As we know, there are many wavelength lasers that can be used for marking/engraving. The predominant ones are CO2 and YAG lasers. These wavelengths extend the spectrum from the far infrared to the near infrared. The choice of which type of laser to use is really based on the material to be marked.
For this article, we are going to focus on Yb: fiber lasers ranging from 1060 to 1070 nanometers. These are most often used to mark metals, achieve contrast on certain plastics, and remove paint/ink. Since the laser sources are essentially the same between the galvo and flatbed units, the actual beam delivery system is the critical decision point.
First, a quick definition of each type is warranted. Galvo is short for “galvanometer,” which is a high-speed, high-precision motor used to direct the beam to a location in space. The term “directed beam” is commonly used as a description of this type of laser. The mirrors are mounted at the end of two independent galvo motors and very fast deflection of the two mirrors working in tandem will cover an area with the focused beam. Special optics called “flat field” lenses allow the beam to be delivered perpendicular to the work piece over a given area. The most common field sizes are 4″ square (5.5″ in diameter) and 7″ square or 8″ in diameter. Generally speaking, the quality of the marking is almost the same throughout the field.
Flatbed lasers, also known as “gantry” lasers, deliver the beam via an XY tracer system, usually driven by AC or DC servo motors. This is a more common supply type for CO2 lasers, but is being used extensively with Yb – fiber lasers and YVO4 vanadate lasers. The combination of servo motors and belt-driven gantry arms allows a large area to be covered. There are several gantry-style fiber lasers that can target areas as large as 24″ x 36″. Based on the delivery style of the plotter, the beam is focused through the center of a single lens and onto the work piece. The XY axis then moves the focused beam around the marking area in a linear motion (usually in raster mode).
So why is one better than the other? In fact, you can’t tell which one is better without using the actual app or process as a driving indicator. I have had the opportunity to work for companies that supply both types. This is both a blessing and a curse from a seller’s perspective. Most companies that make a flatbed system do not have the experience or knowledge to make a competitive galvo drive. On the other hand, it’s nice to have every technology to fall back on.
So perhaps the first rule of thumb is to consider what the vendor’s key products are. If you make flatbeds, rotary engravers, hammer stampers, etc., galvo lasers are probably not your primary concern. I work for Electrox, which does nothing but make directed beam laser marking systems. There are several other companies that operate in the same mode, where galvos are their specialty. Similarly, there are a number of companies where flatbed lasers are their bread and butter. When selecting technology, consider the vendor’s knowledge base.
If cycle time is not the primary issue, I recommend that both technologies process the samples for evaluation. Having marked parts that can be compared side by side, with different types of lasers is a luxury not to be passed up. If marking speed is the key, galvo systems are the only way to go. If your parts are very large, the flatbed system may be preferable, although most electroplating vendors offer a programmable XY table option. Evaluate the price and quality of the brands if this is your situation.
Galvos are much better if the marking is to be “in-line”, ie on an automated production line. Most flatbeds are not suitable for customization. Flatbeds, while having a slower processing speed, actually sometimes produce more when run in batch mode. Batch mode is when you put similar parts into an array and then process them in a row and column format. The relatively slow speed of the rigs will normally allow the operator to perform other operations in parallel with marking. One suggestion is to ask your supplier to provide a time study based on your exact production requirements.
Fiber lasers, I mean the actual “engine” of the system, are very reliable and durable. Galvo systems require less maintenance than platform systems, but this is nominal for either. The longer stroke of the gantry types creates conditions where belt adjustment is necessary and alignment is more critical. Still, this is a very easy process and is generally not a problem in production.
Flatbed systems generally work with a more graphics-oriented program like CorelDraw. So if you are doing a lot of manipulation of images, logos, photos, this may be the best option. If you are interested in variable text, such as barcoding, serialization, and date encoding, galvo systems are often superior. Always request a software demo when selecting a laser. Note: I even wrote a previous article on selecting laser marking software. Ease of use is key.
Equipment selection is something you will have to live with for some time, so it is essential that you evaluate all options. Make sure you understand what you will be using the laser for now and what you will need it for in the future. We as manufacturers can’t make machines bigger, faster, and easier to use after the fact, so be sure to buy equipment that can grow with you as your business expands.
So in conclusion, never buy strictly by price. Consider all of the performance characteristics of each type of beam delivery system, and most importantly, which type will be the greatest benefit to you and your business.
