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Stuart Kellock asks, "Have you got problems with label application?"

By Helen Dugdale.
Label Application

After talking to potential new clients about their issues and challenges, I’ve been amazed by the number who have reported label application issues, including snapping liners and labels that don’t come away from the backing paper.

The cost to the packer or manufacturer can be expensive and shouldn’t be under estimated. There is the obvious downtime and waste through having to second work items or rejection at a later QC point. Then there is also the significant, but very underestimated, non-tangible costs, which are an irritation to the operator. If left to fester or if the operator is held accountable for downtime caused by label issues, then these hindrances can be contributory factors to staff leaving.

Thankfully, there is a range of things you and your printer can do to eliminate these issues. When it comes to labels not leaving the backing paper the most significant cause of this is poor die strike. The die strike is a technical term given to the point where the cutter hits the paper. Modern cutters are designed to have a very fine tolerance and are very hard wearing but they do get worn and will need replacing from time to time.

Do you need a Malachite Test?

How do we know when to replace the cutter? A good printer will be keeping a tight eye on his cutters and will regularly check them for worthiness. This is done in a very cheap and simple way using a standardised test called a ‘Malachite Test’. Malachite is a copper carbonate that we mix with white spirits to give us a blue dye. We then take a roll of labels and strip the labels off, leaving us with the backing or liner paper. By rubbing the malachite solution over the face of the backing material we will be able to see if we have a die strike issue that might cause issues later in the process.

If we can see the shape of the label picked out on the backing paper or any areas of the shape of the label showing up in a dark blue, then this will indicate you have a die strike issue. What you are seeing is where the cutter has been forced down and is not only cutting through the face material but in to the backing paper as well. Flat spots on the cutter can cause this; a general wear and tear issue or the cutter has become uniformly blunt. To compensate the operator has had to put more pressure down on the cutter to get it to work. The ideal situation is that the malachite solution leaves no marks.

If you are having an issue with cutters not coming off the backing paper on the roll, then ask your printer for a malachite test.

Other things to consider

Other things to check would be the suitability of the cutter for the material. Different materials require different knife shapes and getting the right knife for the right material is crucial. Get this wrong and you will have a die strike issue that will again be shown up by the malachite test. Also, watch out for changes in backing materials. Each cutter is designed to cut to a certain depth, if a thicker or thinner backing material is used than specified when the cutter was ordered, then the operator will have to compensate with pressure, again this will be shown up in a malachite test.

If you think you’ve got an issue with die strike then we’ll happily help you do some exploratory testing.