Growth tied to performance and versatility from micro to 3D printing
You don’t have to look too far to find the reasons for the growth of fiber lasers for production applications. On price per watt, beam quality, electrical consumption, and maintainability required, fiber lasers typically score the lowest on the cost side and very high on the performance side. Applications continue to expand from the most basic laser machine alignment to traditional cutting, welding, drilling, and marking. Newer growing applications include some obvious ones like 3D printing and some not-so obvious but equally attractive applications like surface texturing. Laser power required ranges from that of a simple laser pointer to the 6-kW and 8-kW lasers that will be widely exhibited at Fabtech 2016. How lasers are applied depends on the engineering ingenuity of laser suppliers and systems integrators working in conjunction with end users asking the right questions and getting the right answers. Here are some thoughts for Q&A.
Matching the Right Laser to the Right Delivery System
Laser Mechanisms Inc. (Novi, MI) designs and manufactures laser beam delivery components and articulated arm systems for every type of laser and industrial application including cutting, welding, drilling, scribing, and surface treatment among others processes. At FABTECH, Laser Mechanisms will exhibit its newest high-power fiber-delivered lasers in powers from 6 kW up to 30 kW. “Typical applications for high-power fiber, disk laser, and direct-diode lasers include cutting machines for fast cutting of thick flat sheet and high power welding processes,” said Tom Kugler, fiber systems manager. “We offer both standard products and custom-engineered laser solutions and sell to both system integrators and direct to end users.”
Laser Mechanisms’ additions to its standard product line include the FiberWeld HR and FiberCut HR lines for welding and cutting. These new products can be incorporated on flat sheet bed cutters and high-power welding machines in the 6 kW and higher power ranges. “The heads use reflective optics instead of transmissive lenses, allowing us to run at higher power with a much lower thermal focus shift,” said Kugler. “When a lens is heated by the laser beam, the focal point will shift. It’s manageable, but can cause a problem with any contaminating debris, for example. Our high-power reflective optics units can easily work with laser powers above 20 kW. The focal shift is generally less than 10% of the focus shift of lenses with speed of the focal shift less than a second.”
To design a successful laser delivery system, certain basic information is needed. “For laser cutting, we’ll want to know what type, 2D flat sheets or 3D cutting, with or without robots or five-axis machines. What laser power and type or wavelength, the kind of material, stainless or mild steel, and how thick or thin. Based on the responses we get, we’ll recommend the best fit, a standard product or a custom solution. Generally, the same laser can cut all those materials. What does change is the type of gas that is used, the power level of the laser, and where we would position the laser focus relative to the surface of the materials.
“For high-pressure inert gas cutting, which is generally done with stainless or aluminum, or titanium, we’ll generally run gas pressures over 200 psi [1.38 MPa] and we’ll be pushing focus down into the material. If we’re cutting mild steel, the gas pressure might only be between 7 to 15 psi [1 bar] and we’ll focus in a different place either near the surface or above the surface,” said Kugler. “In the micro area, fiber lasers are cutting a lot of features that are less than 25-µm kerf widths and very fine welding all done with fiber and disk lasers. Typical applications include lasers for medical devices such as stents and welding very small components for medical implants, small copper parts for micro electronics, batteries, and fuel cells.”
In the automotive industry, robotically delivered laser systems are being used for 3D cutting of HSS, hot stamped boron steels, and those that require laser cutting due to hardness and toughness. “We can also easily cut aluminum and our heads are used to cut aluminum vehicle bodies. Welding to 6-mm penetration is typical, but we can go deeper for automotive transmission welds to 10-mm penetration. We also weld fuel injectors and other small medical components where weld penetration might only be 1 mm or a half or 0.1 mm, depending on the size of the part and the strength required,” said Kugler. “For aerospace applications drilling turbine blades and vanes is the most common application, with hole sizes of about 0.4–0.6-mm diam at angles as low as 20° to the surface and up to 20-mm deep.”
Femto Lasers Provide Surface Textures for Medical Devices
Surface texture has become an important aspect of product design for medical devices and molds, according to Gisbert Ledvon, director of business development, GF Machining Solutions (Lincolnshire, IL). “Surface texture not only provides the means to refine the physical appearance of an item, but also increases an item’s surface grip qualities. Through surface texturing, manufacturers can create medical tools that pick up less fluid and/or debris, mark implants for tracking and add textures that aid in implant acceptance. Also laser texturing can be used indirectly in the production of molds and dies for medical components.”
For these applications, the most recent developments in laser texturing are the femto lasers and dual laser systems. “Femto cold lasers create perfectly sharp corners and edges because they generate completely burr-free surfaces. Burrs are even undetectable when the cutting surface is viewed under a microscope. This new class of laser opens up a variety of new materials for medical applications including ceramics and gems—such as sapphire, various polymers and glass,” said Ledvon. Femto lasers are able to cut more intricate patterns than previous laser technologies because the laser beams are smaller and can create smaller details in parts. More intricate cutting capabilities boost laser texturing’s benefits for the smallest of medical applications.
