Hyrel 3D "color extruder"

[Joseph Chiu]

It'll be interesting to see how this RGB extruder comes out in the end:

http://www.maclife.com/article/features/hyrel_developing_tricolor_3d_printer_extruder_release_2013

I think that proper color mixing requires RGBKW (or natural instead of white) to be able to control the color intensity/saturation - so it'd really have to be a 5-filament input extruder.

[Guy Dascalu]

I think the RGB system works only with light, where the CYMK system would work with real colors, although you would still need the white/natural there as well...

[Joseph Chiu]

Ah, yes, I was thinking CMYK (subtractive color), but since the article I linked to mentioned RGB (additive color), I just pasted that in without thinking.  

And, of course, since you don't get "white for free" as you do printing on paper, it would really be CMYKN or CMYKW.  

On Fri, Nov 2, 2012 at 3:43 AM, Guy Dascalu <guyda...@gmail.com> wrote:

I think the RGB system works only with light, where the CYMK system would work with real colors, although you would still need the white/natural there as well...

--
You received this message because you are subscribed to the Google Groups "MakerBot Operators" group.
To view this discussion on the web visit https://groups.google.com/d/msg/makerbot/-/E528pNGFgGEJ.
To post to this group, send email to make...@googlegroups.com.
To unsubscribe from this group, send email to makerbot+u...@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/makerbot?hl=en.

[Big-E]

Actually, I don't think you guys are fully grasping this concept. I've checked their site, and from the scant information I've been able to take from it, it's a fairly interesting system they've come up with.

The color extruder is not on the printer itself. It appears to be a separate cabinet, with several reels of filament in different colors. This cabinet blends multiple filament colors, and extrudes a pre-mixed filament that then goes to the printer's extruder, all on the fly.

And as for colors,  well, I don't think it's either RGB or CMYK, the colors will probably be red, yellow, blue and white (not natural) Primary colors can be mixed in different ratios to create other colors, white to lighten them up. addition of a black reel would provide sharp black colors and shades of grey when mixed with white. Natural would only be used for adding translucency, as it would only thin the mix, and not contribute anything to the palette.

Keep in mind, you're not printing photos, your printing solid objects. An artist who paints on canvas, or illustrates on other media, don't paint with cyan and magenta much, they use derivatives of primary colors on their palette, and mix from those to create those secondary colors, filament is colored with pigments normally, rather than dyes.

Coming from a design and illustration background here, so I know a few things about color theory.

[Cymon]

On Friday, November 2, 2012 7:06:34 AM UTC-6, Big-E wrote:

Coming from a design and illustration background here, so I know a few things about color theory.

What you said about the system itself is correct. But what you said about color theory is all wrong. You may be a fine illustrator as you mix your primary colors to paint your happy little trees, but your lack of knowledge of the science about what you're doing is apparent. Red, yellow and blue are not the primary colors and can not be used to make any other color. In particular RYB can not be mixed to make black no matter what you try. We tell children red, yellow, blue because it's simple and good enough for most cases, but it's wrong. It's cyan, yellow and magenta and if mixed equally those three make a black. It's not a very good black, but theoretically a black filament spool could be ignored in the initial build. However a white spool would be necessary.

[Big-E]

Read and educate yourself:

Wikipedia RYB_color_model

They are indeed primary colors.

Cyan, magenta and yellow can't make a perfect black either, btw. That's why it's essential to include black and white filament to include the intermediate grayscale as well. Guess you missed that part of my post.

Color printers incorporate a black cartridge as well, mixing the CMY palette to create black by itself produces a muddy color. for good grayscale and true black, you need to use black ink. Any printer will tell you this

Incidentally, Black isn't a color to begin with.

Also, fyi, I have a degree in commercial design, if you think there is no science involved in color theory, you are mistaken. I've most likely forgotten more about the use of color/how it's mixed than you've ever learned. My name's not Bob Ross, so you're "Happy little tree's" comment just comes off as juvenile. Not that Bob was a bad artist, I quite enjoyed his show, but there are major differences between a commercial artist, and a painter, the major one being that we are paid by a client to produce an illustration as per their specifications, where a fine artist does whatever they want and prays someone buys their work so they can pay the mortgage.

Cyan and magenta are used in printing (Which I am also quite familiar with) because most inks are dye based, and when you are printing on paper, reproducing images and photographs with dyes, you are trying to make an image more vivid. The use of these two shades rather than blue and red are quite effective in reproducing the subtle hues in a photo. There was a time when color prints were made using the RBY palette, but that may be before your time.

