Machine tool maker Heller and transmission manufacturer Voith Turbo AG have developed a horizontal machining centre bevel gear manufacturing solution, uP-Gear.
This innovation enables significant increases in the productivity of both pre-milling and gear milling operations, with all operations performed on a single machine.
The solution, patented by both Heller and Voith, sees Heller's F and MCH-C series machines able to support gear manufacturing. Currently the maximum diameter tackled is 1,800 mm, but a new machine will take that to 3,000 mm.
Software is key in the solution. It held that there is no comprehensive mathematical models for items such as bevel gear tooth systems, consequently every CAD model used for gear related CAD/CAM processes are approximated models.
As traditional gear cutting machines are based on a specific machine structure with corresponding kinematics, they generate the appropriate tooth shape on the basis of the setting parameters entered into the machine. The revolutionary approach taken by Heller differs totally from the traditional, inefficient method.
Although resembling a hobbing process, gear parameters specified on drawings can be input directly into the machine control. The control then uses the data to generate the 5-axis paths for both roughing and finishing in real time. As a result, no mathematically accurate 3D geometry model is required, rather, pre-defined gear data from drawings is used. Measuring machine compensation data reports can also be directly entered in the machine control for processing.
A further, major benefit of this progressive approach is that current, real time tool data, such as tool wear, can be incorporated into the ongoing process. Through the use of this information component precision is enhanced, scrap rates reduced and considerable manufacturing time is saved.
In addition to tooth space machining, Heller also provide an advanced process for the pre-milling of blanks. As a result, the complete pre-machining of both external and internal contours is possible in the first set-up, with tooth milling taking place in the second set-up. Specially adapted NC cycles have been developed to facilitate process control, allowing the complete workpiece to be machined on a single machine.
Other 5-axis machining centre manufacturers offer gear cutting solutions, but, according to Eric Pollard, Heller UK sales manager, this method is not particularly efficient and productive. "We operate in fields with high chip removal rates and aim to achieve the same in gear milling. Therefore, we co-operated with Sandvik Coromant to develop a customised crown-milling cutter with indexable inserts - a type of hob. This has played a major role in increasing productivity, by a factor of three, compared to conventional methods. This means the wider the tooth space, the more productive we will be."