Laser Cutting Machines
What are laser cutting machines?
Integrated machines that cut metals, plastics, dielectrics, and more using a focused laser beam rather than a mechanical blade or drillbit. A typical machine combines a laser, beam delivery optics, motion hardware to move the part and/or the optics, optional vision system, and integrated control software.
In brief, a laser cutting machine uses a focused or shaped laser beam to act as a precise tool that selectively removes (ablate) material. The ablation process can be photothermal or (cold) photoablation depending on the laser parameters and the type of material being cut. This ablation can be used to deliver through-cuts, drill holes, or to scribe, i.e., to cut down to a specific depth or material interface. The material can range from thin plastic film to metal several mm in thickness.
Some machines scan the laser beam over a fixed workpiece. Some move the workpiece relative to a fixed laser beam. And some machines use a combination of both. Importantly, all the different parts of the machine and its operation are seamlessly integrated in software, and usually controlled through a user-friendly GUI. The latest machines are compatible with IoT and Industry 4.0. Some users also chose to package their machine purchase with applications development where the machine manufacturer supplies software/hardware loaded with a “recipe” for specific target tasks.
Let’s take a closer look at some of these components.
Move the beam, the part, or both
As with a mechanical lathe or milling machine, a laser cutting machine creates cuts by moving the focused beam relative to the substrate being machined. There are three ways this can be implemented (a) move the part with a stationary laser beam, (b) move the laser beam relative to a stationary part, or (c) a combination of moving both. The latter combination provides the most flexibility in terms of cutting geometries. The two common ways to move a part are xyz translations using linear motion stages, or by rotation using a rotary stage. The former is used for flat parts, the latter for tubular or 3D shaped parts. The laser beam can be moved using “flying optics” where the focusing lens moves across the part in some type of gantry, or fast scanning by optogalvanic mirrors behind a so-called f-theta lens which gives a flat scanning field.
The ability to move both the part and the focused laser enables a laser cutting machine to be designed to process just about any geometry: tubular parts, flat patterns, and all kinds of 3D shapes. If you can create it in a CAD file, then there is a laser cutting machine that can create it from a blank substrate.
Common laser types
The three most common types of lasers that are integrated into laser cutting machines are sealed CO2 lasers, nanosecond fiber lasers, and ultrashort pulse (USP) lasers. The optimum choice depends on the type of material being cut, its thickness, and the required edge quality.
Sealed CO2 lasers deliver high power in the mid-infrared making them a great match for cutting materials as diverse as ceramics, paper, stone, and plastic. With power from a few watts to hundreds of watts, they can deliver both high power and a high power/cost ratio, so they are well-suited for fast cutting. But the edge quality often exhibits thermal effects and may require post-processing in some applications.
Nanosecond fiber lasers currently represent the largest share of the laser cutting market. With a choice of infrared and visible outputs, they can be applied to many different materials: metals, plastics, other organics. They can cut with micron precision making them suitable for cutting medical devices and re-usables. But for applications like stents that need high edge quality, post-processing is required.
USP lasers with picosecond or femtosecond pulse widths are available with infrared, visible or UV outputs. Their short pulse widths deliver unmatched edge quality with virtually no heat affected zone (HAZ). This often eliminates the need for post processing in even the most demanding cutting and scribing applications. But they represent the highest cost per watt. And their relatively low power – watts to tens of watts - limits their cutting speed.
Bottom line: If you want to be sure you’re really being supplied with the optimum laser for your cutting application, only use a vendor who offers all these options.
Software, automation, and process monitoring
The obvious purpose of a laser cutting machine is to provide a turnkey solution for your cutting application without the need to be an expert on using lasers. Depending on the format. operation ranges from semi-manual to fully automated under closed loop control. With the option of automated part feeders, this enables long runs of unattended operation, cutting hundreds or even thousands of parts.
Software control typically is implemented through an object-driven user-friendly GUI. An example is Laser Framework supplied with many of the cutting machines from Coherent, which streamline visual process design, execution, and monitoring. This all results in faster job setup, higher operator productivity, fewer production errors, and reduced personnel training.
Advanced laser cutting machines also offer the option of laser monitoring to ensure the beam is working exactly to specification. Thanks to AI, the monitoring system can even tell you the probably reason for any laser error.
In terms of applications optimization, laser cutting machines vary all the way from general purpose machines, to machines optimized for a particular set of applications or industries, to machines optimized for one specific task.
General purpose machines like the MPS family from Coherent are characterized by lots of choices and options. The size of the machine, the details of the cutting platform, the choice of laser, the motion axes (linear and rotary) are all user specified.
Examples of machines optimized for a set of applications are the StarCut Tube series which are particularly popular in medical device manufacturing (MDM). These machines are optimized for precision cutting of small parts using a fiber laser or USP laser. They are mainly intended for tubular parts but can also cut from small, flat substrates.
An example of the “single task” machine type is the NA Needle Drilling System. This product series is configured solely to drill blind holes in traditional and miniaturized surgical needles with no undesirable thermal damage.