In a basic laser marking or laser engraving machine the scan head, otherwise known as the beam deflection unit or the galvo head, is a key component with regard to the performance and reliability of the system.
There are many manufacturers of these types of device with significantly variable performance characteristics but one major differential to consider is whether or not the unit is digital or analogue.
Lower cost laser marking machines tend to use analogue technology because the component cost is significantly lower. The downside to using an analogue scan head is that it is more prone to drift out of accuracy especially if the unit is worked hard and builds-up a significant degree of retained heat (thermal drift).
Over time, especially after suffering significant wear and tear the galvanometers (motors) within an analogue scan head can become permanently misaligned. The only way to fix this is to recalibrate the scan head, which is a laborious task that can only be performed by a skilled professional with reasonably sophisticated equipment.
In the case where a galvanometer totally fails an analogue scan head needs to be return to the factory for repair.
Analogue scan heads are in general slower and less accurate too.
While visually there is little to differentiate the two, in all other aspects the digital alternative is a far superior product. Not only can it work faster and more accurately (sometimes up to twice the speed of an analogue alternative), it will not suffer from misalignment in the same way that an analogue scan head can.
A well designed laser marking machine incorporating the latest digital scan head technology will benefit from a self calibration process on start-up. This test process occurs during the first 30 seconds or so after powering-up the unit. Self calibration not only corrects minor misalignments but is particularly useful if, for example, one of the galvanometers fails and requires replacement because rather than having to send the whole unit back to the factory for repair the galvanometer can be changed in the field, saving significant time and costs for the repair.
Digital scan heads are faster to response to control signals, which significantly contributes to overall performance speeds. This is not only beneficial to increase throughput but also is useful in terms of system set-up too: an analogue unit can take hours to perfectly calibrate conversely a digital alternative can be set-up in a matter of minutes.
Lastly, the more efficient electronics of the digital unit contributes to lowering the overall operating temperature of the scan head, which in turns enhances performance and extends the working life of the component.
In recent times the premium to be paid for a digital scan head has reduced to near zero, so there is no longer any reason to use analogue scan heads in a laser marking machine. Therefore, should the vendor offer such a head take care to inspect the machine very carefully as it is likely other design/performance comprises have been made to the disadvantage of the customer.
At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.