In addition to femto/cold lasers, the other significant technological breakthrough in laser texturing is the development of five-axis dual-laser systems. A dual-laser system is one that can automatically change its laser source from one type to another within seconds. This allows manufacturers to machine a wider variety of materials on a single machine than with single-laser systems. Such increased versatility means that manufacturers can perform more work from one laser texturing machine than was previously possible.
“With single-laser systems, operators can manipulate the laser’s strength by changing the laser power settings, which give a certain degree of control, but the ability to change to a different type of laser entirely offers much more substantial control over the laser texturing process,” said Ledvon. “Fast changes between laser sources are especially important for those medical shops that experience frequent shifts in part demands and designs. Those shops depend on flexible equipment to quickly respond to the needs of their customers.”
As the use of laser texturing continues to grow, five-axis machine movement has further improved it. With five-axis capability, manufacturers dramatically improve their productivity because this machining process dramatically reduces the need to manually manipulate workpieces during the part production cycle. Laser texturing technology also undercuts round shapes, meaning that the underside of a sphere can be machined without turning the part over. The reduction in necessary setups also eliminates stacked errors from finished parts.
“A current limitation to laser texturing is the size of the laser field, which is only as wide as the lens of the laser. Once texturing is complete within that field, the machine must readjust to place an untexturized surface under the lens. However, new technology in automatic laser positioning is on the horizon and will eliminate this barrier. Such cutting-edge technology will enable lasers to follow along a machining surface without having to stop and reposition. Automatic adjustments could make the laser texturing process up to 20 to 30% faster than it is currently,” said Ledvon.
GF Machining offers modular workholding systems and automation to further enhance the productivity of laser texturing. Process automation makes laser texturing a more viable machining process for high-production environments because the automation increases the production capacity of the machine. Additionally, modular workholding systems easily integrate laser texturing with other processes that a manufacturer may already use. Production parts can mount on pallets with a reference system that transfers across multiple machining processes and eliminates the need to re-reference parts between steps, which drastically reduces setup times.
“On the design side of manufacturing, laser texturing opens the door for greater legal protection of innovative and proprietary textures and patterns. Also, laser texturing can be used to protect against counterfeit parts. Through the part program, a user can create a unique texture code on a nano scale. Industry experts predict that nano-sized textures will eventually be used in medical component traceability. In these instances, a manufacturer would create a unique pattern, invisible to the naked eye, to mark parts and identify those they produced,” said Ledvon.
3D Printing Metal Parts Quickly and Flexibly
The emergence of 3D printing/additive manufacturing technology as a dynamic growth industry has important impacts on lasers, which are the predominant heat source used in the process. Trumpf Inc. (Farmington, CT) is expanding its technology product range in additive manufacturing with the introduction of its TruPrint 1000, the latest solution in laser metal fusion (LMF), which gives the ability to build up a component layer by layer. It has also continued developing its laser metal deposition (LMD) process, which provides the ability to add volume and structures/features to existing parts. Trumpf has continuously improved its process first established 15 years ago and offers a complete package for industrial 3D printing, including the laser beam source, machine powder, services and application consulting.
The new TruPrint 1000 uses a laser and metallic powder to build any desired component, based on data supplied directly by a CAD program. LMF systems create the component, layer by layer, from metal powders with grain sizes as small as 20 µm. Additive manufacturing technology is well-suited for parts that are complex in geometry, such as those with internal channels and hollow spaces, and for manufacturing individual parts or short production runs economically. The compact LMF unit is a perfect fit for job shops, medical or dental customers, or for R&D environments. It can generate parts that are a maximum of 100 mm in diameter and 100 mm in height. The user interface with touch-screen control steps the operator intuitively through the individual phases of the process. All the components, including the laser, optics, process enclosure, filter unit and control cabinet, are integrated into the compact housing of the TruPrint 1000.
The supply cylinder, construction chamber, and the overflow receiver are all aligned inside the enclosure. The supply cylinder contains the stainless steel, aluminum or any weldable material in powdered form. During the build, a layer of metal powder is applied to a substrate plate and then a 200-W laser is used to fuse the cross section of the geometry to the plate. After the exposure the plate is lowered and the next layer of powder is applied. This procedure is repeated until the part is finished. The entire process takes place inside the enclosure, blanketed by protective gas, and at an oxygen content of 0.1% for maximum part quality.
