Special Xtrimium production line

Peter Janeczek, Key Account Manager / Application Engineer Gears Automotive at Saint-Gobain Abrasives: "We do everything we can to enable the user to get the best out of Norton Xtrimium grinding wheels. The latest grain and bond technologies from Norton are combined under Xtrimium. Each abrasive grain, such as ceramic sintered alumina, high-performance fused alumina and innovative bonds are individually matched to the process and play to their strengths in their respective areas. To manufacture them, we have set up a special Xtrimium production line at our plant in Gerolzhofen, Germany."

In Gerolzhofen, the production of each individual grinding worm follows the strictest quality control procedures to achieve perfect geometry and balancing and to ensure safe grinding at up to 110 m/s during subsequent use. This includes adherence to tighter tolerances and higher dimensional accuracy for all wheel dimensions, an axial and radial run-out of ≤0.1 mm and the ability to pre-profile all grinding worms. Among other things, the dynamic unbalance is measured on two levels and geometric and speed tests are carried out in accordance with DIN EN 12413. From the wide range of possible combinations of abrasive grain, bond system, structure and hardness, the user then receives a tool that is precisely tailored to individual requirements. This high-performance formulation makes the manufacturing process more productive, efficient and economical when used later on with cool grinding.

Norton Xtrimium offers complete grinding solutions. These are high-performance tools for profile and spiral gear grinding, classic generating grinding and special applications such as superfinishing with dual grinding wheels or baby worms for grinding workpieces with interfering contours, for example. The advantages are evident in the various applications.

Continuous generating grinding

The Norton Xtrimium grinding wheels for continuous generating grinding have a homogeneous grinding wheel structure with long tool life, increased dimensional stability and a high number of components per dressing cycle as well as long tool life for long dressing cycles. Thanks to the cool grinding, the components are protected against heat damage and structural changes.

In practice, when grinding a spur gear made of 20MnCr5 with a hardness of 60 to 62 HRC (module = 7.24 mm, number of teeth, pressure angle = 24°, gear width = 80 mm), the Xtrimium grinding worm achieves a surface quality of Ra < 0.8 μm, Rz < 4.0 μm, ffα = DIN1, ffβ = DIN 1 and reduces the grinding time by 30 percent compared to a grinding tool with ceramic grit. The Xtrimium tool also needs to be dressed much later. The number of possible dressing intervals is 30 percent higher.

Dual grinding worms

The Norton Xtrimium dual grinding worm is a special solution. It can be used to produce extremely fine surfaces without grinding burn over the entire wheel service life with process reliability, dimensional stability and high repeat accuracy, making transmissions in electric vehicles, for example, more efficient, more durable and quieter. The highlight: The dual rolling worm performs both the actual grinding task for material removal and, with a separate area and a correspondingly adapted specification, polishing - in other words, it combines two machining processes in one clamping. This eliminates the need for retooling and adjustment work, shortens production time and significantly increases quality. Peter Janeczek: "Norton has developed its own formula for this, which, unlike conventional systems, does not expand and can therefore be dressed in a defined manner."

In practice, the strengths of the special design and the ability to grind in a single clamping operation become apparent: When machining an idler gear made of 20MnCr5 with a hardness of 60-62 HRC (module = 2.9 mm, number of teeth = 73, pressure angle = 20°, tooth width = 74 mm), the grinding time is reduced by 25 % compared to conventional methods, and the dressing intervals are increased by 50 %! In addition to its long service life, the dual wheel also boasts a very good, uniform surface quality, as there are no unwanted changes to the gear profile or geometry, even in nuances, as the wheel does not push away. In this example, the surface quality is Rz < 1.5 μm, ffa DIN1, ffβ = DIN 1.

Baby sanding snail

Baby grinding worms (D < 180 mm) can be used to grind closely positioned gears directly on the shaft in hybrid vehicles or e-bikes, for example. This follows the trend towards smaller assemblies in transmissions for alternative drives. Due to the special production technology, Xtrimium baby grinding worms are particularly stable, homogeneous and wear-resistant thanks to their very high homogeneity.

The Norton Xtrimium bevel gear grinding wheel has been specially developed to meet the requirements of pinion and ring gears. The homogeneous and open structure of the grinding wheel ensures optimized coolant transport into the contact zone. This results in cooler grinding with increased performance. The bottom line is that the costs per unit are significantly reduced.

Profile grinding wheels

Profile grinding wheels offer a high degree of flexibility in the design of the gear geometry through the machining of a wide variety of modules, grinding from the solid (soft machining) to the grinding of very hard materials and special materials.

Alexander Heubes, Key Account Manager / Application Engineer Gears Germany at Saint-Gobain Abrasives: "Norton Xtrimium offers excellent porosity to ensure optimum coolant transport into the contact zone and thus ensures cool grinding. In combination with a special microcrystalline grain structure, the Xtrimium profile wheel simultaneously meets the highest performance requirements as well as gearing quality that complies with DIN ISO standard 1328-1."

When manufacturing a planetary gear from 18MnCr6 with a hardness of 58-62 HRC (module = 9 mm, pressure angle = 20°, number of teeth = 25, tooth width = 160 mm), the Xtrimium wheel achieves ultra-fast grinding to DIN 3 tolerance. Compared to a conventional grinding tool with ceramic grit, in this particular case the related metal removal rate Q'w (mm3 / mm / sec) increases by 160 %! At the same time, very high quality according to DIN 1 tolerance is achieved. This means extremely uniform results and very good topography with Ra < 0.8 μm / Rz < 4.0 μm.