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System Design and Information from Mfg News.

Laser Machining for Fine Details

Laser removal is ideal for manufacturing fine structures and cavities and offers short machining times and low personnel attendance. "The advantages of the laser are greater when compared with conventional cavity EDM production methods," said a Deckel Maho Gildemeister (DMG) spokesperson. "Above all the directness of laser machining brings with it a time saving of up to 70%. And in the ratio of attended to unattended machining times, the laser proves to be up to 90% better than the EDM process."

From its machine range Lasertec offers two variants in the category of laser removal. The LaserOnly machines of the DML 40 series can create the finest of contours and cavities without tool costs. In addition to the pure laser removal machines of the DML 40 series, last year the combination machine DML 60 HSC was introduced. The HSC milling head with maximum spindle speeds of 42,000 RPM first of all removes material in a preliminary stage. Immediately afterwards, the laser head - in the same fixture - takes over for the finishing stages of fine details, sharp edges, cavities, and lettering.

The method of laser removal is based on a complex system of optics and is the same for the DML 40 and DML 60 HSC series. The cutting tool is an Nd:YAG laser beam of 100 W mean power previously pulsed over a Q switch for a top power output of between 13.4 and 26.8 hp. Focusing the beam to a diameter of 0.1 mm concentrates at this point very high power densities that cause the material to vaporize. Depending on the targeted surface quality, material is removed in thicknesses of 1 to 5 ?m.

The beam itself is controlled by a laser head with high dynamic response. The distance from the lens to the material is 100 mm. The corresponding controller for the optics then guides the laser beam, focused to a diameter of 0.04 or 0.1 mm, at ultra high speed step by step over the surface for machining until the layer has been removed and work can commence on the next step.

In addition to the "normal" CNC, the machine is connected to a standalone computer with high-resolution monitor, computer keyboard, and mouse that is used to prepare CNC programs independently of the control. A network facility allows the computer to be integrated easily in host networks for importing CAD data and providing ready-to-run programs for the control.

The geometrical data from CAD systems are transferred in the STL format. Programming itself requires solely the geometry of the material to be machined - the programming system then automatically breaks down these data into layers which finally provide the basis for generating the laser machining paths. The greatest part of the calculation is done automatically, and also the control itself does not need specific CNC skills to operate.  

Laser removal is today being used in a large number of applications. These include, for example, prototype mold construction and rapid tooling where micro switches, electronic and semiconductor structures, medical engineering components, injection molds, mold inserts, and seals are machined by laser. Further applications are recessing and embossing for reliefs, logos, coins, form punches, molding stamps, and lettering. And also tool makers can now profit from the laser's potential: laser removal makes indexable inserts, PCD and CBN materials, chip breakers, and hard-metal molds ready for use in manufacturing. Other examples are miniature models (model cars, model railways, toys) and job lots (flexible manufacturing from simple cavities to fine, high-precision structures on the one machine).