Doubled color support


There are three modes of "double black" in the Duralink RIP.  Each mode requires that you have two printheads (or print bars) for black.

0. Duplicate identical channels; overprinted.  

1. Duplicate channels, screened differently; overprinted.

2. A single black channel split across two printheads; Interleaved.


Mode zero is intended to double density and is default behavior.  It requires no extra configuration or settings beyond the expected press configuration.  Modes 1 and 2 are alternate ways of achieving the greatest speed on a monochrome printer.  These modes both require extra configuration in Navigator.


0. Duplicate identical channels; overprinted

This feature simply duplicates the color channel and delivers it to two printhead systems.


Use case:  To achieve very high density by printing the same channel, twice, with two printing blades. 


Once you configure the printer correctly, it is automatic.

Configure your print engine with CMYKK inks (See Memjet documentation for any requirements).  Make sure both black blades register themselves with the same name: "Black".

When this happens the Xitron system will notice.  We will then deliver the black channel to both Black blades.  It will be ripped once and duplicated on both blades.


This method is not restricted to black.  Thus far we have not yet encountered any use case that wasn't black.  But this method can be used to double print any CMYK ink.  As long as there are two C, M, Y, or K ink blades registering themselves with the same name then the Xitron RIP will deliver that ink channel to both of those print blades.


Note:  This needs no configuration as it is the default behavior of the system.  However, some configuration is possible.  Originally, this was all there was to it.  After we added the two additional modes in Duralink RIP release 2.4, we added configuration options in the ini file and we added the ability to screen the two channels differently. This screening option can now (in r2.4 and later) be configured for this double black mode.


This setting can be controlled in the NxM plugin .ini file. If there is no entry inside that file for DoubleColorMode then the system behaves as described above.  This is because it is the default behavior when there are two identical print blades.


However, if you are experimenting with doubling modes or wish to screen the two channels differently, you may follow along below.

 

The entry inside the plugin ini file:


[NxM]

DoubleColorMode=x


Possible entries are 0, 1, and 2.

x=0: (or if there is no INI entry about DoubleColorMode at all)  (Duplicate identical channels; overprinted)

x=1: (Duplicate channels, screened differently; overprinted)

x=2: ( A single black channel split across two printheads; Interleaved. )

So, in this case the correct NxM plugin .ini file entry would be:


[NxM]

DoubleColorMode=0


Screening the two colors differently is optional.  

If you choose to do that it might look like this:

[NxM]

DoubleColorMode=0

Black_1 = K

Black_2 = S1


Why would you want to screen the two identical colors differently?  Look to the end of the document for a possible explanation.


1. Duplicate channels, screened differently; overprinted.

This mode allows two different heads to overprint the same channel but screened using different dither patterns. This mode was added in r2.4.


It is similar to mode 0.  This mode is only supported in monochrome presses and only at 395dpi. The RIP must use the monochrome separation style. 


Use case:  To run the press at the fastest possible speed.  If running at 395dpi produces too light a density, then doubling the coverage with this feature can allow for an acceptable density while still achieving the greatest speed.


This is controlled in the NxM plugin .ini file,

 

[NxM]

DoubleColorMode=x

Black_1 = K

Black_2 = S1


Possible entries are 0, 1, and 2.

x=0: (or no INI entry about DoubleColorMode at all)  (Duplicate identical channels; overprinted)

x=1: (Duplicate channels, screened differently; overprinted)

x=2: ( A single black channel split across two printheads; Interleaved. )

So, in this case the correct NxM plugin .ini file entry would be:


[NxM]

DoubleColorMode=1

Black_1 = K

Black_2 = S1


2. A single black channel split across two printheads; Interleaved.

Half of a page is printed with 1 printhead and half of the page is printed with a 2nd printhead.  The scan lines alternate between the 2 printheads.  For example, the odd scanlines print on the 1st printhead, and the even scan lines print on the 2nd printhead.  The scan lines are interleaved and put back together again in the correct order on paper.  This mode was added in r2.4.


This is only supported in monochrome presses and only at 395 dpi. The press is run at 395dpi but the RIP is run at 790 dpi,  Monochrome separation style. The resulting output is 790 dpi.  


Use case:  To run the press at the fastest possible 395dpi speed with 790 dpi output.   However, this probably requires precise control over the paper path and other variables.  Tests should be run to see if your press design can accommodate this mode.  If not, you could try mode #1 instead.


This is controlled in the NxM plugin .ini file,

[NxM]

DoubleColorMode=x

DoubleColorDeinterleaveMode=y

Black_1 = K

Black_2 = K


Possible x entries are 0, 1, and 2.

x=0: (Duplicate identical channels; overprinted)

x=1: (Duplicate channels, screened differently; overprinted)

x=2: ( A single black channel split across two printheads; Interleaved. )


Possible y entries are 1 and 2.

y=1: Odd scanlines of the image will be sent to the instance 1 printbar, and even scanlines to the instance 2

printbar.

y=2: Even scanlines of the image will be sent to the instance 1 printbar, and odd scanlines to the instance 2

printbar.


So, in this case the correct NxM plugin .ini file entry might be:

 

[NxM]

DoubleColorMode=2

DoubleColorDeinterleaveMode=1

Black_1 = K

Black_2 = K


Or, if you wish to have every other scanline screened differently, then do this:


[NxM]

DoubleColorMode=2

DoubleColorDeinterleaveMode=1

Black_1 = K

Black_2 = S1


Why might you screen the alternating lines or overprinted channels differently?

A reason why you might get better results using two different screens is because it would be less sensitive to slight misalignments between the heads.

 

To get the idea, think about printing a 50% black tint. If everything fits exactly, you have 50% ink coverage on the paper.

Now misalign two lines. 50% black dots with identical placement overlay each other and you get 100% coverage. Big difference.


Alternatively if you use two screen patterns with less in common, this sensitivity is reduced or eliminated.