I am new to 3D printing. I have a Longer LK5 Pro. I was making a part that has raised letters, and wanted to have white letters on the black part. I used a Post Processing script on the Cura program called "change filament", which is supposed to stop printing, retract the head, and allow you to change the filament. Mine just keeps on printing. I've tried "pause" and done the filament change, but unsuccessfully so far because of blobs deposited on the letters.
Any suggestions?
I've done it a few ways depending on the desired effect I'm after.
Manually pausing the machine is what seems to come out best. If you design for it, you can sometimes have it pause while it's over infill and therefore has no blobs to worry about. I haven't looked into doing it automatically, but perhaps it's possible to pause partway through a layer.
If the design doesn't have to be flat, then I'll do a solid colour and the last top layers another colour with the design cut out. This is to my mind optimal as you get a bit of texture with the design inset as well as different colour and makes for a nice clean method.
The other way was z-hopping which is an idea I got from a Youtube video. Cura has a setting for this. Basically you can make the nozzle lift when it moves. You split the colours into two separate objects and you print in one colour. Then you change filament and print another colour as a separate print right over the top of it and the nozzle hops over the original print.
Manually pause and immediately do an X-home or Y-home so nozzle is not over the work. Swap filament. Repeat an X-home and a Y-home to assure printer knows where the nozzle is (it's possible to disturb the print head position while changing filament). Manually turn on extruder heater if it's off and allow to reach printing temperature. Advance filament to purge old color and assure heating chamber is filled. Resume.
It works pretty reliably for me...
Cura's "Filament change" post-process script relies on the insertion of the G-code M600. This only works when your printer manufacturer has activated this in the firmware!
The Marlin default is that the M600 command is not functional, see e.g. the following line of code of the advanced configuration file:
//#define ADVANCED_PAUSE_FEATURE
In order to enable the functionality to "add" the M600 code to the firmware you need to rebuild the firmware by removing the // in front of the #define ADVANCED_PAUSE_FEATURE. This may require some additional skills to do, downloading firmware, setting the proper settings in the configuration for your specific printer model, compiling and installing the firmware.
The alternative is manual pausing from the display, but this requires you to be present at the printer.
Another alternative is that you alter the G-code yourself to insert a dwell code (G4), which can be supplemented by a move away from your print), note this requires you to also sit next to the printer, the dwell command will allow for a pause for a specified amount of time, be sure not the miss the window.
I found that raised letters look and work better when picked-out using paint or permanent marker.
Print your lettering in your part but don't even bother changing filament. Instead carefully use a marker pen or paint brush to colour in the top of the lettering. Depending on the paint you might choose to do several layers.
Nail polish is an excellent paint option - it comes in a plethora of colours and the budget stuff works fine. Gold/silver/metallic "art markers" give a nice look on black or white PLA too.
Note, white/light filament jobs may encourage pigments to track between the layers, giving a shadow look. Test before committing.
When dry, you might chose to do a clearcoat of spray paint on top for durability.
IMO changing filament colour is a feature that doesn't work very reliably.