To apply high volumes of metal at high deposition rates, Trumpf continues to develop its LMD technology, which is well-suited for adding volume and structures/features to existing parts. In LMD systems, the laser forms a melt pool on the surface of a component and fuses the powder—applied simultaneously and coaxially—to create the desired shape. Applying multiple layers enables the user to expand the form in any direction. With the ability to add material at rates as great as 500 cc/hour, this process can be more economical than conventional manufacture. In addition, complex structures can be added to existing parts allowing for the design of common base structures that have features and strength added where needed. Based on the specifics of the application, fabricators can choose either the large TruLaser Cell 7040 or the more compact TruLaser Cell 3000 with the new LMD package.
Improved Process for Laser Welding Aerospace Alloys
Prima Power Laserdyne (Champlin, MN) has introduced improved process parameters for laser welding nickel-based aerospace alloys to meet stringent airframe and aero-engine requirements. High-quality butt and lap joint weld are possible and practical in a number of common nickel-based aerospace alloys following guidelines established by Laserdyne applications engineers.
Here’s how Prima Power Laserdyne describes the improved process. Using Prima Power Laserdyne’s SmartRamp, which makes use of Laserdyne S94P laser and motion control, weld dimensions on both the top and bottom sides of the weld—with or without filler metal—are controlled with no observable porosity within the weld fusion zone. Integrated laser and motion control with the Laserdyne S9P laser process control enables production of crack-free welds through use of laser process parameters that take into account the relatively large solidification temperature range of nickel-based aerospace alloys and the fact that brittle phases can form when solidification rates are low.
Joint cleaning to remove contaminants before welding nickel-based aerospace alloys is essential. At high temperatures, nickel alloys are susceptible to embrittlement from sulfur, phosphorus, lead, and other low-melting point substances that are often present in materials used in everyday manufacturing processes. Typical contaminants include grease, oil, paint, cutting fluids, marking crayons and inks, machine lubricants and lacquers.
Correct fixturing to control thermal expansion during welding is similarly important. The thermal expansion characteristics of nickel-based aerospace alloys are similar to those of carbon steel. When welding, the forces and distortion generated by both materials are similar and require component restraint by a properly designed holding fixture. The restraint provided can be used to control stress in the weld. For example, if an appropriate clamping force is used to restrain the material near the weld joint, the expansion created in the weld joint will lead to a compressive force in the weld. This compressive force will in turn lead to upsetting of the weld metal and corresponding reinforcement, or crown, of the top and bottom of the weld, even without filler metal.
In addition to proper clamping, the fixture must also provide the proper shielding of the top and back sides of the weld. Shield gas is provided to the top of the weld using Laserdyne’s SmartShield welding nozzle. Shield gas is provided to the back side of the weld through a special groove in the fixture beneath the weld.
Multiaxis Laser Workcell for Cutting, Drilling, Welding
IPG Photonics’ (Oxford, MA) Multiaxis Laser Workcell is a cost-efficient tool for cutting, drilling and welding a wide range of metal components, enclosures and fabrications. Configurable with IPG’s high-efficiency CW lasers or high peak power QCW lasers, the Multiaxis Workcell provides fast processing of even highly reflective materials.
Available as either a manual load system or with IPG-designed automated part handling, the Multiaxis Workcell has application in the manufacture of medical devices, automotive components, electrical enclosures, or any similar metal structures.
Machine construction and the system are based on a granite table and superstructure for thermal and mechanical stability. High-force linear motors provide precision high-speed X-Y motion compatible with processing intricate components, with a 300-mm travel Z-stage enabling machining of 3D parts. Rotary motion can be applied to any, or each of the primary stage axes, with a process head tilting option also available. The motion and laser processing system is integrated within a Class 1 laser safety enclosure with a laser safe viewing window. Automation is enabled by an industrial CNC controller having a custom Windows-based HMI and software for G- and M-code programming.
The Multiaxis system can be configured for welding or cutting by selection of the appropriate IPG fiber laser and processing head. For welding, the high peak power QCW laser combined with the Wobble and Seam Tracker head provides the flexibility to handle dissimilar metals and badly fitting parts, in addition to improving the weld quality of materials prone to poor formation and thermal cracking. Spot welding, seam welding, and formation of hermetic seals are among the typical applications. For customers with smaller parts, the Compact Multiaxis provides a lower-cost solution with a smaller footprint. Both system types can be configured for cutting, drilling or welding by choosing the appropriate IPG processing head.
Cutting applications benefit from IPG’s wide selection of lasers. With an emission wavelength of 1 µm, fiber lasers’ efficiency in cutting metals is better than CO2 alternatives; higher beam quality allows for faster cutting of parts or the option of using a lower power laser. Selecting between the higher-power FLC-30 cutting head or the higher-precision Micro-cutting head allows further optimization of the systems cutting capabilities.
This article was first published in the November 2016 edition of Manufacturing Engineering magazine. Read “Fiber Lasers Capture Market Share, Applications” as a PDF.