In order for labels to move through a label printer, the printer
mechanism relies on label sensors that detect a gap, notch, slot or
line between labels. In identifying the material, the mechanism
then adjusts the stock intake so that print properly aligns on each
label.Theses sensors work based on the concept that a label will
block light going between two sensors while a gap does not block
the light. It’s almost like flipping a light switch on, off and
then on again.
Label Gap Between each die cut label, material is typically stripped away
leaving behind what is called a “label gap.” The carrier or liner supporting the label is usually
less opaque than the label and liner together. Special transmissive sensors read the opacity
changes where one label ends and a new label begins. Label gaps are commonly 0.125” (1/8th inch)
tall although they can be virtually any size you want. "Asource" teamtries to limit the size of a label
gap to avoid wasting material and raising costs, but sometimes, due to automatic application
equipment, label perforations and other engineering, gaps have to belargerthan normal.Ifthere is not enough
contrast between a label and its liner, then not enough light will passthrough for the printer
to find its “top-of-form”. Sometimes you can recalibrate the
sensors to adjust to a new liner; otherwise you will have to choose
another way to detect your labels:
Sensing Slot or Notch To create more contrast you may need slots or side notches cut in
the liner. Before deciding whether to use slots or notches, you will need to determine whether your
sensors are “fixed” and locked into one position or if the are “movable.” Fixed sensors are commonly
located either at the very edge of a label or in the center. Movable sensors can be located anywhere
across the web to give you much more flexibility as to where you can locate your cut outs.Sensing
NotchesSensing slots are narrow oval holes often centered in the
liner between labels. They usually require larger-than-normal label
gaps.Trying to cut and remove a tiny slot from a normal 0.125” gap
is difficult, especially if you also have perforations between
labels. EIM usually recommends increasing a slot gap with a minimum
of 0.25”.Sensing notches are cut out at the edge of the liner and
may not require a larger gap. Not only are notches used with labels on brown or highly opaque liners, but
also when working with tag materials that have no liner or label gap. This explains why you often see
hang tags with perforations between each tag and four rounded corners that create those
notches.The size, shape and location of a sensing slot or notch is
dependent on your printer specifications. Slots and notches will
require special cutting tools.Subject to the size of your label
gap, you may also need a new label tool which adds to your initial
investment but will make your label printing much easier.
Black Mark Some label printers may also have a “reflective” sensor that relies
on black lines or marks printed on the back of the label liner. The width of the black mark is
synchronized with the label size to tell the printer when to print label to label. Black marks are
particularly useful when labels or tags are “butt cut” and separated only by a perforation or face cut. Since
we will have to print the black marks for you, this method does add
a bit to you supplies cost.
NOTE: Black marks, sensing slots or notches are usually necessary when
printing clear labels where there is absolutely no contrast between
the labels and liner. "A-Source" pharmaceutical team does offer
special printing on clear labels to provide a solid print area and
sufficient contrast to calibrate your labels without liner marks or
holes. We can add this to any clear label material. If you have any questions on how to design your label so it will
properly run in your label printer, don’t hesitate to contact with
our sales team to discuss your label design requirements.
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