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Send mail to: sales@appliedlaser.co.uk with questions or comments about this web site. Copyright Applied Laser Engineering Ltd 2002

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Wobble multi-hit

This system of multi-hit allows the axial dwelling of the laser beam locus as described in Clunk-clunk multi-hit but does so without the need to stop/start the main engraving carriage.  This has been achieved in a number of ways including the mounting of the final engraving lens onto a high speed linear actuator such as a voice coil or piezo device.  During the engraving phase the actuator negates the constant movement of the main carriage.  When all hits have been achieved the actuator flies forward to move the locus of the focussed laser beam to the next column of cells.  The advantages of this technique include the smoother motion of the main carriage being less mechanically demanding as well as the more rapid fly-forward possible thereby increasing productivity.

 

Wobble emulation operates in a similar way to the regular wobble multi-hit except it uses a beam deflector to move  the focus spot.

The Jump And Dwell Engraving Method: JADE

 

Jump And Dwell Engraving, JADE, has two basic forms.  They are, Axial JADE and Circumferential JADE.  ALE's Multi Beam Anilox uses the Axial JADE method.  This method has two basic advantages:

 Firstly high productivity can be achieved because time is not wasted waiting for the roller to move to the next cell to be engraved, instead the laser beam is moved rapidly axially and circumferentially to the next position for a cell to be engraved.

The second advantage is that, as a consequence of moving the beam axially, slower rotational speed is required in order to achieve a given productivity.Circumferential JADE uses a Dynamic Beam Tracking technique in order to keep the laser beam in a constant circumferential position while engraving an Anilox cell. The

Circumferential JADE method has a number of key advantages:

Firstly long laser pulses can be used without creating a elongated or elliptical cells, this is due to the Dynamic Beam Tracking.  Since the laser can track the roller for up to 99% of the time available between two anilox cells only 1% of the time is used for the laser to move to the next cell position, this means there is a very high utilisation of the available laser power.  Typical non JADE laser engraving systems have a laser utilisation of around 25%.  This means that around 75% of potential productive laser power is just simply wasted.  For example a 200 watt laser could only be used to deliver 50 watts!

Long laser pulses can give high volume engraving, normally long pulses will elongate a cell but with Dynamic Beam Tracking they do not.  In addition longer laser pulses mean that there is more time for the ceramic to absorb the laser power.

Secondly, as a result of the longer exposure time, the ceramic is more able to melt.  For some ceramics in some applications this factor may well improve roller life.

Circumferential JADE can produce engraving with the look of an old CO2 type engraving.  This is because CO2 engravings would normally use a longer laser pulse, which allows the ceramic to melt.  Circumferential JADE can do this by the Dynamic Beam Tracking technique.  This gives both ceramic melting, and improved productivity.  The Dynamic Beam Tracking technique can be used to produce round anilox cells.  However if the tracking is allowed to "Slip", an elongated or oval cell is produced.  This is ideal when engraving long hexagon cells.  Furthermore the degree of "Slip" controls the elongation or ovality of the anilox cell, even though whether the cell be round or elongated, 99% of the available laser power can be put into the anilox cell.  This is a different way of thinking, appropriate to the Dynamic Beam Tracking technique.  ALE is developing a Custom Slip spreadsheet application.  This will allow cell elongation to be set; zero percent being round, and higher percentages being varying degrees of oval.  In addition along the length of the cell, relative depth can be set.  This is achieved by controlling the rate of change of Slip in up to 64 different points along the cell length.  This Custom Slip system will allow cell profile to be controlled, while using the maximum time available to heat the ceramic.

 

The Dynamic Beam Tracking technique can also be used for laser applications whereby, because of the laser type being used, the laser is unable to be pulsed at a varying rate.  Some very short pulse lasers can only be "free run", they pulse at a fixed rate, or an externally controlled rate that can only be changed slowly, but the Dynamic Beam Tracking technique can direct the laser pulse to the correct position on a roller.

Linear engraving

Most ALE engraving applications involve the engraving the external surface of a rotating generally cylindrical shaped workpiece.  There are a number of applications which may make use of some existing ALE technology, but differ in that they are applied to a linear process.  Key examples might be conveyor or web based applications.  For example a number of laser beams may be arranged to vary their position and/or amplitude where on axis of the process is the linear movement of the workpiece.

 

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ALE GLOSSARY - Page 4