This article is part of the FLEXO FLAW FIXING series
What Causes the Problem of Low Colour Strength in Flexo Printing?
Low colour strength is a common problem in flexo printing, often due to insufficient colourant in the ink formulation.
This can be due to a number of factors, including incorrect pigmentation or inadequate dispersion of the colourants in the ink.
In most cases, slight to moderate variations in colour strength will not cause any noticeable problems with print accuracy or quality.
However, if the strength is too low, it can result in print jobs that are either faint or streaky. Low-strength prints can also suffer from more pronounced colours and inconsistencies in different parts of the print job.
To minimise the chances of this happening, it’s important to use a quality flexo ink formulation with enough colourant to achieve the desired strength. It’s also important to ensure that you have correctly calibrated and optimised all the components of the job for flexo printing, such as the checkpoints listed below, as failure to do so can result in poor colour strength.
Checkpoint 1 – Print Cylinders
The print cylinders need cleaning. This is a simple operation that every operator should perform on a regular basis.
Checkpoint 2 – Ink supply
The ink supply may be low. Check the ink levels and refill the ink tanks.
Checkpoint 3 – Press settings
The press settings may be incorrect. It is recommended that you check these settings and adjust them as required.
How to Determine if the Colour Strength is Too Low
To check if the colour strength is too low, print a sufficient length of material and compare it with a printed page from a high colour strength press.
The colours should be very vibrant on the test page and much less vibrant on the printed page from a low-strength press.
When you print on a flexographic press, the dots used to create an image on the paper are created by a very fine metal rod that moves back and forth across the paper. The size of the dots is controlled by the size of the nozzles that guide the metal rod.
The smaller the nozzles, the finer the dots that are printed. Since flexo presses use toners that have a lower concentration of colour than conventional presses, it’s important to make sure your flexo press’s dot strength is set correctly to get accurate prints. If your dot strength is too low, you’ll get blurry images and inconsistent colours.
If you are printing with low colour strength inks, the colours may not be as bright as they should be. This is because the ink doesn’t have the strength to hold onto the pigment particles in the paper.
How to Improve Colour Strength
- Check the ink levels and make sure they are full.
- Check the doctor blade for nicks or damage.
- Adjust the anilox roller to the correct position.
- Ensure that the anilox roller is properly cleaned and maintained.
- Make sure the print cylinder is clean and free of debris.
- Analyse the print quality of your substrate.
Apart from those, when printing with lower ink strength, the inks may be washed out and the print quality may be reduced. There are several things you can do to improve colour strength.
- Use a higher quality paper. This will produce stronger colours and will not wash out as quickly.
- Increase the ink coverage. This will make the colours more vibrant and the print will look stronger.
- Use different colour inks. This will counteract any problems with colour strength.
There are a few things you can do to fix the problem.
First, check your anilox rollers for debris or clogging. Cleaning or replacing the rollers should solve the problem. Second, check the thickness of your ink film. If it’s too thin, increase the amount of ink you’re using. If all else fails, try increasing the viscosity of your ink.
By following these steps, you should be able to get your flexo prints looking great again in no time!