Why Lasers Shine In Job Shops
These are competitive times and job shops are the most practical of environments. The use of lasers in job shops is growing for one fundamental reason--they are effective which means they earn their keep. We will take a brief look at what they do, how they do it, why it makes sense to start with a laser job shop and where it may be headed.
Lasers are astonishingly versatile. In metalworking, they are used mainly for drilling, cutting, welding and heat treating. With plastics, rubber and some composite materials, lasers are used mainly for drilling and cutting. In many industries, bar codes and alphanumerics can be marked and engraved with dazzling speed and accuracy using lasers. In the electronics manufacturing industry, lasers are used extensively at all levels from the silicon wafer to the packaged product.
The above processes and many more can all be found in laser job shops. The number of processes and techniques keeps growing, sometimes as a result of applications developed in the job shop. It is important to realize that lasers perform some specific kinds of things well and some not so well. For instance, lasers are used extensively for drilling many small holes in jet engine components made of inconel, hastalloy and titanium, all of which are difficult to machine by conventional methods. By contrast, lasers are not notably competitive in cutting aluminum or copper because of their high reflectivity and conductivity which make the laser less effective. Lasers are not generally used to cut metal several inches thick or to make accurate square sided grooves of uniform depth. There are probably lasers somewhere that can do those things but the use is not widespread because they are not competitive or economical.
The table below gives an abbreviated list of some of the more common applications. Please note that in a fast moving field such as lasers, any statement can be rendered inaccurate by progress. For instance, where it is mentioned that lasers are more effective in drilling materials to about 1/4 of an inch, an article showing some beautiful, narrow laser drilled holes into two inch thick material was recently published. The purpose is to show the more common applications, the ones that would be more likely to be found in a job shop.
|Aluminum Alloys||Cut, Weld and Drill||Performance varies with alloy|
|Stainless Steels||Cut, Weld and Drill||Up to 1/4" thick|
|Inconel, Hastalloy, Waspalloy||Cut, Weld and Drill||Up to 1/4" thick|
|Titanium||Cut, Weld and Drill||Up to 1/8" thick|
|Composite Materials||Cut and Drill|
|Ceramics||Cut and Drill||Widely used for Alumina|
|Semiconductors||Cut and Drill|
|Plastics||Cut and Drill||Varies with plastic type|
|Rubber||Cut and Drill|
A laser consists of a very intense beam of energy which is directed on the material to be processed. Depending on the rate of application of the energy and the area, heating occurs which if gradual can be used for heat treating. If more intense, it can be used to melt and weld material, and when even more intense, can be used to evaporate and ablate it to create holes.
The effect of the interaction of the laser and the material depends on a number of features in the material, notably the surface condition, reflectivity and thermal properties. For the laser, the amount of energy, rate of energy and particularly the energy density and wavelength are important factors. As most people know by now, the L in laser stands for light although many lasers emit their electromagnetic energy in the infrared or ultraviolet parts of the spectrum.
Some of the most commonly used lasers are ruby, glass and YAG which are solid state lasers where the light or radiation is emitted from a solid rod. The active lasing medium in C02 lasers is a mixture of carbon dioxide and other gases. Ruby lasers as you would expect emit light at the red end of the spectrum at .7 of a micron (a micron is a millionth of a meter). Glass and YAG emit their radiation at 1.06 microns in the near infra-red and C02, at 10.6 microns, are much further in the infra-red. Materials absorb very differently over this wide range of wavelengths.
This is the reason why ruby, glass and YAG are commonly used to drill, cut and weld metals. C02 lasers, in addition to being able to process metals, are usually more effective with wood, plastic, ceramic and some composite materials. The solid state lasers usually emit short pulses of very intense radiation suitable for cutting or drilling. C02 lasers more commonly emit continuously and are good for cutting and welding but also heat treating.
It makes sense to start with a laser job shop because you can get your feet wet and try to project at very modest costs and low risk. It takes advantage of the ability to spread capital in technology across many customers. This is particularly important in view of the relatively high cost of lasers. It is not uncommon to spend $300,000 on a laser system and it certainly would be a good idea to make sure your application warranted this expense. In addition, lasers are still new enough that it requires a competent operator and technician to get the best out of them. The people in job shops have obviously dealt with a whole range of applications and can be more effective in any given project.
Since lasers become even more cost effective in conjunction with other technologies and techniques, it is often possible to manufacture a complete item using the technology available in a job shop. For instance, it might be possible to laser cut items which subsequently require to be laser or electron beam welded and then helium leak tested after assembly. Often too the technical staff of the job shop can offer invaluable suggestions concerning part design which will improve manufactureability on subsequent items.
When a customer has had interaction with the job shop and understands just what the laser's capabilities and limitations are, they are often able to completely redesign the part in what is called the third phase of automation, often gaining further improvements in quality and cost effectiveness. A smart company therefore can ease into the use of lasers and make prototypes in small quantities with the help of the job shop. Obviously when the volume of products has reached a critical level, it makes sense for the manufacturer to have his own laser but at this point, the process is completely under control.
The client would have a back-up source of manufacture available and his people would know enough about it to specify quite accurately what they need and to know what production rates are feasible and possible. It is possible then to gain phase three type productivity improvements by the redesign or modification of the dedicated system to be more effective on the large volume item by the addition for instance of different software or improved handling techniques.
It would be made more effective than the general purpose systems available in the job shop. Having real manufacturing numbers available makes it a lot simpler to justify the purchase of a system.
Since even a laser crystal ball is fairly unreliable, only educated guesses can be made as to the future directions. Expectations fall in three major areas:
- Improvements or upgrades in lasers
- Improvements or upgrades in associated systems
- Improvements or upgrades in job shop management
For the first, there are more manufacturers making multi-kilowatt C02 lasers. The prices are very competitive and the applications are growing. We see a growth in heat treating applications and should begin to see some growth in laser assistant cladding and hardfacing. Subsequently, we should see more large C02 lasers, that is lasers above 1 kilowatt and perhaps in the range of 5 kilowatts. This will improve the speed and thickness capabilities available for laser cutting of metals and other materials. There will be some upgrading of the power available in YAG lasers, industry sources indicate, with the ability to drill deeper, more parallel holes on the horizon.
We expect to see an increased use in excimer lasers which give short intense pulses in the ultraviolet part of the spectrum. The application would be for very fine, precise hole drilling in thin film materials, especially plastics.
As far as systems are concerned, the obvious thing to do is to have computer capability on the laser system such that it can readily interact with available CAD/CAM systems. The smoothing of the interface between the designer and the laser output would bring tremendous benefits in terms of reduced programming time and cost, reduction of errors and more readily available experimentation with prototypes.
This technology is available and we expect to see its use in job shops beginning soon. Once computers that are smart enough to interact with CAD/CAM are on board and running, then the obvious next thing for them to do is to keep track of the number and value of parts so that the job shop can keep track of its own records more readily and also provide feedback in terms of future pricing in order to keep the shop cost effective and keep overhead down.
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