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  1. RamblinDan
  2. 3D Printing
  3. Sunday, September 22 2019
Two Color Printing
KautzCraft (me) now has the privilege of having the ability to produce multi-colored FDM 3D prints. I have a decent quality, single nozzle (mixing) extruder that accepts two filament feeds.
This permits printing solid color for each feed and the ability to feed both filaments in any ratio between 1:100%. If one is at 20 % the other is 80%. Always equaling 100%.
Interesting is the fact the two colors don’t mix like tinting a bucket of paint. They extrude side-by-side like striped toothpaste. With a 0.40mm nozzle, each color leaves on the side where it was introduced into the extruder.
There is some blending/mixing from the nozzle travel movement. Blue and yellow will make green. But the printed item will definitely have one side more yellow and the other bluer, that exactly matches the side of the nozzle where the filament was introduced.
The effect is interesting and attractive, but I cannot create a solid green evenly colored print with a two-color feed.
There may be extruders that can do a better job of blending, but this is my experience with my printer. The uneven output does provide a very artistic effect. I like it.
I use a third-party software (not CAD) that converts a single color gcode file into a two (or more) color gcode output that can be blended 1:100 as the height of the print increases. A 100 layer print can start at the bottom solid blue and end at the top solid yellow. This works for any layer height.
Again, the print will have the imbalance in color shift side to side and while the percentage of mix percentage change is linear, the color change is very far from linear. The pictures show the effects. One owl, bottom to top, is blue to yellow and the other is green to hot pink.
Solid colored layers stacked one on top of the other are the easiest to print. The same effect as can be obtained on a single color printer by stopping the print and swapping the filament. No purge stack is required as the 100% color change will quickly blend between layers.
Printing colors side-by-side in the same layer height is much more complicated. Single nozzle printers must purge out the previous color before resuming the print with the new color. This requires a purge area on the print bed. Usually a rectangle solid block (stack) that grows in height at the same rate as the print layers. The print head moves to the stack to clear the old color but must also print a layer when a color does not change. It seems like a lot of waste but is absolutely necessary.
I have developed some routines in Simplify3D (slicer program) that can minimize (stop) the purge if there are no color changes after a prescribed layer height. That is for another post…
General Opinion
I will state, I don’t think a two-color single nozzle printer is the machine for a first-time user. The two-color printer adds considerably more features and printing options. But that is exactly what a new user doesn’t need.
It is best to not be distracted by double and even triple the number of variables when “learning the ropes”. Master single color printing first, then consider broadening abilities.
My research shows that many if not most two-color printers are used in a single-color mode. This may be most prevalent with DUAL nozzle printers. One nozzle is left cold and the printer is operated as a single extruder printer.
Multi or single extruder Printers have their own and differing features and abilities. One style is not superior to the other. A choice is based on the features desired. Not a topic for this post.
The main requirement in two color printing is producing the necessary CAD and subsequent common origin .stl files for printing. Each color must be isolated in a separate entity or .stl file. The process is far too complicated for explanation here.
Two color prints have brought a totally new and fun experience to my 3D printing. I am totally hooked on color variation. I had to study and polish my CAD skills to produce the necessary files. That was not a major hurdle for me, but a newbie to CAD may have a steep learning curve to work through. Worth the effort for custom and personal 3D prints.
The 3D printer is a machine tool. Nothing more, or less. Albeit a very complex tool. It follows a set of instructions containing a great many variables. It does not (yet) contain artificial intelligence (AI) so it must be told everything in very exacting detail and correctness.
I started playing with personal computers in the mid 70’s. Before they were a commercial product. One thing I discovered early was computers are extremely stupid machines. Just like 3D printers today. They must be told (instructed) what to do, to the very smallest possible detail. They then follow those instructions, exactly. But they do so very fast, it seems like they are smart.
There is a term in computing, not heard much these days, call “fuzzy logic”. It too was not thinking, but a programmed random output option.
Point here is that the 3D printer is doing what it is told. The last PERSON telling it what to do is the operator using the tool. Take control, avoid being fuzzy. It is all about cause and effect and can produce wonderful output with the right instructions. The operator is only controlling the last few percent of all those very complex instructions.
It may seem like a lot to master, but a lot of invisible human effort has made a highly automated tool that will actually do what you tell it to do… If you are very precise.
It doesn’t surprise me how computer control has given us so much power and capabilities with machines like 3D multi-color printers.
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