Oh, and if you can source magenta and cyan filament easily, that's all fine and dandy, Of course, red and blue is more commonly available. It's just a matter of applying common sense in this regard

[Big-E]

One last bit, The CMYK palette can't reproduce all colors within the human spectrum of vision either. Many commercial print shops and home photo printers will use 6 or more colors to get the full range of color in a typical photograph. As an example, My HP printer utilizes a photo cartridge that contains black, and two additional colors. it can be put in place of the black cartridge to produce a wider range of color when doing photo prints.

CMY is not, and has never been a catch-all solution.

[Laird Popkin]

All printing gives you a range of color that (in a color space) fills a polygon between the colors (pigments, LEDs, etc.) that you use. So RGB, RYB, CMYK, are all systems that can mix colors to cover the intermediate colors. To be precise, each color system (RGB, CMYK, etc.) has its own set of "primary colors" that system chooses to work with - there's no such thing as a "primary color" in the natural world - all colors are exact frequencies in a linear spectrum (to simplify a bit) - the term "primary color" is an artifact of trying to approximate that full spectrum given a limited number of paints/inks/LEDs. While process color is pretty standardized these days, using CMYK on white paper, that system only covers a subset of the full range of colors in the real world (though CMYK's area of coverage is better than RGB's). That's why in fine art printing it's often more effective to pick specific inks, and even paper, to best match the colors used in the image being printed. I've seen a few books and posters use over a dozen colors in order to more precisely capture the vivid colors of the original, because printing 100% with the ink that matches the original really does look different from printing a mixture of CMYK that "adds up to" the same color, because they're actually tiny dot patterns that only form an approximation of the right color, and only from enough of a distance that the tiny dots aren't visible. And if it makes you feel better, no color system with a finite number of "primary colors" can cover the entire visible spectrum, so the best you can do is pick the color space that fits the image you want to print.

Wow, don't get a change to geek out about this stuff too often. Hope I didn't go on too long.

For plastic, my guess that it's even harder to mix "primary colors" into an extruder because the mixing in the extruder isn't instantaneous, and isn't perfect. That is, if I want to print an object with red and white stripes, I can't make that a hard edge, but have to fade from red to pink to white as the white plastic gradually displaces the red plastic, and the transition won't be evenly mixed in the extruder (e.g. there will be white on one side of the extruder and red on the other, so the printed object will be striped). That's a cool effect, but I think that if you want to print color changes freely, while the idea of using "primary colors" feeding into an extruder to create any color sounds appealing, I don't think it'll work too well. I think that when you want sharp color transitions, it'll likely be more effective to buy filament in exactly the color you want, and switch extruders to switch colors. Or use some other technology entirely to inject the color, like the way the Zcorp 650 uses a full color print head (like an ink jet printer) to print the full color image onto the printed material as it's printing.

- LP

[JohnA.]

I think the discussion has gotten super informative, but my take was that it just seems wrong for them to be talking "RGB" when talking physical mixing.   How do they expect to get yellow?   With light it's easy, but mix that same red and green plastic and you're in for mud.

JohnA.

[Z LeHericy]

With physical materials, you need CMYKW

-Zeno LeHericy

//((=:Z:=))\\
INVENTIONS
Technologies
zinventions.com

--

You received this message because you are subscribed to the Google Groups "MakerBot Operators" group.

To view this discussion on the web visit https://groups.google.com/d/msg/makerbot/-/MnfGsFUQ38AJ.

[Big-E]

You are100% correct Laird, and illustrated the point way better than I did; The opacity of the plastic requires the colors to be mixed, hence my paint analogy. In fact, I see the biggest issue with this whole process is the actual "blending" of different filaments to make a specific color.

If you've ever gotten paint mixed at the hardware store, you know they usually have to put the mix on a shaker for at least 5-10 minutes to ensure it's mixed properly. you still need to stir the paint after you open the can most of the time. Automotive finishes are even more complicated, having to be mixed to a greater degree on the ol' paint shaker.

now imagine taking equal parts of magenta and yellow abs filament, melting them in a pot, and stirring them to get a uniform shade of red. I don't think the actual melting of filament colors and extruding them is the issue, it's the agitation and blending part that concerns me; Trying to mix your own filament colors, on the fly, would most likely result in a multi-color swirl rather than a uniform color.

At best, we would be best off extruding the filament first, and then a day or two later, once the filament has been rendered, you run it through your printer. Doing this in real time seems like the unlikely part. a better option would be to use the printer cartridge/white filament solution , or to use the colors of filament you want to use in a given print, and have a bot that changes the filament out automatically on color changes.

It would also give greater flexibility. If you were to print an object that was mostly red hues, you would use a family of red filaments. You could simply omit colors you weren't using for a given job.

[Big-E]

Oh, and to avoid the gradient issue on color changes, the solution is easy, the print job would pause on a color change, and the plastic would be purged on an unused area of the build plate until the desired color is extruding, at which point the print job would resume, You would require some sort of chromatic sensor to determine when the correct color was being extruded to make this work.