this extruder tool. the code still has the E increasing, but it does not appear to move the extruder

 

thanks for pointing me in the right direction.

[GregValiant 1,240]

Did you try "M17 E" to turn the extruder back on?  Typically they will turn themselves back on when they are sent any signal from the printer processor.  When they start up they don't know their own location so you might have to add a G92 E0 when they come back to life.  That probably isn't required with the M221 S0 command as they aren't really being turned off.

[FredFish 4]

for now the M221 seems to work well when i add it to the start and stop g-codes of the ink pen extruder T1, Cura is ok with the filament cool down and resets the temperature back and waits for it when switching back to using the T0 extruder, so I am happy with this work around.

 

Thanks for your help.