Monthly Archives: November 2017

Automated Lasers—The Role of Flexibility

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By: Michael Sharpe

 

FANUC Laser Welding Robot. Image courtesy of FANUC America Corp.

The role of flexibility in supporting the pace of advanced manufacturing through laser innovations is critical for success. Flexibility is essential when designing and building systems to address current and future manufacturing needs. Versatility of core motion control performance, whether in machine or robotic applications, is key to driving the confidence in users and the success of the application. Motion control features for cutting and welding of tomorrow’s products need to build on capabilities which compliments the advances of the past while anticipating unique solutions to meet future functionality. Laser technology demands and deserves progressive and intelligent developments with a strong focus on flexibility and versatility.

Computer Numerical Controls most commonly used on laser processing equipment are mature and readily accepted throughout the industry. Customers have been quite successful at utilizing the full capabilities of laser oscillators when coupled to advanced motion control. At the dawn of NC control and high capacity industrial lasers, manufacturers were mostly using CNC controls in a rectilinear machine. These machines were a simple moving bridge to carry the processing optics in an X, Y plane with Z height control. Rudimentary but they were effective for the application demands of the day.

FANUC high-speed motion control. Image courtesy of FANUC America Corp.

Robots have witnessed recent advancements that have improved motion path performance and I/O trigger accuracy, refining process quality. The downward cost trend of industrial 1μm fiber lasers and increased robotic processing performance has given the industry new vigor, providing the best cost point for high production applications. CNC applications continue to prosper with improved accuracy and speed but are limited in overall flexibility. Customers have more choices than ever based on their manufacturing requirements for laser applications, benefiting all manufacturers of CNC, lasers, and robots.

While it appears straightforward to compare a robot to CNC, they have physical attributes and control nuances that make them each suited for different markets. A laser in motion can produce incredible results but only with the precision of motion control and synchronized input and output control. To effectively use either motion device, it must have the ability to adjust the laser output based on position and velocity. As the motion device accelerates it must have a proportional controlled output to allow the laser power to follow, thereby providing uniform energy distribution along the cut or weld path. Despite their differences, they have similar control functions with different markets. CNC lasers may appear to be more easily deployed as they are mostly configured by machine tool builder in series production, preconfigured for the application purpose. The machines typically offer limited motion range from three degrees of axis motion and up to five degrees in machines with multi-axis heads for orientation control. Most CNCs are rectilinear so they can only do work with one laser processing head at a time, and within their motion envelope. This design cannot support motion overlap of more than one bridge and gantry structure since it will interfere within its own structure. Despite the mechanical design limits, CNCs have enjoyed a large market share in CO2 laser applications as the beam delivery is well suited for the rectilinear structure and its Cartesian motion envelope.

FANUC Robot HiYAG Remote Laser Welding On the Fly. Image courtesy of FANUC America Corp.

The use of CO2 on robots has been limited to specialized applications and was tried early on with some success. The largest problem is beam delivery can become quite complex if not designed properly, though some good solutions exist. Today the robotic CO2 market is primarily plastics trimming where the 10-micron wavelength is more suitable. While fiber delivery is nearly as simple as routing the optical fiber cable along the arm and to the processing head. The cost per watt of a fiber laser has come down significantly while robot motion performance has increased steadily over the last decade and this is where the market has gone in the way of laser processing.

Robot manufacturers continually improve the mechanical structure and motion control to achieve higher path accuracies with improved laser output response. Many features that enhanced the CO2 market are readily available to robot users, including laser height control to adjust the focus, automatic power control to adjust the output to be constant to the travel speed, and laser monitoring. Robotic applications are more flexible because they are not dependent on the rectilinear motion envelope described above. A six-axis robot has the ability to work with other robots and on the same part, improving laser on time. By coordinating or sharing the laser output you can improve efficiency with a smaller investment and with a more compact footprint since the robot takes up only a ‘slice’ of vertical space in the work cell.

FANUC Robot HiYAG Remote Laser Welding. Image courtesy of FANUC America Corp.

