Mixing hot end issues and cura

[Delanjp]

Hello.
When printing anything from Cura or Sli3r the printer always mixes 50/50.
for example I print the Sleeping Panda from https://www.thingiverse.com/. A simple 2 color print. I select part A from extruder 1 and part B on extruder 2. With Extruder 1 for the Brim and supports(not needed in this model) It slices fine and shows the purge tower and all moves fine, But when I send it to the printer, the printer select 50/50 on the mixer and prints the Brim and all part including the purge tower at 50/50 mix.
If I send a single color print to the printer it does the same thing.

I reinstalled Cura and Sli3r. even tried it via RepieterHost, All slices do the same thing.
I have even flashed the firmware on the printer using the firmware from the Geetech pages.
This made no difference but to enable the BLtouch (works fine)

I at a loss on what to do to rectify this issue.
Any thoughts on what I could be doing wrong.

This is happening Via direct USB and Via Octoprint. No difference.

Regards

James

[William]

Hi, the A20M is a two-in-one-out setting.
If you choose the color mixing ratio on the LCD, select 50/50;
It refers to the left side of the extruder, half of the consumables on the right, and half of the consumables.
Then flow out from the same nozzle.

[Delanjp]

So the A20m is not supported to do 2 separate colours. , So I would be best to alter the config to do 2 In 1 out non mixing to enable what I want to do?
This is not what I want to do. I would like to be able to just select which extruder I want to user and mix if i want to.

[William]

Hi, for the color mixing settings on the screen you can refer to this:
Set the variable mix ratio
First, you need to get the current z-axis coordinate, which can be found on the screen,

“Gradient mix”: Adjust the filament ratio of E0 and E1.

“start Z”: The starting position (z-axis height) of automatic change of mixing; automatically change the mix based on the current Z height obtained in the previous step.

“end Z”: The end of an automatic change of mixing (z-axis height).
Choose “start z” and “end z”, press and rotate the knob to set the starting and ending position of mixing.

[Delanjp]

I dont want to mix the colours. The model s have a different colour in different areas., It not done on the Z height or layer change. I need it to use extruder 1 on on area and extuder 2 on another. I select the part to be in the Model in Cura. and the model slices fine and reads as it should. send it to the printer and the printer ignores the parts allocations and sets itself to 50/50. Even a 1 colour print only using extruder 1 the printer switches to 50/50

This is frustrating. I cannot get the printer to work as advertised or as it should

[Jarda3d]

See my A10M profile, there is example of dual colour ship without mixing. Mixing is not ideal, so I use it in rare case only.

[Fatumpch]

Hi James,

To confirm the A20M has ONE Hotend and TWO Extruders (E0 and E1) - for anyone unfamiliar with this printer.

Having exactly the same issue - unless I'm being really thick, I get the following problem:

a] I find a 2 colour example stl file - it has 2 clearly defined colour segments with NO graduation between the two colours
b] I load these (2) files into Cura (with A20M profile already loaded in)
c] I then assign a colour to the respective segments and merged the print
d] This I then sliced
e] Saved as GCODE ready for print
f] (only did this in case I was going mad) I then open the GCODE file in text editor and search to make sure the "M163 E1 P1.00; Set Left to 100%
M163 E0 P0.00; Set Right to 0% M164 E1; Save Mix" commands don't say anything other than either 100% on or 100% off (so either E0 or E1 are exclusively in play at any specific time) - having checked the entire file, there is absolutely NO mention of anything else (so no 50/50 commands)
g] Save this fie onto SD card and pop into A20M SD card slot
h] Select the file for print and cross fingers
I] Printer switches randomly to 50/50 throughout print resulting in something that resembles a badly printed smudge. If I'm lucky, one colour might be 100%, but the second is a 50/50 mix....

Like you, pretty new to this perhaps, but I'm totally perplexed as to what else to do - there must ether be something wrong with 1.1.8 firmware or a command that needs to be sent to say NO DON'T MIX THE COLOURS just please print it as a solid 100%, like the GCODE told you to...

Will cross post this as its driving me insane

Fatumpch

[Fatumpch]

Hi

Ok after a little research I’ve discovered the issue. There is a post elsewhere that incorrectly tells you to use E0 and E1 instead of S0 and S1! Having now update the code, I get 100% on both colours. The post you linked to explaining about virtual extruders was a good clue - so thanks!

Just need to experiment with the amount of purging between colours as the current result shows significant colour contamination... using purge tower but about to switch to a purge bucket and script which I’m hopeful will get me to where I want the colour clarity to be much improved.

[Jarda3d]

Bucket is easy. See my topic for A10M profile, there is complete solution for dual color printing.

[Fatumpch]

Thanks for that - have been trying to get the script to work, but it almost seems that after a purge - the head returns to the print and is good for the first layer, on subsequent layers however the head grinds into the the print (black section especially) Stringing is present but I'm considering playing with temperature and flow rate to see what the sweet spot needs to be to reduce this as the yellow seems to have gone down really well in comparison.

One thing I have noticed is the head tends to pause after the purge (after it travels past the silicone wiper) and a blob forms which seems to increase the stringing. I've adjusted the nozzle switch retraction to zero as advised (see picture) in the machine profile in Cura but left it at 6.5mm in the material profiles as I presumed the note referred to.

The end result (see picture) is better but the black PLA seems to bubble, whereas the yellow lays very smoothly... both are Geetech reels - am I missing something obvious?

nozzle switch retraction to zero as advised

Screenshot 2019-11-19 at 12.27.23.png (319.97 KiB) Viewed 11457 times

initial layer

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Initial layer profile

IMG_2491.JPG (263.69 KiB) Viewed 11457 times

end result

IMG_3564.JPG (715.79 KiB) Viewed 11457 times