Accuracy and repeatability are frequently the guiding principles when vision systems are implemented. In today’s complex manufacturing lines, vision systems are an integral part of process accuracy, repeatability and quality control.
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We previously wrote about the four key features that every vision system must incorporate: cameras, lighting, optics, and software controls. In this post, we’ll take an in-depth look at how these variables manifested in two real-world laser systems.
Two different clients came to us with different manufacturing needs, but a similar requirement: an automated process to provide vision system guidance to laser processes: marking and cutting. Each one presented its own unique challenges; our engineering team was able to design and build a custom system that added accuracy, efficiency, and speed to their overall manufacturing process. Let’s take a look.
A client came to us seeking a laser-based solution for marking and cutting PCBs (small FR4 PCBs) from a large consolidated panel – a process known as singulation. Here’s an overview of the custom solution we successfully developed and delivered:
An ultra-violet (UV) laser was chosen to produce high-contrast 2D marks and perform cuts on the FR4 PCB to produce singulated parts. Adjustable laser power allows the laser to perform both functions: Laser marking is set for lower power settings while cutting uses higher power settings to fulfill its application needs. With adjustable power, the system is able to make clean cuts through the board, or leave the pieces partially attached, depending on the client’s requirements.
The goal of the camera is to align the laser marking locations and laser cutting path. In this case, we integrated a high-resolution camera to ensure accuracy in both laser processes.
The vision system setup was configured on-axis, also called “through the optics” as the camera is integrated to use the same lens and galvanometer mirrors as the laser.
This configuration allows the camera to efficiently perform both key functions in this system: guidance and verification. In pre-processing, the vision system locates the fiducials to accurately align the laser to mark and cut out the pieces on the PCB board. In post-processing, the camera verifies the laser marked 2D code and confirms cut accuracy before moving forward to conduct the same process on the next part. With the on-axis configuration, this whole process is done in real-time enabling maximum efficiency.
The custom software designed by CMS supported the entire laser process in this system, including control of the laser’s power and confirmation of the laser marking accuracy.
This vision system design uses a versatile lighting system to provide optimum contrast for fiducial location and 2D matrix code content verification. Our engineers chose a bright field diffuse ring light for even illumination to ensure fiducial detection and proper contrast of the laser marked 2D code.
We recently designed and incorporated a vision system into a laser-based solution for barcode decoding and laser marking of sensor housings located in conveyor pallets. Each conveyor pallet housed a single product; a through conveyor delivered the pallets to the system, which triggered the camera to perform a database lookup based on the vision system’s decoding of the serialized part barcode label.
Utilizing software with database stored procedures, the laser then imprinted the pallet with a laser marking file that included a 2D barcode, graphics, and regional markings. The system then needed to verify the laser marking to confirm accuracy. Let’s take a closer look at the vision system’s components:
As we mentioned above, the vision system performed two functions in this system: pre-processing identification and post-processing verification. Utilizing a high-resolution camera maximized processing efficiency and speed.
An off-axis at angle configuration was chosen for this system. The camera is angled such that the center the camera field matches the center of the laser field. This angled vision caused perspective distortion, but we corrected this distortion within the vision system calibration.
To properly illuminate the barcode on the curved laser marking area, a bright field diffuse lighting system was employed. The diffuse lighting provided uniform illumination across the sensor housings multiple surfaces and cylindrical region where a pre-applied barcode label was affixed.
Software played a key role in this laser marking solution. The vision system needed to communicate with the software to retrieve information on the laser marking process and verify location and content accuracy post-processing.
In addition, the software was employed to correct the perspective distortion resulting from the off-axis at angle optics configuration.
Vision systems are an integral part of the laser application process. The automated vision system is carefully integrated within both laser cutting and marking applications to ensure complete guidance throughout the process.
We hope you’ve enjoyed this series on vision systems. In the upcoming weeks, we’ll be taking an in-depth look at the several methods used for the depaneling of PCBs through laser processing within the electronics industry.
Do you have questions regarding vision systems within your laser applications? Contact us today to discuss your needs and specifications.
As handheld laser welding grows in popularity among large-scale manufacturers, medium-sized fabricators, and even individual craftsmen, it is more important than ever to make sure that welders and shop managers are informed about laser welding safety.
