SilverLine has been part of the WNT (Ceratizit Group brand) product range for over 10 years, so it was time to look again at this key product and update it, not only with the latest in cutting-tool technology, but expand its application range by adding new cutters to the portfolio. While cautious not to make change for change’s sake, the development team was tasked with improving the three key elements that give a solid-carbide tool high performance, namely the carbide substrate, coating and geometry.
For example, increasing the number of flutes allowed for a larger core diameter to be created, which in turn generates much greater cutter rigidity and reduces cutter deflection, with tensile strength increased by 50%. This upgrade, along with associated changes to the chip gullet and the addition of through-tool coolant, improved chip flow, reduced cutting forces and ensured the cutter generates less heat and noise. In addition, cutting data has been increased between 20 and 40% (material dependant), with tool life up by as much as 50%.
Helping to maximise these performance levels is the latest Dragonskin coating, which is silver in colour and compatible with most materials, including stainless steel or steel flame-cut, uncoated or scaled billets. The high temperature resistance of the coating makes it suitable for either wet or dry machining applications.
“In short SilverLine cutters are now stronger, last longer and are faster than their predecessors,” says Adrian Fitts, business development manager. “The tools are now available with three, four, five, six and eight flutes dependent on application and diameter and, with the burgeoning aerospace sector in mind, we’ve added many more options when it comes to corner radii and cutter diameters.”
As with all successful product development processes, the customer was central to many aspects of the SilverLine changes, not least the extension of the range to encompass greater choice in cutter styles, including ripper and torus.
“We listened to customers who were asking for heavier-duty roughing cutters and, thanks to the increased core size and rigidity, we can now offer a ripper version of SilverLine,” says Fitts. “As customers wanted to run faster, this created a problem: higher cutting data equates to greater chip volume and evacuating those chips became an issue. Now, with the strengthened core, through-tool coolant and Dragonskin coating, combined with a ripper-style geometry to create smaller chips, we can push tools harder as evacuation is no longer the challenge it once was. For more specific high-speed milling application, we’ve added HA-style shanks to the standard range. This plain shank is ideal for use in heat-shrink and hydraulic chucks, allowing increased spindle speeds to be used.”
To prove that SilverLine was a “good tool made even better”, extensive field trials were undertaken in Germany. The test results speak for themselves, as highlighted by the example at long-standing SilverLine user Heinz Knöpfle GmbH.
“As a big fan of the original SilverLine tools, we had very high expectations, but the amazing results that we’ve achieved with the upgrade have far exceeded expectations," says production director Christian Knöpfle.
The results showed a tangible increase of between 20 and 40% in cutting speeds. At the same time, service life increased by 30 to 40%.
"We noticed straight away that the new SilverLine tools are quieter, thus reducing the burden on the machine,” says Knöpfle. “The values obtained over the months then confirmed this; we have a new favourite tool.”
During the tests, SilverLine was initially used for machining a stainless steel polygon shaft, which Knöpfle produces in various sizes for a water management company.
"We use the tool at extremely high cutting speeds and therefore achieve excellent chip evacuation, with a service life and level of process security that other milling cutters never reach,” says Knöpfle. “This is ideal for users like us, who only wish to use a small selection of tools."