Laser Systems: How They Work for Converters
Before we delve into what a laser system can do, let’s think about the types of solutions converters are searching for:
- How would you like to seamlessly cut a variety of part sizes and shapes within a single run?
- Do you want to minimize tooling and product setup?
- Do you have a product that requires extremely tight tolerance cutting?
- Does your product require cutting of exposed adhesive or removal of numerous small slugs?
- Have you ever been asked to produce sample parts for your customers, but found you had no easy way of doing so?
Likely the answers are yes, yes, yes, yes and — surprise, surprise — yes.
With the help of Dirk Müller of Coherent, let’s take an in-depth look at how laser systems can answer those questions. He’ll reveal insights into how laser systems function, and how they can open up the door for new converting opportunities.
Coherent is a provider of photonics solutions, which includes lasers for medical, commercial and scientific applications.
How do converters most commonly manipulate the laser beam for cutting?
The most common choice for laser systems involve the use of a laser and a galvanometric (galvo) scanner, the beam steering and maybe even the control software that coordinates the laser scanner.
The word “laser” is actually an acronym. It stands for Light Amplification Stimulated Emission Radiation. It is “coherent light,” which produces narrow beams rather than emitting light into all directions.
Isn’t it called a galvo laser?
Technically, that term isn’t correct. The laser and the galvo scanner are two separate pieces, even though “galvo laser” is a term that is commonly used in the converting industry.
How does it work?
The laser system with a galvo scanner incorporates two moving mirrors that are at an angle to each other in order to steer the laser beam to any point within the galvo scanner’s field of view. Small rotations of the mirrors allow the laser beam to be moved from one cutting spot to another at speeds of several meters per second.
How small of a focus can you achieve with this type of laser system?
The laser system with a galvo scanner can easily focus the beam down to 10 – 20 microns, which is a fraction of the diameter of a human hair (about 60µm), but for most cutting applications larger spot sizes are used. In the event you need an even tighter focus, you would choose a fixed optic. In this case, a tight focusing lens keeps the laser beam fixed at all times and the workpiece is moved around.
In order to move the workpiece one would ordinarily use translation stages. It’s like a little sled that moves back and forth in an x or y direction. Through the use of a 3D or 3-axis galvo scanner, we can move in the z direction, too.
Combining a fixed focusing optic with translation stages allows for cuts that go down to just a few microns, if the material is very thin.
How is the laser system used in the converting industry?
The converting industry can apply a variety of different cuts, holes and scores to various materials.
Laser scoring for easy tear-off
Drilling holes for breathable packages
Cutting greeting cards & labels
Scribing & sequential numbering
Medical / Pharmaceutical Industry
Through cuts and slug removal
Ablation for Electronic circuits & RFID tags
What types of materials can the laser system cut?
Using a galvo scanner, a laser system can be used to cut plastics, metals, ceramics and semiconductors — almost any materials. But each material may require different laser parameters and beam delivery mechanisms.
How do you choose the right laser for the application?
It’s not an easy task. There are so many different laser types, and you have to choose the right wavelength and pulse duration. Laser system providers and tool providers base their choices on many years of practical experience, so in practice, “The tool builder doesn’t start from zero,” Müller said.
Let’s say you have established a recipe to cut a plastic film as thick as paper and you are getting good results. But then the client requests a slight change in material and perhaps requires a higher throughput. This may impact your laser choice and a different laser may now be better suited for the job.
This is why it is so important to present all of your possible applications to a laser vendor and think ahead to what you might be doing next year. Some laser systems provide the flexibility to cut most of the materials used by a converter. However, there are instances when a material requires a different laser. All parties should take the time to ensure you have the right fit.
Are lasers interchangeable if the parameters change?
Some are. If you have a laser that’s within a certain wavelength, pulse duration and power level, you can swap for a different model.
However, a change in wavelength could necessitate a change in the beam delivery optic. Let’s say you have beam delivery mirrors that work best for infrared and you want to change to a laser beam with UV. Such a change will likely require a swap of beam delivery optics.
Why would one want to change the wavelength (color) of the laser that is being used? This has to do with how the laser interacts with the materials. You want the laser power to be absorbed by the material in order to heat the material. The material’s absorption is based on the wavelength of the laser, so for best results material absorption and laser wavelength have to be matched.
Have you ever noticed how you can sit behind glass on a sunny day and not get sunburned? That’s because the glass is absorbing the ultraviolet rays. Fortunately, the sun’s UV intensity is comparatively low, so it doesn’t cut the glass.
When using a laser to cut glass, one might want to use UV radiation in order to have all the laser energy absorbed by the glass. The laser also allows to focus high power to a small spot, so small that the concentrated heat leads to melting of the glass.
What types of mistakes do people make when selecting lasers?
One of the biggest pitfalls is failing to factor in the cost of downtime into the purchase decision.
The kneejerk reaction is always to choose the lowest cost laser and beam delivery. But if your operation relies on a tool that operates 24×7, then experiencing downtime because of a faulty optic could be costly. Reliability translates into uptime: It’s a fundamental truth that customers tend to overlook.
Too often a tool builder or laser manufacturer wants to save a few dollars on a lens or mirror component only to be later frustrated that a multi $100,000 tool is down because of a small component’s failure.
What are some subtleties that should be considered when purchasing a laser?
Sometimes the mechanical engineers who are involved in a laser choice overlook the subtleties of the optical system. They may look at the laser as a black box with light coming out and just worry about the mechanical precision and reliability.
But the devil is in the details. Understanding the nuances of optics coatings and materials used in the beam path, for example, can have an impact on the reliability, throughput and quality of the laser tool.
Making the right choice with your laser system purchase
If you have a galvo laser system operating in your converting machine and you’re delivering orders, that’s great. Everyone’s happy.
But consider the points we raised here when you move forward on the next purchase of a laser die cutting machine. We mentioned a number of questions at the beginning of this post that many converters are asking. You can see how the right laser system can provide the answer.