Perhaps the most iconic – and in the case of laser welding, the most misunderstood – piece of welding gear, welding helmets are a critical piece of PPE for 100% of manual welding jobs. Beyond being a way for welders to customize their look, welding helmets protect the face, eyes, and skin from harmful light, heat, debris, and sparks.
In this guide, we will go over everything you need to know about laser welding helmets, including how they’re different from traditional welding helmets, when you need one, and how to avoid buying something that won’t protect you.
Before we dive into laser welding helmets, it’s worth mentioning a few things about other critical laser safety measures.
First, laser safety eyewear. Anyone with any chance of being exposed to direct, reflected, or scattered laser light from a Class 4 laser (a.k.a. virtually any laser used for manufacturing) should be wearing laser safety eyewear. In the case of handheld laser welding equipment, this applies to bystanders and observers but also to the welder themselves. While a proper laser welding helmet is technically enough to protect the welder’s eyes, wearing laser safety eyewear like goggles or glasses underneath as a second layer of protection is a good idea.
Second, laser-safe barriers. These can help define who and who isn’t considered a bystander. Since direct and reflected laser light emitted by a handheld laser welder can travel for hundreds of feet, utilizing some kind of barrier is necessary in most cases. Existing walls as well as laser welding booths and curtains can all work, depending on the requirements of the space.
Third, laser safety officers (LSO). Despite the intimidating sounding name, an LSO is essentially just someone responsible for understanding and managing proper laser safety measures in an operation. Choosing an LSO is as simple as naming an existing employee willing and able to take on this responsibility in addition to their current responsibilities. An LSO can be expected to source, maintain, and ensure welders are wearing their laser welding helmets.
If you take nothing else from this guide, at least remember this: traditional arc welding helmets will not provide the necessary protection from laser light. Under no circumstances is a welding helmet rated only for arc welding an acceptable substitute for laser welding.
With that out of the way, let’s examine why.
The primary difference between arc welding helmets and laser welding helmets has to do with the lenses and filters they use.
How Arc Welding Helmets Work
Arc welding helmets are designed to protect welders from the visible, ultraviolet (UV) and infrared (IR) light given off by arc welding processes like MIG, TIG, and stick. The typical design utilized by most modern arc welding helmets sandwiches a UV/IR filter, polarization filters, and Liquid Crystal Cell (LCC) filters between two ordinary clear lenses designed to protect the assembly.
UV and IR filters
UV and IR interference filters use a mixture of glass, aluminum oxide, and silver to reflect and filter out harmful light while still allowing the welder to see the weld pool. These lenses are static and not impacted by auto-darkening.
Polarization filters
Polarized filters are made from polarized material, meaning they block light that is polarized in a specific direction. Without getting into the mechanics of light polarity, multiple polarization filters are used to dim visible light. Polarization filters, like UV and IR filters, are static and unimpacted by shade settings or auto-darkening.
Liquid Crystal Cell (LCC) filters
LCC filters are responsible for auto-darkening. Auto-darkening, a feature found in most modern arc welding helmets, allows welders to balance the level of protection with the visibility required to lay down a good weld. Using power provided by a battery in the helmet, LCCs reflect and redirect incoming light based on the shade the auto-darkening helmet is set to.
How Laser Welding Helmets Work
Laser welding helmets are designed to protect welders both from the IR light produced by handheld laser welding machines and the visible and UV light generated by the laser welding process. More specifically, laser welding helmets protect welders’ eyes using lenses and filters that reflect and absorb IR light at the specific wavelength produced by the laser.
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Here are some of the specs and certifications to look out for:
Optical Density (OD): As with laser safety glasses and goggles, laser welding helmets should be rated with an OD of at least 6 for a range of wavelengths that includes nm, such as - nm. An OD of 6 indicates that the lens assembly allows through .% of the light within the given wavelength range.
Laser Beam (LB): LB ratings specify that the laser equipment can be exposed to a given laser beam for 10 seconds without losing protection.
For laser welding helmets, there are two important types of LB ratings, each based on laser mode: DLB and ILB.
DLB refers to continuous wave laser beams. ILB refers to pulsed laser beams (specifically with a pulse duration between 1 microsecond and 0.25 seconds).
ANSI Z136: An American standard that indicates that the laser welding helmet meets the required OD rating outlined above.
EN 207: A European standard, EN 207 requires that laser welding helmet filters endure at least a 10 second pulse from a continuous wave laser beam or 50 pulses/10 seconds for pulsed lasers.
