Five-axis milling machines and the latest InvoMilling™ functionalities open up new options for small batch production. InvoMilling™ is a method developed by Sandvik Coromant for the flexible machining of spur and straight bevel gears.
by Elena Magistretti
Increasing demands on speed and flexibility call for new gear manufacturing solutions. How will gear milling change in the future? What about current trends in the field of gear milling? According to Prof. Dr.-Ing. Tillmann Körner, from Aalen University, a true specialist, gear manufacturing needs to get faster and more flexible. This is especially true in the case of one-off and small batches for prototypes and spare parts, where customers expect more and more bespoke and special gears in shorter delivery times. Therefore, gear cutting will become increasingly differentiated in regard to both the duration of the manufacturing process and the gear geometry and its parameters. Most notable of all, according to the Professor, gear production will become independent of conventional gear-cutting machines.
The impact on tools, machines and production methods
“A decoupling of the gear-cutting process at the interface between the traditional machine tool and traditional gear-cutting tool – Prof. Ing. Tillmann Körner says – is essential for faster and more flexible gear manufacturing. As a result, machine tools that are independent in terms of kinematics, and can produce gears using just module-independent standard tools, are trending. In addition, operations from soft gear machining to burring are increasingly being combined on one machine. In short, the future belongs to five-axis milling machines with precise, easy-to-use cutting tools and special 3D software. This combination enables fast, low-cost and individual gear production for single run and small batch orders. The software controls both pre-development and subsequent production implementation on the machine”.
In this scenario, the importance of manufacturers of gear cutting tools for five-axis gear cutting is growing as they are positioned between machine tool suppliers and gear manufacturers. By providing the appropriate interface software, in addition to gear-cutting tools, they retain their independence from manufacturers of five-axis machine tools. With innovative software solutions and suitable interfaces, tool manufacturers ensure the feasibility of a flexible and efficient gear-cutting process. Moreover, the sizing function of their software enables the customer to independently design, define and manufacture individual gear geometries.
An innovative software solution for a fast and flexible production of gears
The InvoMilling™ process, offered by Sandvik Coromant, is a user-friendly and intuitive software solution with matching tools that marks the beginning of a paradigm shift. This is precisely what industry demands: the production of fast, high-quality individual gears, either soft or hard, flexible and at an acceptable cost on standard five-axis milling machines. The latest version of InvoMilling™ software, which was developed by PhD students at the Aalen University of Applied Sciences, allows spur gears and bevel gears to be machined. As a result, the software offers even more options for five-axis gear manufacturing, further driving the development and spread of this technology. Getting more into the detail, InvoMilling™ exploits machine tool kinetics for the effective and flexible manufacturing of high-quality gears and splines in quality level 6 or better (according to DIN 3962). After entering the required gear data, the intuitive CAD/CAM software defines the optimum machining strategies and generates a CNC program that allows the production of different gear profiles using just a few standard precision tools. The software also offers excellent graphics as well as features to create and simulate milling paths. As well as upcoming options for herringbone, double helical (with and without gap), and straight bevel gears (end of 2017), an additional new function available in the latest version of InvoMilling™ is flank correction. This applies to tip relief and crowning in both the flank and profile directions as well as helix and pressure angle corrections. Numerous improvements have also been made to the tools. For instance, adapted tools have been introduced to the tool library.