Finishing of high speed thermoformats: laser scan

Tuesday 18 September 2018

The finishing of the thermoformed products often requires operating at very high speeds, at which the robot can not guarantee the precision of the cut: the laser scan is the solution to this problem (see fig. 1)

Fig. 1 - RX3 system equipped with laser scan

How laser scan works

The main advantage of the laser scan lies in the perfect execution of the cutting geometry that guarantees the scanning head is mounted on the robot's wrist and the laser beam, focused by a particular objective, is moved by two mirrors mounted on two galvanometers, whose axes they are perpendicular to each other. 

The objective, positioned upstream of the galvanometers, is equipped with a linear galvanometer which guarantees the correct focusing of the laser beam on all points of the laser scan operating range.

Figure 2 - components of the laser scan

The operating field is set by the manufacturer, optimizing between the times of the scanning cut and those necessary for the robot to reach the various positions. In general, a small enough field is always chosen, for example 200x200 mm2, to cut at the maximum possible speed, so as to compensate for the increase in the movement time of the robots. 

 The laser scan is mounted on the wrist of the robot and, as soon as it is positioned on the cutting area, it gives the green light the laser scan that performs the cuts foreseen in its operative field. The robot positions and the laser scan cuts.

A practical example of laser

Nel caso in cui dovessimo eseguire su una lastra piana sottile 2 fori di diverso diametro in una zona e 2 quadrati che hanno diverso lato su un’altra zona della lastra (vedi figura 2), il programma del robot, partendo dalla home, posizionerà quest’ultimo così che i 2 fori risultino all’interno del campo operativo del laser scan. Una volta raggiunta la posizione, il robot darà il comando di eseguire il programma dei 2 fori. Quando il taglio è finito, la scansione dà al robot il via per posizionarsi sulla zona successiva, dove il laser scan effettuerà il programma di taglio dei 2 quadrati.

Finita questa operazione il laser scan indicherà al robot di tornare il posizione di partenza così da essere pronto per il lavoro successivo.

The programming of laser system robot with laser scan

The laser laser system, equipped with laser scan, requires two different programs; cutting paths that can be programmed offline and then loaded onto the scan controller; the sequence of positions that the robot must assume that is generally performed by self-learning, taking care to position the scan at the correct focal distance from the cutting plane.

The laser laser with the laser scan finds application for the finishing of thermoformed which present, on most of their walls, thin thicknesses, such as cold rooms or freezers (inner liner). This type of thermoformed products have surfaces with thickness even less than one millimeter, on which cutting speeds of more than 25 m / min are reached (420 mm / s). 

Despite the high speed the system maintains the cutting geometry with great accuracy. Here are some examples obtained with the RX3 system equipped with laser scan and a Cutlite production RF899 laser source Penta. These openings, made on a thickness of 1 mm, were performed at a speed of 22 m / min99 di produzione Cutlite Penta.