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 stretch the spectrum from far infrared to near infrared. The choice as to which laser type to use is really based on the material being marked.
For this article, we are going to concentrate on Yb: Fiber lasers that range from 1060 to 1070 nanometers. These are most often used for marking metals, achieving contrast on certain plastics and paint/ink removal. As the laser sources are essentially the same between 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 accuracy motor that is used to direct the beam to a location in space. The term “steered beam” is commonly used as a descriptor for this type of laser. Mirrors are mounted to 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 allows the beam to be delivered perpendicular to the work piece over a given area. The most common field sizes are 4″ sq (5.5″ diameter) and 7″ sq, or 8″ diameter. Generally speaking the marking quality is about the same across the entire field.
Flatbed lasers, also known as “gantry” lasers deliver the beam via a XY plotter system most usually driven by AC or DC servo motors. This is a delivery type more common to CO2 lasers but is becoming widely used with Yb: Fiber lasers and YVO4 Vanadate lasers. The combination of the servo motors and belt driven gantry arms allows for large area to be covered. There are several gantry type Fiber lasers that allow areas as large as 24″ x 36″ to be addressed. Based on the plotter style of delivery the beam is focused through the center a simple lens and down on to 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 another? In fact, you can’t say one is better without using the actual application or process as the driving indicator. I have had the opportunity to work for companies who supply both types. This both a blessing and curse from a salesman’s perspective. Most companies who manufacture a flatbed system do not have the experience or expertise to put out a competitive galvo unit. On the other hand, it is nice to have each technology to fall back on.
So perhaps the first rule of thumb is to consider what the vendor’s key products are. If they make flatbeds, rotary engraver, percussion stampers etc…galvo lasers are probably not their main concern. I work for Electrox, who does nothing but make steered beam, laser marking systems. There are several other companies who operate in the same mode, where galvos are their specialty. Likewise, there are a number of companies where flatbed lasers are their bread and butter. In selecting the technology, consider the knowledge base of the supplier.
If cycle time is not the main issue, I recommend getting samples processed for evaluation by both technologies. Having marked parts that you can compare side by side, with different laser types is a luxury that one should not pass up. If speed of the mark is the key, galvo systems are the only way to go. If your parts are very large, the flatbed system may be preferable though most galvo suppliers offer a programmable XY table option. Evaluate the pricing and the quality of the marks if this is your situation.
Galvos are much better if the marking is going to be “inline”, i.e. on a automated production line. Most flatbeds are not suited for customization. Flatbeds, though slower in processing speed actually sometimes yield more production when you are running in batch mode. Batch mode is when you lay like parts out in a matrix and then process them in a rows and columns format. The relatively slow speed of the flatbeds typically will allow the operator to conduct other operations in parallel with the marking. A hint is to ask your vendor to supply a time study based on your exact production requirements.
Fiber lasers, I am speaking of the actual “engine” of the system, are very reliable and long lasting. Galvo systems require less maintenance that flatbeds, but this is nominal for either. The longer stroke of the gantry types does create conditions where belts need to be adjusted and alignment is more critical. Still this is a very easy process and generally not an issue in production.
Flatbed systems usually operate off of a more graphic oriented program such as CorelDraw. So if you are doing a lot of image manipulation, logos, photos this may be the better choice. If you are interested in variable text such as bar coding, serialization, and date coding the galvo systems are usually superior. Always ask for a demo of the software when selecting a laser. Note: I even wrote an earlier article about selecting laser marking software. Ease of use is key.
The selection of the equipment is something that you will have to live with for some time, so it is mission critical that you evaluate all the options. Make sure that you understand what you will be using the laser for now and what you may need it for in the future. We as manufacturers cannot make machines bigger, faster and easier to use after the fact, so make sure you purchase equipment that can grow with you as your business expands.
So in conclusion, never buy strictly on price. Consider all of the performance characteristics of each type of beam delivery system and most importantly which type will be the biggest advantage to you and your business.