High-speed gear cutting new horizons

To produce durable, low-noise, high-efficiency gears, such as gears in drive applications, this requires manufacturers not only to have a very high quality requirements system, but also to have a correspondingly high level of production. This is in line with the rules of the game in the industrial market competition - in addition to the shortest production time, but also have lower production costs. A basic survey of production process cost analysis and cost saving space shows the following features.

 

       The average overall manufacturing cost of about 8% comes from the tool, including its coating. Even the most favorable purchase conditions here can only bring insignificant savings.

 

        Cooling costs account for approximately 12%, depending on the cutting process chosen. Dry machining has advantages here, so it is often used for gear cutting but not for all applications.

 

                  Preparation costs for machines to approximately 24%, which can be reduced by extending tool life, thereby reducing configuration time

 

        At least 26% of manufacturing costs are due to other factors that cannot be adjusted.

 

       About 30% of the actual processing cost, accounting for the largest proportion. By increasing the cutting speed, this part of the cost can be most effectively reduced.

 

       Application of protective coatings

 

        Modern wear-resistant coatings are increasingly important for cost savings. They are widely used in dry processing and continue to improve. Abrasion-resistant coatings extend tool life and reduce machine preparation costs. But the most important thing is that they directly show their advantages in cutting applications, that is to achieve a significant increase in cutting speed. “Today, more than 60% of the world's hobs use our AlCrN-coated BALINIT ALCRONA PRO. They were first used in the automotive industry.” Wolfgang Oerlikon Balzers, head of cutting tool marketing and product management at Oerlikon Balzers Dr. Kalss said.

 

       After these coatings are processed, the cutting speed can be increased and the cost can be reduced. The data shows that if the gear cutting speed can be increased from 200m/min to 300m/min, the processing time (primary and secondary machining) of each gear will be reduced from 0.56min to 0.42min. According to the calculation of machine man-hour rate, this means that the processing cost is reduced by about 25%. If the overall production cost of the gear is calculated, this represents a cost reduction of about 10%. Therefore, the investment in new substrates or coatings is value for money.

 

       Making higher cutting speeds possible

 

        To better utilize this principle to allow manufacturers to achieve higher cutting speeds, coating performance needs to be tailored to specific applications while continuously improving efficiency. Oerlikon Balzers took another big step in this direction and made further progress. The BALINIT ALTENSA coating, introduced in 2015, is the latest addition to the highly successful AlCrN series with excellent wear resistance and red hardness. Taking into account the market's increasing demand for cutting speeds, the performance of coatings at high temperatures in particular needs to be optimized. "We have actually further reduced the thermal conductivity of the coating and increased the red hardness of the coating by about 20%," explains Dr. Kalss. It is specifically designed for crater wear that is easily generated at high temperatures and reduces tool life. When using carbide inserts for bevel gear machining, BALINIT ALTENSA achieves higher tool life even in dry machining conditions.

 

       Furthermore, anti-abrasion and oxidation resistance can be optimized to around 35%. It also reduces flank wear at medium and high cutting speeds. Even with dry machining, tool life can be extended. In the end, a large number of improvements in coating development have not only led to a significant increase in productivity, a further extension of the tool life, but also the processing performance of various substrates (powder metallurgy high-speed steel, hard alloy, MC90 grade steel) at the highest cutting speeds. Significantly increased, at the same time, the cutting speed and feed rate are also higher. The customer test for different application areas has verified this result one by one. >

 

       Test Results

 

       Benefit from BALINIT ALTENSA's application, a well-known European car manufacturer can effortlessly increase the cutting speed (vc) of its powder metallurgical high-speed steel hobbing cutters (90mm in diameter) by 30 %, that is, from 200m/min to 260m/min. At the same time, the service life of the tool is also increased by 20%. The second series of tests showed that even at a cutting speed of 300 m/min (ie a 50% increase), the service life of the tool is still longer than the original service life. The coating for carbide hobs also has a significant set of data: In the high-speed cutting environment (vc = 480m/min), the tool life can be extended by more than 30%.

The versatility of BALINIT ALTENSA is also suitable for wet processing. The initial results show that the tool life can be significantly extended.

 

       Tests from another auto supplier show that the productivity of carbide inserts can also be significantly improved. When the cutting speed is increased by 35%, ie, vc=200m/min, the tool life is increased by 30% at the same time. Another automotive supplier conducted a wet (lubrication) test on the coated high-speed steel pinion cutter (130mm in diameter) and the tool life was extended to the original 140%.

 

       Improving product performance

 

       "Our new coating sets a new performance standard for gear cutting, making it possible to achieve better process reliability at previously higher tool speeds with previously unimaginable tool life. For the user, this means better product performance with lower manufacturing costs, concluded Dr. Kalss.