Opportunities abound for robotic laser applications and are being largely driven by new materials and construction techniques in the automotive market to the latest in 3D printing technology. The requirements for the latest Café fuel consumption standards and the overweighting of cars with safety equipment has forced manufacturers to seek improvements in materials strength to weight ratio, or light-weighting. Components that are made with hot-pressed steel are more difficult to trim to shape and weld. Fiber lasers offer the flexibility to work in these areas by using the robot to cut and trim hot-stamped components with ease. Robotic fiber laser cutting is a natural extension of the robot’s work envelope or range to process a variety of formed parts that have a 3D profile. Offline programming provides maximum uptime of the laser system, allowing quick changeover since the cutting path can be programmed offline, maximizing valuable laser on time. Path control features allow the robot to self-tune the motion performance to get the most accurate feature. Laser power is controlled through output level, duty, and pulse rate, providing the best cut quality. These functions are automatically adapted to the robot speed, easing the programming.
A popular welding application is remote scanner welding where the beam delivery is controlled by a galvanometer system to steer the beam while coordinating the motion of the robot through its path. This technology is well suited to high throughput applications in automotive body welding and specialty applications for marking and surface treatment. Control techniques to coordinate the robot, scanner, and laser offer precise positioning and are easy to use through a single point of control. Higher throughput is achieved when the robot and scanner’s movements are coordinated with simultaneous control. More nameplate manufacturers are using aluminum for automotive body structures and with class ‘a’ finishes. Complex body shapes have become popular as well as further integration of sensors for safety. The challenge is to form the body shapes and hide the sensors so they do not disrupt the cars’ aesthetics. Wire-fed laser welding solutions help support these initiatives by providing a well-controlled feed rate of filler wire into a body seam while precise laser power control causes the weld to form. All of the welding functions are controlled through the robot and are automatically adapted to the robot tool center point velocity along the weld joint. A high-quality weld is formed without the operator programming special ramping techniques with program outputs, the new adaptive welding systems can handle the welding filler wire and laser power repeatedly.

Aluminum laser welding at a General Motors plant. Image courtesy of
General Motors.

Robotic laser control has matured from the cumulative learning experience of CNC applications while offering the utmost in flexibility. The future looks very bright as more and more laser processes and markets mature such as material conditioning, 3D printing, and future flexible robotic laser applications.

Michael Sharpe is a Staff Engineer in the Materials Joining Group at FANUC America Corp.

High Growth Areas in Industrial Laser Processing & Monitoring

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By Craig Bratt & Rahul Patwa

The brilliant light of the laser promises unlimited possibilities for materials processing. Its use in manufacturing dates back to the late 1960s where laser drilling was developed for jet engine components. As laser technology has progressed, fast-paced advances in computers and sensor technologies have enabled the development of improved process monitoring devices which has further enhanced the performance, reliability and ease of use of industrial laser systems.

In 2014, the total global market for laser systems for material processing which include both the source and the components was $9.2 Billion (Source: Optech Consulting, VDMA). From this, the total global laser source revenue was $2.9 Billion, according to the data presented by Industrial Laser Solutions (Feb 2016). In 2015, this revenue (only the global laser source revenue) increased by 6.9% to $3.2 Billion. Although, the largest market share has been and continues to be (61% in 2015) in the laser cutting and laser marking/engraving, their % year-over-year growth has been limited to <5%. More interestingly, the higher % Y-O-Y growth areas are laser welding (17%), laser surface treatment (31%) and laser additive manufacturing (71%).

Courtesy Image

In this article, we present a clear view of how advances in laser power and beam quality along with a significant drop in laser cost per watt and improved laser wall plug efficiency has contributed to major innovations in laser material processing. We have identified four broad laser processing segments and analyzed what is driving innovation.

