Category Archives: Fiber Lasers

Diode Lasers in Cladding, Additive and Hybrid Manufacturing

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By Oleg Raykis

Today there exist a number of technologies for additive manufacturing of components.

The two most prominent types utilizing lasers for generating parts out of metals are either powder bed based solutions or direct energy deposition, often referred to as laser metal deposition. As a company Laserline focuses mainly on the second type. Depending on the application it allows you to produce larger part sizes with higher productivity (deposition rates and therefore higher productivity) due to the fact of not being limited by the size of the building chamber as it would be in the case of a powder bed machine. It is also much faster in many cases.

Laserline identified four main application areas for AM in which we operate and be described based on examples in this article. Those areas include, besides generating complete parts by terms of additive manufacturing, also repair welding application or hybrid machines – a combination of conventional machining and laser technology the fourth main application area would be providing functional areas on conventionally manufactured parts.

Additive manufacturing technology allows generating shapes and structures in a single production step with little material loss, post machining and tool wear (near-net-shape manufacturing). Thereby you can use material in powder or wire form. The advantage of using wire is that you will have a 100% material utilization; the compromise on the other hand might be the directional dependency when you supply the wire laterally and not coaxial. Pic. 1 shows an example of a free form application as a rocket nozzle demonstrator part made out of Inconel 625.

Pic.1 Free form powder AM of a rocket nozzle demonstrator (Source: Fraunhofer CLA)

The part was done without any type of process control. Another interesting example of AM with Titanium is shown in Pic.2.

Pic. 2 Ti64 powder AM with closed loop process control (Source: Fraunhofer CLA)

Compared to the rocket nozzle, process control was used when producing the demonstrator part in pic.2. The camera based system (in this case E-MAqS) is capable of measuring the size and temperature of the melt pool. Furthermore it can give feedback to the laser source and adjust the laser power accordingly to maintain the desired size of the melt pool. This in turn ensures consistent reproducible part build ups with no defects.

Another very interesting and promising approach is to integrate the laser source into machine tools. There are several hybrid machine tool concepts being developed; one of them is the combination of additive and subtractive tools which achieves a new level of manufacturing. One example is the merger of a laser with a 5-axis milling machine. The integrated diode laser deposits the powdered metal layer by layer, generating a solid, fully dense metal part. The following milling operations directly finish machines surfaces in areas necessary, without changing setup.

Pic.3 An example of a conventional milling machine with integrated AM technology (Source: DMG Mori-Seiki)

This flexible switch between laser and mill also allows the machining finish of areas, which would be impossible to reach on the final component. Designs with undercuts, internal geometries and overhangs without support structure are no problem. The manufacturing of completely new structures and designs are now possible. All weldable metals, which are available in powder form, can be used, for example steel, nickel and cobalt alloys as well as titanium, bronze or brass.

A third important field of AM from our perspective are repair welding applications. Probably the most prominent and widely industrially utilized are the repairs of turbine blades. Turbine blades in steam engines, especially in the first two rows, experience a lot of wear through erosion. Instead of replacing the whole part it is possible to repair the worn area by putting a couple of layers (mostly nickel / cobalt based super alloys) and machine them down to the finished surface, see Pic.4.

Pic.4 Turbine blade repair (Source: Fraunhofer ILT)

This remanufacturing procedure saves up to 90% of material and energy cost compared to manufacturing a new blade. Even though turbine blades are the most prominent example of laser repair welding a wide variety of other parts can be restored using the procedure, e.g. worm shafts, helical gears, molds, etc. to name a few. When speaking about additive manufacturing most people have the production of complete parts in mind. This doesn’t always have to be the case. Often it makes more sense from an economic standpoint to add to a conventionally (and relatively inexpensively) produced part functional areas where they are needed. Pic. 5 shows one such example.

Pic. 5 Extruder barrel demonstrator (Source: Fraunhofer CLA)

In this case 100 lbs. of hard and wear resistant Stellite 21 powder material was deposited on a metal pipe base structure to form the extruder thread. One further example of it can be functional layers on drill bits where sensors need to be shielded from magnetic interference. By creating heat resistant layers out of non-magnetic materials it is possible to place those sensors.Through a clever combination of the usage of conventional and additive manufacturing technologies it is possible to produce advanced parts without increasing the cost.

Recap: CO2 vs. fiber laser shootout by Cincinnati Incorporated

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In case you missed today’s CO2-vs.-fiber shootout by Cincinnati Incorporated using its 4,000-watt CL440 CO2 and CL940 fiber lasers to cut identical parts side by side, here’s a quick rundown.