While some laser welding helmets take a different approach with their lens assemblies (such as including auto-darkening features to double as arc welding helmets), the following diagram outlines the basic components.
Outer clear lens
Similar to arc welding helmets, laser welding helmets often use one or more ordinary plastic layers to protect the other portions of the assembly from surface damage and impacts. These plastic lenses do not provide meaningful protection from laser light since most IR light passes right through.
Reflective optic
Made from specially treated laser glass, the reflective optic reflects the vast majority of laser light. As a result, nearly all of the energy from incoming IR light never makes it to the following layers.
Absorptive filter
Rather than reflecting, a special polycarbonate layer absorbs almost 100% of IR light. While thicknesses may vary, this polycarbonate layer is effectively identical to the material used in laser safety eyewear.
UV and visible filter
This layer is designed to absorb the harmful UV and visible light created by the laser welding process. The intensity of UV and visible light generated during laser welding is significantly less than what is generated during arc welding, but prolonged exposure can still be harmful.
Laser welding helmets intended to double as arc welding helmets may use more powerful UV and visible light filters with adjustable shades and auto-darkening filters.
When it comes to arc welding, a welding helmet made from simple plastic is often enough, as long as the filters work. These inexpensive helmets won’t win any awards for comfort, style, or durability, but they are safe enough.
As a result, many welders are unaware that the materials used in a laser welding helmet’s outer shell are actually important.
While laser welding primarily presents a danger to the eyes of welders and bystanders, it is important to recognize that laser beams designed to melt metal can also burn skin.
Here’s the good news: since most handheld laser welders will not fire if the nozzle is not in contact with a metal part, it is nearly impossible to fire a beam directly at yourself or a bystander unintentionally.
However, reflected light can be dangerous in some situations. Typically, holding a laser welding torch at the appropriate angle makes it unlikely that any light will reflect directly back at the welder.
Handheld laser welding beams couple with most metals within milliseconds to form a molten pool, at which point the reflection intensity is very low. When welding reflective metals like aluminum or copper, particularly with rounded or otherwise complex geometries, there is a chance of laser back-reflection. If the laser’s energy density is not high enough to melt the metal, or in the event that an improper torch angle is used, a high intensity beam can be reflected at the welder.
What this means is that not only should the lens assembly protect a welder’s eyes, but the outer shell should be able to withstand at least 10 seconds of direct or reflected laser light. While this is a very unlikely occurrence, this gives welders ample time to shut off the laser or move out of the reflected light’s path.
What Materials Are Acceptable for Laser Welding Helmets?
There are two primary materials that are sufficiently laser resistant.
The first, surprisingly, is aluminum. Although handheld laser welders are excellent for welding aluminum, the material’s natural reflectivity provides excellent protection from reflected laser light, which is more diffused and less intense. Of course, a helmet made entirely from aluminum might not be ideal, which is why LightWELD helmets that rely on this material use it only on the front of the hood.
The second is carbon fiber. Carbon fiber is light enough and strong enough to serve as a good welding helmet material in its own right. But the material is also resilient enough to resist at least 10 seconds of direct or reflected laser light from a handheld laser welder.
A Note on Laser Welding Face Shields
While there are fewer laser welding face shields on the market than arc welding equivalents, they do still exist. It’s easy to see the appeal – laser welding face shields do a decent job protecting from sparks and debris and provide sufficient protection from laser light in the vast majority of situations, all while being more compact and lightweight.
Although some experienced laser welders prefer to use a laser welding face shield, it is important to recognize that these shields do not provide as much protection as welding helmets made with aluminum or carbon fiber.
At the time of writing, there are only a handful of sufficiently protective laser welding helmets on the market. As the popularity of laser welding continues to grow, this will likely change.
If you are looking for a truly safe laser welding helmet, we recommend asking the seller or manufacturer the following questions:
What are the OD and LB ratings of the helmet’s lenses?
From what wavelengths are the helmet’s lenses designed to protect?
What norms, ratings, or standards (ex: ANSI Z136, EN207) does the helmet adhere to?
Can the helmet withstand at least 10 continuous seconds of exposure to direct and reflected laser light?
What material(s) is the laser welding helmet’s outer shell made from?
If you have your eye on a laser welding helmet, whether it’s a LightWELD helmet or not, you can also reach out to one of our laser welding experts. We’ll be happy to help you understand if it’s the right pick for you.
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