Having trouble with single extruder - multicolor printing  

Having trouble with single extruder - multicolor printing

I am trying to print an object in one color with a logo on one face in a different color on a Core One without MMU. I import the object and the logo .stl files. I click on the logo in the Object list and right-click to change it to a modifier. I set the logo thickness to 0.4 (2x layer height). I use the rotation, arrow keys, and Object coordinates to get the logo aligned, centered and flush to the main object. I orient the package so the logo is flat on the bed and that face will print first.

I set Printers tab / General / Capabilities / Extruders to "2" (the number of colors I will print) and  check “Single Extruder multi material". At Printers tab / Custom G-code / Tool change G-code / I type “M600; Filament change”. Under the Print Settings tab / Multiple extruders / Wipe tower / I set “Enable” to OFF. Print Settings  tab / Layers and perimeters /  Vertical shells / Perimeters: set to “1”.

Under the Plater tab, the right menu now shows two filaments. I set each to the same filament type (PLA in this case) and choose the color of each to more or less represent the color of filaments I will be using. The menu displays the object name and its two sub-names. Extruder lists (default) for the object and I select extruder 1 for the main sub-object and extruder 2 for the logo sub-object.

I slice and step through the layers on the plater. I scroll through the extruder position. All looks good. The colors are laid down in the position and sequence I expect. I upload the G-code file to the Core One and load the first PLA filament color. It loads OK, purges, asks if all OK, thumbs up. I select the file in the Print menu and click Print. Then I get the surprises. 

Surprise #1: When I select the file and hit print I get the warning "A filament specified in the G-code is either not loaded or wrong type." I am not sure why I am getting this as the proper filament is indeed loaded. I select "OK" (Change/OK/Abort) to bypass the error message. The printer heats up, does its bed leveling routine, then parks in the right front corner for more bed heating. When the bed gets to the proper temperature I get the next surprise.

Surprise #2: The extruder moves up, about 30mm to the left, then down and prints a purge line. Instead of starting the print as I would have expected, the extruder then parks in the upper right front corner, disgorges the filament and prompts for a filament change without having printed anything. But the filament I need is the same filament that's already loaded. I can follow the on-screen prompts and "reload" the same filament, which then does a long purge, counting up to ? 96% and then asking if the color is OK. There is no option to abort the purge should the color be OK at any time earlier than the 96-100% point.

Surprise #3: At this point there is now a wad of coiled purged filament still hanging from the extruder. When I click OK to acknowledge the color is OK, the extruder moves to start the print, dragging some of the purged filament with it onto the print bed. If you open the door to try and grab the filament wad, the extruder returns to the park position until the door is closed again. Meanwhile the extruder continues to ooze out a little bit of melted filament between when you close the door and the extruder moves back to the print position.  You can go around and around on this, opening the door to grab the prematurely extruded filament, but it parks again then starts oozing filament. If you ignore this, there is a wad of filament hanging from the extruder when it starts its print. I mitigated some of this by using a skirt, but there are still sometimes blobs hanging from the extruder that can mess up the logo.

Surprise #4: After the first color prints, the extruder parks and requests a filament change. It burps out the old filament and asks if the filament was removed OK. Click OK or Continue and it asks you to load the next filament color. It goes through its purge cycle, again with no way to abort the purging if the color is OK before it gets to 96% purged. Same thing now as in surprise #3: there is a coil of purged filament hanging from the extruder. You can try opening the door and pulling it off, but a little keeps oozing out and by the time you can close the door and hit the Continue button, there is another 10mm string of melted filament hanging down from the extruder ready to mess up the beginning of the next layer all over again.

So my questions are 1) why is the Core One telling me I have incorrect filament loaded, 2) why is it going through a filament reload at the beginning right after printing the purge line when the proper filament is already loaded, and 3) what can I do about the filament that is oozing between removal/door close/print?

I tried doing all this with the Purge tower option turned on and it marginally improved the hanging ooze in that it got wiped away on the purge tower, but that brought on Surprise #5, which is that the extruder was moving right over and through previously extruded filament that was wadded up and already hardened. I could hear the extruder scraping through the old material.

I apologize for so many questions. One would think that PrusaSlicer should be able to do what I want without being so complicated. Help, advice and suggestions are greatly appreciated. Thank you.