October 21, 2010
We are really struggling to get our anilox and print sleeves on and off our mandrels do you have any tips as to what we could do to reduce these issues?
The first key point with all sleeves and mandrels is to keep them absolutely clean.
Any ink, water, cleaning solution residue, tape or adhesive that gets onto the surface of the mandrel or the inside of the sleeve will cause removal problems of the sleeve from the mandrel.
Remember most sleeves only expand by a few thousandths of an inch, so even the slightest amount of contamination on the surface of the mandrel or the inside of the sleeve can and will cause major problems.
Care should be taken not to damage the surface of the mandrel, so any scratches or burrs should be polished to a smooth finish. Similar damage to the inside of the sleeve will not only cause removal problems but may actually cause it to split when put under pressure so even greater care should be taken with the inside of the sleeve to prevent any form or scratching or scoring of the sleeve.
If you are using a simple air mandrel with an inlet hole through the journal or header and air holes drilled through the wall of the core near the end of the core face and in the middle, great care should be taken to ensure that your air that is pushed into it is free from any moisture or oil. Even the slightest moisture whether it is in the form or oil or water will cause major release issues if it gets between the inside of the sleeve and the outer surface of the mandrel. In addition water moisture or vapor can and will cause corrosion within the core itself which in turn can build up in the air outlet holes and also cause further contamination between the sleeve and mandrel face. In extreme instances it can even weaken the core structure which could lead to catastrophic failure.
In my experience mandrels that have air piped to each individual hole are far safer and in fact make the air mandrel no longer an air vessel that would under normal circumstances be certified to be able to withstand the air pressure used to lift the sleeve off the mandrel.
Having a small bevel on the end of the mandrel where the sleeve is introduced will certainly help to push the sleeve onto the mandrel instead of having to walk it on, which can cause cracking of the edge of the sleeve.
Make sure that your sleeves are never dropped on their sides, as this will more than likely distort the sleeve making it oval instead of round and the only solution is to replace it.
This is particularly pertinent with regard to the anilox sleeve with its multi layer construction. If your anilox sleeve has an end ring and you see a crack appear between the ring and the sleeve it should be glued with a suitable epoxy resin to help reduce the complete failure rate of the sleeve, but it is usually inevitable once this has occurred and is just a matter of time before the sleeve becomes unusable.
Even spraying silicon or wax to the mandrel surface can cause problems if it is allowed to build up on the mandrel surface.
If you mandrels are not fixed on press, you also need to invest in a suitable jig to hold the journal of the mandrel so that the roll can be held in the air to allow the removal of the sleeve from the opposite end.
The truth is parallel sleeves will always have some removal issues at some point during its lifetime no matter how good your housekeeping is.No Comments