CJV150 from 8-color to 4-color

Absolutely. It's not an official procedure which is why there are no formal instructions. See below for the basics.

1. Discharge the ink currently in the system
2. Flush the system with wash cartridges (I usually do two flush cycles to be sure and also check the lines to make sure all the ink is out and the solution is in it's place.)
3. Change the dampers and discharge the flush solution
4. Edit the parameters to turn the machine into a 4 color machine
5. Fill the machine up with the new ink

 

May I ask why you decided to go to 4 color? Simply for speed increase?

 

That is an incorrect assumption.

 

The short answer is that the profile you use in the RIP interpolates the colors specified in the file to make them look like what you intended. When you don't make your own profiles for your own machine with the substrates you use, then the interpolation gets it wrong oft times. Manually turning off the profile as you have done, gives you a different result. But changing the ink setup in the printer will not fix the problem if you continue to use improper profiles.

 

Another inconvenience with 8 color is that you have to have 8 different ink cartridges at stock and some may expire before you use half the ink (my orange is half full after 2 years)

 

If the colors come out wrong, the profile is wrong. You may have downloaded a canned profile, but it could still be wrong. In addition, there are other steps along the way where color interpolations can be added. You need to check the color management settings of your design software, and what it does or doesn't do when exporting the file. You need to check the color settings of your RIP and see what else it is doing to alter the output.

That said, you can test your theory by making a profile that doesn't use the orange ink, and trying it out. I don't know how much profiling ability Rasterlink has, but we have a 10 color Epson and use Onyx Production House. The orange ink Epson uses is not as UV durable as the CMYK inks are, so though the red looks normal at first, if we use orange ink it begins to turn pink after 6 months to a year in sunlight. The RIP uses some orange instead of yellow to mix up the red color. You actually get more true reds that way, but since the orange ink is less durable, for outdoor signs we have a profile that only uses CMYKlclm. For colors like M100Y100 that are in the gamut, they come out looking just the same, and in general nobody can tell the difference unless there are a lot of orange colors in the sign, and they are comparing it with a print using the orange ink.

But if the profiles and color management isn't right, it still won't print the right colors.

 

What exact Parameter I need to change to go from 8 to 4 colors in cjv150 ?

 

Stop designing in CMYK first off and design in RGB. When someone tells you otherwise find someone else. but but but but: no: RGB.
If you are ok with a slower machine I would just leave it alone.
If you want more speed then do it.
Don't switch a machine's wider color gamut hitting ability because you are not happy with the black. (I am guessing black isn't the only color you are having problems with)
Black of all colors is the easier to hit and your problem is indicative of a problem usually with incorrect design color space settings and profile selection/settings.
I would consider speaking with a mimaki dealer and ask to speak with their color profiling expert at Mimaki on the phone.
You can also give Flexi subscription a 1 month try and use the profiles they have easily available to download for your machine. They will help you remotely set it up.
I would consider getting away from an OEM Rip sooner than later if this is not a hobby.