printing on already printed plastic

Hi,

I got a printjob for 100 keychains. Its in 4 colors so I can print everything separately and glue the pieces on top of the base and even make a stencil so I can hold everything in place while gluing.

BUT to save myself the gluing I could print the base, leave it on the printer, load a new color, adjust the height of the printer by the height of the base and print the 2nd color on top.
If I only print the 2nd color .2-.5 mm high the lift z should jump over the existing colors (there is also lots of space between different part that are printing on top of the base)

So my question is, if the heat of the freshly extruded filament is enough to bond it good enough onto the base? anyone ever heard of an experiment like that?

The typical way to do this is to do one print, with pauses for changing colours programmed into the G-Code by the slicer at the right heights. This avoids the need to lift Z to get to the top of the existing print.

Sure if it were only two colors.

Im just thinging that I can just raise the 2nd level in gcode then i dont need to change the firmware.

You can use a text editor to insert pauses or to manually cut a single gcode into several files to be run in sequence. I've used that strategy to embed captive nuts inside the x carriage for my Mendel. You'll either need to devise gcode to do the unload and the load or disengage motors and re-home after the change.

Another option, if the cut-over point isn't critical and your extruder loads smoothly, is to figure out approximately how much extrusion it takes to get from your drive gear to your nozzle, look back from the color change that much extrusion, and, when the printer gets to that point, cut the first filament and feed the second in behind it. This will generate some stringing for a little while since retraction won't work properly while the filament going through the drive and the filament going through the nozzle are separate pieces.

Quote
sungod3k
Sure if it were only two colors.

Im just thinging that I can just raise the 2nd level in gcode then i dont need to change the firmware.

Sorry? I don't understand why 2 or 4 colours is different. And there's no need to change the firmware to do this (assuming you have a reasonably recent version of Marlin).

Or is it that the colours are not in horizontal bands?

Can you post a photo of what you're trying to achieve?

No horizontal bands indeed.
If i have the base in color 1 and I only print the rest in color 2 its now problem. one comes after the other. But if I have the base and some part or island in color 2, other parts in color 3 etc and the dont come after each other but mixed, I would need a lot of filament changing.

Im gonna test it. Im resonable sure it will stick. Ill post pics when Ive done it.