Coating specialist Oerlikon Balzers, in collaboration with sawing technology expert Ott + Heugel, has succeeded in increasing the service life of circular saw blades by a factor of seven to eight when cutting gold and brass alloys. At the same time, process costs have dropped significantly with the Balda Variastiegen coating.
Company owner Fabian Heugel is the fourth-generation head of the Württemberg-based family business Ott + Heugel. One of his customers, a jewelry and watch manufacturer, cuts round bars and square materials made of yellow, white, and rose gold, as well as brass, using solid carbide (VHM) saws from the Ötisheim-based manufacturer. These non-ferrous metals are ductile and relatively soft. During machining, their tendency to stick and adhere quickly leads to built-up edges on the tool. One consequence is burr formation on the workpiece, which complicates further processing. To take timely countermeasures, the customer regularly monitors the sawing machine’s current consumption as an indicator of increased force and incipient wear.
Diamond Coating for Both Soft and Hard Materials
A trial switch from uncoated to AlTiN-coated solid-carbide saw blades already doubled tool life. Heugel, however, remained persistent and, on the recommendation of Klaus Springer, a customer advisor at Oerlikon Balzers, introduced the company’s new diamond coating, Balda Varia. “The coating was still uncharted territory in terms of sawing technology, but we decided, together with the customer, to start testing it,” says Heugel. It paid off: After ten weeks of use, no wear was visible, but the tool life was seven to eight times longer, depending on the material being machined. The tool, with a 63-mm diameter and special tooth geometry, operates in three-shift production on the same machine type at all times.
According to Oerlikon Balzers, the Balda Varia coating is a versatile CVD diamond coating for cutting tools that can also machine special materials such as carbon-fiber-reinforced plastic (CFRP), graphite, and zirconia ceramics. It ensures consistent results across a wide range of tool sizes and geometries—with high wear resistance and consistent machining quality. Thanks to plasma technology, the controlled growth of the diamond creates a dense, nanocrystalline coating structure. The result: uniform wear that extends tool life. The progressive wear behavior makes it easier to monitor the tool and reduces the risk of sudden failures.
In the specifications, the supplier lists a coating hardness(HIT) of 80 to 100 GPa for the dark gray coating, measured by nanoindentation according to ISO 14577. For multilayer coatings, the hardness of the individual layers may vary. According to Oerlikon Balzers, the hardness can be tailored to the specific application. The typical coating thickness ranges from 6 to 12 µm; other thicknesses are available upon request. The maximum application temperature is specified as approximately 600 °C, while the process temperature remains below 900 °C.
Narrower cutting widths save a lot of material
Thanks to the improved performance, the saw blade thickness was reduced from 0.7 mm to 0.5 mm. This 0.2 mm reduction in cutting width pays off over the course of a year: Ott+Heugel’s customer can save approximately 800 m of precious and non-ferrous metals through this measure alone. In addition, there are fewer tool changes, setup times, machine downtimes, and checks of power consumption. Although tool reconditioning is no longer possible, the benefit in terms of tool life more than makes up for it. For this reason, the precious and non-ferrous metal processor also plans to use five of these tools.
The specialized plasma CVD (chemical vapor deposition) technology for diamond coatings on the Indiama coating system developed by Oerlikon Balzers offers further advantages: First, it enables uniform and cost-effective diamond coating of large volumes. Second, the system can accommodate shank tools with a total length of 330 mm and a coating length of up to 150 mm, or saw blades with a diameter of up to 200 mm. This allows for a price point comparable to that of high-quality PVD coatings, as reported by Oerlikon Balzers. However, the greatest benefit stems from longer service life, greater stability, reduced process complexity, and consequently lower cutting costs per component.
Follow-up Project Already in Sight
With a hardness of up to 10,000 HV, the Balda Varia nanocrystalline diamond coating outperforms most PVD coatings, which typically reach 3,000 to 4,500 HV. The diamond-like hardness ensures sharp cutting edges over long periods for burr-free cutting of non-ferrous metals, as well as resistance to abrasion. In addition, the very smooth, slippery coating also resists adhesive wear and material buildup.
According to Heugel, his company was unable to find comparable and cost-effective coating systems from other coating providers. The CEO already has a follow-up project in mind with Oerlikon Balzers: the use of saw blades and drill bits coated with Balda Varia for machining lead-free brass in the electrical industry. To this end, he is conducting long-term tests with a mass manufacturer on rotary transfer machines, with the primary goal of reducing the cost per component.