Laser Energy...Just In Time

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North America's job shops offer the latest manufacturing technology to their customers. That's one of the benefits OEMs get from outsourcing -- another company provides the advanced, high-tech equipment that does the job faster, better, or maybe, cheaper.

One of those technologies is use of laser systems.

By using a job shop's laser cutting or welding abilities to process either an important single part--or multiple parts--manufacturers can determine if there is sufficient production volume to justify buying their own laser system. Manufacturers also benefit from the expertise of the laser shop. That's especially useful if laser processing doesn't already exist at the manufacturer.

Industrial laser systems are most commonly used for welding, cutting, and marking. Because laser systems are computer controlled, laser marks can be changed from part to part. They can also be made small enough that they are difficult to see with the naked eye.

But other uses, such as hardening specific areas of tools and dies, are being discovered. Cladding, another laser application, melts a thin surface on a workpiece together with hardfacing material. In a similar process known as laser surface melting, a thin layer of the surface material on a workpiece is melted and 'self-quenched' to create beneficial surface properties.

Reverse engineering is another use of the laser beam. The laser is integrated with a scanning system to capture and computerize the shape of a part's surface. The computerized shape data can be used in many ways.

There are an estimated 8,000 to 10,000 industrial laser systems now in use. Their growth in popularity can be attributed to at least three factors: the just-in-time (JIT) manufacturing philosophy, engineering awareness of their capabilities, and more sophisticated integration of system components.

Just In Time

The use of industrial lasers really took off with industry's broad acceptance of the JIT concept, which often requires processing small batches of material.

According to David Belforte of Belforte Associates, consultants in industrial materials processing with particular expertise in laser technologies, "Lasers tend to be extremely cost effective when you have small quantities, or mixed batch quantities.

"In the late 1980's, when the U.S. really turned to JIT manufacturing, there was a real shot in the arm for lasers. Today, there is a complete acceptance in the U.S. of JIT manufacturing, which says, 'don't have an inventory of parts, build only what you need on order.' The way you do that is to process small batches of material. That lends itself to an interrupted process operation like lasers where you don't have tools and setup to worry about. It is a natural solution to the JIT or low volume, on-order cutting. Many manufacturers are now outsourcing their work to laser job shops that can make the parts cheaper, and can be turned off and on like a faucet."

Engineering Acceptance

Engineering acceptance of laser system technology has also helped the use of industrial lasers to grow. Lumonics Corporation is a leading producer of laser systems under the Laserdyne™ trade name. Terry VanderWert, Product Manager for Laserdyne, points out, "Today, design engineers and manufacturing engineers have finally gained enough awareness of the capabilities of lasers that they are starting to design components or processes around the capabilities of the laser.

"Before the late 1980s, the laser was typically evaluated for some productivity improvement or quality improvement, but the part that it was processing had been designed for manufacture by another process.

"For example, in the case of turbine engines, many components were once designed for drilling by EDM. Now, to reduce costs and to support the JIT philosophy, laser drilling is used to provide greater throughput and reduce manufacturing costs.

"I think we have reached a level of maturity where we now start to see more and more people designing components based on what lasers can do."

System Integration

A laser by itself is just a laser. What industry has been using to cut, weld, scan, and mark parts are laser 'systems'.

Laser systems consist of a method of delivering the beam to the workpiece, a mechanism to rapidly move the beam or the workpiece, probably a material load/unload feature, and software that integrates the several aspects of the system. Together, these components comprise the laser system and represent the technologies that have enabled the application of laser technology to accelerate.

Advances in component integration and software programming are areas that continue to enhance the capabilities of laser systems. One of Lumonics' contributions was a machine teaching program called TeachVision™ which has significantly reduced the time it takes to develop laser operating programs. It also improves the accuracy of the processing path.

Another leading producer of laser systems, ESAB L-TEC, has a unique laser cutting system, called the Phaser, that has two laser cutting heads in a single machine. This gives it the ability to cut out two identical parts, simultaneously.

Advancements such as these have made the processing speed of lasers much more competitive with other forms of processing.

Belforte says, "The new laser systems being produced today have such high speed processing capability that they are beginning to replace punch presses. Lasers can produce parts at such a high rate on demand that they compete very nicely with punch presses that are turning out 10,000 to 15,000 parts.

"I can think of two major manufacturers in the U.S. that have publicly stated they are going to replace all their punch presses with lasers. And we're talking a lot of lasers here. They are ideal for interrupted, short order processing, as opposed to punch presses. They are also fully automated and can run multi-shift."

Laser Excitement

The process of creating a laser beam is fairly complex. Laser is an acronym for light amplification by stimulated emission of radiation. In layman's terms, an external source of energy stimulates, or excites, the atoms in a material developed for the purpose. The action of the electrons in these excited atoms produces the energy that is released as a beam. It happens in extremely short amounts of time.

The two most common forms of lasers are CO2 lasers and Nd:YAG lasers. The YAG laser is referred to as a solid state laser. The CO2 laser is referred to as a gas laser.

They get their names from the material that is excited. In Nd:YAG lasers, the material is a crystal rod consisting of about two percent neodymium (Nd), which is the active medium, contained in a host crystal of yttrium, aluminum, and garnet. The atoms of Nd are excited by a flashlamp, or an arc lamp, depending on whether a pulsed wave or continuous wave is needed.

The CO2 gas lasers use a mixture of helium and carbon dioxide within a chamber to produce laser energy rather than a solid rod. An electrical discharge is used to excite the carbon dioxide atoms.

The beams from these two types of lasers exhibit different characteristics. The Nd:YAG laser has a wave length about one tenth the wave length of the gas laser. This shorter wave length often produces less of a heat affected zone in the material.

