Eccentricity, out-of-level and droop tolerant system
When a graphical pattern is engraved onto a cylinder
which is not mounted perfectly concentrically to the
axis of rotation, or is not mounted perfectly level, or
suffers from droop, the positioning and/or size of the
graphical features can become distorted in the
significantly circumferential direction. This can be
particularly problematic if a roll is to be engraved
more than once in register or if it is to be used in
register with another roll. Furthermore it can be
difficult to set the concentricity of a roll to a
tolerance smaller than the required feature positioning
required. A system can be provided to substantially
correct for the mis-positioning of the engraved features
due to mounting eccentricity. This may consist of a
distance measuring device mounted directly below the
belly of the roll travelling axially with the engraving
head. The engraved data is shifted vertically at the
side engraving position by a magnitude and direction to
correct for the measured vertical distance variation.
Loci, Form and Function.
ALE laser engraving machines can be made up of a rotating roller
with the meansto progress a focused laser beam along the
axis of the roller. The circumferential direction around
the Roller Being Engraved is considered to be the Y
axis. The X axis is the axis parallel to the axis of the
Roller Being Engraved (RBE). ALE laser engraving
machines can equally be supplied as an X/Y engraving
platform. For simplicity's sake, we consider a roller to
be flat, therefore X/Y and roller engraving are
considered to be identical processes. The following
rollers but is equally applicable to X/Y engraving
Engraving Locus (HEL).
This is the most elementary beam locus and the foundation of nearly
all other beam loci. This beam locus is achieved by a
laser beam being focused onto the surface of a rotating
roller, at the same time as the focused beam is being
mechanically moved along the axis of the roller.
Alternatively, this locus can be achieved by a laser
being focused onto the surface of a roller that is
simultaneously rotating, as well as moving along its own
axis, past the focused laser beam. The distance along
the X axis between two adjoining convolutions of this
locus is called the Engraving Pitch Rate (EPR).
It is worth noting there are four possible ways to produce the
engraving helices. The roller can rotate clockwise or
anti clockwise and the axial movement can be right to
left or left to right. For simplicity, we call these
four engraving helices: E0, E1, E2, E3. Subtle engraving
asymmetries are often engraving direction sensitive.
This is why the Laminar Sequence of Engraving command, LSEQ, is
available to define any sequence of engraving helices,
in order to produce highly symmetric engraving.
ALE engraving machines are often equipped with high speed beam
deflectors, in order to move the beam rapidly in the
circumferential and the axial directions. By adding
positive or negative, circumferential and/or axial
deflection components to the elementary helices: E0, E1,
E2, E3, a myriad of beam loci can be formed.
These two components are called Delta Y and Delta X respectively,
for brevity sake DY and DX.
Software controlled beam and data sequencing allow ALE customers to
define their own beam loci. In the Anilox marketplace
wavy structures have become very popular. However there
are many pre-defined beam loci, that can either be used
without alteration or they can be automatically added
together , or they can be end
user modified to suit the needs of a particular
Cylindrical Engraving Mode (CEM).
beam locus is formed by subtracting DX from the HEL,
where DX takes the form of a saw-tooth waveform, having
a period equal to the time taken for one rotation of the
RBE and an amplitude of EPR. The function of this locus
produce an engraving that is orthogonal to the X axis
and parallel to the Y axis.
Axial Jump And Dwell Engraving JADE Mode.
beam locus is formed by adding DX to the HEL, where DX
takes the form of a
staircase waveform. See
for the function of this locus.
Circumferential Jump And Dwell Engraving JADE Mode .
This beam locus is formed by adding DY to the HEL, where
DY takes the form of a saw-tooth waveform. See
for the function of this locus.
Hop And Drop Engraving HADE Mode .
beam locus is formed by adding a DY and a DX to the HEL
repetitively and cumulatively. Typical incremental
values for DY would be one Y pixel, this is the Drop.
Typical incremental values for DX would be ten X pixels,
this is the Hop. The accumulation of DY and DX would
typically last for four Hops. Thus a total Hop of forty
X pixels would have occurred, as well as a total Drop of
four Y pixels. It is important to note, that in the case
of this example, once the process restarts, the first
pixel to be engraved with zero Hop and zero Drop will be
four pixels in Y, after the last pixel was engraved with
zero Hop and zero Drop. This amounts to a Y Hop of four
pixels. So, the Hop and Drop is hopping pixels in X and
functional advantages of this mode are, not only do you
obtain a wide X separation of temporally adjoined laser
pulses, but you also obtain wide temporal separation for
spatially adjoining pixels in the Y axis. As a result,
all pixels are
either widely spatially
separated or widely temporally separated
Multi Beam Engraving Mode
beam locus is formed by adding a DX to the HEL
repetitively and cumulatively.
incremental values for DX would be ten X pixels. This
would be typically four accumulations of DX. Thus, in
this example, a total of forty X pixels would have
occurred before the process restarts. It is important to
note that, in the case of this example, once the process
restarts, the first pixel to be engraved with zero DX
will be one Y pixel offset from the last pixel engraved
with DX equal to zero.
functional advantage of this mode is, you obtain a wide
X separation of temporally adjoined laser pulses.
However, when you return to DX zero no additional Y
separation is gained and only a modest temporal gain is
Multi Graphic Channels.
laser engraving machines receive multiple graphic
channels of real time data.
data can be used to define laser power, laser set up
parameter sets, laser focus position, move focused beam
in X and move focused beam in Y. All of this data can be
changed dynamically, or at the start of each of the
layers of a multilayer engraving. As a result, within
one engraving, different laser powers can be used.
Different laser parameters sets can be used; eg. pulse
length, pulse energy and pulse repetition rate. Within
an engraving, the laser beam focus can be changed. The
focused laser spot can also be dynamically moved, in X
and Y, in real time.