1. Determining which customer files can be separated for which 5, 6 or 7 color process is very manual and requires a lot of expertise and if wrong, can cost printer a lot of money
2. Very difficult and expensive (dedicated press run) to profile a 4 color press and keep the press in this condition for a long period of time due to variables changing which makes the profile obsolete, 7 color press is that much more demanding and hard to manage. Cost of dedicated press run and controlling all variables over time with a decreasing skill set of press operators.
3. All systems and processes required for 7 color printing are immature and result in unpredictability. Hard and soft proofing, verification on the press, preparing files.
4. Post finishing (lamination) on the press sheet dramatically changes the result and becomes that much more difficult to manage and predict.
5. Software and procedures to manage and control multi-color printing are very expensive and require a lot of training and expertise.
6. Screening technologies for more than four channels are complex and expensive. Additionally, some customers don't accept rostered corporate colors - spot colors give them a better visual surface appearance –  free of screening artifacts.
7. Conversion spot to ECG requires advanced iterations. LUTs may need to be frequently tuned.
8. Our company tried it and our customers were not satisfied with the reproduction of their brand colors so we went back to using spot colors.

Please note:

For the traditional CMYK printing, standardized printing conditions have been created, which are the result of averaged measurements from many printing presses and thus in a certain averaged way show the conditions that can be obtained on the selected substrate. A profile made just once will never accurately reflect the real conditions of printing. It is influenced by environmental conditions, such as temperature, humidity, parameters of the humidifying solution, condition of rollers and blankets, most often quite randomly. In printing based on a standard-averaged profile, by analyzing the current print, we can adjust the press to get closer to the averaged conditions. If we have a profile made of one single sheet - it may happen that the restoration of similar conditions may be very difficult or even impossible.

Another problem is related to the primary colors - while the CMYK colorimetric coordinates have been developed and described with the ISO standard, the value for such colors as Orange, Violet or Green seems to be a field of attempts by manufacturers to exceed the gamut - hence it is difficult to determine universal reference coordinates. Vendors of new solutions take advantage of the lack of standards to achieve wider gamuts - because it gives them a marketing advantage. For various printing technologies, the matter becomes even more complicated, and taking into account the richness of modern printing substrates makes the situation very difficult to standardize

Solution

Track all important parameters of the printing process to understand system variables and variations, In unknown areas much more data have to be collected. When typical variations are defined and factors that have an influence on the process recognized it is possible to optimize captured data.