Performed at the company’s Customer Productivity Center in Harrison, Ohio, about 20 miles west of Cincinnati, this demonstration by the longtime LIA exhibitor used their machines to fashion parts out of 20-gauge mild steel, 1/2-inch mild steel and 1/8-inch aluminum. Both systems have identical drive systems.

In broad terms, of course, fiber lasers — which have been carving out more and more market share — cut thinner materials faster, while CO2 performs better with materials thicker than 10 gauge.

The results:

Cincinnati Incorporated pits its CL940 fiber laser against its CL440 CO2 laser.

• 20-gauge mild steel (assisted by shop air): Fiber laser cut the part at 27 seconds at a rate of 2,160 inches per minute vs. 31 seconds for the CO2 laser run at 850 inches per minute. Estimated cost of the process is $6.90 per hour for fiber vs. $9.88 for CO2.
• ½-inch mild steel (oxygen): CO2 cut the part at about 79 seconds at a rate of 60 inches per minute vs. about 99 seconds for fiber run at 45 inches per minute. Estimated hourly operating cost is $6.52 for fiber vs. $10.33 for CO2.
• 1/8-inch aluminum (piercing with nitrogen, cutting with oxygen): Fiber cut the material at 56 seconds at 950 inches per minute (vs. 500 inches per minute if cutting with nitrogen).

Audience polling during the demonstration yielded an interesting look into laser purchasing habits:

• 32 percent said they had two to five lasers in their facility; 30 percent said one, 30 percent said none and 9 percent said more than five.
• 82 percent said they had not purchased a new laser within the past three years.
• 45 percent said they might consider automation with their next laser purchase, 40 percent said yes and 15 percent said no.
• 51 percent said they would be more likely to purchase a fiber laser, 30 percent a CO2 laser, 19 percent unsure.

The presentation is scheduled to be made available at Cincinnati’s website.

— Geoff Giordano

Sapphire Cutting with Pulsed Fiber Lasers

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By Christoph Ruettimann, Noémie Dury and Markus Danner

With almost 40 years of experience in precision processing of synthetic crystalline materials, Swiss laser manufacturer ROFIN-LASAG AG has developed a process for cutting sapphire glass, which is now increasingly used in mobile electronic devices and high-quality mechanical watches. Synthetic sapphire is a mono-crystalline aluminum oxide with outstanding technical properties, such as a high thermal conductivity, very high light transmission and complete acid resistance. In addition, it is an outstanding electric insulator and extremely scratch-resistant: With a Mohs’ hardness of 9 sapphire is beaten only by diamond.

Sapphire can be cut with a variety of laser technologies. Ultrashort pulse lasers, such as picosecond lasers, cut the material using very short pulses. The energy of these pulses is transferred so quickly to the electrons that the chemical bonds of the atoms are destroyed. In contrast to that, pulsed fiber lasers with a pulse length in the range of microseconds to milliseconds work with another cutting process, so-called fusion cutting. Continue reading →

Local Laser Joining of Glass and Silicon

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By Assi Hansen, Isamu Miyamoto, Tiina Amberla, Yasuhiro Okamoto

One of the most employed material combinations in microtechnology is the glass-silicon pair. Since the huge growth of the microelectromechanical devices, sensors and micro-fluidic devices, bonding of this couple has become more and more critical issue. Many of these glass-silicon bonding processes, for example anodic bonding, fusion bonding and eutectic bonding, have reached their limits in terms of flexibility. In addition, high temperature and electrical field applied in the process can limit the application. Compared to conventional methods, local laser joining technique can provide many advantages, such as localized and flexible joining, non-contact manufacturing, high precision and repeatability, easiness and minimization of heat effects. The technique is based on the principle of transmission welding, where glass is transparent to the wavelength used and hence the laser beam passes through the glass wafer and is absorbed to silicon. As a result, silicon is melted and upon resolidification bonding is realized between the two substrates. Continue reading →

A Technical and Commercial Comparison of Fiber Laser and CO2 Laser Cutting

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By John Powell, Alexander Kaplan

Since the advent of commercial fiber and disk laser cutting machines, there has been a lot of controversy about the performance of these devices – particularly in comparison to their more established CO2 counterparts. In the early days, the sales staff promoting fiber technology would often declare that the new lasers would completely take over from CO2 technology very quickly – but this has not happened. Even taking into account the entrenched position of the older technology, fiber and disk lasers have not been as widely accepted as was predicted, although they have been proven to out-perform CO2 lasers in certain important areas.

This paper presents a discussion of the advantages and disadvantages of both types of cutting technology from a commercial point of view – written from the perspective of a laser cutting job shop owner trying to decide between buying a fiber or CO2 laser cutting machine. A quantitative comparison of the two machines is surprisingly difficult – having given several talks on the subject the best analogy we can give is that it’s like comparing a sports car with a family car. Continue reading →