Label Printing Snippet Part 26: Cleaning your flexo plates, anilox rolls and print stations
In printing, cleaning is not just the wash-up part of the job but an essential part of keeping your flexo plates, print stations, and anilox rolls maintained and performing as intended.
The use of correct solvents and wash solutions is also critical for longevity.
Many cleaning methods are available. I’ll go through examples and point out which systems and wash solutions are available. It’s important to consider what inks you use and what machine may be required depending on cleaning volume.
Another consideration is the proper disposal of solvents, chemicals, and waste chemicals whether in liquid form or on the rags used for washing. Can you recycle or re-claim your chemicals and what benefits does it have for your company?
Proper storage of chemicals is also crucial, especially if they are flammable.
1. Flexo plate cleaning
A number of factors are important to consider when cleaning flexo plates, as they are expensive and take time to make.
If a damaged plate is not detected before making it to the press, the additional cost of downtime or lifting a job can decrease the job’s profit or even lose money.
FlexoWash Plate Washer
- Manual cleaning
When manually cleaning a flexo plate, it’s important to use the right method. This will depend on the type of plate: line, solid, text fine or large and screen.
If the plate has lines or a solid image, the common method is to clean it gently with a rag. For a plate with type or a screen, a soft bristle brush and dabbing the wet areas with a lint-free cloth or rag is best. This will prevent damage to any small type or the removal of dots in your screen area.
Be sure not to use solvents such as acetate. Even if it’s difficult to clean the plate, acetate can swell the text or screen and render the plate unusable.
Manual plate cleaning is good during runs, or for smaller or small quantities of plates to be cleaned daily. This isn’t recommended for larger volumes.
The right chemical for cleaning your plate can be discussed with your plate supplier. You can use an existing plate wash that complies with any environmental requirements, or HACCP procedures your company may have in place.
- Automatic plate washing
An automatic flexo plate washer is good for large volumes of plates to be cleaned every day. It also helps prevent plate damage and provides consistent results.
The design is simple, usually with an infeed roller and nozzles to wet the plate with a plate cleaning solution. It then passes through soft bristle brushes that move from side to side cleaning the plate. The plate is then rinsed and usually hot-air dried before placed into a collection basket.
Depending on how long the plate was used and how dirty it is, this process may need to be done multiple times. It’s also important to double check if the plate is dry, even with manual cleaning.
Never store plates touching – they need to have a foam divider between them to prevent damage.
NOTE* If you follow these basic steps and train your operators in manual or automatic cleaning, this can save your company thousands of dollars per year.
It’s also advisable to have a monitoring program to check the plates when the job bag is returned. This must be done by an experienced person and new plates should be immediately ordered if required so they’re ready for the next run. This step will help prevent issues and ensure a smooth start up next time a job goes to press.
2. Anilox Cleaning
The anilox roll plays an important part in flexo printing in providing exact and consistent amounts of inks to the printing plate. It’s a precise and expensive piece of equipment and needs to be maintained to keep cell volumes at their manufactured specifications.
Cleaning Anilox Manually
Cleaning and maintaining your anilox starts on day one and continues throughout the life of the anilox. To keep on top of this process, a schedule or checklist can be set up and random checking can also be done. This will ensure the cells are clean, at full cell depth, and that inking of your printing plate remains consistent.
Different methods of cleaning anilox rolls are:
- Manual cleaning
Cleaning anilox rolls by hand is good method but doesn’t always provide the deep cleaning required. Depending on the type of ink and run length, build-up occurs in the cells and they need to be cleaned.
With liquid cleaning, a special anilox cleaning solution is applied by hand and left for 5 to 30 minutes, depending on the time available or how dirty the anilox is. After this, an anilox brush or high-pressure wash can also help remove ink build-up in cells, but this doesn’t always achieve a consistent, completed cleaning.
Try not to use fast-drying solvents as these can promote ink build-up on the bottom of the cell by drying out the ink. The anilox may look clean to the naked eye, but an electron microscope or a special anilox camera inspection system can reveal a different picture. Once you inspect it, you will see leftover ink residue and may decide to clean it again by hand or use an automated cleaning system.
- Ultrasonic cleaning
Ultrasonic cleaning is an effective method which will remove all types of inks, adhesives, and varnishes. Depending on the design, the anilox or multiple anilox rolls lie in a bath of water mixed with a special solution while the anilox slowly rotates and vibrations clean the anilox.
A low frequency provides a deep clean and a higher frequency provides a faster, quick clean; the frequency used depends on the condition of the anilox. This is like a video or radio frequency: a 1.3GHz system has more penetration and range than a 2.4GHz or 5.8GHz system but, just like the anilox rolls themselves, all have their different purpose and use.
The only downfall I’ve come across using this system in a humid environment, like we have here in Asia, is evaporation. Due to the cost of the ultrasonic solution and transportation hassles, it may be something to consider. Having said this, I must admit ultrasonic cleaning has brought many old and unusable anilox rolls back to life.
Ultrasonic cleaning is also widely used in the jewelry industry for its gentle cleaning capability. One costly mistake is not following the instructions on the mixing ratio of the solution: if it is too concentrated, damage can occur.
- Laser cleaning
This is a relatively new process that cleans the anilox with the latest, state-of-the-art lasers and requires no liquids or solutions. The fact that there is no liquid waste requiring costly disposal is a benefit. With this method, multiple anilox rolls can be cleaned at the same time but requires the operator to be trained.
It can recall multiple aniloxes for LPI and BCM to provide accurate cleaning for your range of aniloxes. This is done with firmware to recall and log data to keep records of the anilox cleaning for different printing presses. The laser breaks down the ink, which then evaporates, effectively extracting the ink particles from the anilox cells.
This process doesn’t clean as many anilox rolls as possible by hand each day, but provides better cleaning and frees up employee resources.
3. Print station cleaning
Cleaning the print station is important for the unit to work as intended.
Proper care and cleaning of the print unit allows the ink tray, pan roller, chamber/doctor blade, anilox and plate to function properly. Using correct solvents or cleaning solutions is essential to preserve parts such as slides and bearings while cleaning.
Cleaning MPS EFA Flexo Print Station
Don’t use harsh solvents when cleaning near rubber or plastic. If you use acetate on a plastic guard, it will turn white and ruin the guard and make it translucent as rubber parts can swell.
Always oil and grease the appropriate parts. I went through this in my first snippet which you can find here; called ‘CILT’ (Clean, Inspect, Lubricate, and Tighten).
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My other label printing snippets are available here.
Kane Marsh is Regional Printing Instructor Asia Pacific with MPS Systems Asia, providing training on MPS' narrow web flexo presses and specialized label applications. Kane has direct print experience on multiple presses in a range of printing technologies including flexo, gravure, offset, screen and a variety of applications.