A question we get asked a lot when talking to print shops is regarding color bar requirements for our SpectroVision inline spectrophotometer. It seems like a simple question, but when you take into account all of the little nuances it can be a little tricky. Below you will find answers for many of those questions we get that will hopefully help you understand how the system works and the efficiencies that can be garnered if you create a good colorbar.
Space or real-estate is all consuming problem when it comes to flexo printing. The popular question is “how big does this color bar need to be and where can I put it”? If you are like many other Flexo companies, shaving even a half of an inch of stock off the side of the roll can save thousands over the course of a year. The good news is that the colorbar for our SpectroVision inline system only needs to be 3/16” wide and it can be inside of the bearer bar if you run with one.
Ok…so now that the color bar will fit on my print, what should it contain? Well that can get complicated. Obviously solid color patches for each ink will allow you to measure density and deltaE’s. Then, if you want to control pressure you need tint patches to make sure that your dots are getting printed properly, so at minimum we would recommend a 50% TV patch. Then to compute TVI, we also require at least 1 paper patch as well. So that is likely the very minimum you need, and if the repeat is short, it’s possible that is all you can fit on there. However, if you have more room along the web, then we might also recommend a few gray balance patches, especially if you are printing full color process work that cannot look BLUE, or PINK, or have any color cast to it.
So now I know how wide, and what color patches types, but what is the patch length requirement for the SpectroVision? Well, this one depends on the fastest speed you will print at. Notice I did not say the fastest your press will go but instead I said “the fastest speed you will print at”. This is because the patch length is directly related to the print speed where the faster you print, the longer the color patch must be. This then also directly affects the number of color patches you will have space for in the artwork. Generally speaking, slower print speeds means shorter color patch lengths which also means more color patches will fit in the space you have reserved for the color bar. We can work with you to determine the optimum patch size for your application.
Now that I have a color bar defined and know where I can place it on the repeat, what other tips do you have? This one is obvious but is a mistake that we see in many places where they are manually stopping the press to cut off a color bar or measure color. As with all Flexo presses you can have variability across the web due to pressure imbalances. Many times I see an operator cut off a sample from one side and check it, and if it is ok, then they run it. However, what about the other side? Too often we hear things like “looks good enough” or “takes too long”. Well SpectroVision easily solves that issue of not knowing, with real numbers, by allowing you to put color bars on BOTH sides of the web, measure them both, and see the measured difference from one side to the other.
So that’s it; making your colorbar, placing it in the work, and ensuring that you are covering all the bases.
Inline color measurement makes it easy to check if you’re hitting your solid densities, hitting aim TVI’s or smashing your dots, and doing so in real time without stopping the press! Let us know if you have any questions.