No longer an emerging technology, laser drilling is now used in almost every industry. Once thought to be only for those "impossible" applications, laser drilling is shedding its last-resort image and is taking its place on the shop floor as an effective alternative to conventional machining.
Laser drilling is widely regarded as a non-conventional approach to be used when you have exhausted all other methods. While these "impossible" applications account for a large portion of the laser processing market, many manufacturers are beginning to use laser drilling to compete directly with conventional methods for speed, quality and cost.
The process uses a highly coherent, focused beam of light as its drill bit. Because there is no mechanical contact with the part at the point of drilling there is no tool wear, bit breakage, excessive part heating, or chips produced. The laser accomplishes this by heating the metal to above its melting point. The metal that is vaporized then expels the molten metal from the hole. This action, coupled with the short pulse duration (typically 1 millisecond or less), reduces parent metal heating to almost nothing. This typically reduces heat-affected zones to 0.005" or less.
With laser drilling there is no physical contact with the part. The hardness of the metal and the angle of incident do not affect drilling. This is a great benefit when drilling holes on an angle because the holes do not drift or move out of location. In many instances, hardened materials process more consistently and react to the laser more uniformly.
Laser drilling can produce holes with diameters 75 times smaller than a human hair (0.000039") up to 0.045" using peck drilling (without beam trepanning). Holes larger than 0.045" are produced by laser cutting and hole/depth ratios change. While on either extreme of the laser's range the maximum depth decreases, thickness to hole ratios of 100:1 can be achieved in specific applications. Ratios of 40:1 are common when using laser drilling.
One of the main drawbacks of laser drilling is hole taper. Laser drilled holes almost always exhibit "laser taper". This is a bell mouth taper at the entrance, minimal taper in the hole's midsection and a final straight section at the exit. In most cases tolerances quoted by laser drolleries are for exit hole sizes and do not apply to the entire length of the hole. Once thought to be an almost fatal disadvantage of laser drilling, the purposeful use of the laser taper effect has developed into a very useful tool that engineers and producers have put to great use in a variety of applications.
In flow applications it was found that a laser drilled hole of a given size would produce a larger flow than a similar, conventionally drilled hole. This allows mold manufacturers to use smaller gas vent holes for the same flow rates. This in turn means a smaller hole "footprint" on the molded part and, in many instances, can eliminate marking from the vent holes completely. This taper was also shown to assist in "automatic" cleaning of plugged holes. If any material gets into the hole, the taper allows it to pass through easily and keep the laser-drilled holes open longer. When taper is not desired, laser parameters can be adjusted to minimize, and even in some instances eliminate the taper.
Standard laser drilling tolerances are 0.002" but can be held much tighter if the application requires it. It is important to remember that the hole tolerance is an important factor in pricing, so it is beneficial to use the largest tolerances possible. Materials that can be laser drilled range from ceramics to super alloys, common steels to precious metals and virtually all non-metals. Laser drilling has been used for everything from single parts for research, to long term production runs in the millions.
Even if your requirements don't justify purchase of a laser system, many laser job shops exist that can help you with your applications. These job shops offer diverse experience that they can apply to your situation. Some of the fields that have benefited from this experience include: electrical power distribution, bar code scanners, mass spectrometry, electron microscopy, carburetor and fuel systems, automotive interiors, glass molding, flow orifices, research, spray drying, aircraft lock wire holes, combustion liners and turbine blades for aerospace, thread guides for the textile industry, carpet dyeing, and nuclear steam.
Other common laser processes include laser welding--a viable alternative when heat input, thermal damage, distortion, and weld appearance are important; laser cutting, an effective way to produce parts without expensive dies or machining; and laser heat treating and etching for innovative and cost effective results compared to conventional methods.
As the laser finds additional uses in materials processing, it is ever more likely that you or your competitors can effectively use laser drilling. In the race to produce faster, better and less expensive parts, don't overlook laser drilling as an efficient, cost effective tool.
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