The job of a doctor blade chamber is to help deliver a precise, consistent ink film thickness to the substrate. Like other parts of the press, the doctor blade chamber needs to be maintained and inspected on a regular basis to ensure its peak performance. Taking the time to do this is a smart way to maximize press uptime and minimize costs.
What Can Go Wrong
1. The chamber needs cleaning – The doctor blade chamber requires regular cleaning to make sure it functions properly. Dried ink and coating particles can interfere with doctor blade seating in the blade holder and cause the chamber to go out of alignment.
2. The doctor blade chamber is not aligned properly – The doctor blade and anilox roll work best together when there is light, consistent contact between the two. If the blade does not have even contact with the roll due to chamber misalignment, it will not shear the ink cleanly and consistently from the anilox roll surface.
3. There is corrosion or pitting in the chamber components – Over time, regular exposure to harsh cleaning chemicals can cause corrosion and pitting in parts of the chamber. This can create recesses in the metal that prevent the blade from lying flat in the holder. Pitting also makes cleaning difficult, and particles from a corroded chamber can dislodge, settle into the ink and score anilox rolls.
4. The chamber is bowed or warped – Due to the length of the doctor blade chamber, it can bow and become warped from being mishandled. When bowing or warping occur, the blade will not lay flat along the full surface of the blade holder and contact the anilox roll uniformly when engaged.
Oftentimes, the press operator may try to correct some of these issues by increasing pressure to force contact between the anilox roll and doctor blade. While this may fix the problem temporarily, it often makes it worse. The added friction from excessive blade-anilox contact can cause chamber leaks and accelerated wear on the blade and roll.
What To Do
1. Clean the chamber – A cleaning routine involves wiping down the chamber with a cloth and flushing with approved cleaning solutions every day to remove ink deposits and particles from the doctor blade and blade clamp. (This can take place when the press is shut down to clean the anilox roll which is also recommended on a daily basis.)
2. Verify chamber alignment – Operators should take the time to make sure the system is properly aligned and parallel on a regular basis. This will prevent early and excessive doctor blade and anilox wear and ink leaks. If aligned properly, the system will remain stable even at increasing press speeds.
3. Inspect the chamber for defects – Chamber bodies should be flat and straight. This should be confirmed periodically (such as when other scheduled maintenance is taking place). To check, take a long straight edge and lay it along the full length of the doctor blade. Look for gaps which indicate that the chamber is bowed or warped. Also, examine the blade mounting surface and holder for corrosion and pitting. The chamber should be replaced if any of these conditions are evident.
4. Replace consumable parts – It is important to replace doctor blades and end seals when needed. Skimping on these inexpensive consumables is penny-wise and pound-foolish! Using new blades and seals to ensure a good contact area with the anilox roll and a tight chamber seal will prevent chamber leaks and anilox roll damage.
5. Standardize a cleaning and maintenance routine – Establish a recommended schedule of cleaning and maintenance for the doctor blade chamber. Make sure that procedures are documented and press operators are properly trained and evaluated.
6. Convert to a carbon fiber chamber system – In addition to other benefits, carbon fiber chamber constructions, such as the ones pictured here by Celmacch and Tresu, offer superior resistance to corrosion and pitting.
The doctor blade chamber is a precision tool that plays a vital role in producing a consistent product, and a regular routine of cleaning and maintenance will ensure its peak performance. A small investment here will go a long way to guarantee that this press component does its part in keeping your bottom line healthy and your customers happy!