Manufacturers in many industries have long used laser welding to tackle traditional welding challenges, but laser welding technologies are evolving for even greater utility. Hybrid welding where laser welding is combined with other conventional arc welding methods such as GMAW (MIG) and GTAW (TIG), laser welding with filler wire, and part pre-heating have been successfully implemented in Industry. This has been possible now due to the availability of higher power lasers at lower cost. In turn, materials that were considered difficult to weld until now such as higher carbon steels and cast iron can now be successfully laser welded. The additional filler material changes the composition of the weld, preventing the formation of hard and brittle microstructures. Likewise, induction preheating can be used to help prevent cracking due to martensite formation by slowing down the cooling rate after welding. For instance, in an automotive transmission part, a bolting process was replaced with laser welding, cost savings were achieved through reduced material and processing costs (drilling operations / bolting operations and the bolts themselves), and an overall part weight reduction was accomplished with a more efficient production method using laser technology.

Laser welded transmission part versus traditionally bolted assembly (Courtesy image)

Laser remote welding(Courtesy image)

Remote laser welding is another laser welding process which dramatically reduces welding process cycle times compared to conventional welding and is now possible due to availability of higher beam quality lasers and high speed scanners. It involves the use of moving optics in order to rapidly scan the laser beam across the workpiece over large distances both for high speed and for high precision point to point movement.

To capture the higher potential of laser welding, there has been substantial yet continuous development in laser welding head technology which includes the welding optics themselves and also the sensor optics. Some of these process monitoring technologies have been in development for some time. Some are not yet ready for application at scale. But camera based laser monitoring is now at a point where its greater reliability and lower cost is starting to make sense for high power welding applications.

Fraunhofer CLA has developed a high speed camera vision system which can record the welding process in high clarity in real-time and provide both image and video data from the process. This information is processed and calibrated with reference data based on pre-determined actual ‘good’ weld measurements using reinforcement learning. Using customized image processing software algorithms, it is possible to detect many of the most common weld defects.

One laser processing technology which has recently been moving up to forefront of innovative, or even disruptive technologies is laser additive manufacturing (LAM). This process uses laser beam as heat source and is primarily divided in two processes: Selective laser melting (SLM) and Laser metal deposition (LMD).

In the SLM process, a layer of powder is deposited on a build platform and then a rapidly scanned laser beam fuses powder together in the right shape and multiple thin powder layers are deposited to create complex 3D parts.

Fraunhofer Coax wire deposition head allows multi directional build up using wire. (Courtesy image)

In the LMD process (also known as direct energy deposition or laser cladding), the laser is used to melt metal powder fed through the nozzle which is then deposited in layers onto a substrate, which results in a full metallurgical bond with a small heat affected zone and minimal dilution. It has been developed for surface wear and corrosion coatings, component repairs/remanufacturing, and generation of complete components from scratch.

Fraunhofer process monitoring system hardware (Courtesy image)

Two other variations of LMD—hot/cold wire cladding and internal diameter cladding—have now evolved into successful industrial processes and are now widely used in the oil industry, agriculture, power generation and remanufacturing sectors. A recent key development by Fraunhofer IWS is a new coax laser deposition head COAXwireTM which provides
omni-directional welding performance for the use of metallic wires as filler material which is of particular use for 3D build up additive manufacturing of metallic components.

One area of laser material processing that has benefitted the most from technology improvements in both spatial and temporal properties of the laser is laser machining. In addition, the advent of lower cost and smaller footprint laser power sources has lead to much wider industrial adoption of laser technology. The latest generation of pulsed lasers with pulse lengths—from millisecond all the way to femtosecond—has led to a rich pipeline of innovations impacting virtually every manufacturing industry. For example, laser cutting of battery electrodes can produce excellent cut quality and achieve high cutting speeds for application in lithium-ion battery cell production. Similarly lasers can be used for coating removal for electrical contacts on battery foils. Large area coating removal for paint stripping, deoxidization, mold and die cleaning or removal of special coatings is conducted by applying high power lasers. Lasers are also used for high rate drilling process for up to 15,000 holes/second.

Fraunhofer high speed camera system software (Courtesy image)

In summary, the current pace of innovations leading to new laser technologies and products is constantly increasing with a wide array of new applications being developed for every industry imaginable.

Craig Bratt, Executive Director, Fraunhofer USA, Center for Laser Applications, cbratt@fraunhofer.org

Rahul Patwa, Project Manager, Fraunhofer USA, Center for Laser Applications, rpatwa@fraunhofer.org