Composites in Manufacturing hears how CemeCon’s diamond coatings help Dürr achieve a brilliant performance in countersinking in CFRP, GFRP and composite materials.
In order to reduce weight while maintaining high strength in complex components, lightweight materials such as CFRP, GFRP and CFRP-titanium/CFRP-aluminium stacks have become indispensable in the construction of aircraft.
However, machining them is no easy task. Anyone wishing to perform precise countersinking in sandwiched materials with high surface qualities will need special tools such as the CCDia AeroSpeed coated countersink from Dürr Präzisionswerkzeuge.
“Composites consist of several layers,” begins Wilhelm Marx, CEO and production manager at Dürr, outlining the challenges of CFRP machining. “The individual materials exhibit different properties and are often highly abrasive. Protruding fibres and delamination must be avoided at all costs, as components with these defects end up on the reject pile. With countersinking, the fact that the tool penetrates the material with its angular cutting edges quickly causes tool vibrations that result in chatter marks in the countersink.”
Dürr specialises in the manufacture of drilling, countersinking and reaming tools for a wide range of materials, in standard and customised designs. With the innovative ENORM plus countersink for machining wear-resistant and structural steels with tensile strengths of up to 1,750N/mm2, the company says it has successfully established itself on the market as a problem solver. In order to master the challenges of developing a countersink for machining composite materials, the company brought the know-how of CemeCon, one of the market leaders in diamond coating and PVD coating of precision tools for machining.
“Wear-resistant tools with extremely smooth, hard surfaces and special geometries with very sharp cutting edges were required,” says CemeCon’s sales manager, Marco Furrer. “As part of our Premium Plus Service, we approached the optimum solution with a targeted variation of several factors for both the tool and the coating.”
Throughout the partnership, Dürr further developed its tried and tested cutting geometry to meet the special requirements of CFRP machining.
“The customised geometry prevents delamination and cuts the fibres of the laminates very accurately throughout the entire countersink area,” says Marx. “This yields countersinks with smooth surfaces – with no objectionable fibre protrusions.”
Therefore, it was important to maintain the extremely sharp cutting edges during coating.
“The ultra-thin coating specification based on CCDia AeroSpeed has no influence on the microgeometry and, therefore, does not affect the sharpness either,” states Marco Furrer. The extremely smooth surface topography of the coating allows the countersinks to operate without vibrations or chatter, and this optimises the removal of swarf and heat from the machining zone. With a coating hardness of approximately 10,000 HV0.05 – nearly that of natural diamond – the tool also provides outstanding resistance to the very strong, highly abrasive fibres.
An inspiring result
The DIAplus countersink is the result of intensive cooperation – the perfect combination of optimised cutting geometry, a selected grade of carbide and a customised diamond coating.
“Countersinking in composites and stacks was previously considered a major challenge,” enthuses Marx. “The symbiosis of our countersink and the customised CCDia AeroSpeed coating now ensures brilliant performance in the machining of GFRP and CFRP as well as CFRP-titanium and CFRP-aluminium stacks. The service life of the tools is disproportionately long, and DIAplus guarantees almost unrivalled process reliability for machining tasks. Countersinking in installed components can even be done with hand-held machines under difficult operating conditions.”
Dürr’s CEO and sales manager, Uwe Späth concludes by saying how pleased he is with the large volume of positive feedback from users: “Satisfied customers are our top priority; firmly convinced users are important to us. With the DIAplus, we have achieved this brilliantly and have been able to prove our status as a solution provider yet again. Last but not least, thanks to our intensive cooperation with CemeCon, we now offer lightweight construction a perfect solution for countersinking in composites.”