Also, there are different beam delivery systems for the different types of lasers.

The beam from an Nd:YAG laser system is delivered through a fiber optic cable. The end of the cable is moved around above the workpiece to deliver the laser beam.

In higher power lasers, such as CO2 lasers, the beam is usually delivered through a set of mirrors. In some systems, the mirrors are stationary, and the workpiece is moved around under the laser beam. In other cases, the mirrors and the beam are moved around as a unit above the workpiece in a set-up known as 'flying optics'.

Welding and Cutting

Welding and cutting are the most common applications of laser systems. The two processes are similar to keyhole welding in which a hole is burned into the workpiece and moved across the material. The molten material that forms around the walls of that hole eventually cools and hardens.

Laser welding and cutting also move a hole across the material. During cutting, a jet of assist gas blows away the molten material, leaving a clean cut. In welding, the molten material is not blown away. It is allowed to solidify.

There are also different forms of laser marking, which is usually done with relatively low power lasers. One, known as laser annealing, uses just enough power to create a surface discoloration. A molecular change caused by the heat alters surface color, producing a readable mark.

Laser engraving uses just enough energy to vaporize material so that a legible mark is cut into the material. It requires a higher power setting than used in laser annealing.

A laser system performs best when it is configured for one type of processing. That is why companies generally use a laser for one process though a laser system can be designed to perform more than one function. For instance, if the company is in the cutting business, then they'll use the laser for cutting. If they're in the welding business, they'll use the laser for welding.

However, in some job shops, lasers must have enough versatility to do more than one thing. And many job shops will have more than one laser, each configured to perform different applications.

When searching for a shop to provide laser processing, the type of laser system to look for depends on the thickness and type of the material you're dealing with, and the type of work that you want to perform on that material. As in most cases, engineers should talk to more than one shop to learn the cost and quality performance that each can provide before choosing a laser service provider.

As Belforte stated, "You have your choice today of high-powered CO2, high powered YAG, low powered CO2, or low powered YAG. Some materials are better processed by YAG than they are by CO2, and others are much better processed by CO2 than YAG. It is something that is very much material dependent."

A Big Gun

One of the improvements that laser cutting technology has made deals with the versatility of the equipment available. Recently, job shops looking to offer greater capabilities and gain a competitive edge have increasingly turned to multi-axis laser systems.

GBC Inc. of Lakewood, Colorado is a leading shop specializing in large components for the machinery, aircraft, mining, and packaging industries. The company was close to buying a two axis, flat sheet, laser cutting system that would have enabled them to quickly cut panels of just about any size and shape.

But Geoffrey Gray, President of GBC, noticed that projects requiring close-tolerance machining of large workpieces were being sent out-of-state. Missile cylinder components and food processing system assemblies were two examples. To qualify for this work, GBC had to add larger equipment.

When GBC compared Lumonics' five-axis Laserdyne™ 890 BeamDirector® laser cutter to a flat sheet cutting laser, they saw that the five-axis cutter could add considerably more to GBC's part making capabilities. It could also save customers the cost of shipping parts out of the area for laser processing.

GBC began telling customers and prospects they "were now armed with the biggest gun in the West."

GBC used the multi-axis laser to process a 120 inch diameter x 30 inch high steel assembly used to join two sections of a missile. These cylindrical components came to GBC painted. GBC had to accurately cut assembly slots across welds on the contoured surface without marring the exterior finish paint. The five-axis laser cutter made this possible. First, the laser etched the surface, removing a narrow band of paint without burning, melting, or discoloring the adjacent paint finish.

On the second pass, the slot was cut in the contoured surface. The laser head was able to access the curvature inside and outside the part. Also, the laser head provided easy access into difficult-to-access surfaces in one setup.

When GBC etched and cut the assembly slots in the missile components, there was never any apprehension about the laser head 'crashing' into the part and marring the finish. The system immediately disengages at the slightest impact to avoid damage. The system also remembers its position for quick restart.

GBC quickly found another application for its five-axis unit, welding cylindrical parts at intersecting angles. Manufacturers of cryogenic and food processing equipment require these types of assemblies in many different materials, including stainless steel. The unit was ideal for cutting and drilling dome and cylindrical shaped parts and for welding the intersecting cylinder assemblies.

For cutouts in large tubes that cannot be rotated with the sixth axis rotary table, or other complex three-dimensional parts, another technique is used. According to David Wortman, head of GBC's laser department, "We use our CAD system to draw the full part model and then tape a paper template onto the workpiece. We then teach the path defined by the template using the TeachVision feature of the multi-axis laser. This process is fast and a cost effective alternative to five axis off-line programming."

GBC has also replaced a silver soldering assembly operation with laser welding. The assembly is used in a food processing system for preparing fruit. Up to 700 of these assemblies at one time are required by the customer. Because the job involves repeat orders, GBC created a permanent tool setup, which cost the customer about $4,000. Usually, the five-axis cutter does not require custom tooling; only simple standard clamps are needed. In this case, the tool is needed because of the higher quantities required and the repeat nature of the project. The new unit welds the assembly in just three minutes compared to the 10 minutes per assembly using the silver soldering process.

"As for the flat sheet cutting, GBC's five-axis cutter routinely performs these chores between the complex, multi-axis jobs. It's a ruggedly built machine and operates so many different ways non-stop, around-the-clock when needed," observes Wortman.

Within six months after installing the system, the laser department went to two shifts.

As for the future, GBC sees lasers playing an even more central role in their business.

The majority of jobs that come through GBC's shop now have one or more laser operations performed on them. They have already added a four-axis laser system with automatic loading to their arsenal of machines, "Giving them a pair of the biggest guns in the West!"

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