CNC Engraving from Halftones

I'm interested in having a photographic image (photoshop file) converted
into 4-color plates for intaglio printing.
The process would go something like this:
1. Convert the CMYK image into 4 separate halftone files.
2. Use the individual files to engrave or mezzotint four separate copper
(or other metal) plates, keeping the image placement on each plate
(registration) consistent. Registration marks would also be needed.
I googled around on this, and it appears there is software available
which converts halftones to G-code.
Some more details: I usually use 12x18 copper plates, but for initial
trial of this idea, smaller plates would be fine, eg, 5x7. Although I
use copper, steel plates would be fine, and might even be preferable.
In addition to straightforward (ha) milling of the halftones, I'm
interested in the idea of "cnc mezzotinting." Instead of the milling
implement cutting the metal, imagine it "pecking" the metal with a sharp
point. The number of "pecks" would be in proportion to the size of the
halftone dot. I suspect this could lead to some interesting results in
terms of metal being displaced above the surface, in addition to holes
below the surface.
If anyone can provide this service, or you know someone who can, please
let me know. I'm also interested in hearing estimates on what it might
cost to have this done.
Reply to
Jedd Haas
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Signlab from Cadlink has a similar feature, this "Pecking" action based on dot concentration... It will actually machine small shapes like stars and little lightning bolt shapes on either the lighter or darker areas based on your wants. I have the program but have not used the feature in years.
Other programs out there will take a bitmap image convert it along the lines of how an STL file might represent the colors..... Meshcam comes to mind;
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but this method does create a full 3 axis toolpath and not the peck action you seek.
Here is a shareware version of one similar to above.... it actually does 99% of what the payware does as I recall:
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One other new contender is PhotoVCarve :
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This is a really different approach to others I have come across....... almost looks like absolutely nothing until you backfill or backlight it. Pretty radical actually. I have it and have used it, and by changing variables, you can get MANY different results.
The other Vectric programs are pretty fantastic for the money too.Their VCarve software is spectacularly easy, and has put anyone else with such a program on full alert for what they are selling it for.
Grummy
Reply to
grumtac
Photoshop has switches to do all of this in the print module.
A much easier way to achieve the same effect would be to halftone your CMYK separations with a randomised dither pattern instead of a line or dot screen. Again, this is very easy to do in Photoshop.
Having done that, you would output to transparencies & use a UV transfer process onto your plates, or laser print directly to a transfer sheet & bake it onto your plates as a etch resist.
Um. I think it'd be more likely to just reduce overall contrast, due to ink retention around the resulting 'doughnuts'.
If you don't feel comfortable doing the above yourself, & you have the cash, I might be able to help you. How big do you need your plates?
Reply to
Lionel
I'm familiar with the etching process. That's not what I'm looking to do.
Additional ink retention is the idea. Look up the intaglio printing process (eg, drypoint, engraving).
Reply to
Jedd Haas
PhotoVCarve looks like it could do the trick. Just to elaborate on what I wrote previously, I would be using the finished plates for intaglio printing. The cuts in the plate are filled with ink, then transferred to paper with a press.
So how much would it cost to make plates using this system?
(I'm not looking to put together my own system for doing this just yet.)
Reply to
Jedd Haas
Yes, I've done drypoint & engraving. I think I can visualise how the displaced metal would affect the print, & depending on how much metal is raised, I suspect it'd either make no difference, or would simply give you a dirtier ground in the 'pecked' areas. Your work, your choice, of course.
Reply to
Lionel
Mach2 and Mach3 are versions of control software for hobby-sized CNC machines and both include a utility that will convert a bitmap image to gray scale and then convert the image to G-code with cutter depths dependent on the gray scale level. I believe that you can select full black or full white to zero Z-depth. It will do either line or dot engraving. I've only used it once to photoengrave a photo onto a 2x2 aluminum block and that took about 25 minutes of machine time. The time will be dependent on how much resolution you want. I think I was working to 0.030 depth and with 0.005" stepovers using a feed rate of around 10 ipm and a spindle speed of 4500 rpm which is pretty slow for most commercial CNC machines.
So far as cost goes, my guess would be to figure $50-65 per hour for machine time and that a 5x7 plate could be done in around 1 hour on a fast machine. That would mean $200 & up for 4 plates at a really rough guess.
Mike
Reply to
Mike Henry
Hey Jedd,
From what little I know of seeing intaglio printing (a son with an MFA), it requires the non-inked surface areas to be very flat, as in almost polished. Any rotating mechanical cutter will tend to leave both a "burr" and a peened (raised) area that will be very difficult to keep equal or to remove. Hence the historical use of etchants that do the "opposite".
Try a small test patch before you spend any time or money.
Good luck.
Brian Lawson, Bothwell, Ontario.
ps.....of course, if you are related to the Haas Machinery Company, please disregard my last comment about time and money . XXXXXXXXXXXXXXXXXXXXXXXXXXXX
Reply to
Brian Lawson

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