EWAG’S LASER LINE ULTRA PUSHES THE BOUNDARIES OF LASER-PROCESSED MICRO TOOLING

As users in the electronics, medical and micromechanics industries, for example, continue to push the boundaries in terms of miniature products, Ewag – a member of the United Grinding Group – has likewise continually developed its laser-based machining technology to meet these demands. 

Indeed, the company’s Laser Line Ultra machining centre, available in the UK from Walter Ewag UK, is unrivalled in the laser ‘fabrication’ of cutting tools including spiral tools from 0.4 mm to 3 mm diameter and made from hard/ultra-hard materials such as tungsten carbide (WC), polycrystalline diamond (PCD), chemical vapour deposition diamond (CVD-D) and cubic boron nitride (CBN).

The machine can be successfully applied to cutting edge preparation, post-sharpening, chip breaker and cylindrical margin fabrication as well as to the laser-modification of ground cutting tools. And complex micro geometries can be machined due to the machine’s eight-axis kinematic concept and the use of an industrial laser source that emits pulses in pico-seconds.

For example, a four-flute PCD end mill can be produced from cylindrical blank with its primary and secondary clearance faces machined at both at the tip and circumference. The corners at the edges are protected by a chamfer and, as with all lasered spiral tools, the result is a smooth and uninterrupted interface between PCD and WC.

Laser processing removes material in line with thermal-based mechanisms, and because the Laser Line Ultra uses ultra-short laser pulses and appropriate laser machining parameters, the resulting pulse is so short that there is insufficient time for a significant amount of heat to conduct into the cutting tool, so there is negligible heat-affected zone.

Indeed, carbide drill bits laser-fabricated by the machine can subsequently be coated (by the physical vapour deposition process) with a single layer of TiAlN or AlTiN alloy and the coating processing method is the same as that applied to ground cutting tools.

Ewag has worked closely with two of Switzerland’s foremost surface technology companies to ensure successful coating and together they have used a number of inspection methods (such as optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, hardness indentation tests and destructive break tests) to validate the process.

In terms of micro drills, for instance, the advantages of using laser technology compared to conventional techniques, include:

• [] Diameter-to-length ratios of up to 1:20
• [] Ability to process additional small features such as tip thinning and tip chamfers
• [] There’s no tool breakage and no need for a steady-rest because lasering is a force-free process
• [] The process enables a high degree of geometrical flexibility since brazed plate-based tools and spiral tools can be fabricated without re-tooling.

On spiral micro tools, the lasered surfaces are homogenous and do not show any form of directional feed marks compared to the ground surface. Furthermore, the surface quality of the lasered WC surfaces is 20% better than the ground WC drill bit.

For lasered PCD surfaces, excellent surface quality is also achieved and in general, lasered spiral tool surfaces – regardless of material – exhibit surface roughness values for Ra and Rz of <0.25 micron and <1.5 micron, respectively. Cutting edge radii are typically ≤5 microns and are symmetric with a K-factor typically equal to 1±0.2. In terms of diameter stability, a tolerance of ±0.005 mm can be achieved in a 12-hour production run in climatic-controlled conditions.

Going forwards, based on the Laser Line Ultra’s success in producing complex micro cutting tool geometries, Ewag is continually improving the process (laser processing and the machine’s software) for the fabrication of CVD-D and CBN spiral tools – with the former, for example, producing a four-flute polycrystalline CVD-D end mill and with the latter, laser-turning from a solid cylindrical blank a PCD tool for chip-free machining of carbide and tool steel, producing mirror finishes and chip-free hole expansion for ultra-precise diameters.